JP7732472B2 - Method for manufacturing a wiring board - Google Patents

Description

The present invention relates to a method for manufacturing a wiring board using a resin sheet.

A known manufacturing technique for printed wiring boards is the build-up method, in which insulating layers and conductor layers (circuit layers) are alternately stacked. In build-up manufacturing methods, insulating layers are generally formed by laminating a resin composition layer onto an inner layer substrate using an adhesive sheet containing a resin composition layer, and then curing the resin composition layer. After the insulating layer is formed, a circuit is formed on the insulating layer.

When using an adhesive sheet with a resin composition layer formed on a metal foil, it is possible to form circuits using the metal foil using a subtractive method or a modified semi-additive method. For example, Patent Document 1 discloses an adhesive sheet including copper foil and a resin composition layer made of a specific resin composition formed on the copper foil.

When using the subtractive or modified semi-additive method, it is possible to easily manufacture circuit boards, but traditionally it has been necessary to use a resin sheet with metal foil and to make it compatible with processes including vacuum hot pressing.

Japanese Patent Application Laid-Open No. 2002-359444

For example, one possible method involves adhering a roll of a metal foil-attached resin sheet onto a circuit board, cutting it, and then subjecting the cut metal foil-attached resin sheet to a vacuum hot press. However, it has been found that when a metal foil-attached resin sheet is temporarily attached to a circuit board using a temporary attachment machine and then cut, resin chipping tends to occur at the cut surface due to differences in hardness between the metal foil and the resin sheet. Furthermore, if the minimum melt viscosity of the resin composition layer is set low to prevent the above-mentioned resin chipping problem, the thickness of the resin composition layer (insulating layer) tends to decrease after thermocompression bonding using a vacuum hot press. Large thickness variations reduce the uniformity of the insulating layer thickness, so preventing this thickness reduction becomes a challenge. Furthermore, a low minimum melt viscosity also poses the problem of a lower glass transition temperature of the insulating layer. On the other hand, if the minimum melt viscosity is too high, in addition to the above-mentioned resin chipping problem, problems such as reduced adhesion of the metal foil to the resin composition layer arise.

The objective of the present invention is to provide a method for manufacturing wiring boards in which circuits are formed using metal foil by a subtractive method or modified semi-additive method, which can suppress the above-mentioned resin chipping, changes in the thickness of the resin composition layer (insulating layer) after vacuum hot pressing, decreases in metal foil adhesion, and decreases in glass transition temperature.

After extensive research, the inventors discovered that the problem of resin chipping that occurs when cutting a resin sheet can be solved by laminating a resin sheet having a support and a resin composition layer onto a substrate, peeling off the support, and then thermocompressing a metal foil to the resin composition layer. They also discovered that by setting the minimum melt viscosity of the resin composition layer before thermocompression to 2,000 poise to 20,000 poise, changes in the thickness of the insulating layer can be suppressed and good metal foil adhesion and glass transition temperature can be achieved, leading to the completion of the present invention.

That is, the present invention includes the following.
[1] (1) A step of heating and laminating a resin sheet having a support and a resin composition layer provided on the support to a substrate so that the resin composition layer of the resin sheet is bonded to the substrate;
(2) peeling the support from the resin composition layer; and (3) heating and pressing a metal foil to the resin composition layer by vacuum hot pressing,
In the step (3), the minimum melt viscosity of the resin composition layer before thermocompression bonding is 2,000 to 20,000 poise when measured in a temperature range from 60°C to 200°C.
[2] The method for producing a wiring board according to [1] above, further comprising the step of drying the resin composition layer (A) as a step carried out after the step (1) and before the step (2), or after the step (2) and before the step (3).
[3] The method for producing a wiring board according to [1] above, wherein the minimum melt viscosity of the resin composition layer before lamination in the step (1) is lower than the minimum melt viscosity of the resin composition before heat-pressure bonding in the step (3).
[4] The method for producing a wiring board according to the above [1], wherein the heating temperature during lamination in the step (1) is 80 to 140°C.
[5] The method for producing a wiring board according to the above [1], wherein the heating temperature during thermocompression bonding in the step (3) is 170 to 230°C.
[6] The method for producing a wiring board according to the above [1], wherein the pressure conditions during the thermocompression bonding in the step (3) are 0.5 to 2.0 MPa.
[7] The method for producing a wiring board according to the above [1], wherein the thickness of the resin composition layer before lamination in the step (1) is 40 μm or less.
[8] The method for producing a wiring board according to the above [1], wherein the glass transition temperature of the resin composition layer after the heat-pressure bonding in the step (3) is 140°C or higher.
[9] The method for producing a wiring board according to the above [1], wherein the thickness of the resin composition layer after heat-pressure bonding in the step (3) is more than 10 μm.
[10] The method for producing a wiring board according to the above [1], wherein the thickness reduction rate of the resin composition layer after the heat-pressure bonding in the step (3) relative to the resin composition layer before lamination in the step (1) is 40% or less.
[11] The method for producing a wiring board according to the above [1], wherein the content of the organic solvent in the resin composition layer before heat-pressing in the step (3) is 0.3 to 2.5% by mass, where the total amount of all components in the resin composition layer is 100% by mass.
[12] The method for producing a wiring board according to the above [1], wherein the support is a plastic film.
[13] (4) A method for producing a wiring board according to the above [1], comprising a step of forming a circuit pattern from a metal foil by a subtractive method.
[14] (4') A method for producing a wiring board according to the above [1], comprising the step of forming a circuit pattern from a metal foil by a modified semi-additive process.
[15] The method for producing a wiring board according to the above [1], wherein the resin composition layer contains a thermosetting resin.
[16] The method for producing a wiring board according to [15] above, wherein the thermosetting resin comprises a thermosetting resin selected from the group consisting of epoxy resin, cyanate ester resin, maleimide resin, and thermosetting modified polyphenylene ether resin.
[17] The method for producing a wiring board according to the above [1], wherein the resin composition layer contains an inorganic filler.
[18] The method for producing a wiring board according to the above [17], wherein the content of the inorganic filler in the resin composition layer is 40 to 75% by mass, when the non-volatile components in the resin composition layer are 100% by mass.
[19] The method for producing a wiring board according to the above [1], wherein the resin composition layer contains a thermoplastic resin.
[20] The method for producing a wiring board according to [19] above, wherein the thermoplastic resin comprises a thermoplastic resin selected from thermoplastic polyimide resin, polycarbonate resin, phenoxy resin, polyvinyl acetal resin, and copolymers.
[21] The method for producing a wiring board according to the above [20], wherein the copolymer is a copolymer obtained by polymerizing two or more monomers selected from styrene, ethylene, propylene, isoprene, butadiene, acrylate, and methacrylate, or a hydrogenated product thereof.
[22] The method for producing a wiring board according to [19] above, wherein the weight average molecular weight of the thermoplastic resin is 5,000 to 100,000.

The wiring board manufacturing method of the present invention can prevent resin chipping that occurs when cutting a resin sheet, and even when undergoing processes including vacuum hot pressing, it can prevent changes in the thickness of the insulating layer and achieve good metal foil adhesion and glass transition temperature.

The present invention will now be described in detail with reference to preferred embodiments. However, the present invention is not limited to the following embodiments and examples, and can be modified and implemented as desired without departing from the scope of the claims of the present invention and their equivalents.

<Method of manufacturing a wiring board>
The present invention provides a method for manufacturing a wiring board, comprising the steps of: (1) heating and laminating a resin sheet having a support and a resin composition layer provided on the support to a substrate so that the resin composition layer of the resin sheet is bonded to the substrate; (2) peeling the support from the resin composition layer; and (3) heating and pressing a metal foil to the resin composition layer using a vacuum hot press, wherein in step (3), the minimum melt viscosity of the resin composition layer before heat and pressure bonding is 2,000 to 20,000 poise when measured in a temperature range from 60°C to 200°C.

Step (1) is a step in which a resin sheet having a support and a resin composition layer provided on the support is heated and laminated to a substrate so that the resin composition layer of the resin sheet is bonded to the substrate.

The support in the resin sheet can be, for example, a plastic film.

Examples of plastic film materials include polyesters such as polyethylene terephthalate (hereinafter sometimes abbreviated as "PET") and polyethylene naphthalate (hereinafter sometimes abbreviated as "PEN"), polycarbonate (hereinafter sometimes abbreviated as "PC"), acrylics such as polymethyl methacrylate (PMMA), cyclic polyolefins, triacetyl cellulose (TAC), polyether sulfide (PES), polyether ketone, polyimide, etc. Among these, polyethylene terephthalate and polyethylene naphthalate are preferred, with inexpensive polyethylene terephthalate being particularly preferred.

The surface of the support that will be bonded to the resin composition layer may be matte-treated, corona-treated, or antistatic-treated. Alternatively, a support with a release layer, which has a release layer on the surface that will be bonded to the resin composition layer, may be used. Examples of release agents used in the release layer of the support with a release layer include one or more release agents selected from the group consisting of alkyd resins, polyolefin resins, urethane resins, and silicone resins. Commercially available support with a release layer may be used, including PET films with a release layer primarily composed of alkyd resin-based release agents, such as "SK-1," "AL-5," and "AL-7" manufactured by Lintec Corporation, "Lumirror T60" manufactured by Toray Industries, Inc., "Purex" manufactured by Teijin Limited, and "Uni-Peel" manufactured by Unitika Limited.

The thickness of the support is not particularly limited, but is preferably in the range of 5 μm to 75 μm, and more preferably in the range of 10 μm to 60 μm. When using a support with a release layer, it is preferable that the overall thickness of the support with a release layer be in the above range.

The thickness of the resin composition layer before lamination in step (1) is, for example, 100 μm or less. From the viewpoint of thinning the printed wiring board, it is preferably 70 μm or less, more preferably 60 μm or less, even more preferably 50 μm or less, and particularly preferably 40 μm or less. From the viewpoint of ensuring sufficient insulation, it is preferably 5 μm or more, preferably 10 μm or more, preferably 13 μm or more, and preferably 15 μm or more.

In step (1), the minimum melt viscosity of the resin composition layer before lamination is preferably 300 poise or more, more preferably 500 poise or more, even more preferably 700 poise or more, and particularly preferably 1000 poise or more, from the viewpoint of achieving an appropriate film thickness during lamination. From the viewpoint of sufficiently embedding the inner layer circuits, the minimum melt viscosity is preferably 10,000 poise or less, even more preferably 8,000 poise or less, and even more preferably 7,000 poise or less. In particular, the minimum melt viscosity of the resin composition layer before lamination in step (1) is even more preferably less than 2,000 poise, and particularly preferably 300 poise or more but less than 2,000 poise, from the viewpoint of achieving both the embeddability of the inner layer circuits during lamination in step (1) and an appropriate minimum melt viscosity in step (3) described below. Here, the minimum melt viscosity refers to the minimum melt viscosity when the dynamic viscoelastic modulus is measured in the temperature range from 60°C to 200°C.

The content of organic solvent in the resin composition layer of the resin sheet before lamination used in step (1) is, when all components in the resin composition layer are taken as 100% by mass, for example, 0% by mass or more, 0.1% by mass or more, or 0.3% by mass or more. From the viewpoint of embedding inner layer circuits, it is preferably 0.5% by mass or more, more preferably 1.0% by mass or more, even more preferably 1.2% by mass or more, and particularly preferably 1.5% by mass or more. From the viewpoint of suppressing the generation of voids due to the tackiness of the resin sheet, it is preferably 3.0% by mass or less, more preferably 2.8% by mass or less, and even more preferably 2.5% by mass or less.

The substrate used in step (1) is a component that will become the substrate for the wiring board, and examples include glass epoxy substrates, metal substrates, polyester substrates, polyimide substrates, BT resin substrates, and thermosetting polyphenylene ether substrates. The substrate may also have a conductor layer on one or both sides, and this conductor layer may be patterned. A substrate with a conductor layer (circuit) formed on one or both sides is sometimes called an "inner layer circuit board." The substrate also includes intermediate products on which insulating layers and/or conductor layers are to be formed during the production of a wiring board. The wiring board may also be a component-embedded circuit board with built-in components.

Lamination in step (1) can be performed, for example, by thermocompression bonding the resin sheet to the substrate from the support side of the resin sheet. Examples of the member that thermocompresses the resin sheet to the substrate (hereinafter also referred to as the "thermocompression bonding member") include a heated metal plate (such as a stainless steel panel) or a metal roll (such as a stainless steel roll). It is preferable to press the thermocompression bonding member not directly onto the resin sheet, but rather via an elastic material such as heat-resistant rubber, so that the resin sheet can adequately conform to the surface irregularities of the substrate.

The lamination in step (1) may be performed by a vacuum lamination method. Lamination by the vacuum lamination method can be performed using a commercially available vacuum laminator. Examples of commercially available vacuum laminators include a vacuum pressure laminator manufactured by Meiki Seisakusho Co., Ltd., a vacuum applicator manufactured by Nikko Materials Co., Ltd., and a batch-type vacuum pressure laminator. The lamination in step (1) may also be performed using a press. Commercially available presses can be used.

The heating temperature during lamination in step (1) is preferably 60°C or higher, more preferably 70°C or higher, even more preferably 80°C or higher, and particularly preferably 90°C or higher, from the viewpoint of obtaining sufficient resin flowability. From the viewpoint of suppressing resin viscosity increase during lamination, it is preferably 160°C or lower, more preferably 150°C or lower, even more preferably 140°C or lower, and particularly preferably 130°C or lower. The pressure conditions during lamination in step (1) are preferably 0.2 MPa or higher, more preferably 0.3 MPa or higher, from the viewpoint of obtaining sufficient resin flowability. From the viewpoint of obtaining uniformity in film thickness during lamination, it is preferably 30 MPa or lower, more preferably 25 MPa or lower. The heating and pressure application time during lamination while maintaining the heating temperature and pressure conditions within the above ranges is preferably 10 seconds or higher, more preferably 20 seconds or higher, and particularly preferably 30 seconds or higher, from the viewpoint of obtaining sufficient resin flowability. From the viewpoint of suppressing resin viscosity increase during lamination, it is preferably 40 minutes or lower, more preferably 35 minutes or lower, and particularly preferably 30 minutes or lower.

When step (1) is performed by a vacuum lamination method, it is preferable to perform vacuum suction after the resin sheet and substrate are superposed on each other before applying pressure for lamination. In a preferred embodiment, the lamination method in step (1) involves superposing the resin sheet and substrate, raising the temperature to a vacuum suction temperature, performing vacuum suction, and then applying pressure under vacuum without cooling the resin composition layer and support to room temperature, thereby continuously performing vacuum suction and pressurization. The vacuum suction temperature before pressurization can be the same as or close to the heating temperature during lamination, and is preferably within ±10°C of the heating temperature during lamination, and more preferably within ±5°C. The vacuum suction time before pressurization, which maintains the above vacuum suction temperature range, is preferably 0.5 minutes or more, more preferably 1 minute or more, particularly preferably 2 minutes or more, and preferably 40 minutes or less, more preferably 35 minutes or less, and particularly preferably 30 minutes or less.

After lamination in step (1), the laminated resin sheets may be smoothed under normal pressure (atmospheric pressure), for example, by pressing the support side with a thermocompression member. The pressing conditions for the smoothing treatment may be the same as those for the lamination described above. The smoothing treatment may be performed using a commercially available laminator. Note that lamination and smoothing may be performed consecutively using the commercially available vacuum laminator described above.

The thickness of the resin composition layer after lamination in step (1) is, for example, 100 μm or less. From the viewpoint of thinning the wiring board, it is preferably 70 μm or less, more preferably 60 μm or less, even more preferably 50 μm or less, and particularly preferably 40 μm or less. From the viewpoint of ensuring sufficient insulation, it is preferably 5 μm or more, preferably 10 μm or more, preferably 13 μm or more, and preferably 15 μm or more.

Step (2) is a step of peeling the support from the resin composition layer. Step (2) is performed after step (1).

The support in step (2) may be peeled off manually or mechanically using an automatic peeling device. Examples of methods for peeling off the support in step (2) include a method in which the resin composition layer and substrate are transported while the support is fixed and then the support is peeled off, a method in which the resin composition layer and substrate are fixed and then the support is pulled and then the support is peeled off, and a method in which the resin composition layer and substrate are transported while the support is pulled and then the support is peeled off. However, the method is not limited to these methods as long as the support can be peeled off from the resin composition layer without damaging the resin composition layer.

The temperature conditions for peeling off the support in step (2) are not particularly limited, but it is preferably carried out at room temperature (preferably 10°C to 40°C). Peeling off the support is preferably carried out after cooling the substrate, resin composition layer, and support to room temperature following step (1).

The angle formed by the support peeling direction relative to the surface of the resin composition layer when the support is peeled off in step (2) is not particularly limited, but is preferably 70° or less, more preferably 50° or less, and even more preferably 30° or less. The support peeling speed in step (2) is preferably 1 m/min to 20 m/min, more preferably 3 m/min to 10 m/min.

Step (3) is a step in which the metal foil is heated and pressed onto the resin composition layer using a vacuum hot press. Step (3) is performed after step (2).

In step (3), the minimum melt viscosity of the resin composition layer before heat and pressure bonding (particularly immediately before the metal foil is superimposed on the resin composition layer) is 2,000 to 20,000 poise. Here, the minimum melt viscosity refers to the minimum melt viscosity when the dynamic viscoelastic modulus is measured in the temperature range from 60°C to 200°C. The minimum melt viscosity of the resin composition layer before thermocompression bonding is preferably 3,000 poise or more, more preferably 4,000 poise or more, even more preferably 4,500 poise or more, particularly preferably 5,000 poise or more, and the upper limit is preferably 17,000 poise or less, more preferably 15,000 poise or less, even more preferably 13,000 poise or less, particularly preferably 12,000 poise or less, 11,000 poise or less, 10,000 poise or less, or 9,000 poise or less. When adjusting the minimum melt viscosity of the resin composition layer before thermocompression bonding, the drying temperature, drying time, drying method of any step (A) (drying step) described below, the vacuum suction time of step (1), vacuum suction temperature, heating temperature, pressurization conditions, heating and pressurization time, or the selection of components to be contained in the resin composition layer can be performed. This can preferably be done through step (A) (drying step).

From the perspective of achieving both the embeddability of the inner layer circuit during lamination in step (1) and an appropriate minimum melt viscosity in step (3), the minimum melt viscosity (V1) (poise) of the resin composition layer before lamination in step (1) is preferably lower than the minimum melt viscosity (V3) (poise) of the resin composition layer before heat-pressure bonding in step (3) (V1 < V3). The relationship between the V1 value (poise) and the V3 value (poise) is more preferably V1 + 100 < V3, even more preferably V1 + 500 < V3, and particularly preferably V1 + 1000 < V3.

In step (3), the content of organic solvent in the resin composition layer before heat-pressing (particularly immediately before the metal foil is superimposed on the resin composition layer) is, for example, 0% by mass or more, assuming that all components in the resin composition layer are 100% by mass. From the viewpoint of favorable curing of the resin composition layer, the content is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, even more preferably 0.3% by mass or more, and particularly preferably 0.4% by mass or more. From the viewpoint of suppressing the generation of voids in the resin composition layer, the content is preferably 2.5% by mass or less, more preferably 2.0% by mass or less, preferably 1.7% by mass or less, and preferably 1.5% by mass or less.

The metal used for the metal foil to be pressure-bonded in step (3) is not particularly limited, but examples include gold, silver, copper, aluminum, nickel, iron, chromium, manganese, molybdenum, and alloys containing a total of 90% or more of at least one metal selected from these metals. Copper is particularly preferred in terms of its thermal expansion coefficient, electrical conductivity, and economy.

The thickness of the metal foil to be pressed in step (3) is not particularly limited, but is preferably 5 μm or less, more preferably 1 to 5 μm, and even more preferably 1.5 to 4 μm.

In one embodiment, a metal foil with a carrier may be used as the metal foil to be pressed in step (3). The metal foil with a carrier is a layered metal material comprising a carrier metal foil and a metal foil (thin metal foil) thinner than the carrier metal foil, which is peelably laminated on the carrier metal foil, if necessary via another film. When using a metal foil with a carrier as the metal foil, the carrier metal foil can be superimposed with the thin metal foil side in contact with the resin composition layer, and then heated and pressed.

The metal used in the carrier metal foil in the carrier-attached metal foil is not particularly limited, but examples include gold, silver, copper, aluminum, nickel, iron, chromium, manganese, molybdenum, and alloys containing a total of 90% or more of at least one metal selected from these metals. Copper is particularly preferred from the standpoints of thermal expansion coefficient, conductivity, and economy. Metals used in the thin metal foil in the carrier-attached metal foil include the same metals as those used in the carrier metal foil. The metal used in the carrier metal foil and the metal used in the thin metal foil in the carrier-attached metal foil may be the same metal.

The thickness of the carrier metal foil in the carrier-attached metal foil is not particularly limited, but is preferably 5 to 60 μm, and more preferably 10 to 30 μm. The thickness of the thin metal foil in the carrier-attached metal foil is not particularly limited, but is preferably 5 μm or less, more preferably 1 to 5 μm, and even more preferably 1.5 to 4 μm.

Commercially available carrier-attached metal foils include "MT18Ex" (carrier copper foil thickness 18 μm, thin copper foil thickness 2 μm) and "MT18FL" (carrier copper foil thickness 18 μm, thin copper foil thickness 3 μm) manufactured by Mitsui Mining & Smelting Co., Ltd.

The heating temperature during thermocompression bonding in step (3) is preferably 160°C or higher, more preferably 170°C or higher, even more preferably 180°C or higher, and particularly preferably 190°C or higher, from the viewpoint of sufficient thermal curing of the resin; and is preferably 250°C or lower, more preferably 240°C or lower, even more preferably 230°C or lower, and particularly preferably 220°C or lower, from the viewpoint of metal foil peelability. The pressure conditions during thermocompression bonding in step (3) are preferably 0.2 MPa or higher, more preferably 0.3 MPa or higher, even more preferably 0.4 MPa or higher, and particularly preferably 0.5 MPa or higher, from the viewpoint of sufficient adhesion to the metal foil; and are preferably 30 MPa or lower, more preferably 20 MPa or lower, even more preferably 10 MPa or lower, even more preferably 5.0 MPa or lower, and particularly preferably 2.0 MPa or lower, from the viewpoint of resin film thickness uniformity after thermocompression bonding. The heating and pressing time during thermocompression bonding, while maintaining the heating temperature and pressure conditions within the above ranges, is preferably 30 minutes or more, more preferably 40 minutes or more, and especially preferably 50 minutes or more, from the viewpoint of sufficient thermal curing of the resin, and is preferably 200 minutes or less, more preferably 180 minutes or less, and especially preferably 150 minutes or less, from the viewpoint of productivity.

From the viewpoint of heat resistance reliability, the glass transition temperature of the resin composition layer after heat-pressure bonding in step (3) is preferably 130°C or higher, more preferably 135°C or higher, even more preferably 140°C or higher, even more preferably 145°C or higher, and particularly preferably 150°C or higher.

From the viewpoint of ensuring sufficient insulation, the thickness of the resin composition layer after heat and pressure bonding in step (3) is preferably greater than 10 μm, more preferably greater than 11 μm, even more preferably greater than 12 μm, even more preferably greater than 13 μm, even more preferably greater than 14 μm, and particularly preferably greater than 15 μm.

The thickness reduction rate of the resin composition layer after heat-pressure bonding in step (3) relative to the resin composition layer before lamination in step (1) is preferably 58% or less, more preferably 55% or less, even more preferably 50% or less, even more preferably 45% or less, and particularly preferably 40% or less. The thickness reduction rate can be calculated as the percentage reduction in the thickness of the resin composition layer after heat-pressure bonding in step (3) relative to the thickness of the resin composition layer before lamination in step (1).

In a preferred embodiment, the method for manufacturing a wiring board of the present invention includes, after step (3), step (4) of forming a circuit pattern from metal foil by a subtractive process.

In step (4), unnecessary portions of the metal foil that was pressure-bonded to the resin composition layer in step (3) are selectively removed by etching or other methods to form a circuit pattern.

In a preferred embodiment, step (4) includes (4a) applying an etching resist to the metal foil, (4b) etching the metal foil portions where the etching resist is not applied to remove unnecessary portions and form a circuit pattern from the metal foil, and (4c) removing the etching resist. In step (4a), the etching resist may be applied by placing a resist resin layer on the metal foil, and then placing a mask film on the resist resin layer, followed by exposure and development through the mask film.

In another preferred embodiment, the method for manufacturing a wiring board of the present invention includes, after step (3), a step (4') of forming a circuit pattern from metal foil by a modified semi-additive process.

In step (4'), a thick layer of metal is applied by electrolytic plating to a portion (circuit formation portion) of the metal foil that was pressure-bonded to the resin composition layer in step (3), and unnecessary portions of the metal foil are removed by etching or the like to form a circuit pattern.

In a preferred embodiment, step (4') includes the steps of (4a') applying a plating resist to a portion of the metal foil, (4b') electrolytically plating the metal on the portions of the metal foil where the plating resist is not applied, (4c') removing the plating resist, and (4d') etching the metal foil to remove the portions of the metal foil where the metal is not applied, thereby forming a circuit pattern. In step (4a'), a resist resin layer may be placed on the metal foil, and a mask film may be placed on the resist resin layer, followed by exposure and development through the mask film, to apply the plating resist.

In a preferred embodiment, the wiring board manufacturing method of the present invention may further include a step of drying the resin composition layer (A) as an optional step performed after step (1) and before step (2), or after step (2) and before step (3). Drying may be performed by known methods such as heat drying, hot air blowing, vacuum drying, etc.

When step (A) is performed after step (1) and before step (2), the support is not removed in step (A), and the resin composition layer is dried through the support. From the viewpoint of suppressing adhesion of foreign matter to the resin composition layer, step (A) is preferably performed after step (1) and before step (2). When step (A) is performed after step (1) and before step (2), step (A) may be performed continuously from step (1) without cooling the resin composition layer and support to room temperature, or may be performed by temporarily cooling the resin composition layer and support to room temperature after step (1) and reheating. When step (A) is performed after step (2) and before step (3), step (A) may be performed continuously from step (2) without cooling the resin composition layer, or may be performed by temporarily cooling the resin composition layer to room temperature after step (2) and reheating.

The drying temperature in step (A) can be the same as or close to the heating temperature during lamination in step (1), and is preferably ±30°C, more preferably ±20°C, of the heating temperature during lamination in step (1).

The drying temperature in step (A) is preferably 80°C or higher, more preferably 90°C or higher, even more preferably 100°C or higher, and particularly preferably 110°C or higher; it is preferably 160°C or lower, more preferably 150°C or lower, even more preferably 140°C or lower, and particularly preferably 130°C or lower. The drying time for maintaining a drying temperature within the above range is preferably 1 minute or longer, more preferably 2 minutes or longer, and particularly preferably 3 minutes or longer, and is preferably 10 minutes or shorter, more preferably 8 minutes or shorter, and particularly preferably 6 minutes or shorter.

From the perspective of simultaneously achieving circuit embeddability of the inner layer circuit in step (1) and void suppression, suppression of changes in the insulating layer thickness, metal foil adhesion, and a good glass transition temperature in step (3), it is preferable to perform step (A). By performing step (A), the minimum melt viscosity of the resin composition layer in step (1) can be set relatively high in consideration of circuit embeddability, and by reducing the amount of residual solvent in step (A), it is possible to easily adjust the minimum melt viscosity of the resin composition layer before heat-compression bonding in step (3) to an appropriate range.

In a preferred embodiment, the wiring board manufacturing method of the present invention includes, as an optional step performed after step (3) and before step (4), (B) forming holes (e.g., via holes) in the resin composition layer.

Step (B) may be carried out using known procedures, such as using a drill, laser, or plasma, depending on the composition of the resin composition layer. The dimensions and shape of the holes (e.g., via holes) may be determined appropriately depending on the design of the wiring board.

In a preferred embodiment, the method for manufacturing a wiring board of the present invention includes, as an optional step carried out after step (B) and before step (4), (C) a step of performing a desmear treatment on the holes formed in the resin composition layer.

In step (C), the desmearing procedure and conditions are not particularly limited, and known procedures and conditions commonly used in forming resin composition layers for wiring boards can be used. Desmearing can be carried out, for example, by a method that involves swelling with a swelling liquid, roughening with an oxidizing agent, and neutralization with a neutralizing liquid.

The swelling liquid is not particularly limited, but examples include alkaline solutions and surfactant solutions. Alkaline solutions are preferred, and sodium hydroxide and potassium hydroxide solutions are more preferred. Commercially available swelling liquids include "Swelling Dip Securigans P" and "Swelling Dip Securigans SBU" manufactured by Atotech Japan. The swelling treatment using a swelling liquid is not particularly limited, but can be carried out by immersing the insulating layer in a swelling liquid at 30°C to 90°C for 1 to 20 minutes, for example. To keep swelling of the resin in the insulating layer to an appropriate level, it is preferable to immerse the insulating layer in a swelling liquid at 40°C to 80°C for 5 to 15 minutes.

The oxidizing agent is not particularly limited, but examples include alkaline permanganate solutions prepared by dissolving potassium permanganate or sodium permanganate in an aqueous solution of sodium hydroxide. Roughening treatment using an oxidizing agent such as alkaline permanganate solution is preferably carried out by immersing the insulating layer in an oxidizing agent solution heated to 60°C to 100°C for 10 to 30 minutes. The concentration of permanganate in the alkaline permanganate solution is preferably 5% to 10% by mass. Commercially available oxidizing agents include alkaline permanganate solutions such as "Concentrate Compact CP" and "Dosing Solution Securigance P" manufactured by Atotech Japan.

The neutralizing solution is preferably an acidic aqueous solution, and a commercially available product such as "Reduction Solution Securigant P" manufactured by Atotech Japan is an example.

Treatment with a neutralizing solution can be carried out by immersing the surface that has been roughened with an oxidizing agent in a neutralizing solution at 30°C to 80°C for 5 to 30 minutes. From the standpoint of workability, etc., it is preferable to immerse the object that has been roughened with an oxidizing agent in a neutralizing solution at 40°C to 70°C for 5 to 20 minutes.

Wiring boards manufactured by the wiring board manufacturing method of the present invention can be used in semiconductor devices. Examples of semiconductor devices include various semiconductor devices used in electrical products (e.g., computers, mobile phones, digital cameras, and televisions) and vehicles (e.g., motorcycles, automobiles, trains, ships, and aircraft).

<Resin composition layer>
The components contained in the resin composition that forms the resin composition layer of the resin sheet used in step (1) will be described.

In a preferred embodiment, the resin composition layer of the resin sheet used in step (1) contains a thermosetting resin. Examples of thermosetting resins include epoxy resins, phenolic resins, thermosetting polyimide resins, cyanate ester resins, maleimide resins, benzoxazine resins, and thermosetting modified polyphenylene ether resins. The resin composition layer preferably contains a thermosetting resin selected from epoxy resins, cyanate ester resins, maleimide resins, and thermosetting modified polyphenylene ether resins, and more preferably a thermosetting resin selected from epoxy resins, maleimide resins, and thermosetting modified polyphenylene ether resins. Thermosetting resins also include epoxy resin curing agents and radical polymerization crosslinking agents that have the function of curing thermosetting resins through crosslinking reactions such as addition reactions and condensation reactions. One type of thermosetting resin may be used alone, or two or more types may be used in combination.

In one embodiment, the resin composition layer of the resin sheet used in step (1) preferably contains an epoxy resin as the thermosetting resin. One type of epoxy resin may be used alone, or two or more types may be used in combination. The epoxy resin is a curable resin having an epoxy group and an epoxy equivalent of 5,000 g/eq. or less.

Examples of epoxy resins include bixylenol type epoxy resins, bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol S type epoxy resins, bisphenol AF type epoxy resins, dicyclopentadiene type epoxy resins, trisphenol type epoxy resins, naphthol novolac type epoxy resins, phenol novolac type epoxy resins, tert-butyl-catechol type epoxy resins, naphthalene type epoxy resins, naphthol type epoxy resins, anthracene type epoxy resins, glycidylamine type epoxy resins, glycidyl ester type epoxy resins, cresol novolac type epoxy resins, phenol aralkyl type epoxy resins, biphenyl type epoxy resins, linear aliphatic epoxy resins, epoxy resins having a butadiene structure, alicyclic epoxy resins, heterocyclic epoxy resins, spiro ring-containing epoxy resins, cyclohexane type epoxy resins, cyclohexane dimethanol type epoxy resins, naphthylene ether type epoxy resins, trimethylol type epoxy resins, tetraphenylethane type epoxy resins, isocyanurate type epoxy resins, and phenolphthalimidine type epoxy resins.

The resin composition layer of the resin sheet used in step (1) preferably contains an epoxy resin having two or more epoxy groups per molecule. The proportion of epoxy resin having two or more epoxy groups per molecule relative to 100% by mass of epoxy resin is preferably 50% by mass or more, more preferably 60% by mass or more, and particularly preferably 70% by mass or more.

Epoxy resins are classified into two types: epoxy resins that are liquid at a temperature of 20°C (hereinafter referred to as "liquid epoxy resins"), and epoxy resins that are solid at a temperature of 20°C (hereinafter referred to as "solid epoxy resins").

The resin composition layer of the resin sheet used in step (1) may contain only a liquid epoxy resin as the epoxy resin, or only a solid epoxy resin, or both a liquid epoxy resin and a solid epoxy resin, but it is particularly preferred that it contain both a liquid epoxy resin and a solid epoxy resin.

Preferably, the liquid epoxy resin is one having two or more epoxy groups per molecule.

Preferred liquid epoxy resins include glycerol-type epoxy resins, bisphenol A-type epoxy resins, bisphenol F-type epoxy resins, bisphenol AF-type epoxy resins, naphthalene-type epoxy resins, glycidyl ester-type epoxy resins, glycidyl amine-type epoxy resins, phenol novolac-type epoxy resins, alicyclic epoxy resins with an ester skeleton, cyclohexanedimethanol-type epoxy resins, cycloaliphatic glycidyl ethers, and epoxy resins with a butadiene structure.

Specific examples of liquid epoxy resins include Nagase ChemteX's "EX-992L," Mitsubishi Chemical's "YX7400," and DIC's "HP4032," "HP4032D," and "HP4032SS" (naphthalene-type epoxy resins); Mitsubishi Chemical's "828US," "jER828EL," "828EL," "825," and "Epikote 828EL" (bisphenol A-type epoxy resins); and Mitsubishi Chemical's "jER807" and "1750" ( bisphenol F type epoxy resin); Mitsubishi Chemical Corporation's "jER152" (phenol novolac type epoxy resin); Mitsubishi Chemical Corporation's "630", "630LSD", and "604" (glycidylamine type epoxy resin); ADEKA Corporation's "ED-523T" (glycilol type epoxy resin); ADEKA Corporation's "EP-3950L" and "EP-3980S" (glycidylamine type epoxy resin); ADEKA Corporation's "EP-4088S" (dicyclopentasiloxane type epoxy resin). bisphenol A type epoxy resin); "ZX1059" manufactured by Nippon Steel Chemical & Material Co., Ltd. (a mixture of bisphenol A type epoxy resin and bisphenol F type epoxy resin); "EX-721" manufactured by Nagase ChemteX Corporation (glycidyl ester type epoxy resin); "EX-991L" manufactured by Nagase ChemteX Corporation (an epoxy resin containing an alkyleneoxy skeleton and a butadiene skeleton); "Celloxide 2021P" manufactured by Daicel Corporation (an alicyclic epoxy resin having an ester skeleton) ), Daicel Corporation's "PB-3600," Nippon Soda Co., Ltd.'s "JP-100" and "JP-200" (epoxy resins with a butadiene structure); Nippon Steel Chemical & Material Co., Ltd.'s "ZX1658" and "ZX1658GS" (liquid 1,4-glycidylcyclohexane-type epoxy resin); Osaka Gas Chemicals Co., Ltd.'s "EG-280" (fluorene structure-containing epoxy resin); and Nagase ChemteX Corporation's "EX-201" (cyclic aliphatic glycidyl ether).

As a solid epoxy resin, a solid epoxy resin having three or more epoxy groups per molecule is preferred, and an aromatic solid epoxy resin having three or more epoxy groups per molecule is more preferred.

Preferred solid epoxy resins include bixylenol-type epoxy resins, naphthalene-type epoxy resins, naphthalene-type tetrafunctional epoxy resins, naphthol novolac-type epoxy resins, cresol novolac-type epoxy resins, dicyclopentadiene-type epoxy resins, trisphenol-type epoxy resins, naphthol-type epoxy resins, biphenyl-type epoxy resins, naphthylene ether-type epoxy resins, anthracene-type epoxy resins, bisphenol A-type epoxy resins, bisphenol AF-type epoxy resins, phenol aralkyl-type epoxy resins, tetraphenylethane-type epoxy resins, and phenolphthalimidine-type epoxy resins.

Specific examples of solid epoxy resins include DIC Corporation's "HP4032H" (naphthalene-type epoxy resin); DIC Corporation's "HP-4700" and "HP-4710" (naphthalene-type tetrafunctional epoxy resin); DIC Corporation's "N-690" (cresol novolac-type epoxy resin); DIC Corporation's "N-695" (cresol novolac-type epoxy resin); DIC Corporation's "HP-7200," "HP-7200HH," "HP-7200H," and "HP-7200L" (dicyclopentadiene-type epoxy resin); DIC Corporation's "EXA-7311" and "E XA-7311-G3, EXA-7311-G4, EXA-7311-G4S, HP6000, HP6000L (naphthylene ether type epoxy resin); EPPN-502H (trisphenol type epoxy resin) manufactured by Nippon Kayaku Co., Ltd.; NC7000L (naphthol novolac type epoxy resin) manufactured by Nippon Kayaku Co., Ltd.; NC3000H, NC3000, NC3000L, NC3000FH, NC3100 (biphenyl type epoxy resin) manufactured by Nippon Kayaku Co., Ltd.; ESN475V manufactured by Nippon Steel Chemical & Material Co., Ltd. "ESN4100V" (naphthalene-type epoxy resin); "ESN485" (naphthol-type epoxy resin) manufactured by Nippon Steel Chemical & Material Co., Ltd.; "ESN375" (dihydroxynaphthalene-type epoxy resin) manufactured by Nippon Steel Chemical & Material Co., Ltd.; "YX4000H", "YX4000", "YX4000HK", and "YL7890" (bixylenol-type epoxy resins) manufactured by Mitsubishi Chemical Corporation; "YL6121" (biphenyl-type epoxy resin) manufactured by Mitsubishi Chemical Corporation; "YX8800" (anthracene-type epoxy resin) manufactured by Mitsubishi Chemical Corporation; Examples include "YX7700" (phenol aralkyl type epoxy resin); "PG-100" and "CG-500" manufactured by Osaka Gas Chemicals Co., Ltd.; "YL7760" (bisphenol AF type epoxy resin) manufactured by Mitsubishi Chemical Corporation; "YL7800" (fluorene type epoxy resin) manufactured by Mitsubishi Chemical Corporation; "jER1010" (bisphenol A type epoxy resin) manufactured by Mitsubishi Chemical Corporation; "jER1031S" (tetraphenylethane type epoxy resin) manufactured by Mitsubishi Chemical Corporation; and "WHR991S" (phenolphthalimidine type epoxy resin) manufactured by Nippon Kayaku Co., Ltd. These may be used alone or in combination of two or more types.

When a liquid epoxy resin and a solid epoxy resin are used in combination as the epoxy resin, the mass ratio between them (liquid epoxy resin:solid epoxy resin) is preferably 10:1 to 1:50, more preferably 2:1 to 1:30, even more preferably 1:1 to 1:20, and particularly preferably 1:2 to 1:15.

The epoxy equivalent of the epoxy resin is preferably 50 g/eq. to 5,000 g/eq., more preferably 60 g/eq. to 2,000 g/eq., even more preferably 70 g/eq. to 1,000 g/eq., and even more preferably 80 g/eq. to 500 g/eq. The epoxy equivalent is the mass of resin per equivalent of epoxy groups. This epoxy equivalent can be measured in accordance with JIS K7236.

The weight-average molecular weight (Mw) of the epoxy resin is preferably 100 to 5,000, more preferably 250 to 3,000, and even more preferably 400 to 1,500. The weight-average molecular weight of the resin can be measured as a polystyrene-equivalent value using gel permeation chromatography (GPC).

The content of epoxy resin in the resin composition layer of the resin sheet used in step (1) is not particularly limited, but is preferably 1 to 50% by mass or less, more preferably 5 to 40% by mass or less, even more preferably 8 to 35% by mass, and particularly preferably 10 to 30% by mass, assuming that the non-volatile components in the resin composition layer are 100% by mass.

In one embodiment, when the resin composition layer of the resin sheet used in step (1) contains an epoxy resin as the thermosetting resin, it may further contain an epoxy resin curing agent as an optional component. The epoxy resin curing agent may be used alone or in any combination of two or more types. When an epoxy resin is included as the thermosetting resin, the epoxy resin curing agent may have the function of reacting with the epoxy resin to cure it.

The epoxy resin curing agent is not particularly limited, but examples include active ester curing agents, phenolic curing agents, carbodiimide curing agents, acid anhydride curing agents, amine curing agents, benzoxazine curing agents, cyanate ester curing agents, and thiol curing agents. In one embodiment, the epoxy resin curing agent preferably contains one or more epoxy resin curing agents selected from active ester curing agents, phenolic curing agents, and cyanate ester curing agents. In one embodiment, the epoxy resin curing agent particularly preferably contains an active ester curing agent from the viewpoint of further reducing the dielectric loss tangent. In one embodiment, the epoxy resin curing agent particularly preferably contains a phenolic curing agent from the viewpoint of further improving curability.

Active ester curing agents generally include compounds with two or more highly reactive ester groups per molecule, such as phenol esters, thiophenol esters, N-hydroxyamine esters, and esters of heterocyclic hydroxy compounds. These active ester compounds are preferably those obtained by the condensation reaction of a carboxylic acid compound and/or a thiocarboxylic acid compound with a hydroxy compound and/or a thiol compound. From the perspective of improving heat resistance, active ester compounds obtained from a carboxylic acid compound and a hydroxy compound are preferred, and active ester compounds obtained from a carboxylic acid compound and a phenol compound and/or a naphthol compound are more preferred. Examples of carboxylic acid compounds include benzoic acid, acetic acid, succinic acid, maleic acid, itaconic acid, phthalic acid, isophthalic acid, terephthalic acid, and pyromellitic acid. Examples of phenol compounds or naphthol compounds include hydroquinone, resorcinol, bisphenol A, bisphenol F, bisphenol S, phenolphthalene, methylated bisphenol A, methylated bisphenol F, methylated bisphenol S, phenol, o-cresol, m-cresol, p-cresol, catechol, α-naphthol, β-naphthol, 1,5-dihydroxynaphthalene, 1,6-dihydroxynaphthalene, 2,6-dihydroxynaphthalene, dihydroxybenzophenone, trihydroxybenzophenone, tetrahydroxybenzophenone, phloroglucin, benzenetriol, dicyclopentadiene-type diphenol compounds, and phenol novolak. Here, "dicyclopentadiene-type diphenol compounds" refer to diphenol compounds obtained by condensing one dicyclopentadiene molecule with two phenol molecules.

Specific examples of active ester curing agents that are preferred include dicyclopentadiene-type active ester compounds containing a dicyclopentadiene-type diphenol structure, naphthalene-type active ester compounds containing a naphthalene structure, active ester compounds containing an acetylated phenol novolac, and active ester compounds containing a benzoylated phenol novolac, with at least one selected from dicyclopentadiene-type active ester compounds and naphthalene-type active ester compounds being more preferred.

Commercially available active ester curing agents include active ester compounds containing a dicyclopentadiene-type diphenol structure, such as "EXB9451," "EXB9460," "EXB9460S," "HPC-8000L-65TM," "HPC-8000-65T," "HPC-8000H," and "HPC-8000H-65TM" (manufactured by DIC Corporation); and active ester compounds containing a naphthalene structure, such as "HP-B-8151-62T," "EXB-8100L-65T," "EXB-9416-70BK," and "HPC-8150-62T." and "EXB-8" (manufactured by DIC Corporation); a phosphorus-containing active ester compound such as "EXB9401" (manufactured by DIC Corporation); an active ester compound which is an acetylated product of phenol novolac such as "DC808" (manufactured by Mitsubishi Chemical Corporation); active ester compounds which are benzoylated products of phenol novolac such as "YLH1026," "YLH1030," and "YLH1048" (manufactured by Mitsubishi Chemical Corporation); and an active ester compound containing a styryl group and a naphthalene structure such as "PC1300-02-65MA" (manufactured by Air Water Inc.).

As a phenolic curing agent, a phenolic curing agent having a novolac structure is preferred from the viewpoint of heat resistance and water resistance. Furthermore, from the viewpoint of adhesion to the adherend, a nitrogen-containing phenolic curing agent is preferred, and a triazine skeleton-containing phenolic curing agent is more preferred. Of these, a triazine skeleton-containing phenolic novolac resin is preferred from the viewpoint of highly satisfying heat resistance, water resistance, and adhesion. Specific examples of phenolic curing agents include "MEH-7700," "MEH-7810," and "MEH-7851" manufactured by Meiwa Kasei Co., Ltd.; "NHN," "CBN," and "GPH" manufactured by Nippon Kayaku Co., Ltd.; "SN-170," "SN-180," "SN-190," "SN-475," "SN-485," "SN-495," "SN-375," and "SN-395" manufactured by Nippon Steel Chemical & Material Co., Ltd.; and "LA-7052," "LA-7054," "LA-3018," "LA-3018-50P," "LA-1356," "TD2090," and "KA-1160" manufactured by DIC Corporation.

Carbodiimide-based curing agents include curing agents having one or more, preferably two or more, carbodiimide structures in one molecule, such as aliphatic biscarbodiimides such as tetramethylene-bis(t-butylcarbodiimide) and cyclohexane-bis(methylene-t-butylcarbodiimide); aromatic biscarbodiimides such as phenylene-bis(xylylcarbodiimide); and aliphatic polycarbodiimides such as polyhexamethylenecarbodiimide, polytrimethylhexamethylenecarbodiimide, polycyclohexylenecarbodiimide, poly(methylenebiscyclohexylenecarbodiimide), and poly(isophoronecarbodiimide). Examples of polycarbodiimides include aromatic polycarbodiimides such as poly(phenylenecarbodiimide), poly(naphthylenecarbodiimide), poly(tolylenecarbodiimide), poly(methyldiisopropylphenylenecarbodiimide), poly(triethylphenylenecarbodiimide), poly(diethylphenylenecarbodiimide), poly(triisopropylphenylenecarbodiimide), poly(diisopropylphenylenecarbodiimide), poly(xylylenecarbodiimide), poly(tetramethylxylylenecarbodiimide), poly(methylenediphenylenecarbodiimide), and poly[methylenebis(methylphenylene)carbodiimide].

Commercially available carbodiimide curing agents include, for example, "Carbodilite V-02B," "Carbodilite V-03," "Carbodilite V-04K," "Carbodilite V-07," and "Carbodilite V-09" manufactured by Nisshinbo Chemical Inc.; and "Stavaxol P," "Stavaxol P400," and "Hykasil 510" manufactured by Rhein Chemie AG.

Acid anhydride curing agents include those having one or more acid anhydride groups in one molecule, with those having two or more acid anhydride groups in one molecule being preferred. Specific examples of acid anhydride curing agents include phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, methylnadic anhydride, hydrogenated methylnadic anhydride, trialkyltetrahydrophthalic anhydride, dodecenyl succinic anhydride, 5-(2,5-dioxotetrahydro-3-furanyl)-3-methyl-3-cyclohexene-1,2-dicarboxylic anhydride, trimellitic anhydride, pyromellitic anhydride, and benzophenonetetracarboxylic dianhydride. anhydride, biphenyltetracarboxylic dianhydride, naphthalenetetracarboxylic dianhydride, oxydiphthalic dianhydride, 3,3'-4,4'-diphenylsulfonetetracarboxylic dianhydride, 1,3,3a,4,5,9b-hexahydro-5-(tetrahydro-2,5-dioxo-3-furanyl)-naphtho[1,2-C]furan-1,3-dione, ethylene glycol bis(anhydrotrimellitate), polymeric acid anhydrides such as styrene-maleic acid resins in which styrene and maleic acid are copolymerized, and the like. Commercially available acid anhydride curing agents include "HNA-100," "MH-700," "MTA-15," "DDSA," and "OSA" manufactured by New Japan Chemical Co., Ltd.; "YH-306" and "YH-307" manufactured by Mitsubishi Chemical Corporation; "HN-2200" and "HN-5500" manufactured by Hitachi Chemical Co., Ltd.; and "EF-30," "EF-40," "EF-60," and "EF-80" manufactured by Clay Valley.

Amine-based curing agents include those containing one or more, preferably two or more, amino groups in one molecule. Examples include aliphatic amines, polyether amines, alicyclic amines, and aromatic amines. Of these, aromatic amines are preferred from the perspective of achieving the desired effects of the present invention. Amine-based curing agents are preferably primary or secondary amines, with primary amines being more preferred. Specific examples of amine-based curing agents include 4,4'-methylenebis(2,6-dimethylaniline), 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfone, m-phenylenediamine, m-xylylenediamine, diethyltoluenediamine, 4,4'-diaminodiphenyl ether, 3,3'-dimethyl-4,4'-diaminobiphenyl, 2,2'-dimethyl-4,4'-diaminobiphenyl, 3,3'-dihydroxybenzidine, and 2,2-bis(3-amino-4-hydroxyphenyl)propanol. propane, 3,3-dimethyl-5,5-diethyl-4,4-diphenylmethanediamine, 2,2-bis(4-aminophenyl)propane, 2,2-bis(4-(4-aminophenoxy)phenyl)propane, 1,3-bis(3-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, 1,4-bis(4-aminophenoxy)benzene, 4,4'-bis(4-aminophenoxy)biphenyl, bis(4-(4-aminophenoxy)phenyl)sulfone, bis(4-(3-aminophenoxy)phenyl)sulfone, and the like. Commercially available amine-based curing agents may be used, such as "SEIKACURE-S" manufactured by Seika Corporation, "KAYABOND C-200S", "KAYABOND C-100", "KAYAHARD A-A", "KAYAHARD A-B", and "KAYAHARD A-S" manufactured by Nippon Kayaku Co., Ltd., and "Epicure W" manufactured by Mitsubishi Chemical Corporation.

Specific examples of benzoxazine-based curing agents include "JBZ-OP100D" and "ODA-BOZ" manufactured by JFE Chemical Corporation; "HFB2006M" manufactured by Showa Highpolymer Co., Ltd.; and "P-d" and "F-a" manufactured by Shikoku Chemicals Corporation.

Examples of cyanate ester curing agents include bifunctional cyanate resins such as bisphenol A dicyanate, polyphenol cyanate (oligo(3-methylene-1,5-phenylene cyanate)), 4,4'-methylenebis(2,6-dimethylphenyl cyanate), 4,4'-ethylidene diphenyl dicyanate, hexafluorobisphenol A dicyanate, 2,2-bis(4-cyanate)phenylpropane, 1,1-bis(4-cyanate phenylmethane), bis(4-cyanate-3,5-dimethylphenyl)methane, 1,3-bis(4-cyanate phenyl-1-(methylethylidene))benzene, bis(4-cyanate phenyl)thioether, and bis(4-cyanate phenyl)ether; multifunctional cyanate resins derived from phenol novolac and cresol novolac; and prepolymers in which these cyanate resins are partially converted to triazine. Specific examples of cyanate ester curing agents include Lonza Japan's "PT30" and "PT60" (both phenol novolac-type multifunctional cyanate ester resins), "BA230" and "BA230S75" (prepolymers in which part or all of bisphenol A dicyanate has been triazinated to form a trimer).

Examples of thiol-based curing agents include trimethylolpropane tris(3-mercaptopropionate), pentaerythritol tetrakis(3-mercaptobutyrate), and tris(3-mercaptopropyl)isocyanurate.

The epoxy reactive group equivalent of the epoxy resin curing agent is preferably 50 g/eq. to 3000 g/eq., more preferably 100 g/eq. to 1000 g/eq., even more preferably 100 g/eq. to 500 g/eq., and particularly preferably 100 g/eq. to 300 g/eq. The epoxy reactive group equivalent is the mass of the epoxy resin curing agent per equivalent of epoxy reactive groups.

The content of the epoxy resin curing agent in the resin composition layer of the resin sheet used in step (1) is not particularly limited, but is preferably 0.1 to 30% by mass, more preferably 1 to 25% by mass, even more preferably 3 to 20% by mass, and particularly preferably 5 to 15% by mass, assuming that the non-volatile components in the resin composition layer are 100% by mass.

In one embodiment, the resin composition layer of the resin sheet used in step (1) preferably contains a thermosetting modified polyphenylene ether resin as the thermosetting resin. The thermosetting modified polyphenylene ether resin preferably contains a modified polyphenylene ether resin having two or more radical reactive groups. One type of thermosetting modified polyphenylene ether resin may be used alone, or two or more types may be used in combination.

A radical-reactive group is a group having a radical-reactive ethylenically unsaturated bond. Examples include, but are not limited to, (1) an acryloyl group, (2) a methacryloyl group, (3) an allyl group, (4) a methallyl group, and (5) a phenyl group substituted with a group selected from a vinyl group and an isopropenyl group and which may further be substituted with an alkyl group (for example, a vinylphenyl group (i.e., a 4-vinylphenyl group, a 3-vinylphenyl group, a 2-vinylphenyl group), an isopropenylphenyl group (i.e., a 4-isopropylphenyl group, a 2 ... (6) benzyl groups substituted with a group selected from vinyl groups and isopropenyl groups and which may further be substituted with an alkyl group (for example, vinylbenzyl groups (i.e., 4-vinylbenzyl groups, 3-vinylbenzyl groups, 2-vinylbenzyl groups), isopropenylbenzyl groups (i.e., 4-isopropenylbenzyl groups, 3-isopropenylbenzyl groups, 2-isopropenylbenzyl groups), etc.).

The term "alkyl group" refers to a linear, branched, and/or cyclic monovalent aliphatic saturated hydrocarbon group. Unless otherwise specified, the alkyl group is preferably an alkyl group having 1 to 14 carbon atoms, more preferably an alkyl group having 1 to 6 carbon atoms, and even more preferably an alkyl group having 1 to 3 carbon atoms. Examples of the alkyl group include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, isopentyl, sec-pentyl, neopentyl, tert-pentyl, hexyl, isohexyl, heptyl, isoheptyl, octyl, isooctyl, tert-octyl, cyclopentyl, cyclohexyl, and cyclohexylmethyl.

In one embodiment, the thermosetting modified polyphenylene ether resin is particularly preferably represented by formula (1):

[In the formula,
R ¹¹ and R ¹² each independently represent an alkyl group;
R ¹³ , R ¹⁴ , R ²¹ , R ²² , R ²³ and R ²⁴ each independently represent a hydrogen atom or an alkyl group;
R ^a and R ^b each independently represent (1) an acryloyl group, (2) a methacryloyl group, (3) an allyl group, (4) a methallyl group, (5) a phenyl group substituted with a group selected from a vinyl group and an isopropenyl group and which may further be substituted with an alkyl group, or (6) a benzyl group substituted with a group selected from a vinyl group and an isopropenyl group and which may further be substituted with an alkyl group;
X ¹ represents a single bond, —C(R ^c ) ₂ —, —O—, —CO—, —S—, —SO—, or —SO ₂ —;
Each R ^c independently represents a hydrogen atom or an alkyl group;
s represents 0 or 1;
t and u each independently represent an integer of 1 or more.
The t units and u units may be the same or different for each unit.

^R11 and ^R12 each independently represent an alkyl group, and in one embodiment, preferably a methyl group. ^R13 and ^R14 each independently represent a hydrogen atom or an alkyl group, and in one embodiment, preferably a hydrogen atom. ^R21 and ^R22 each independently represent a hydrogen atom or an alkyl group, and in one embodiment, preferably a hydrogen atom or a methyl group, more preferably a methyl group. ^R23 and ^R24 each independently represent a hydrogen atom or an alkyl group, and in one embodiment, preferably a hydrogen atom or a methyl group.

R ^a and R ^b each independently represent (1) an acryloyl group, (2) a methacryloyl group, (3) an allyl group, (4) a methallyl group, (5) a phenyl group substituted with a group selected from a vinyl group and an isopropenyl group and which may further be substituted with an alkyl group, or (6) a benzyl group substituted with a group selected from a vinyl group and an isopropenyl group and which may further be substituted with an alkyl group.

In one embodiment, R ^a and R ^b are each independently preferably (1) a phenyl group substituted with a group selected from a vinyl group and an isopropenyl group and optionally further substituted with an alkyl group, or (2) a benzyl group substituted with a group selected from a vinyl group and an isopropenyl group and optionally further substituted with an alkyl group; more preferably a 4-vinylphenyl group, a 3-vinylphenyl group, a 2-vinylphenyl group, a 4-isopropenylphenyl group, a 3-isopropenylphenyl group, a 2-isopropenylphenyl group, a 4-vinylbenzyl group, a 3-vinylbenzyl group, a 2-vinylbenzyl group, a 4-isopropenylbenzyl group, a 3-isopropenylbenzyl group, or a 2-isopropenylbenzyl group; particularly preferably a 4-vinylbenzyl group, a 3-vinylbenzyl group, or a 2-vinylbenzyl group.

^X1 represents a single bond, -C( ^Rc ) _2- , -O-, -CO-, -S-, -SO-, or _-SO2- , and in one embodiment, is preferably a single bond, -C( ^Rc ) _2- , or -O-. Each ^Rc independently represents a hydrogen atom or an alkyl group, and in one embodiment, is preferably a hydrogen atom or a methyl group.

s represents 0 or 1, and in one embodiment, preferably 1. t and u each independently represent an integer of 1 or greater, and in one embodiment, preferably an integer of 1 to 200, more preferably an integer of 1 to 100.

The radical reactive group equivalent of the thermosetting modified polyphenylene ether resin is preferably 300 g/eq. to 2500 g/eq., more preferably 400 g/eq. to 2000 g/eq. The radical reactive group equivalent represents the mass of resin (compound) per equivalent of radical reactive groups.

The number average molecular weight of the thermosetting modified polyphenylene ether resin is preferably 800 to 10,000, more preferably 900 to 5,000, and even more preferably 1,000 to 2,500. The number average molecular weight of the resin can be measured as a polystyrene-equivalent value using gel permeation chromatography (GPC).

Commercially available thermosetting modified polyphenylene ether resins include "OPE-2St 1200" and "OPE-2St 2200" (vinylbenzyl-modified polyphenylene ether resins) manufactured by Mitsubishi Gas Chemical Company, Inc., and "SA9000" and "SA9000-111" (methacrylic-modified polyphenylene ether resins) manufactured by SABIC Innovative Plastics.

The content of the thermosetting modified polyphenylene ether resin in the resin composition layer of the resin sheet used in step (1) is not particularly limited, but is preferably 0.1 to 40% by mass or less, more preferably 1 to 20% by mass or less, even more preferably 3 to 15% by mass, and particularly preferably 5 to 10% by mass, assuming that the non-volatile components in the resin composition layer are 100% by mass.

In one embodiment, the resin composition layer of the resin sheet used in step (1) preferably contains a maleimide resin as a thermosetting resin. Maleimide resin refers to a curable resin containing at least one maleimide group (2,5-dihydro-2,5-dioxo-1H-pyrrol-1-yl group) per molecule. One type of maleimide resin may be used alone, or two or more types may be used in combination.

In the first embodiment, the maleimide resin preferably has the formula (2'):

[In the formula,
Ring B is an optionally substituted monocycloalkane ring or an optionally substituted monocycloalkene ring;
i and j each independently represent an integer of 0 or 1 or more, and the sum of i and j is 6 or more;
* indicates a binding site.]
The number of maleimide groups in one molecule of the maleimide compound in the first embodiment is preferably 2 or more, and particularly preferably 2. The maleimide compounds in the first embodiment may be used alone or in combination of two or more at any ratio.

The "substituent" on ring B in formula (2') is not particularly limited, but examples include a halogen atom, an alkyl group, an alkenyl group, an aryl group, an aralkyl group, an alkyl-oxy group, an alkenyl-oxy group, an aryl-oxy group, and an aralkyl-oxy group.

A halogen atom is a fluorine atom, chlorine atom, bromine atom, or iodine atom.

An alkenyl (group) refers to a linear, branched, and/or cyclic monovalent aliphatic unsaturated hydrocarbon group having at least one carbon-carbon double bond. Unless otherwise specified, the alkenyl (group) is preferably an alkenyl (group) having 2 to 14 carbon atoms, more preferably an alkenyl (group) having 2 to 6 carbon atoms, and even more preferably an alkenyl (group) having 2 or 3 carbon atoms. Examples of alkenyl groups include vinyl groups, propenyl groups (allyl groups, 1-propenyl groups, isopropenyl groups), butenyl groups (1-butenyl groups, crotyl groups, methallyl groups, isocrotyl groups, etc.), pentenyl groups (1-pentenyl groups, etc.), hexenyl groups (1-hexenyl groups, etc.), heptenyl groups (1-heptenyl groups, etc.), octenyl groups (1-octenyl groups, etc.), cyclopentenyl groups (2-cyclopentenyl groups, etc.), and cyclohexenyl groups (3-cyclohexenyl groups).

An aryl (group) refers to a monovalent aromatic hydrocarbon group formed by removing one hydrogen atom from an aromatic carbon ring. Unless otherwise specified, the aryl (group) is preferably an aryl (group) having 6 to 14 carbon atoms, and more preferably an aryl (group) having 6 to 10 carbon atoms. Examples of aryl (groups) include phenyl, 1-naphthyl, and 2-naphthyl groups.

An aralkyl (group) refers to an alkyl group substituted with one or more (preferably one) aryl groups. Unless otherwise specified, the aralkyl (group) is preferably an aralkyl (group) having 7 to 15 carbon atoms, and more preferably an aralkyl (group) having 7 to 11 carbon atoms. Examples of aralkyl (groups) include benzyl, phenethyl, hydrocinnamyl, α-methylbenzyl, α-cumyl, 1-naphthylmethyl, and 2-naphthylmethyl.

The term "monocycloalkane ring" refers to a monocyclic aliphatic saturated hydrocarbon ring. The monocycloalkane ring is preferably a monocycloalkane ring having 4 to 14 carbon atoms, more preferably a monocycloalkane ring having 4 to 10 carbon atoms, and particularly preferably a monocycloalkane ring having 5 or 6 carbon atoms. Examples of monocycloalkane rings include a cyclobutane ring, cyclopentane ring, cyclohexane ring, cycloheptane ring, and cyclooctane ring. The term "monocycloalkene ring" refers to a monocyclic aliphatic unsaturated hydrocarbon ring having at least one carbon-carbon double bond. The monocycloalkene ring is preferably a monocycloalkene ring having 4 to 14 carbon atoms, more preferably a monocycloalkene ring having 4 to 10 carbon atoms, and particularly preferably a monocycloalkene ring having 5 or 6 carbon atoms. Examples of monocycloalkene rings include cyclobutene rings, cyclopentene rings, cyclohexene rings, cycloheptene rings, cyclooctene rings, cyclopentadiene rings, and cyclohexadiene rings.

Ring B represents a monocycloalkane ring which may have a substituent, or a monocycloalkene ring which may have a substituent. Ring B is preferably a monocycloalkane ring which may have a substituent selected from an alkyl group and an alkenyl group; or a monocycloalkene ring which may have a substituent selected from an alkyl group and an alkenyl group. Ring B is more preferably a monocycloalkane ring which may have a substituent selected from an alkyl group having 1 to 14 carbon atoms and an alkenyl group having 2 to 14 carbon atoms; or a monocycloalkene ring which may have a substituent selected from an alkyl group having 1 to 14 carbon atoms and an alkenyl group having 2 to 14 carbon atoms.

i and j each independently represent an integer of 0 or 1 or greater, and the sum of i and j is 6 or greater (preferably 8 or greater, more preferably 10 or greater). i and j are preferably each independently an integer from 0 to 20, and the sum of i and j is 6 or greater (preferably 8 or greater, more preferably 10 or greater). i and j are more preferably each independently an integer from 1 to 20, and the sum of i and j is 6 or greater (preferably 8 or greater, more preferably 10 or greater). i and j are even more preferably each independently an integer from 5 to 10. i and j are particularly preferably 8.

In the first embodiment, the maleimide resin is particularly preferably a maleimide resin represented by formula (2):

[In the formula,
Each R ¹⁰ independently represents a substituent;
ring C independently represents an aromatic ring which may have a substituent;
D ¹ and D ² each independently represent a single bond, —C(R ^x ) ₂ —, —O—, —CO—, —S—, —SO—, —SO ₂ —, —CONH—, —NHCO—, —COO—, or —OCO—;
Each R ^x independently represents a hydrogen atom or an alkyl group;
c's each independently represent 0 or 1;
Each d independently represents 0 or an integer of 1 or more;
e each independently represents 0, 1 or 2;
n represents 0 or an integer of 1 or more;
Other symbols are the same as above.]
The d unit, the e unit and the n unit may be the same or different from each other.

The "substituent" in R ¹⁰ of formula (2) and the "substituent" in ring C are not particularly limited, and examples thereof include a halogen atom, an alkyl group, an alkenyl group, an aryl group, an aralkyl group, an alkyl-oxy group, an alkenyl-oxy group, an aryl-oxy group, and an aralkyl-oxy group.

An aromatic ring refers to a ring that conforms to Hückel's rule, in which the number of electrons contained in the π-electron system on the ring is 4p+2 (p is a natural number). An aromatic ring may be an aromatic carbocyclic ring containing only carbon atoms as ring constituent atoms, or an aromatic heterocyclic ring containing heteroatoms such as oxygen, nitrogen, or sulfur atoms in addition to carbon atoms as ring constituent atoms. In one embodiment, an aromatic carbocyclic ring is preferred. In one embodiment, the aromatic ring is preferably a 5- to 14-membered aromatic ring, more preferably a 6- to 14-membered aromatic ring, and even more preferably a 6- to 10-membered aromatic ring. Specific examples of suitable aromatic rings include a benzene ring, a naphthalene ring, an anthracene ring, and a phenanthrene ring. A benzene ring or a naphthalene ring is more preferred, and a benzene ring is particularly preferred.

Ring C independently represents an aromatic ring which may have a substituent, and is preferably a benzene ring which may be substituted with a group selected from alkyl groups.

^D1 and ^D2 each independently represent a single bond, -C( ^Rx ) _2- , -O-, -CO-, -S-, -SO-, _-SO2- , -CONH-, -NHCO-, -COO-, or -OCO-, and preferably a single bond, -C( ^Rx ) _2- , or -O-. Each ^Rx independently represents a hydrogen atom or an alkyl group, and preferably a hydrogen atom or a methyl group.

Each c independently represents 0 or 1, preferably 0. Each d independently represents 0 or an integer of 1 or more, preferably 0, 1, 2, or 3, and more preferably 0, 1, or 2. Each e independently represents 0, 1, or 2, preferably 0. Each n independently represents 0 or an integer of 1 or more, preferably 0.

Formula (D) contained in formula (2):

[In the formula, * indicates a binding site; other symbols are as defined above.]
The partial structure represented by the formula (D-1) to (D-3):

[In the formula, * is the same as above.]
Examples of the partial structure include:

In the first embodiment, the maleimide group equivalent of the maleimide resin is preferably 200 g/eq. to 2500 g/eq., more preferably 250 g/eq. to 2000 g/eq., and even more preferably 300 g/eq. to 1500 g/eq. The maleimide group equivalent of the maleimide resin represents the mass of the resin per equivalent of maleimide groups.

The weight-average molecular weight of the maleimide resin in the first embodiment is preferably 400 to 10,000, more preferably 500 to 7,000, and particularly preferably 600 to 5,000.

Commercially available maleimide resins for the first embodiment include, for example, "BMI-689," "BMI-1500," "BMI-1700," and "BMI-3000J" manufactured by Designer Molecules, Inc., and "SLK-6895-T90" manufactured by Shin-Etsu Chemical Co., Ltd.

In the second embodiment, the maleimide resin preferably has the formula (3):

[In the formula,
Each R ²⁰ independently represents a hydrogen atom or an alkyl group;
Ring E, ring F, and ring G each independently represent an aromatic ring which may have a substituent;
Z ¹ 's each independently represent a single bond, —C(R ^z ) ₂ —, —O—, —CO—, —S—, —SO—, —SO ₂ —, —CONH—, or —NHCO—;
^Rz each independently represent a hydrogen atom or an alkyl group;
f represents an integer of 1 or more;
Each g independently represents 0 or 1;
Each h independently represents 0, 1, 2, or 3.
The f units and h units may be the same or different for each unit. The maleimide compound in the second embodiment may be used alone or in combination of two or more types in any ratio.

The "substituents" in rings E, F, and G in formula (3) are not particularly limited, but examples include halogen atoms, alkyl groups, alkenyl groups, aryl groups, aralkyl groups, alkyl-oxy groups, alkenyl-oxy groups, aryl-oxy groups, and aralkyl-oxy groups.

Each R ²⁰ independently represents a hydrogen atom or an alkyl group, preferably a hydrogen atom or a methyl group, and more preferably a hydrogen atom.

Ring E, ring F, and ring G each independently represent an aromatic ring which may have a substituent, preferably a benzene ring which may have a substituent, more preferably a benzene ring which may be substituted with a group selected from an alkyl group and an aryl group, and particularly preferably an (unsubstituted) benzene ring.

Each ^Z1 independently represents a single bond, —C(R ^z ) ₂ —, —O—, —CO—, —S—, —SO—, —SO ₂ —, —CONH—, or —NHCO—, preferably a single bond. Each R ^z independently represents a hydrogen atom or an alkyl group, preferably a hydrogen atom or a methyl group.

f represents an integer of 1 or greater, preferably an integer from 1 to 10. Each g independently represents 0 or 1, preferably 1. Each h independently represents 0, 1, 2, or 3, preferably 0, 1, or 2, more preferably 0 or 1, and particularly preferably 1.

In the second embodiment, the maleimide group equivalent of the maleimide resin is preferably 150 g/eq. to 1000 g/eq., more preferably 200 g/eq. to 500 g/eq.

The weight-average molecular weight of the maleimide resin in the second embodiment is preferably 100 to 10,000, more preferably 150 to 5,000, and particularly preferably 200 to 3,000.

Commercially available maleimide resins for the second embodiment include, for example, "MIR-3000-70MT" and "MIR-5000-60T" manufactured by Nippon Kayaku Co., Ltd.

In the third embodiment, the maleimide resin preferably has the formula (4):

[In the formula,
Each R ³⁰ independently represents an alkyl group;
Ring H and ring I each independently represent an aromatic ring which may have a substituent;
m represents an integer of 1 or more.
The m units may be the same or different for each unit. The maleimide compounds in the third embodiment may be used singly or in combination of two or more types in any ratio.

The "substituents" in ring H and ring I of formula (4) are not particularly limited, but examples include halogen atoms, alkyl groups, alkenyl groups, aryl groups, aralkyl groups, alkyl-oxy groups, alkenyl-oxy groups, aryl-oxy groups, and aralkyl-oxy groups.

Each R ³⁰ independently represents an alkyl group, and in one embodiment, preferably a methyl group. Each H ring independently represents an aromatic ring which may have a substituent, and in one embodiment, preferably a benzene ring which may have a substituent, more preferably a benzene ring which may be substituted with a group selected from alkyl groups, and even more preferably a benzene ring substituted with a group selected from alkyl groups.

Ring I independently represents an aromatic ring which may have a substituent, and in one embodiment, is preferably a benzene ring which may have a substituent, more preferably a benzene ring which may be substituted with a group selected from alkyl groups, and even more preferably an (unsubstituted) benzene ring. m represents an integer of 1 or greater, preferably an integer from 1 to 20.

The maleimide resin in the third embodiment can be produced, for example, using the method described in Japan Institute of Invention and Innovation's Technical Bulletin No. 2020-500211 or a method equivalent thereto.

The maleimide resin may contain any one of the preferred compounds in the first embodiment, the preferred compounds in the second embodiment, or the preferred compounds in the third embodiment, or may contain two or more of these in combination in any ratio.

The maleimide group equivalent weight of the maleimide resin is preferably 30 g/eq. to 2500 g/eq., and particularly preferably 75 g/eq. to 2000 g/eq.

The content of maleimide resin in the resin composition layer of the resin sheet used in step (1) is not particularly limited, but is preferably 5 to 50% by mass, more preferably 10 to 40% by mass, even more preferably 15 to 35% by mass, and particularly preferably 20 to 30% by mass, assuming that the non-volatile components in the resin composition are 100% by mass.

In one embodiment, the resin composition layer of the resin sheet used in step (1) may contain a radically polymerizable crosslinking agent as a thermosetting resin.

The radically polymerizable crosslinking agent is preferably a low-molecular-weight compound (e.g., a molecular weight of less than 800) that has two or more radically reactive groups. Examples of such compounds include polyfunctional (meth)acryloyl group-containing compounds, polyfunctional vinylphenyl group-containing compounds, and polyfunctional (meth)allyl group-containing compounds.

A polyfunctional (meth)acryloyl group-containing compound is a compound having two or more acryloyl groups or methacryloyl groups. Examples of polyfunctional (meth)acryloyl group-containing compounds include aliphatic (meth)acrylic acid ester compounds such as cyclohexane-1,4-dimethanol di(meth)acrylate, cyclohexane-1,3-dimethanol di(meth)acrylate, tricyclodecane dimethanol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,8-octanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, 1,10-decanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, trimethylolethane tri(meth)acrylate, glycerin tri(meth)acrylate, and pentaerythritol tetra(meth)acrylate; dioxane glycol Examples of the ether-containing (meth)acrylic acid ester compounds include ether-containing (meth)acrylic acid ester compounds such as bisphenol A di(meth)acrylate, 3,6-dioxa-1,8-octanediol di(meth)acrylate, 3,6,9-trioxaundecane-1,11-diol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, 9,9-bis[4-(2-acryloyloxyethoxy)phenyl]fluorene, ethoxylated bisphenol A di(meth)acrylate, and propoxylated bisphenol A di(meth)acrylate; and isocyanurate-containing (meth)acrylic acid ester compounds such as tris(3-hydroxypropyl)isocyanurate tri(meth)acrylate, tris(2-hydroxyethyl)isocyanurate tri(meth)acrylate, and ethoxylated isocyanuric acid tri(meth)acrylate. Commercially available polyfunctional (meth)acryloyl group-containing compounds include, for example, "A-DOG" (dioxane glycol diacrylate) manufactured by Shin-Nakamura Chemical Co., Ltd., "DCP-A" (tricyclodecane dimethanol diacrylate) and "DCP" (tricyclodecane dimethanol dimethacrylate) manufactured by Kyoeisha Chemical Co., Ltd., and "KAYARAD R-684" (tricyclodecane dimethanol diacrylate) and "KAYARAD R-604" (dioxane glycol diacrylate) manufactured by Nippon Kayaku Co., Ltd.

A polyfunctional vinylphenyl group-containing compound is a compound containing two or more vinylphenyl groups. Examples of polyfunctional vinylphenyl group-containing compounds with a molecular weight of less than 800 include 4,4'-divinylbiphenyl, 1,2-bis(4-vinylphenyl)ethane, 2,2-bis(4-vinylphenyl)propane, and bis(4-vinylphenyl)ether.

A polyfunctional (meth)allyl group-containing compound is a compound having two or more allyl or methallyl groups. Examples of polyfunctional (meth)allyl group-containing compounds include aromatic carboxylic acid allyl ester compounds such as diallyl diphenate, triallyl trimellitate, diallyl phthalate, diallyl isophthalate, diallyl terephthalate, diallyl 2,6-naphthalenedicarboxylate, and diallyl 2,3-naphthalenecarboxylate; isocyanuric acid allyl ester compounds such as 1,3,5-triallyl isocyanurate and 1,3-diallyl-5-glycidyl isocyanurate; epoxy-containing aromatic allyl compounds such as 2,2-bis[3-allyl-4-(glycidyloxy)phenyl]propane; benzoxazine-containing aromatic allyl compounds such as bis[3-allyl-4-(3,4-dihydro-2H-1,3-benzoxazin-3-yl)phenyl]methane; ether-containing aromatic allyl compounds such as 1,3,5-triallyl ether benzene; and allyl silane compounds such as diallyldiphenylsilane. Commercially available polyfunctional (meth)allyl group-containing compounds with a molecular weight of less than 800 include "TAIC" (1,3,5-triallyl isocyanurate) manufactured by Nippon Kasei Chemical Industry Co., Ltd., "DAD" (diallyl diphenate) manufactured by Nisshoku Techno Fine Chemical Co., Ltd., "TRIAM-705" (triallyl trimellitate) manufactured by Wako Pure Chemical Industries, Ltd., "DAND" (2,3-diallyl naphthalenecarboxylate) manufactured by Nippon Distillation Industry Co., Ltd., "ALP-d" (bis[3-allyl-4-(3,4-dihydro-2H-1,3-benzoxazin-3-yl)phenyl]methane manufactured by Shikoku Chemical Industry Co., Ltd., "RE-810NM" (2,2-bis[3-allyl-4-(glycidyloxy)phenyl]propane) manufactured by Nippon Kayaku Co., Ltd., and "DA-MGIC" (1,3-diallyl-5-glycidyl isocyanurate) manufactured by Shikoku Chemical Industry Co., Ltd.

In one embodiment, the radically polymerizable crosslinking agent is particularly preferably a compound represented by formula (5):

[In the formula,
R ^d and R ^e each independently represent (1) an acryloyl group, (2) a methacryloyl group, (3) an allyl group, (4) a methallyl group, (5) a phenyl group substituted with a group selected from a vinyl group and an isopropenyl group and which may further be substituted with an alkyl group, or (6) a benzyl group substituted with a group selected from a vinyl group and an isopropenyl group and which may further be substituted with an alkyl group;
^X2 and ^X3 each represent a single bond or an alkylene group;
Ring A is an optionally substituted non-aromatic carbocyclic ring or an optionally substituted non-aromatic heterocyclic ring.
The compound includes a low molecular weight compound (for example, a molecular weight of less than 800) represented by the formula:

The "substituents" included in the definition of the symbols in formula (5) are not particularly limited, but examples include halogen atoms, alkyl groups, alkenyl groups, aryl groups, aralkyl groups, alkyl-oxy groups, alkenyl-oxy groups, aryl-oxy groups, and aralkyl-oxy groups.

^Rd and ^Re each independently represent (1) an acryloyl group, (2) a methacryloyl group, (3) an allyl group, (4) a methallyl group, (5) a phenyl group substituted with a group selected from a vinyl group and an isopropenyl group and which may further be substituted with an alkyl group, or (6) a benzyl group substituted with a group selected from a vinyl group and an isopropenyl group and which may further be substituted with an alkyl group. In one embodiment, ^Rd and ^Re each independently represent preferably an acryloyl group or a methacryloyl group.

^X2 and ^X3 each represent a single bond or an alkylene group. The alkylene group refers to a linear and/or branched divalent aliphatic saturated hydrocarbon group. The alkylene group is preferably an alkylene group having 1 to 6 carbon atoms. Examples of the alkylene group include -CH2-, _-CH2 -CH2-, -CH(CH3)-, _-CH2 - _{CH2 -CH2-} , _-CH2 -CH( _CH3 )-, _-CH ( _CH3 ) _-CH2- , -C( _CH3 ) _2- , -CH2- _CH2 - _{CH2 -} CH2-, -CH2 _{-CH2 - CH2-} , _-CH2 - _CH2 -CH( _CH3 )-, _-CH2 -CH( _CH3 ) _-CH2- , -CH( _CH3 ) _-CH2 - _CH2- , -C( _CH3 ) _{2 -CH2-} , _-CH2 -C( _CH3 ) _2- , etc. In one embodiment, ^X2 and ^X3 are each independently preferably an alkylene group.

Ring A represents an optionally substituted non-aromatic carbocyclic ring or an optionally substituted non-aromatic heterocyclic ring.

A non-aromatic carbocycle refers to a ring whose ring constituent atoms are solely carbon atoms that are not aromatic throughout the ring. The non-aromatic carbocycle may be a monocyclic non-aromatic carbocycle or a polycyclic non-aromatic carbocycle. The non-aromatic carbocycle may be a saturated carbocycle consisting of only single bonds, or an unsaturated carbocycle having a double bond in addition to a single bond. The non-aromatic carbocycle is preferably a 3- to 21-membered non-aromatic carbocycle, more preferably a 4- to 18-membered non-aromatic carbocycle, and even more preferably a 5- to 14-membered non-aromatic carbocycle. Specific preferred examples of the non-aromatic carbocyclic ring include monocyclic saturated carbocyclic rings such as a cyclobutane ring, a cyclopentane ring, a cyclohexane ring, a cycloheptane ring, a cyclooctane ring, a cyclononane ring, a cyclodecane ring, a cycloundecane ring, and a cyclododecane ring; bicyclic saturated carbocyclic rings such as a bicyclo[2.2.1]heptane ring (norbornane ring), a bicyclo[4.4.0]decane ring (decalin ring), a bicyclo[5.3.0]decane ring, a bicyclo[4.3.0]nonane ring (hydrindane ring), a bicyclo[3.2.1]octane ring, a bicyclo[5.4.0]undecane ring, a bicyclo[3.3.0]octane ring, and a bicyclo[3.3.1]nonane ring; and tricyclo[5.2.1.0 ^2,6 ]decane ring (tetrahydrodicyclopentadiene ring), tricyclo[3.3.1.1 ^3,7 ]decane ring (adamantane ring), tricyclo[6.2.1.0 ^2,7 ]undecane ring, and other saturated tricyclic carbocyclic rings are also included.

A non-aromatic heterocycle refers to a ring that is not aromatic throughout the entire ring and contains heteroatoms such as oxygen, nitrogen, and sulfur atoms in addition to carbon atoms as ring-constituting atoms. A non-aromatic heterocycle may be a monocyclic non-aromatic heterocycle or a polycyclic non-aromatic heterocycle. A non-aromatic heterocycle may be a saturated heterocycle consisting of only single bonds, or an unsaturated heterocycle having double bonds in addition to single bonds. A non-aromatic heterocycle is preferably a 3- to 21-membered non-aromatic heterocycle, more preferably a 4- to 18-membered non-aromatic heterocycle, and even more preferably a 5- to 14-membered non-aromatic heterocycle. Specific examples of suitable non-aromatic heterocycles include a 1,3-dioxane ring, a 1,3-dioxolane ring, a tetrahydropyran ring, and a tetrahydrofuran ring.

In one embodiment, ring A is preferably a non-aromatic carbocyclic ring optionally substituted with an alkyl group, or a non-aromatic heterocyclic ring optionally substituted with an alkyl group; more preferably a tetrahydrodicyclopentadiene ring optionally substituted with an alkyl group, or a 1,3-dioxane ring optionally substituted with an alkyl group.

The radical-reactive group equivalent weight of the radical-polymerizable crosslinking agent is preferably 30 g/eq. to 400 g/eq., more preferably 50 g/eq. to 300 g/eq., and even more preferably 75 g/eq. to 200 g/eq.

The molecular weight of the radically polymerizable crosslinking agent is preferably 100 to 700, more preferably 200 to 400, and even more preferably 250 to 500.

The content of the radically polymerizable crosslinking agent in the resin composition layer of the resin sheet used in step (1) is not particularly limited, but is preferably 0.1 to 40% by mass or less, more preferably 1 to 20% by mass or less, even more preferably 3 to 15% by mass, and particularly preferably 5 to 10% by mass, assuming that the non-volatile components in the resin composition layer are 100% by mass.

The content of thermosetting resin in the resin composition layer of the resin sheet used in step (1) is not particularly limited, but is preferably 1 to 60% by mass or less, more preferably 10 to 50% by mass or less, even more preferably 15 to 45% by mass, and particularly preferably 20 to 40% by mass, assuming that the non-volatile components in the resin composition layer are 100% by mass.

In a preferred embodiment, the resin composition layer of the resin sheet used in step (1) may contain an inorganic filler. The inorganic filler is present in the form of particles in the resin composition layer.

Inorganic compounds are used as inorganic fillers. Examples of inorganic filler materials include silica, alumina, aluminosilicate, glass, cordierite, silicon oxide, barium sulfate, barium carbonate, talc, clay, mica powder, zinc oxide, hydrotalcite, boehmite, aluminum hydroxide, magnesium hydroxide, calcium carbonate, magnesium carbonate, magnesium oxide, boron nitride, aluminum nitride, manganese nitride, aluminum borate, strontium carbonate, strontium titanate, calcium titanate, magnesium titanate, bismuth titanate, titanium oxide, zirconium oxide, barium titanate, barium titanate zirconate, barium zirconate, calcium zirconate, zirconium phosphate, and zirconium tungstate phosphate. Among these, silica, alumina, and aluminosilicate are preferred, with silica being particularly preferred. Examples of silica include amorphous silica, fused silica, crystalline silica, synthetic silica, and hollow silica. Spherical silica is preferred. The inorganic filler may be used alone or in combination of two or more types in any ratio.

Commercially available inorganic fillers include "SP60-05" and "SP507-05" manufactured by Nippon Steel Chemical & Material Co., Ltd.; "YC100C," "YA050C," "YA050C-MJE," "YA010C," "SC2500SQ," "SO-C4," "SO-C2," and "SO-C1" manufactured by Admatechs Co., Ltd.; "UFP-30," "DAW-03," and "FB-105FD" manufactured by Denka Co., Ltd.; "Silfil NSS-3N," "Silfil NSS-4N," and "Silfil NSS-5N" manufactured by Tokuyama Corporation; "Cellphears" and "MGH-005" manufactured by Taiheiyo Cement Corporation; and "Sfereek" and "BA-1" manufactured by JGC Catalysts and Chemicals Co., Ltd.

The average particle size of the inorganic filler is not particularly limited, but is preferably 10 μm or less, more preferably 5 μm or less, even more preferably 3 μm or less, even more preferably 1 μm or less, and especially preferably 0.8 μm or less. The lower limit of the average particle size of the inorganic filler is not particularly limited, but is preferably 0.01 μm or more, more preferably 0.05 μm or more, even more preferably 0.1 μm or more, and especially preferably 0.2 μm or more. The average particle size of the inorganic filler can be measured using a laser diffraction/scattering method based on Mie scattering theory. Specifically, a particle size distribution of the inorganic filler is created on a volume basis using a laser diffraction/scattering particle size distribution analyzer, and the median diameter is used as the average particle size. A measurement sample can be prepared by weighing 100 mg of inorganic filler and 10 g of methyl ethyl ketone into a vial and ultrasonically dispersing for 10 minutes. The measurement sample was measured using a laser diffraction particle size distribution analyzer, with blue and red light source wavelengths used and a flow cell system to measure the volumetric particle size distribution of the inorganic filler, and the average particle size was calculated as the median diameter from the obtained particle size distribution. Examples of laser diffraction particle size distribution analyzers include the "LA-960" manufactured by Horiba, Ltd.

The specific surface area of the inorganic filler is not particularly limited, but is preferably 0.1 m ² /g or more, more preferably 0.5 m ² /g or more, even more preferably 1 m ² /g or more, and particularly preferably 3 m ² /g or more. The upper limit of the specific surface area of the inorganic filler is not particularly limited, but is preferably 100 m ² /g or less, more preferably 50 m ² /g or less, even more preferably 30 m ² /g or less, and particularly preferably 10 m ² /g or less. The specific surface area of the inorganic filler can be obtained according to the BET method by adsorbing nitrogen gas onto the surface of a sample using a specific surface area measuring device (Macsorb HM-1210 manufactured by Mountech Co., Ltd.) and calculating the specific surface area using the BET multipoint method.

From the perspective of improving moisture resistance and dispersibility, the inorganic filler is preferably treated with a surface treatment agent. Examples of surface treatment agents include fluorine-containing silane coupling agents, aminosilane coupling agents, epoxysilane coupling agents, mercaptosilane coupling agents, silane coupling agents, alkoxysilanes, organosilazane compounds, and titanate coupling agents. Furthermore, one type of surface treatment agent may be used alone, or two or more types may be used in any combination.

Commercially available surface treatment agents include, for example, Shin-Etsu Chemical Co., Ltd.'s "KBM403" (3-glycidoxypropyltrimethoxysilane), Shin-Etsu Chemical Co., Ltd.'s "KBM803" (3-mercaptopropyltrimethoxysilane), Shin-Etsu Chemical Co., Ltd.'s "KBE903" (3-aminopropyltriethoxysilane), Shin-Etsu Chemical Co., Ltd.'s "KBM573" (N-phenyl-3-aminopropyltrimethoxysilane), Shin-Etsu Chemical Co., Ltd.'s "SZ-31" (hexamethyldisilazane), Shin-Etsu Chemical Co., Ltd.'s "KBM103" (phenyltrimethoxysilane), Shin-Etsu Chemical Co., Ltd.'s "KBM-4803" (long-chain epoxy-type silane coupling agent), and Shin-Etsu Chemical Co., Ltd.'s "KBM-7103" (3,3,3-trifluoropropyltrimethoxysilane).

From the perspective of improving the dispersibility of the inorganic filler, it is preferable that the degree of surface treatment with the surface treatment agent falls within a specified range. Specifically, 100% by mass of inorganic filler is preferably surface-treated with 0.2% to 5% by mass of surface treatment agent, more preferably 0.2% to 3% by mass, and even more preferably 0.3% to 2% by mass.

The degree of surface treatment with the surface treatment agent can be evaluated by the amount of carbon per unit surface area of the inorganic filler. From the viewpoint of improving the dispersibility of the inorganic filler, the amount of carbon per unit surface area of the inorganic filler is preferably 0.02 mg/ ^m2 or more, more preferably 0.1 mg/ ^m2 or more, and even more preferably 0.2 mg/ ^m2 or more. On the other hand, from the viewpoint of preventing an increase in the melt viscosity of the resin composition or the melt viscosity in a sheet form, the amount of carbon per unit surface area is preferably 1.0 mg/ ^m2 or less, more preferably 0.8 mg/ ^m2 or less, and even more preferably 0.5 mg/ ^m2 or less.

The amount of carbon per unit surface area of the inorganic filler can be measured after the surface-treated inorganic filler is washed with a solvent (e.g., methyl ethyl ketone (MEK)). Specifically, a sufficient amount of MEK as a solvent is added to the inorganic filler that has been surface-treated with a surface treatment agent, and ultrasonic cleaning is performed at 25°C for 5 minutes. After removing the supernatant and drying the solids, the amount of carbon per unit surface area of the inorganic filler can be measured using a carbon analyzer. A carbon analyzer such as the EMIA-320V manufactured by Horiba, Ltd. can be used.

The content of inorganic filler in the resin composition layer of the resin sheet used in step (1) is preferably 20% by mass or more, more preferably 40% by mass or more, even more preferably 50% by mass or more, even more preferably 55% by mass or more, and particularly preferably 60% by mass or more, based on 100% by mass of the non-volatile components in the resin composition layer. There is no particular upper limit to the content of inorganic filler in the resin composition layer, but it is preferably 90% by mass or less, more preferably 85% by mass or less, even more preferably 80% by mass or less, and particularly preferably 75% by mass or less, based on 100% by mass of the non-volatile components in the resin composition layer.

In a preferred embodiment, the resin composition layer of the resin sheet used in step (1) may contain a thermoplastic resin. Examples of thermoplastic resins include thermoplastic polyimide resins, polycarbonate resins, phenoxy resins, polyvinyl acetal resins, copolymers, polyamide-imide resins, polyetherimide resins, polysulfone resins, polyethersulfone resins, polyetheretherketone resins, and thermoplastic polyphenylene ether resins. The resin composition layer preferably contains a thermoplastic resin selected from thermoplastic polyimide resins, polycarbonate resins, phenoxy resins, polyvinyl acetal resins, and copolymers, and more preferably a thermoplastic resin selected from phenoxy resins and copolymers. One type of thermoplastic resin may be used alone, or two or more types may be used in combination.

Specific examples of thermoplastic polyimide resins include "SLK-6100" manufactured by Shin-Etsu Chemical Co., Ltd., and "Rikacoat SN20" and "Rikacoat PN20" manufactured by New Japan Chemical Co., Ltd.

Examples of polycarbonate resins include hydroxyl group-containing carbonate resins, phenolic hydroxyl group-containing carbonate resins, carboxyl group-containing carbonate resins, acid anhydride group-containing carbonate resins, isocyanate group-containing carbonate resins, and urethane group-containing carbonate resins. Specific examples of polycarbonate resins include Mitsubishi Gas Chemical Company's "FPC0220," Asahi Kasei Chemical Company's "T6002" and "T6001" (polycarbonate diols), and Kuraray Co., Ltd.'s "C-1090," "C-2090," and "C-3090" (polycarbonate diols). Specific examples of polyether ether ketone resins include Sumitomo Chemical Company's "Sumiploy K."

Examples of phenoxy resins include phenoxy resins having one or more skeletons selected from the group consisting of bisphenol A, bisphenol F, bisphenol S, bisphenolacetophenone, novolac, biphenyl, fluorene, dicyclopentadiene, norbornene, naphthalene, anthracene, adamantane, terpene, and trimethylcyclohexane. The terminals of the phenoxy resin may be any functional group, such as a phenolic hydroxyl group or an epoxy group.

Specific examples of phenoxy resins include Mitsubishi Chemical Corporation's "1256" and "4250" (both phenoxy resins containing a bisphenol A skeleton); Mitsubishi Chemical Corporation's "YX8100" (phenoxy resin containing a bisphenol S skeleton); Mitsubishi Chemical Corporation's "YX6954" (phenoxy resin containing a bisphenolacetophenone skeleton), Nippon Steel Chemical & Material Co., Ltd.'s "FX280" and "FX293," and Mitsubishi Chemical Corporation's "YX7200B35," "YL7500BH30," "YX6954BH30," "YX7553BH30," "YL7769BH30," "YL6794," "YL7213," "YL7290," and "YL7482."

Examples of polyvinyl acetal resins include polyvinyl formal resins and polyvinyl butyral resins, with polyvinyl butyral resins being preferred. Specific examples of polyvinyl acetal resins include Denka Butyral 4000-2, Denka Butyral 5000-A, Denka Butyral 6000-C, and Denka Butyral 6000-EP manufactured by Denki Kagaku Kogyo Co., Ltd.; and S-LEC BH series, BX series (e.g., BX-5Z), KS series (e.g., KS-1), BL series, and BM series manufactured by Sekisui Chemical Co., Ltd.

Copolymers are copolymers or hydrogenated products thereof obtained by polymerizing two or more monomers selected from styrene, ethylene, propylene, isoprene, butadiene, acrylate, and methacrylate.

Examples of copolymers include ethylene copolymer resins such as low-density polyethylene, very low-density polyethylene, high-density polyethylene, ethylene-ethyl acrylate copolymer, and ethylene-methyl acrylate copolymer; polyolefin polymers such as polypropylene and ethylene-propylene block copolymer; and the like.

Another example of a copolymer is polybutadiene resin. Examples of polybutadiene resins include hydrogenated polybutadiene skeleton-containing resins, hydroxyl group-containing polybutadiene resins, phenolic hydroxyl group-containing polybutadiene resins, carboxyl group-containing polybutadiene resins, acid anhydride group-containing polybutadiene resins, epoxy group-containing polybutadiene resins, isocyanate group-containing polybutadiene resins, urethane group-containing polybutadiene resins, and polyphenylene ether-polybutadiene resins.

Another example of a copolymer is polystyrene resin. Polystyrene resin may be a copolymer containing, in combination with styrene units, any repeating unit different from the styrene units, or may be a hydrogenated polystyrene resin. Examples of polystyrene resins include styrene-butadiene-styrene block copolymer (SBS), styrene-isoprene-styrene block copolymer (SIS), styrene-ethylene-butylene-styrene block copolymer (SEBS), styrene-ethylene-propylene-styrene block copolymer (SEPS), styrene-ethylene-ethylene-propylene-styrene block copolymer (SEEPS), styrene-butadiene-butylene-styrene block copolymer (SBBS), styrene-butadiene diblock copolymer, hydrogenated styrene-butadiene block copolymer, hydrogenated styrene-isoprene block copolymer, hydrogenated styrene-butadiene random copolymer, and styrene-maleic anhydride copolymer. Specific examples of polystyrene resins include hydrogenated styrene-based thermoplastic elastomers "H1041," "Tuftec H1043," "Tuftec P2000," and "Tuftec MP10" (manufactured by Asahi Kasei Corporation); epoxidized styrene-butadiene thermoplastic elastomers "Epofriend AT501" and "CT310" (manufactured by Daicel Corporation); modified styrene-based elastomers having hydroxyl groups "Septon HG252" (manufactured by Kuraray Co., Ltd.); modified styrene-based elastomers having carboxyl groups "Tuftec N503M," modified styrene-based elastomers having amino groups "Tuftec N501," modified styrene-based elastomers having acid anhydride groups "Tuftec M1913" (manufactured by Asahi Kasei Chemicals Corporation); unmodified styrene-based elastomers "Septon S8104" (manufactured by Kuraray Co., Ltd.); styrene-ethylene/butylene-styrene block copolymers "FG1924" (manufactured by Kraton Corporation), and "EF-40" (manufactured by CRAY Co., Ltd.). (manufactured by VALLEY)

Specific examples of polyamide-imide resins include "Vylomax HR11NN" and "Vylomax HR16NN" manufactured by Toyobo Co., Ltd. Specific examples of polyamide-imide resins also include modified polyamide-imides such as "KS9100" and "KS9300" (polysiloxane skeleton-containing polyamide-imides) manufactured by Hitachi Chemical Co., Ltd.

Specific examples of polyetherimide resins include "Ultem" manufactured by GE.

Specific examples of polysulfone resins include polysulfones "P1700" and "P3500" manufactured by Solvay Advanced Polymers.

Specific examples of polyethersulfone resins include "PES5003P" manufactured by Sumitomo Chemical Co., Ltd.

Specific examples of polyether ether ketone resins include PEEK-150PF and 450PF manufactured by Victrex.

Specific examples of thermoplastic polyphenylene ether resins include "NORYL SA90" manufactured by SABIC.

From the viewpoint of further improving film formability, the weight average molecular weight (Mw) of the thermoplastic resin is preferably 5,000 or more, more preferably 8,000 or more, even more preferably 10,000 or more, and particularly preferably 20,000 or more, and is preferably 100,000 or less, more preferably 70,000 or less, even more preferably 60,000 or less, and particularly preferably 50,000 or less.

The content of thermoplastic resin in the resin composition layer of the resin sheet used in step (1) is not particularly limited, but is preferably 0.01 to 20% by mass, more preferably 0.05 to 15% by mass, even more preferably 0.1 to 10% by mass, even more preferably 0.3 to 5% by mass, and particularly preferably 0.5 to 2% by mass, assuming that the non-volatile components in the resin composition layer are 100% by mass.

In a preferred embodiment, the resin composition layer of the resin sheet used in step (1) may contain additives such as a curing accelerator and a radical polymerization initiator.

The curing accelerator functions as a curing catalyst that accelerates the curing of thermosetting resins. Examples of curing accelerators include phosphorus-based curing accelerators, urea-based curing accelerators, guanidine-based curing accelerators, imidazole-based curing accelerators, metal-based curing accelerators, and amine-based curing accelerators. The curing accelerator preferably includes an amine-based curing accelerator or an imidazole-based curing accelerator. One type of curing accelerator may be used alone, or two or more types may be used in combination.

Examples of imidazole curing accelerators include 2-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, and 1-benzyl-2- Phenylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-phenylimidazolium trimellitate, 1-cyanoethyl-2-phenylimidazolium trimellitate, 2,4-diamino-6-[2'-methylimidazolyl -(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-undecylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-ethyl-4'-methylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine isocyanuric acid adduct, 2-phenylimidazole isocyanuric acid adduct Examples include imidazole compounds such as 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2,3-dihydro-1H-pyrrolo[1,2-a]benzimidazole, 1-dodecyl-2-methyl-3-benzylimidazolium chloride, 2-methylimidazoline, and 2-phenylimidazoline, as well as adducts of imidazole compounds with epoxy resins.

Examples of amine-based curing accelerators include trialkylamines such as triethylamine and tributylamine, 4-dimethylaminopyridine, benzyldimethylamine, 2,4,6-tris(dimethylaminomethyl)phenol, and 1,8-diazabicyclo(5,4,0)-undecene.

The radical polymerization initiator is preferably a thermal radical polymerization initiator that can generate radicals by applying thermal energy. Examples of thermal radical polymerization initiators include peroxide-based polymerization initiators and azo compound-based polymerization initiators.

Examples of peroxide polymerization initiators include dialkyl peroxide compounds such as di-t-butyl peroxide, dicumyl peroxide, and t-hexylperoxy-2-ethylhexanoate; diacyl peroxide compounds such as lauroyl peroxide, benzoyl peroxide, benzoyltoluyl peroxide, and toluyl peroxide; perester compounds such as t-butyl peracetate, t-butyl peroxyoctoate, and t-butyl peroxybenzoate; ketone peroxide compounds; peroxycarbonate compounds; and peroxyketal compounds such as 1,1-di(t-amylperoxy)cyclohexane.

Examples of azo compound polymerization initiators include azonitrile compounds such as 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(isobutyronitrile), 2,2'-azobis(2-methylbutyronitrile), and 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile); azoamide compounds such as 2,2'-azobis{2-methyl-N-[1,1-bis(hydroxymethyl)-2-hydroxyethyl]propionamide}; 2, Examples include azoamidine compounds such as 2'-azobis(2-amidinopropane) dihydrochloride and 2,2'-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride; azoalkane compounds such as 2,2'-azobis(2,4,4-trimethylpentane) and 4,4'-azobis(4-cyanopentanoic acid); azo compounds having an oxime skeleton such as 2,2'-azobis(2-methylpropionamidoxime); and 2,2'-azobis(isobutyrate) dimethyl;

The content of additives in the resin composition layer of the resin sheet used in step (1) is not particularly limited, but is preferably 0.001 to 5% by mass or less, more preferably 0.001 to 1% by mass or less, even more preferably 0.01 to 0.5% by mass, and particularly preferably 0.02 to 0.2% by mass, assuming that the non-volatile components in the resin composition layer are 100% by mass.

In addition to the non-volatile components described above, the resin composition of the present invention may further contain an optional organic solvent as a volatile component. Any known organic solvent may be used as appropriate, and the type is not particularly limited. Examples of organic solvents include ketone-based solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; ester-based solvents such as methyl acetate, ethyl acetate, butyl acetate, isobutyl acetate, isoamyl acetate, methyl propionate, ethyl propionate, and γ-butyrolactone; ether-based solvents such as tetrahydrofuran, 1,4-dioxane, diethyl ether, diisopropyl ether, dibutyl ether, and anisole; alcohol-based solvents such as methanol, ethanol, propanol, butanol, and ethylene glycol; and ether esters such as 2-ethoxyethyl acetate, propylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, ethyl diglycol acetate, γ-butyrolactone, and methyl methoxypropionate. Examples of suitable organic solvents include ester-based solvents; ester alcohol-based solvents such as methyl lactate, ethyl lactate, and methyl 2-hydroxyisobutyrate; ether alcohol-based solvents such as 2-methoxypropanol, 2-methoxyethanol, 2-ethoxyethanol, propylene glycol monomethyl ether, and diethylene glycol monobutyl ether (butyl carbitol); amide-based solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, and N-methyl-2-pyrrolidone; sulfoxide-based solvents such as dimethyl sulfoxide; nitrile-based solvents such as acetonitrile and propionitrile; aliphatic hydrocarbon-based solvents such as hexane, cyclopentane, cyclohexane, and methylcyclohexane; and aromatic hydrocarbon-based solvents such as benzene, toluene, xylene, ethylbenzene, and trimethylbenzene. These organic solvents may be used singly or in combination of two or more in any ratio.

The resin sheet can be produced, for example, by applying a varnish-like resin composition to a support using a die coater or the like, and then drying to form a resin composition layer. Drying for producing the resin sheet may be carried out by known methods such as heating or hot air blowing. For example, a resin composition layer can be formed by drying at 50°C to 150°C, preferably 80°C to 120°C, for 1 minute to 60 minutes, preferably 3 minutes to 10 minutes. The content of organic solvent in the varnish-like resin composition to be applied to a support is not particularly limited, but is preferably 40% by mass or less, more preferably 30% by mass or less, even more preferably 20% by mass or less, and particularly preferably 10% by mass or less, assuming that all components in the resin composition are 100% by mass.

The present invention will be explained in more detail below using examples. The present invention is not limited to these examples. In the following, "parts" and "%" used to express amounts refer to "parts by mass" and "% by mass," respectively, unless otherwise specified. Unless otherwise specified, the temperature conditions are room temperature (23°C), and unless otherwise specified, the pressure conditions are atmospheric pressure (1 atm).

<Production Example 1: Preparation of Resin Sheet 1>
8 parts of tetramethylbisphenol type epoxy resin ("YX4000H" manufactured by Mitsubishi Chemical Corporation, epoxy equivalent 194 g/eq.), 10 parts of biphenylaralkyl type epoxy resin ("NC3000L" manufactured by Nippon Kayaku Co., Ltd., epoxy equivalent approximately 271 g/eq.), 2 parts of naphthalene type epoxy resin ("HP6000L" manufactured by DIC Corporation, epoxy equivalent approximately 213 g/eq.), 2 parts of bifunctional epoxy resin ("ZX1658GS" manufactured by Nippon Steel Chemical Co., Ltd., epoxy equivalent approximately 133 g/eq.), 4 parts of phenolic curing agent having a triazine skeleton and a cresol novolac structure ("LA-3018-50P" manufactured by DIC Corporation, phenol equivalent approximately 151, 2-methoxypropanol solution with a solid content of 50% by mass), 4 parts of activated ester resin ("H" manufactured by DIC Corporation, phenol equivalent approximately 151, 2-methoxypropanol solution with a solid content of 50% by mass), A varnish-like resin composition was prepared by adding 6 parts of phenoxy resin (Mitsubishi Chemical Corporation's "YL7800BH40", MEK and cyclohexane solution with a solid content of 40% by mass), 2 parts of phenoxy resin (Mitsubishi Chemical Corporation's "YL7800BH40", MEK and cyclohexane solution with a solid content of 40% by mass), and 50 parts of silica (Admatechs Co., Ltd.'s "SO-C2", average particle size 0.5 μm, surface treatment amount: 0.6% by mass of amino silane coupling agent relative to 100% by mass of silica), and 1 part of a curing accelerator ("DMAP-5M", MEK solution with a solid content of 5% by mass of 1,4-dimethylaminopyridine). Next, the varnish-like resin composition was uniformly applied to a PET film ("AL5" manufactured by Lintec Corporation, thickness 38 μm) using a die coater so that the thickness after drying would be 25 μm, and the film was dried at 100°C for 5 minutes to produce resin sheet 1.

<Production Example 1': Preparation of Resin Sheet 1'>
Resin sheet 1' was produced in the same manner as resin sheet 1 in Production Example 1, except that the varnish-like resin composition was applied to a copper foil with a carrier "MT18FL (thin copper foil thickness 3 μm)" manufactured by Mitsui Mining & Smelting Co., Ltd. instead of being applied to a PET film ("AL5" manufactured by Lintec Corporation, thickness 38 μm).

<Production Example 2: Preparation of Resin Sheet 2>
Resin sheet 2 was produced in the same manner as in Resin sheet 1 of Production Example 1, except that the amount of surface-treated silica added was changed from 50 parts to 40 parts.

<Production Example 3: Preparation of Resin Sheet 3>
Resin sheet 3 was produced in the same manner as resin sheet 1 in Production Example 1, except that the amount of surface-treated silica added was changed from 50 parts to 100 parts.

<Production Example 4: Preparation of Resin Sheet 4>
Resin sheet 4 was produced in the same manner as resin sheet 1 in Production Example 1, except that the amount of surface-treated silica added was changed from 50 parts to 120 parts.

<Production Example 5: Preparation of Resin Sheet 5>
Resin sheet 5 was produced in the same manner as resin sheet 1 in Production Example 1, except that instead of adding both the phenolic curing agent having a triazine skeleton and a cresol novolac structure and the active ester, 20 parts of a cyanate ester ("BA230S" manufactured by Lonza, cyanate ester equivalent 139 g/eq., MEK solution with a solids content of 75 mass %) was added, and further, the amount of surface-treated silica added was changed from 50 parts to 80 parts.

<Production Example 6: Preparation of Resin Sheet 6>
5 parts of polyphenylene ether resin ("OPE-2S" manufactured by Mitsubishi Gas Chemical Co., Ltd., vinyl equivalent 590 g/eq., toluene solution with a solid content of 65% by mass), 5 parts of maleimide resin ("BMI-689" manufactured by Designer Molecules, maleimide equivalent 345 g/eq.), 10 parts of biphenylaralkyl maleimide resin ("MIR-3000-70MT" manufactured by Nippon Kayaku Co., Ltd., maleimide equivalent 393 g/eq., MEK and toluene solution with a solid content of 70% by mass), 5 parts of liquid acrylate resin ("A-DOG" manufactured by Shin-Nakamura Chemical Co., Ltd., vinyl group equivalent approximately 163 g/eq.), copolymer A varnish-like resin composition was prepared by adding 2 parts of a 30 wt % toluene solution of a polymer elastomer ("P2000" manufactured by Asahi Kasei Corporation), 40 parts of silica ("SO-C2" manufactured by Admatechs Co., Ltd., average particle size 0.5 μm, surface treatment amount: 0.6% by mass of amino silane coupling agent per 100% by mass of silica) surface-treated with an amino silane coupling agent ("KBM573" manufactured by Shin-Etsu Chemical Co., Ltd., N-phenyl-3-aminopropyltrimethoxysilane), and 1 part of a peroxide-based polymerization initiator ("Perhexyne 25B" manufactured by NOF Chemical Co., Ltd., 10% by mass solids toluene solution) to the solution. The varnish-like resin composition was then uniformly applied to a PET film ("AL5" manufactured by Lintec Corporation, thickness 38 μm) using a die coater to a thickness of 25 μm after drying, and then dried at 100° C. for 5 minutes to produce a resin sheet 6.

Example 1
(Lamination process)
The resin sheet 1 obtained in Production Example 1 was superimposed so that a polyimide film ("Kapton H" manufactured by DuPont-Toray Co., Ltd., thickness 50 μm) was in contact with the surface of the resin composition layer, and after vacuum suction at 120°C for 30 seconds using a vacuum pressure laminator ("MVLP-700" manufactured by Meiki Seisakusho Co., Ltd.), the laminate was laminated by pressing the support (PET film) onto the support via heat-resistant rubber for 30 seconds under vacuum at 120°C and a pressure of 0.7 MPa.

(drying process)
After lamination, the resin composition layer was dried at 120° C. for 10 minutes without peeling off the support.

(Peeling process)
After drying, the support was peeled off from the resin sheet.

(Thermal compression bonding process)
After peeling off the support, a copper foil with a carrier "MT18FL (thin copper foil thickness 3 μm)" manufactured by Mitsui Mining & Smelting Co., Ltd. was superimposed on the surface of the resin composition layer so that the thin copper foil side was in contact with the resin composition layer, and using a test press device "KVHC" manufactured by Kitagawa Seiki Co., Ltd., the foil was evacuated to 1.0 MPa and heated from 25°C at a rate of 5°C per minute, and then heated and pressed at a temperature of 200°C for 120 minutes to flatten and harden the copper foil with a carrier, thereby laminating it on the resin composition layer, and an evaluation sample was obtained.

Example 2
An evaluation sample was obtained in the same manner as in Example 1, except that the drying conditions in the drying step of the resin composition layer were changed from 120° C. for 10 minutes to 120° C. for 30 minutes.

Example 3
(Lamination process)
The resin sheet 1 obtained in Example 1 was superimposed so that a polyimide film ("Kapton H" manufactured by DuPont-Toray Co., Ltd., thickness 50 μm) was in contact with the surface of the resin composition layer, and after vacuum suction at 120°C for 30 seconds using a vacuum pressure laminator ("MVLP-700" manufactured by Meiki Seisakusho Co., Ltd.), the sheet was laminated by pressing it onto the support (PET film) via heat-resistant rubber for 30 seconds under vacuum at 120°C and a pressure of 0.7 MPa.

(Peeling process)
After lamination, the support was peeled off from the resin sheet.

(drying process)
After the support was peeled off, the temperature was raised and the resin composition layer was dried at 120° C. for 10 minutes.

(Thermal compression bonding process)
After drying, a copper foil with a carrier "MT18FL (thin copper foil thickness: 3 μm)" manufactured by Mitsui Mining & Smelting Co., Ltd. was superimposed on the surface of the resin composition layer so that the thin copper foil side was in contact with the resin composition layer, and using a test press device "KVHC" manufactured by Kitagawa Seiki Co., Ltd., the foil was heated at 1.0 MPa under vacuum from 25°C at a rate of 5°C per minute, and then heated and pressed at a temperature of 200°C for 120 minutes to flatten and harden the foil, thereby laminating the copper foil with a carrier on the resin composition layer and obtaining an evaluation sample.

Example 4
An evaluation sample was obtained in the same manner as in Example 1, except that the resin composition 2 obtained in Production Example 2 was used instead of the resin sheet 1 obtained in Production Example 1.

Example 5
An evaluation sample was obtained in the same manner as in Example 1, except that the resin composition 3 obtained in Production Example 3 was used instead of the resin sheet 1 obtained in Production Example 1.

Example 6
An evaluation sample was obtained in the same manner as in Example 1, except that the resin composition 4 obtained in Production Example 4 was used instead of the resin sheet 1 obtained in Production Example 1.

Example 7
An evaluation sample was obtained in the same manner as in Example 1, except that the resin composition 5 obtained in Production Example 5 was used instead of the resin sheet 1 obtained in Production Example 1.

Example 8
An evaluation sample was obtained in the same manner as in Example 1, except that the resin composition 6 obtained in Production Example 6 was used instead of the resin sheet 1 obtained in Production Example 1.

<Comparative Example 1>
(Lamination process)
The resin sheet 1' obtained in Production Example 1' was superimposed so that a polyimide film ("Kapton H" manufactured by DuPont-Toray Co., Ltd., thickness 50 μm) was in contact with the resin composition layer surface, and using a vacuum pressure laminator ("MVLP-700" manufactured by Meiki Seisakusho Co., Ltd.), vacuum suction was performed at 120°C for 30 seconds, and then the laminate was laminated on top of a support (copper foil with a carrier) by pressing it together for 30 seconds via heat-resistant rubber under conditions of 120°C and a pressure of 0.7 MPa under vacuum.

(drying process)
After lamination, an attempt was made to dry the resin composition layer at 120° C. for 10 minutes without peeling off the support.

(Thermal compression bonding process)
After drying, the resin sheet with copper foil laminated on the polyimide film was subjected to a vacuum test using a test press machine "KVHC" manufactured by Kitagawa Seiki Co., Ltd., at a pressure of 1.0 MPa, and heated from room temperature at a rate of 5°C each time. The resin sheet was then heated and pressed at 200°C for 120 minutes to be flattened and hardened, thereby obtaining an evaluation sample.

<Comparative Example 2>
The resin sheet 1' obtained in Manufacturing Example 1' was superimposed so that a polyimide film ("Kapton H" manufactured by DuPont-Toray Co., Ltd., thickness 50 μm) was in contact with the resin composition layer surface, and using a test press device "KVHC" manufactured by Kitagawa Seiki Co., Ltd., the sheet was vacuumed to 1.0 MPa, heated from room temperature by 5°C per degree, and heated and pressed at a temperature of 120°C for 30 minutes to obtain an evaluation sample.

<Comparative Example 3>
An evaluation sample was obtained in the same manner as in Example 1, except that the resin composition 2 obtained in Production Example 2 was used instead of the resin sheet 1 obtained in Production Example 1, and the drying process of the resin composition layer was not performed, and the support was peeled off immediately after lamination.

<Comparative Example 4>
An evaluation sample was obtained in the same manner as in Example 1, except that the drying conditions in the drying step of the resin composition layer were 120° C. for 30 minutes.

<Test Example 1: Measurement of Melt Viscosity>
The carrier-attached copper foil and polyimide film were peeled from the evaluation samples prepared in the Examples and Comparative Examples before the lamination process and before thermocompression bonding to obtain 1.2 g of resin samples. The minimum melt viscosity of the obtained resin samples was measured using a dynamic viscoelasticity measuring device ("Rheosol-G3000" manufactured by U.B.M. Co.). Specifically, the temperature was raised in a temperature range from a starting temperature of 60°C to 200°C, and the dynamic viscoelastic modulus was measured, and the minimum melt viscosity (poise) before the lamination process and before thermocompression bonding was calculated, respectively. The minimum melt viscosity before thermocompression bonding was evaluated according to the following evaluation criteria. The measurement conditions were a temperature rise rate of 5°C/min, a measurement temperature interval of 2.5°C, a vibration frequency of 1 Hz, and a strain of 1 deg.

Evaluation criteria:
◯: The minimum melt viscosity is 3,500 poise or more and 10,000 poise or less. Δ: The minimum melt viscosity is 2,000 poise or more and less than 3,500 poise, or more than 10,000 poise and 20,000 poise or less. ×: The minimum melt viscosity is less than 2,000 poise, or more than 20,000 poise.

<Test Example 2: Measurement of resin film thickness after lamination>
The polyimide film and carrier copper foil were peeled off from the evaluation samples after thermocompression bonding produced in the Examples and Comparative Examples, and the thicknesses of the resin and thin copper were measured using a high-precision Digimatic Micrometer (MDH-25MB) manufactured by Mitutoyo Corporation. The resin thickness was calculated by subtracting the thickness of the thin copper (3 μm), and evaluated based on the following evaluation criteria.

Evaluation criteria:
○: Resin film thickness is greater than 12 μm (no voids found in visual appearance inspection)
△: Resin film thickness is greater than 10 μm and less than 12 μm (no voids found in visual appearance inspection)
×: Resin film thickness is 10 μm or less (no voids in visual appearance inspection)
××: Voids found during visual inspection

<Test Example 3: Measurement of Glass Transition Temperature>
The polyimide film and carrier copper foil were peeled off from the evaluation samples after thermocompression bonding prepared in the Examples and Comparative Examples, and the resulting cured products were measured in "tensile mode" using a Seiko Instruments Inc. DMS-6100 thermomechanical analyzer (DMA). The measurement was carried out in the range of 25°C to 240°C with a temperature increase rate of 5°C/min. The glass transition temperature (Tg) was evaluated based on the following evaluation criteria.

Evaluation criteria:
◯: Tg is 150°C or higher △: Tg is 140°C or higher but less than 150°C ×: Tg is less than 140°C

<Test Example 4: Measurement of organic solvent content before heat and pressure bonding>
The amount of residual solvent in the resin sheet obtained in the production example before the lamination step and before the thermocompression bonding step was calculated by drying the resin sheet at 130°C for 15 minutes and measuring the weight before and after drying.

<Test Example 5: Measurement of adhesion strength to copper foil>
The carrier copper foil was peeled from the evaluation samples after thermocompression bonding produced in the Examples and Comparative Examples, and an electrolytic copper plating process was performed using a chemical solution manufactured by Atotech Japan to achieve a copper thickness of 25 μm. A 10 mm wide and 100 mm long cut was made in the plated conductor layer (second conductor layer), and one end of the cut was peeled off and gripped with a gripper. The load [kgf/cm (N/cm)] when 35 mm was peeled off vertically at a rate of 50 mm/min at room temperature (25°C) was measured. A tensile tester ("AC-50C-SL" manufactured by TSE Corporation) was used for the measurement.

Evaluation criteria:
Void: When voids occur. ◯: Adhesion strength with copper foil is 0.6 kgf/cm or more (no voids occur).
×: Adhesion strength to copper foil is less than 0.6 kgf/cm (no voids)

<Test Example 6: Evaluation of resin chipping during cutting>
The resin sheets of Examples 1, 4 to 8 and Comparative Example 1 were cut with a roller cutter (558N type) manufactured by DAHLE, and the cut edges were visually inspected for cracks and chips. No resin chipping was observed in the resin sheets of Examples 1 and 4 to 8, but resin chipping was observed in the resin sheets of Comparative Examples 1 and 2.

The non-volatile components and amounts used of the resin compositions of Examples 1 to 8 and Comparative Examples 1 to 4, the substrate, manufacturing conditions, measurement results for Test Examples 1 to 5, and evaluation results are summarized in Table 1 below.

The results shown in Table 1 above show that in a wiring board manufacturing method that includes the steps of laminating a resin sheet having a resin composition layer onto a substrate, peeling off the support, and thermocompressing a metal foil to the resin composition layer, if the minimum melt viscosity of the resin composition layer before thermocompression is 2,000 poise to 20,000 poise, changes in the thickness of the insulating layer can be suppressed and good metal foil adhesion and glass transition temperature can be achieved, even after a process that includes vacuum hot pressing. Furthermore, the results of Test Example 6 also show that the occurrence of resin chipping due to cutting of the resin sheet can be suppressed.

Claims (20)

(1) A step of heating and laminating a resin sheet having a support and a resin composition layer provided on the support to a substrate so that the resin composition layer of the resin sheet is bonded to the substrate;
(2) peeling the support from the resin composition layer; and (3) heating and pressing a metal foil to the resin composition layer by vacuum hot pressing,
the resin composition layer contains a thermosetting resin and an inorganic filler;
the content of the inorganic filler in the resin composition layer is 40 to 90% by mass, where the non-volatile components in the resin composition layer are 100% by mass;
In the step (3), the minimum melt viscosity of the resin composition layer before thermocompression bonding is 2,000 to 20,000 poise when measured in a temperature range of 60°C to 200° C, at a frequency of 1 Hz, and at a strain of 1 degree. The method for manufacturing a wiring board according to claim 1, further comprising the step of drying the resin composition layer (A) after step (1) and before step (2), or after step (2) and before step (3). The method for manufacturing a wiring board according to claim 1, wherein the minimum melt viscosity of the resin composition layer before lamination in step (1) is lower than the minimum melt viscosity of the resin composition before heat-pressure bonding in step (3). The method for manufacturing a wiring board according to claim 1, wherein the heating temperature during lamination in step (1) is 80 to 140°C. The method for manufacturing a wiring board according to claim 1, wherein the heating temperature during thermocompression bonding in step (3) is 170 to 230°C. The method for manufacturing a wiring board according to claim 1, wherein the pressure conditions during thermocompression bonding in step (3) are 0.5 to 2.0 MPa. The method for manufacturing a wiring board according to claim 1, wherein the thickness of the resin composition layer before lamination in step (1) is 40 μm or less. The method for manufacturing a wiring board according to claim 1, wherein the glass transition temperature of the resin composition layer after heat-pressure bonding in step (3) is 140°C or higher. The method for manufacturing a wiring board according to claim 1, wherein the thickness of the resin composition layer after heat and pressure bonding in step (3) exceeds 10 μm. The method for manufacturing a wiring board according to claim 1, wherein the thickness reduction rate of the resin composition layer after heat-pressure bonding in step (3) relative to the resin composition layer before lamination in step (1) is 40% or less. The method for manufacturing a wiring board according to claim 1, wherein the content of organic solvent in the resin composition layer before heat-pressure bonding in step (3) is 0.3 to 2.5% by mass, where the total amount of all components in the resin composition layer is 100% by mass. The method for manufacturing a wiring board according to claim 1, wherein the support is a plastic film. (4) The method for manufacturing a wiring board according to claim 1, further comprising the step of forming a circuit pattern from a metal foil by a subtractive method. (4') A method for producing a wiring board according to claim 1, further comprising the step of forming a circuit pattern from a metal foil by a modified semi-additive process. 2. The method for producing a wiring board according to claim 1 , wherein the thermosetting resin comprises a thermosetting resin selected from the group consisting of epoxy resin, cyanate ester resin, maleimide resin, and thermosetting modified polyphenylene ether resin. 2. The method for producing a wiring board according to claim 1 , wherein the content of the inorganic filler in the resin composition layer is 40 to 75% by mass, where the non-volatile components in the resin composition layer are 100% by mass. The method for manufacturing a wiring board according to claim 1, wherein the resin composition layer contains a thermoplastic resin. 18. The method for producing a wiring board according to claim 17 , wherein the thermoplastic resin comprises a thermoplastic resin selected from thermoplastic polyimide resin, polycarbonate resin, phenoxy resin, polyvinyl acetal resin, and copolymers. The method for producing a wiring board according to claim 18 , wherein the copolymer is a copolymer obtained by polymerizing two or more monomers selected from styrene, ethylene, propylene, isoprene, butadiene, acrylate, and methacrylate, or a hydrogenated product thereof. The method for producing a wiring board according to claim 17 , wherein the thermoplastic resin has a weight average molecular weight of 5,000 to 100,000.