JP7813566B2 - Laminate and metal-clad laminate using same - Google Patents

Description

This disclosure relates to a laminate and a metal-clad laminate using the same.

In recent years, with the remarkable advances in information network technology and the expansion of services utilizing information networks, electronic devices are being required to handle larger amounts of information and faster processing speeds. To meet these demands, printed wiring boards used in electronic devices are now strongly required to have low dielectric constants and low dielectric dissipation factors in addition to the traditional properties of insulation reliability, heat resistance, rigidity, flame retardancy, etc. Accordingly, further improvements in the dielectric constants and dielectric dissipation factors of resin compositions (hereinafter also referred to as "matrix resin compositions") and glass cloth, which are the main insulating materials that make up printed wiring boards, are being investigated.

As a matrix resin composition, a mixture containing polyphenylene ether (hereinafter also referred to as "PPE"), which has a low dielectric constant, dielectric dissipation factor, and high heat resistance, and other resins is preferably used as the material for the above-mentioned printed wiring board. For example, Patent Document 1 describes a resin composition containing a specific modified polyphenylene ether, a specific cyanurate compound as a crosslinking agent, a copolymer of butadiene and styrene, and an organic peroxide in specified proportions, which results in a matrix resin composition with an excellent low dielectric constant and low dielectric dissipation factor.

As the glass cloth, low-dielectric-constant glass cloth such as NE glass or L glass, which has a composition different from that of general E glass, is preferably used. Generally, to lower the dielectric constant, it is necessary to increase the amount of SiO ₂ and B ₂ O ₃ in the glass composition. To date, low-dielectric-constant glass compositions actually used in glass cloth for printed wiring boards have often been adjusted to contain SiO ₂ in an amount of 45% to 60% by mass and B ₂ O ₃ in an amount of 15% to 30% by mass (Patent Documents 2 and 3). Meanwhile, the use of organic fiber cloth as a low-dielectric-constant substrate other than glass cloth has been investigated (Patent Documents 4 and 5).

JP 2017-82200 A Japanese Patent Application Publication No. 63-2831 Japanese Patent Application Publication No. 11-292567 Special Publication No. 2017-502179 Japanese Patent Application Laid-Open No. 2008-069478

Kono Kenya, Naka Yasuhiro, Tanie Takashi, Kimoto Ryosuke, and Yamamoto Kenichi, "Fatigue Life Prediction Method for Solder Joints Considering High-Temperature Degradation," Journal of the Japan Institute of Electronics Packaging, 17(2), 2014, pp. 123-131

However, with future high-speed transmissions of 200 Gbps or more, the problem of signal skew (skew) is becoming apparent. This problem is primarily caused by local variations in the dielectric constant of the insulating layer of the substrate. While the dielectric constant of a typical low-dielectric constant matrix resin composition is approximately 2.0 to 3.0, that of low-dielectric constant glass cloth is approximately 4.6 to 4.8. Local variations in the dielectric constant of low-dielectric constant glass cloth within the substrate are becoming a major problem. Furthermore, even when organic fiber cloth is used, as described in Patent Documents 4 and 5, a sufficiently low thermal expansion coefficient and heat resistance are not achieved for the cloth, prepreg, or laminate. Thus, when a prepreg or laminate is produced by combining a low-dielectric constant resin composition and a low-dielectric constant glass cloth, the dielectric constant uniformity of the insulating layer required for high-speed transmission cannot be achieved. Even when organic fiber cloth is used, a sufficiently low thermal expansion coefficient and heat resistance are not achieved for the cloth, prepreg, or laminate.

The objective of this disclosure is to provide a laminate that has excellent dielectric constant, dielectric dissipation factor, and dielectric constant uniformity, as well as a low coefficient of thermal expansion and excellent heat resistance.

The inventors have discovered that in a laminate having a core layer including a first resin layer having a glass fiber cloth and a surface layer including a second resin layer having an organic fiber cloth, the above-mentioned problems can be solved by making the thermal expansion coefficient of the second resin layer larger than the thermal expansion coefficient of the first resin layer. Examples of embodiments of the present disclosure are listed in the following items [1] to [19].
[1]
a core layer including at least one first resin layer in which a glass fiber cloth is impregnated or coated with a first matrix resin;
a surface layer laminated on one or both sides of the core layer and including at least one second resin layer in which a second matrix resin is impregnated or coated into an organic fiber cloth,
A laminate in which the thermal expansion coefficient of the second resin layer is greater than the thermal expansion coefficient of the first resin layer.
[2]
Item 2. The laminate according to item 1, wherein the thermal expansion coefficient of the first resin layer is 3 ppm/°C or more and less than 20 ppm/°C, and the thermal expansion coefficient of the second resin layer is 18 ppm/°C or more and 200 ppm/°C or less.
[3]
3. The laminate according to item 1 or 2, wherein the surface layers are laminated on both sides of the core layer.
[4]
4. The laminate according to any one of items 1 to 3, wherein the fibers of the organic fiber cloth are fibers composed of a resin composition containing polyphenylene ether.
[5]
Item 5. The resin composition containing polyphenylene ether comprises, based on the total mass of the resin composition, 5% by mass to 95% by mass of polyphenylene ether and 5% by mass to 95% by mass of at least one selected from liquid crystal polyester and syndiotactic polystyrene.
[6]
Item 6. The laminate according to any one of items 1 to 5, wherein the thermal expansion coefficient of the first resin layer is 3 ppm/°C or more and less than 20 ppm/°C, and the thermal expansion coefficient of the second resin layer is 20 ppm/°C or more and 150 ppm/°C or less.
[7]
7. The laminate according to any one of items 1 to 6, wherein the core layer comprises two or more of the first resin layers.
[8]
8. The laminate according to any one of items 1 to 7, wherein the number of layers of the first resin layer included in the core layer is greater than the number of layers of the second resin layer included in the surface layer.
[9]
Item 9. The laminate according to any one of items 1 to 8, wherein the dielectric constant of the second matrix resin contained in the surface layer is 2.0 or more and 3.0 or less, and the dielectric constant of the organic fiber cloth is 2.0 or more and 3.0 or less.
[10]
10. A metal-clad laminate comprising the laminate according to any one of items 1 to 9 and a metal foil laminated on the surface layer of the laminate.
[11]
a step of laminating at least one first prepreg obtained by impregnating or coating a glass fiber cloth with a first matrix resin and at least one second prepreg obtained by impregnating or coating an organic fiber cloth with a second matrix resin to prepare a prepreg laminate comprising a core layer including the at least one first prepreg and surface layers including the at least one second prepreg laminated on one or both sides of the core layer;
curing the first matrix resin and the second matrix resin;
A method for manufacturing a laminate, comprising:
The method for producing a laminate, wherein the second prepreg has a larger thermal expansion coefficient than the first prepreg.
[12]
Item 12. The method according to item 11, wherein the first prepreg has a thermal expansion coefficient of 3 ppm/°C or more and less than 20 ppm/°C, and the second prepreg has a thermal expansion coefficient of 18 ppm/°C or more and 200 ppm/°C or less.
[13]
13. The method according to item 11 or 12, wherein the surface layers are laminated to both sides of the core layer.
[14]
14. The method according to any one of items 11 to 13, wherein the fibers of the organic fiber cloth are fibers composed of a resin composition containing polyphenylene ether.
[15]
Item 15. The method according to item 14, wherein the resin composition containing polyphenylene ether comprises 5% by mass to 95% by mass of polyphenylene ether and 5% by mass to 95% by mass of at least one selected from liquid crystal polyester and syndiotactic polystyrene, based on the total mass of the resin composition.
[16]
16. The method according to any one of items 11 to 15, wherein the first prepreg has a thermal expansion coefficient of 3 ppm/°C or more and less than 20 ppm/°C, and the second prepreg has a thermal expansion coefficient of 20 ppm/°C or more and 150 ppm/°C or less.
[17]
17. The method according to any one of items 11 to 16, wherein two or more layers of the first prepreg are laminated to the core layer.
[18]
Item 18. The method according to any one of items 11 to 17, wherein the number of layers of the first prepreg laminated on the core layer is greater than the number of layers of the second prepreg laminated on the surface layer.
[19]
19. The method according to any one of items 11 to 18, wherein the dielectric constant of the second matrix resin contained in the surface layer is 2.0 or more and 3.0 or less, and the dielectric constant of the organic fiber cloth is 2.0 or more and 3.0 or less.

This disclosure makes it possible to provide a laminate that has excellent dielectric constant, dielectric dissipation factor, and dielectric constant uniformity, as well as an excellent low coefficient of thermal expansion and heat resistance.

FIG. 1 is a schematic diagram showing a cross section of a laminated plate according to the present disclosure. FIG. 2 is a schematic diagram showing a cross section of a laminate of the present disclosure. FIG. 3 is a schematic diagram showing a cross section of a laminated plate according to the present disclosure. FIG. 4 is a schematic diagram showing a cross section of a laminated plate according to the present disclosure. FIG. 5 is a schematic diagram showing a cross section of a metal-clad laminate according to the present disclosure. FIG. 6 is a schematic diagram showing the stack structure of a laminate for a temperature cycle test by computer simulation according to an embodiment of the present invention. FIG. 7 is a schematic diagram showing the layer structure of a laminate for evaluating electrical signal delay in the surface layer by computer simulation in an embodiment.

Embodiments of the present disclosure will be described below with reference to the drawings as necessary. In the following description of the drawings, identical or similar parts are designated by identical or similar reference numerals. However, the drawings are schematic, and the relationship between thickness and planar dimensions, etc., may differ from reality. Furthermore, the embodiments shown below are examples of devices and methods that embody the technical ideas of the present disclosure, and the technical ideas of the present disclosure do not specify the materials, shapes, structures, arrangements, etc. of the components described below. The technical ideas of the present disclosure may be modified in various ways within the technical scope defined by the claims. Furthermore, in this specification, unless otherwise specified, the term "to" includes the numerical values at both ends as upper and lower limits. In this specification, the upper and lower limits of numerical ranges can be combined arbitrarily.

<Laminate>
The laminate disclosed herein comprises a core layer including at least one first resin layer formed by impregnating or coating a glass fiber cloth with a first matrix resin; and a surface layer laminated on one or both sides of the core layer and including at least one second resin layer formed by impregnating or coating an organic fiber cloth with a second matrix resin. The second resin layer has a thermal expansion coefficient greater than that of the first resin layer. The dielectric constant of the organic fiber cloth is closer to that of the low-dielectric-constant matrix resin than that of the glass fiber cloth, thereby reducing local variations in the dielectric constant within the laminate. By providing a second resin layer containing such organic fiber cloth as a surface layer, local variations in the dielectric constant, mainly near the surface of the laminate, are reduced, thereby reducing signal skew (skew) during high-speed transmission. Furthermore, by providing a first resin layer containing glass fiber cloth as a core layer, the laminate as a whole can achieve a sufficiently low thermal expansion coefficient and heat resistance.

The thermal expansion coefficient of the second resin layer is greater than that of the first resin layer. In other words, if the thermal expansion coefficient of the first resin layer is CTE1 and the thermal expansion coefficient of the second resin layer is CTE2, then the condition CTE2 > CTE1 is satisfied. This allows the thermal expansion coefficient of the entire laminate to be equal to or greater than that of the solder, thereby alleviating strain on the solder caused by temperature cycles when electronic components are mounted. If the thermal expansion coefficient of the laminate is small, the solder is compressed by both the electronic components mounted on the laminate and the laminate. However, if the thermal expansion coefficient of the laminate is equal to or greater than that of the solder, the solder is compressed from the mounted component side and expanded from the laminate side. This structural change alleviates strain on the solder caused by temperature cycles, extending the reliability life of the solder cracks and improving temperature cycle reliability. CTE2 is preferably 10 times or less than CTE1, more preferably 8 times or less than CTE1, even more preferably 6 times or less than CTE1, and particularly preferably 4 times or less than CTE1.

The core layer can have one or more first resin layers, and the surface layer can have one or more second resin layers. The laminate structure is not particularly limited, as long as it has a first resin layer containing the above-mentioned glass fiber cloth as the core layer and a second resin layer containing an organic fiber cloth as the surface layer. For example, Figures 1 to 4 are schematic diagrams showing the cross section of a laminated board of the present disclosure. In Figure 1, the laminated board (100) has a core layer (10) consisting of two first resin layers (1) in which a first matrix resin is impregnated or applied to a glass fiber cloth, and a surface layer (20) laminated on both sides of the core layer (10) and consisting of one second resin layer in which a second matrix resin is impregnated or applied to an organic fiber cloth. In Figure 2, the laminated board (100) has a core layer (10) consisting of two first resin layers (1) and a surface layer (20) consisting of two second resin layers laminated on one side of the core layer (10). In Figure 3, the laminate (100) has a core layer (10) consisting of five first resin layers (1) and a surface layer (20) consisting of two second resin layers laminated on both sides of the core layer (10). In Figure 4, the laminate (100) has a core layer (10) consisting of five first resin layers (1) and a surface layer (20) consisting of two second resin layers laminated on one side of the core layer (10). In this way, by placing a surface layer containing organic fiber cloth on a core layer containing glass fiber cloth, the thermal expansion coefficient of the entire laminate can be reduced. In addition, the delay difference between electrical signals for each wiring on the laminate due to variations in dielectric constant can be reduced.

To more effectively reduce the thermal expansion coefficient of the laminate, it is preferable that the number of first resin layers in the core layer be two or more. Examples of such laminate structures are shown in Figures 1 to 4. By making the number of first resin layers in the core layer two or more, the mechanical strength of the core layer can be increased, and heat resistance can be further improved by reducing warping of the laminate caused by uneven dimensional change between the core layer and the surface layer. From a manufacturing perspective, it is preferable that the number of first resin layers in the core layer be 80 or less. More preferably, the number of first resin layers is 2 to 80, even more preferably 4 to 64, and particularly preferably 8 to 32.

To more effectively reduce the thermal expansion coefficient of the laminate, it is preferable to satisfy the condition m/n<1, where n is the number of first resin layers in the core layer and m is the number of second resin layers in the surface layer. In other words, it is preferable that the number of first resin layers included in the core layer is greater than the number of second resin layers included in the surface layer. Examples of such a laminate structure are shown in Figures 3 and 4. By satisfying this condition, the thermal expansion coefficient of the core layer can dominate the thermal expansion coefficient of the entire laminate, thereby increasing the effect of suppressing the thermal expansion of the surface layers and further reducing the thermal expansion coefficient of the laminate as a whole.

To more effectively reduce the thermal expansion coefficient of the laminate, it is preferable for the surface layers to be laminated on both sides of the core layer. It is even more preferable for the core layer and surface layers to be symmetrically positioned relative to the centerline that bisects the thickness of the laminate in its cross section. Examples of such a laminate structure are shown in Figures 1 and 3. By laminating surface layers on both sides of the core layer, it is possible to reduce the non-uniformity of dimensional change due to temperature changes on both sides, enabling a uniform reduction in the thermal expansion coefficient of the laminate. It is also possible to reduce warping of the laminate that occurs due to non-uniformity of dimensional change. By symmetrically positioning the core layer and surface layers, it is possible to reduce or eliminate the non-uniformity of dimensional change on both sides, achieving a similar thermal expansion suppression effect on both sides. Achieving similar effects on both sides enables a uniform reduction in the thermal expansion coefficient of the laminate. It is also possible to reduce warping of the laminate that occurs due to non-uniformity of dimensional change, improving reliability.

The thickness of the laminate is preferably 1.0 mm or more and 8.0 mm or less. More preferably, it is 1.2 mm or more and 6.4 mm or less, even more preferably, it is 1.4 mm or more and 5.6 mm or less, and particularly preferably, it is 1.6 mm or more and 4.2 mm or less. When the thickness of the laminate is within the above range, it is possible to obtain a laminate that is particularly well balanced between mechanical strength and productivity and is suitable for circuit boards.

The thermal expansion coefficient in the plane direction of the second resin layer forming the surface layer is preferably 8 ppm/°C to 300 ppm/°C, more preferably 14 ppm/°C to 250 ppm/°C, even more preferably 18 ppm/°C to 200 ppm/°C, and even more preferably 20 ppm/°C to 150 ppm/°C. When the thermal expansion coefficient of the second resin layer forming the surface layer is within the above range, the thermal expansion coefficient of the laminate when laminated with the core layer can be made equal to or greater than that of the solder. This can effectively alleviate strain on the solder caused by temperature cycles when mounted on electronic components. If the thermal expansion coefficient of the laminate is small, the solder will be compressed from both the electronic components mounted on the laminate and the laminate itself. However, if the thermal expansion coefficient of the laminate is equal to or greater than that of the solder, the solder will be compressed from the mounted component side and expanded from the laminate side. This structural change can mitigate the strain on the solder caused by temperature cycling, extending the reliability life of the solder cracks and further improving temperature cycle reliability.

The thermal expansion coefficient in the plane direction of the first resin layer that forms the core layer is preferably 1 ppm/°C or more and 100 ppm/°C or less, more preferably 2 ppm/°C or more and 50 ppm/°C or less, and even more preferably 3 ppm/°C or more and less than 20 ppm/°C. This allows the thermal expansion coefficient of the laminate to approach that of the solder, thereby extending the reliability life of the solder cracks. In this specification, unless otherwise specified, the thermal expansion coefficient refers to the average linear expansion coefficient in the range of 50°C or more and 150°C or less.

The first matrix resin used in the first resin layer that forms the core layer and the second matrix resin used in the second resin layer that forms the surface layer may be different compositions or the same composition, and it is preferable that they be made of the same composition. Using the same composition improves the adhesion at the interface between the first resin layer and the second resin layer, prevents delamination due to stress between the first resin layer and the second resin layer that occurs during temperature cycling, and extends the reliable lifespan.

<Method of manufacturing laminate>
The method for manufacturing a laminate disclosed herein first prepares at least one first prepreg formed by impregnating or coating a glass fiber cloth with a first matrix resin, and at least one second prepreg formed by impregnating or coating an organic fiber cloth with a second matrix resin. The second prepreg has a thermal expansion coefficient greater than that of the first prepreg. The first and second prepregs are then laminated together to prepare a prepreg laminate having a core layer containing at least one first prepreg and a surface layer containing at least one second prepreg laminated on one or both sides of the core layer. The first and second matrix resins are then cured to produce a laminate. In this specification, the terms "first prepreg" and "second prepreg" before curing correspond to the terms "first resin layer" and "second resin layer" after curing.

For example, as illustrated in Figures 1 to 4, a core layer made up of one or more layers of a first prepreg and a surface layer made up of one or more layers of a second prepreg can be stacked in the stacking direction of the prepregs. In this case, to more effectively reduce the thermal expansion coefficient of the laminate, it is preferable to stack the prepregs so that the condition m/n<1 is satisfied, where n is the number of core layers and m is the number of surface layers. It is preferable to stack the surface layers on both sides of the core layer in the stacking direction of the prepregs, and it is more preferable to arrange them symmetrically with respect to the center line that bisects the thickness of the laminate in its cross section. The reason for this is as described above.

The lamination method is not particularly limited, but may be, for example, a batch method, or each prepreg may be continuously supplied and continuously laminated using a vacuum laminator, vacuum Becquerel device, etc.

Finally, the first prepreg 201 and second prepreg 202 stacked as described above are heated and pressurized to form the laminated plate of the present disclosure, as illustrated in Figures 1 to 4.

The heat treatment method is not particularly limited, but can be carried out using, for example, a hot air dryer, an infrared heater, a heated roll device, or a flat-plate hot press device. When a hot air dryer or an infrared heater is used, the heat treatment can be carried out without applying substantial pressure to the bonded material. When a heated roll device or a flat-plate hot press device is used, the heat treatment can be carried out by applying a predetermined pressure to the bonded material.

There are no particular restrictions on the temperature during heat treatment, but it is preferable to set the temperature range so that the resin used melts but the resin curing reaction does not proceed too quickly. For example, when using PPE resin, the melting temperature is preferably 120°C or higher, more preferably 150°C or higher. Furthermore, the temperature at which the resin curing reaction does not proceed too quickly is preferably 250°C or lower, more preferably 230°C or lower.

The heat treatment time varies depending on the type of resin used, and is not particularly limited, but can be carried out for, for example, 30 minutes to 180 minutes. The pressure applied is also not particularly limited, but is preferably 0.2 MPa to 5 MPa, and more preferably 2 MPa to 4 MPa.

The surface layer may be laminated using a build-up method. Here, "build-up" refers to the process of laminating prepregs and repeatedly drilling holes and forming wiring for each layer to create a multi-layer laminate.

<First prepreg (first resin layer)>
The first prepreg can be obtained by impregnating a glass cloth with a varnish containing a first matrix resin composition and a solvent (hereinafter, sometimes simply referred to as "varnish"), and then drying and removing the solvent using a hot air dryer, etc. Alternatively, the first prepreg can be obtained by applying the varnish to the glass cloth, and then drying and removing the solvent using a hot air dryer, etc.

The first matrix resin composition preferably contains a thermosetting resin as the first matrix resin, and more preferably contains a thermosetting resin and an inorganic filler. For example, a thermosetting resin that is liquid at room temperature can be used as the thermosetting resin. Alternatively, a mixture of a resin component and a curing agent component can be used as the thermosetting resin. For the resin component, radical polymerization type thermosetting resins such as epoxy resins, unsaturated polyester resins, vinyl ester resins, and maleimide resins can be used.

The first prepreg preferably uses a resin composition containing polyphenylene ether (PPE) as the first matrix resin. By using a resin composition containing polyphenylene ether, better low dielectric properties can be obtained.

The first prepreg may use an epoxy resin as the first matrix resin. Using an epoxy resin can reduce the cost of the laminate while also achieving excellent dielectric constant, dielectric dissipation factor, and dielectric constant uniformity in the surface layer.

The dielectric constant of the first matrix resin constituting the first prepreg is preferably 2.0 or more and 3.0 or less, and more preferably 2.5 or more and 2.8 or less. When the dielectric constant of the first matrix resin is within the above range, better low dielectric properties can be obtained.

The proportion of the first matrix resin (as solids) in the first prepreg is preferably 30% to 80% by mass, and more preferably 40% to 70% by mass, based on the total mass of the first prepreg. Having this proportion of 30% by mass or more tends to result in better insulation reliability when the first prepreg is used for electronic substrates, etc. Having this proportion of 80% by mass or less tends to result in better mechanical properties, such as flexural modulus, when used in applications such as electronic substrates. Similarly, the proportion of the first matrix resin in the first resin layer formed by curing the first prepreg is preferably 30% to 80% by mass, and more preferably 40% to 70% by mass, based on the total mass of the first resin layer.

<Second prepreg (second resin layer)>
The second prepreg according to the present disclosure can be obtained by impregnating an organic fiber cloth with a varnish containing a second matrix resin composition and a solvent (hereinafter, sometimes simply referred to as "varnish"), and then drying and removing the solvent using a hot air dryer, etc. Alternatively, the second prepreg can be obtained by applying the varnish to the organic fiber cloth, and then drying and removing the solvent using a hot air dryer, etc.

The second matrix resin composition preferably contains a thermosetting resin as the second matrix resin, and more preferably contains a thermosetting resin and an inorganic filler. For example, a thermosetting resin that is liquid at room temperature can be used as the thermosetting resin. Alternatively, a mixture of a resin component and a curing agent component can be used as the thermosetting resin. For the resin component, radical polymerization type thermosetting resins such as epoxy resins, unsaturated polyester resins, vinyl ester resins, and maleimide resins can be used.

The second prepreg preferably uses a resin composition containing polyphenylene ether (PPE) as the matrix resin. By using a resin composition containing polyphenylene ether, superior low dielectric properties can be achieved. In one embodiment, the second matrix resin composition contains a low-molecular-weight PPE with a number-average molecular weight of 1,000 to 4,000.

The second prepreg may use an epoxy resin as the second matrix resin. Using an epoxy resin can reduce the cost of the laminate while maintaining a uniform dielectric constant in the surface layer.

The dielectric constant of the second matrix resin constituting the second prepreg is preferably 2.0 or more and 3.0 or less, and more preferably 2.5 or more and 2.8 or less. When the dielectric constant of the second matrix resin is within this range, the difference in dielectric constant with the organic fiber cloth can be reduced, and the difference in delay of electrical signals between wirings that occurs on the laminate due to variations in dielectric constant can be reduced.

The proportion of the second matrix resin composition (as solids) in the second prepreg is preferably 30% to 80% by mass, and more preferably 40% to 70% by mass, based on the total mass of the second prepreg. Having this proportion of 30% by mass or more tends to result in better insulation reliability when the second prepreg is used for electronic substrates, etc. Having this proportion of 80% by mass or less tends to result in better mechanical properties, such as flexural modulus, when used in applications such as electronic substrates. Similarly, the proportion of the second matrix resin in the second resin layer formed by curing the second prepreg is preferably 30% to 80% by mass, and more preferably 40% to 70% by mass, based on the total mass of the second resin layer.

<Glass cloth>
The glass cloth used for the first prepreg is not particularly limited, and known materials used in various printed wiring board materials can be appropriately selected and used depending on the intended application and performance. Specific examples include, but are not limited to, glass fibers such as E-glass, D-glass, S-glass, T-glass, spherical glass, NE-glass, L-glass, NL-glass, L2-glass, and Q-glass, and inorganic fibers other than glass such as quartz. The use of low-dielectric glass can suppress electrical signal loss and electrical signal delay when transmitting electrical signals in the direction perpendicular to the substrate.

Among these, E glass cloth, NE glass cloth, L glass cloth, NL glass cloth, L2 glass cloth, and Q glass cloth are preferred from the viewpoint of low thermal expansion and low dielectric properties. By using low dielectric glass, it is possible to suppress electrical signal loss and electrical signal delay when transmitting electrical signals in the direction perpendicular to the substrate. These glass cloths may be used alone or in combination of two or more types.

The weaving method for the cloth is not particularly limited, but known examples include plain weave, sieve weave, and twill weave. An appropriate weave can be selected from these known weaves depending on the intended application and performance. Glass cloths obtained by opening these or surface-treating them with a silane coupling agent or the like are also suitable. The thickness and mass of the glass cloth are not particularly limited, but typically glass cloths of approximately 0.01 mm to 0.3 mm are preferably used. From the standpoints of strength and water absorption, glass cloths having a thickness of 200 μm or less and a mass of 250 g/m2 or ^less are preferred, and glass cloths made of glass fibers such as E glass, NE glass, L glass, NL glass, L2 glass, and Q glass are more preferred.

<Organic fiber cloth>
The organic fiber cloth used in the second prepreg is not particularly limited, and known organic fibers used in various printed wiring board materials can be appropriately selected and used depending on the intended use and performance. Specific examples of organic fibers include, but are not limited to, polyimide fibers, polyphenylene ether fibers, fluorine fibers, and carbon fibers. Among these, polyphenylene ether fibers are preferred from the viewpoint of low dielectric properties.

The organic fiber cloth is preferably composed of fibers (PPE composition fibers) made from a composition containing PPE. In one embodiment, the organic fiber cloth is a woven fabric in which the weave density of the PPE composition fibers in the warp and weft directions (i.e., the weave density of both the warp and weft) is 20 threads/inch to 90 threads/inch, and the opening ratio is 1% to 30%. In one embodiment, the PPE composition fiber preferably contains a polyphenylene ether resin composition that contains 5% to 95% by mass of polyphenylene ether, and more preferably contains 5% to 95% by mass of at least one of liquid crystal polyester and syndiotactic polystyrene. In one embodiment, the PPE composition fiber is preferably a fiber formed by bundling 10 to 200 single yarns having a diameter of 5 μm to 50 μm.

When polyphenylene ether is used as the organic fiber, it is preferable to use a resin composition containing polyphenylene ether as the second matrix resin. This reduces the variation in dielectric constant within the prepreg, thereby reducing the delay difference of electrical signals on the wiring formed on the prepreg. Furthermore, using a resin composition containing polyphenylene ether for the organic fiber and second matrix resin improves adhesion between the organic fiber and the second matrix resin. This prevents interfacial delamination due to stress between the organic fiber and the matrix resin that occurs with temperature cycling, and extends the reliable lifespan.

The PPE contained in the PPE composition fiber preferably has a number average molecular weight of 9,000 to 21,000. The number average molecular weight is calculated in terms of standard polystyrene by performing gel permeation chromatography (GPC) measurement and using the relationship between the molecular weight of a standard polystyrene sample measured under the same conditions and the elution time.

When the number average molecular weight of the PPE is 9,000 or more, the heat resistance required for the substrate and the chemical resistance to solvents for matrix resin composition varnishes and cleaning solutions for the substrate tend to be good. When the number average molecular weight of the PPE is 21,000 or less, the extrusion moldability during preparation of the PPE composition and during spinning tends to be good. The number average molecular weight of the PPE is more preferably 9,500 or more, or 10,000 or more, and more preferably 17,000 or less, or 16,000 or less.

In one embodiment, the PPE preferably comprises or consists of a combination of a PPE component having a number average molecular weight of 9,000 to 12,000 and a PPE component having a number average molecular weight of 14,000 to 17,000. This improves both heat resistance and moldability. In particular, by adjusting the blending amount of the PPE component having a number average molecular weight of 9,000 to 12,000 to 30% by mass to 60% by mass relative to 100% by mass of PPE, both heat resistance and moldability can be further improved, and the affinity between the organic fiber cloth and the matrix resin composition varnish during prepreg production is increased, improving the heat resistance and adhesiveness of the laminate.

For PPE components having a number average molecular weight of 9,000 to 12,000, the number average molecular weight may more preferably be 9,500 or more, or 10,000 or more, and 11,500 or less, or 11,000 or less, respectively.

For PPE components having a number average molecular weight of 14,000 to 17,000, the number average molecular weight may more preferably be 14,500 or more, or 15,000 or more, and 16,500 or less, or 16,000 or less, respectively.

The structural units of the PPE contained in the PPE composition fiber may be the same as those exemplified below for the low-molecular-weight PPE contained in the matrix resin composition. The PPE composition fiber preferably contains at least one of liquid crystal polyester and syndiotactic polystyrene. Both of these polymers can exhibit crystallinity due to the highly ordered structure of the polymer molecules, while also having excellent fluidity, which can improve the heat resistance, mechanical strength, and solvent resistance of the PPE composition fiber and also contribute to the production of PPE composition fiber with good dimensional stability.

The liquid crystal polyester (hereinafter also referred to as LCP) preferably has a number average molecular weight of 10,000 to 100,000. When the number average molecular weight of the liquid crystal polyester is 10,000 or more, the heat resistance and chemical resistance required for the substrate tend to be good. When the number average molecular weight of the liquid crystal polyester is 100,000 or less, the extrusion moldability during the preparation of the PPE composition and during spinning tends to be good. The number average molecular weight of the liquid crystal polyester is more preferably 15,000 to 95,000, or 20,000 to 90,000.

The syndiotactic polystyrene (hereinafter also referred to as sPS) preferably has a number-average molecular weight of 10,000 to 100,000. When the number-average molecular weight of sPS is 10,000 or more, it tends to have good heat resistance and chemical resistance, which are required for substrates. When the number-average molecular weight of sPS is 100,000 or less, it tends to have good extrusion moldability during the preparation of the PPE composition and during spinning. The number-average molecular weight of sPS is more preferably 15,000 to 95,000, or 20,000 to 90,000.

In one embodiment, the PPE content in the PPE composition fiber is 5% to 95% by mass, preferably 10% to 90% by mass, or 15% to 85% by mass. When the PPE content is 5% by mass or more, the adhesion between the matrix resin and the PPE composition fiber and the permeability of the matrix resin into the PPE composition fiber are excellent, and the cured prepreg exhibits excellent dielectric constant uniformity. When the PPE content is 95% by mass or less, excellent melt spinnability is achieved.

In one embodiment, the sPS content in the PPE composition fiber is 5 to 95% by mass, preferably 20 to 80% by mass, 25 to 70% by mass, or 30 to 60% by mass. When the sPS content is 5% or more, the solvent resistance and dielectric constant/dielectric loss tangent of the PPE fiber composition are improved. In particular, when the sPS content is 30% by mass or more, the effect of the sPS crystallinity is more pronounced, resulting in excellent dimensional stability (low warpage). When the sPS content is 95% or less, excellent heat resistance is achieved.

The LCP content in the PPE composition fiber is 5 to 95% by mass, preferably 5 to 50% by mass, 5 to 40% by mass, or 5 to 30% by mass. When the LCP content is 5% or more, heat resistance and fiber strength are excellent. When the LCP content is 95% or less, spinnability is excellent, and when it is 30% or less, particularly, high-strength spun fibers can be produced.

When the PPE composition fiber contains both LCP and sPS and the total content is 5 to 95% by mass, the dielectric constant/dielectric loss tangent, heat resistance, and mechanical strength properties are particularly excellent. Preferably, the total content is 10 to 90% by mass, 20 to 80% by mass, or 30 to 70% by mass.

In addition, styrene-based elastomers, flame retardants, antioxidants, oils, and other additives may be added as needed. The styrene-based elastomer is preferably at least one selected from the group consisting of styrene-butadiene block copolymers, styrene-ethylene-butadiene block copolymers, styrene-ethylene-butylene block copolymers, styrene-butadiene-butylene block copolymers, styrene-isoprene block copolymers, styrene-ethylene-propylene block copolymers, styrene-isobutylene block copolymers, hydrogenated styrene-butadiene block copolymers, hydrogenated styrene-ethylene-butadiene block copolymers, hydrogenated styrene-butadiene-butylene block copolymers, hydrogenated styrene-isoprene block copolymers, and styrene homopolymers (polystyrenes), with hydrogenated styrene-butadiene block copolymers being more preferred.

Conventional flame retardants can be used. Examples include inorganic flame retardants such as antimony trioxide, aluminum hydroxide, magnesium hydroxide, and zinc borate; aromatic bromine compounds such as hexabromobenzene, decabromodiphenylethane, 4,4-dibromobiphenyl, and ethylene bistetrabromophthalimide; and phosphorus-based flame retardants such as resorcinol bis-diphenyl phosphate and resorcinol bis-dixylenyl phosphate. These flame retardants can be used alone or in combination of two or more.

The PPE composition can be prepared by melt-kneading the above raw materials in a twin-screw extruder or the like, for example, at 300°C or higher. Furthermore, this PPE composition can be produced into a multifilament fiber by heating it to 250°C or higher using a conventional spinning method, specifically, for example, melt spinning, passing it through a spinneret, and extruding and spinning it. In one embodiment, the diameter of the single yarns constituting the multifilament is 5 μm to 30 μm, preferably 5 μm to 20 μm or 5 μm to 15 μm. In one embodiment, the number of single yarns constituting the multifilament is 10 to 200, preferably 10 to 100 or 10 to 50. A single yarn diameter of 5 μm or greater ensures the tensile strength required for the subsequent weaving and fiber-opening processes, reducing the risk of fuzz (single yarn breakage). A single yarn diameter of 30 μm or less can achieve the thickness of 30 μm to 100 μm typically required for substrate applications. When the number of single yarns making up the multifilament is 10 or more, the dielectric constant of the insulating layer of the substrate can be made uniform by adjusting the subsequent weaving and spreading processes, and when the number of single yarns making up the multifilament is 200 or less, the above-mentioned fluffing (single yarn breakage) is less likely to occur.

In one embodiment, the above PPE composition fibers are woven to produce an organic fiber cloth with a warp and weft density of 20 to 90 threads/inch and an opening ratio of 1% to 30% or less. A warp and weft density of 20 threads/inch or more can prevent weave distortion and achieve a uniform dielectric constant for the insulating layer of the substrate. A warp and weft density of 90 threads/inch or less can prevent entanglement of fibers and suppress fuzz (single yarn breakage). The warp and weft weave density is preferably 30 threads/inch to 70 threads/inch, or 40 threads/inch to 60 threads/inch.

When the opening rate is 1% or more, the matrix resin easily penetrates the organic fiber cloth, improving resin impregnation and heat resistance. Furthermore, the presence of adequate areas without organic fiber cloth improves adhesion between the insulating layer of the substrate and the metal foil (e.g., copper foil). When the opening rate is 30% or less, the dielectric constant of the insulating layer of the substrate can be made uniform, and the PPE composition fibers are adequately dispersed, improving heat resistance. The opening rate is preferably 5% to 25%, or 10% to 20%. The warp and weft weave density and opening rate are values measured using the method described in the Examples section of this disclosure. The weave structure is not particularly limited, but examples include plain weave, santana weave, satin weave, and twill weave. Of these, plain weave structures are more preferred.

The fiber surface of the organic fiber cloth may be treated with a silane coupling agent, corona treatment, plasma processing, or the like. In particular, it is preferable that the fiber surface of the organic fiber cloth be treated with an inert gas plasma. Such surface treatments tend to further improve the heat resistance and adhesiveness required for the substrate.

The dielectric constant of the organic fiber cloth is 2.0 or more and 3.0 or less, preferably 2.5 or more and 2.8 or less. When the dielectric constant of the organic fiber cloth is within this range, the difference in dielectric constant from the dielectric constant of the matrix resin can be reduced. This improves the uniformity of the dielectric constant within the second prepreg and the surface layer, and reduces the delay difference of electrical signals between wirings that occurs in the laminate due to variations in dielectric constant.
The use of organic fibers containing a polyphenylene ether composition as the organic fiber cloth can achieve the above-mentioned dielectric constant and can reduce the delay difference of electrical signals. From the viewpoint of achieving both a low dielectric constant and a low dielectric loss tangent and high spinning productivity, the organic fiber preferably contains 5% to 95% by mass of polyphenylene ether and 5% to 95% by mass of either a liquid crystal polyester or a syndiotactic polystyrene, or both.

<Matrix Resin Composition>
The first and second matrix resin compositions may be different compositions or the same composition, and are preferably composed of the same composition. Using the same composition can improve the adhesion at the interface between the first resin layer and the second resin layer, prevent delamination due to stress between the first resin layer and the second resin layer that occurs during temperature cycling, and extend the reliability life. Below, we will explain the features common to the first and second matrix resin compositions.

The matrix resin composition preferably uses a low-molecular-weight PPE having a number-average molecular weight of 1,000 to 5,000. The matrix resin composition preferably contains a low-molecular-weight PPE, a crosslinking agent, and an organic peroxide. In one embodiment, the matrix resin composition may contain (a) a low-molecular-weight PPE, (b) a crosslinking agent, and (c) an organic peroxide, and, optionally, (d) a thermoplastic resin, (e) a flame retardant, and/or (f) a silica filler. The matrix resin composition may also be made into a matrix resin composition varnish containing (g) a solvent. The elements that can constitute the matrix resin composition are described below.

(a) Low molecular weight PPE
Low molecular weight PPE contains phenylene ether units as repeating structural units. The phenylene groups in the phenylene ether units may or may not have substituents. As used herein, the term "polyphenylene ether" includes dimers, trimers, oligomers, and polymers.

The PPE may also contain other structural units in addition to phenylene ether units. The amount of these other structural units is typically 30% or less, 25% or less, 20% or less, 15% or less, 10% or less, or 5% or less of the total number of structural units. However, the amount of these other structural units may exceed 30% of the total number of structural units, as long as it does not impair the effects of the present disclosure.

Specific examples of PPE include poly(2,6-dimethyl-1,4-phenylene ether), poly(2-methyl-6-ethyl-1,4-phenylene ether), poly(2-methyl-6-phenyl-1,4-phenylene ether), poly(2,6-dichloro-1,4-phenylene ether), copolymers of 2,6-dimethylphenol and other phenols (e.g., 2,3,6-trimethylphenol, 2-methyl-6-butylphenol, etc.), PPE copolymers obtained by coupling 2,6-dimethylphenol with biphenols or bisphenols, and PPE with a linear or branched structure obtained by heating poly(2,6-dimethyl-1,4-phenylene ether) or the like in the presence of a phenolic compound such as a bisphenol or trisphenol and an organic peroxide in a toluene solvent to cause a redistribution reaction. Further examples include PPE in which the terminal hydroxyl groups of these PPEs have been replaced with functional groups containing carbon-carbon double bonds. Specific examples of functional groups having a carbon-carbon double bond include vinyl groups, allyl groups, isopropenyl groups, 1-butenyl groups, 1-pentenyl groups, p-vinylphenyl groups, p-isopropenylphenyl groups, m-vinylphenyl groups, m-isopropenylphenyl groups, o-vinylphenyl groups, o-isopropenylphenyl groups, p-vinylbenzyl groups, p-isopropenylbenzyl groups, m-vinylbenzyl groups, m-isopropenylbenzyl groups, o-vinylbenzyl groups, o-isopropenylbenzyl groups, p-vinylphenylethenyl groups, p-vinylphenylpropenyl groups, p-vinylphenylbutenyl groups, m-vinylphenylethenyl groups, m-vinylphenylpropenyl groups, m-vinylphenylbutenyl groups, o-vinylphenylethenyl groups, o-vinylphenylpropenyl groups, o-vinylphenylbutenyl groups, methacryl groups, acrylic groups, 2-ethylacrylic groups, and 2-hydroxymethylacrylic groups.

The number-average molecular weight of the low-molecular-weight PPE is preferably 1,000 to 5,000. By including such a low-molecular-weight PPE in the matrix resin composition, an increase in the viscosity of the matrix resin composition varnish can be suppressed, thereby improving the coatability of the matrix resin composition varnish onto cloth. By improving this coatability, it is possible to improve the various properties required of the matrix resin composition or its cured product. The number-average molecular weight of the low-molecular-weight PPE is preferably 1,000 to 3,500, or 1,500 to 3,000.

The matrix resin composition may contain one type of low-molecular-weight PPE (i.e., PPE with a number-average molecular weight of 1,000 to 5,000), or a combination of two or more types of PPE with a number-average molecular weight of 1,000 to 5,000.

(b) Crosslinking Agent Any crosslinking agent capable of initiating or accelerating a crosslinking reaction can be used. The crosslinking agent preferably has a number average molecular weight of 9,000 or less. When the number average molecular weight of the crosslinking agent is 9,000 or less, an increase in the viscosity of the matrix resin composition varnish can be suppressed, and good resin fluidity can be obtained during heat molding. The number average molecular weight of the crosslinking agent may more preferably be 100 to 6,000, or 200 to 5,000. The number average molecular weight of the crosslinking agent is a value measured using GPC in terms of standard polystyrene.

From the viewpoint of crosslinking reactivity, the crosslinking agent preferably has an average of two or more carbon-carbon unsaturated double bonds per molecule. The crosslinking agent may be composed of one or more compounds. When the crosslinking agent is a polymer or oligomer, the carbon-carbon unsaturated double bond is typically located at the molecular end (i.e., the end of the main chain or branched chain), but this embodiment is not limited thereto. An example of the carbon-carbon unsaturated double bond is the 1,2-vinyl bond in polybutadiene.
Specifically, the crosslinking agent is preferably a styrene-butadiene copolymer containing 20% or more by mass of styrene. This copolymer is highly compatible with both the PPE composition fiber and the low-molecular-weight PPE matrix resin, and tends to improve the heat resistance and interlayer adhesion of the substrate. Examples of such copolymers include Ricon 100, Ricon 181, Ricon 257, and Ricon 184, both of which are products of Cray Valley.

Other examples of crosslinking agents include trialkenyl isocyanurate compounds such as triallyl isocyanurate (TAIC), trialkenyl cyanurate compounds such as triallyl cyanurate (TAC), multifunctional methacrylate compounds having two or more methacrylic groups in the molecule, multifunctional acrylate compounds having two or more acrylic groups in the molecule, multifunctional vinyl compounds having two or more vinyl groups in the molecule such as polybutadiene, vinylbenzyl compounds such as divinylbenzene having vinylbenzyl groups in the molecule, and multifunctional maleimide compounds having two or more maleimide groups in the molecule such as 4,4'-bismaleimidediphenylmethane. These crosslinking agents may be used alone or in combination. It is preferable that the crosslinking agent contains at least one compound selected from the group consisting of triallyl cyanurate, triallyl isocyanurate, and polybutadiene. When the crosslinking agent contains at least one of the compounds described above, the crosslink density during the curing reaction (crosslinking reaction) is further increased, which tends to further improve the heat resistance of the cured product of the matrix resin composition.

In the matrix resin composition, the mass ratio of low-molecular-weight PPE to crosslinking agent is preferably 25:75 to 95:5, and more preferably 32:68 to 85:15, from the viewpoint of balancing the low dielectric constant and low dielectric dissipation factor upon curing with the crosslink density of the crosslinked structure.

(c) Organic Peroxide Any organic peroxide capable of promoting the polymerization reaction of the matrix resin composition containing the low-molecular-weight PPE and the crosslinking agent can be used. Examples of organic peroxides include benzoyl peroxide, cumene hydroperoxide, 2,5-dimethylhexane-2,5-dihydroperoxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3, di-t-butyl peroxide, t-butylcumyl peroxide, di(2-t-butylperoxyisopropyl)benzene, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, dicumyl peroxide, di-t-butylperoxyisophthalate, t-butylperoxybenzoate, 2,2-bis(t-butylperoxy)butane, 2,2-bis(t-butylperoxy)octane, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, di(trimethylsilyl)peroxide, and trimethylsilyltriphenylsilyl peroxide. Radical generators such as 2,3-dimethyl-2,3-diphenylbutane can also be used as a reaction initiator for the matrix resin composition. Among these, 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3, di(2-t-butylperoxyisopropyl)benzene, and 2,5-dimethyl-2,5-di(t-butylperoxy)hexane are preferred from the viewpoint of providing a cured product having excellent heat resistance and mechanical properties, as well as a low dielectric constant and a low dielectric dissipation factor.

The one-minute half-life temperature of an organic peroxide is preferably 155°C to 185°C, or 160°C to 180°C, or 165°C to 175°C. In this specification, the one-minute half-life temperature is the temperature at which the organic peroxide decomposes and its active oxygen content is reduced by half in one minute. The one-minute half-life temperature is determined by dissolving the organic peroxide in a radical-inert solvent, such as benzene, to a concentration of 0.05 mol/L to 0.1 mol/L, and then thermally decomposing the organic peroxide solution under a nitrogen atmosphere.

When the organic peroxide has a one-minute half-life temperature of 155°C or higher, the low-molecular-weight PPE can be fully melted before reaction with the crosslinking agent can begin when the matrix resin composition is subjected to heat and pressure molding, which tends to result in excellent moldability. On the other hand, when the organic peroxide has a one-minute half-life temperature of 185°C or lower, the organic peroxide decomposes sufficiently quickly under normal heat and pressure molding conditions (e.g., a maximum temperature of 200°C), allowing the crosslinking reaction with the crosslinking agent to proceed efficiently and slowly, making it possible to form a cured product with good electrical properties (particularly dielectric tangent).

Examples of organic peroxides with a one-minute half-life temperature in the range of 155°C to 185°C include t-hexylperoxyisopropyl monocarbonate (155.0°C) (the one-minute half-life temperature is in parentheses, same below), t-butylperoxy-3,5,5-trimethylhexanoate (166.0°C), t-butylperoxylaurate (159.4°C), t-butylperoxyisopropyl monocarbonate (158.8°C), t-butylperoxy-2-ethylhexyl monocarbonate (161.4°C), t-hexylperoxybenzoate (160.3°C), 2,5-dimethyl-2 ,5-di(benzoylperoxy)hexane (158.2°C), t-butyl peroxyacetate (159.9°C), 2,2-di-(t-butylperoxy)butane (159.9°C), t-butyl peroxybenzoate (166.8°C), n-butyl 4,4-di-(t-butylperoxy)valerate (172.5°C), di(2-t-butylperoxyisopropyl)benzene (175.4°C), dicumyl peroxide (175.2°C), di-t-hexyl peroxide (176.7°C), 2,5-dimethyl-2,5-di(t-butylperoxy)hexane (179.8°C), and t-butylcumyl peroxide (173.3°C).

The content of organic peroxide, based on 100% by mass of the total mass of the low-molecular-weight PPE and crosslinking agent, is preferably 0.05% by mass or more, more preferably 0.1% by mass or more, even more preferably 0.3% by mass or more, and even more preferably 0.5% by mass or more, from the viewpoint of increasing the reaction rate; and is preferably 3% by mass or less, more preferably 2% by mass or less, and even more preferably 1% by mass or less, from the viewpoint of keeping the dielectric constant and dielectric dissipation factor of the resulting cured product low.

(d) Thermoplastic Resin The matrix resin composition preferably contains a thermoplastic resin other than the low-molecular-weight polyphenylene ether and the crosslinking agent. The thermoplastic resin is preferably at least one selected from the group consisting of a block copolymer of a vinyl aromatic compound and an aliphatic hydrocarbon compound having a carbon-carbon unsaturated double bond, a hydrogenated product thereof (a hydrogenated block copolymer obtained by hydrogenating a block copolymer of a vinyl aromatic compound and an aliphatic hydrocarbon compound having a carbon-carbon unsaturated double bond), and a homopolymer of a vinyl aromatic compound. The content of units derived from a vinyl aromatic compound in the block copolymer or its hydrogenated product is preferably 20% by mass or more, and can be 99% by mass or less. By having the content of units derived from a vinyl aromatic compound in the block copolymer or its hydrogenated product be 20% by mass or more, the compatibility between the low-molecular-weight PPE and the thermoplastic resin is further improved, which tends to further improve the adhesion strength between the cured prepreg and the metal foil.

Vinyl aromatic compounds may be any compounds that contain an aromatic ring and a vinyl group within the molecule, such as styrene. Aliphatic hydrocarbon compounds that contain a carbon-carbon unsaturated double bond may be any compounds that contain an unsaturated hydrocarbon with a linear or branched chain structure within the molecule, such as ethylene, propylene, butylene, isobutylene, butadiene, and isoprene. From the viewpoint of achieving even better compatibility with low-molecular-weight PPE, the thermoplastic resin is preferably at least one selected from the group consisting of styrene-butadiene block copolymer, styrene-ethylene-butadiene block copolymer, styrene-ethylene-butylene block copolymer, styrene-butadiene-butylene block copolymer, styrene-isoprene block copolymer, styrene-ethylene-propylene block copolymer, styrene-isobutylene block copolymer, hydrogenated styrene-butadiene block copolymer, hydrogenated styrene-ethylene-butadiene block copolymer, hydrogenated styrene-butadiene-butylene block copolymer, hydrogenated styrene-isoprene block copolymer, and styrene homopolymer (polystyrene), and more preferably at least one selected from the group consisting of styrene-butadiene block copolymer, hydrogenated styrene-butadiene block copolymer, and polystyrene.

The hydrogenation rate of the hydrogenated product is not particularly limited, and some carbon-carbon unsaturated double bonds derived from the aliphatic hydrocarbon compound having a carbon-carbon unsaturated double bond may remain.

The weight-average molecular weight of the thermoplastic resin is preferably 30,000 to 300,000, more preferably 31,000 to 290,000. A weight-average molecular weight of 30,000 or more tends to result in a matrix resin composition with better heat resistance when cured. A weight-average molecular weight of 300,000 or less tends to result in a matrix resin composition with better resin fluidity when heated and molded. The weight-average molecular weight is a value determined using gel permeation chromatography and converted into standard polystyrene.

The content of the thermoplastic resin is preferably 2 to 20 parts by mass, based on 100 parts by mass of the total of the low-molecular-weight PPE and crosslinking agent. When the content is 2 parts by mass or more, the matrix resin composition tends to exhibit a low dielectric constant, a low dielectric dissipation factor, and good adhesion to the metal foil when cured. When the content is 20 parts by mass or less, the matrix resin composition tends to have even better resin fluidity during heat molding.

(e) Flame Retardant The matrix resin composition preferably contains a flame retardant. From the viewpoint of improving heat resistance, the flame retardant is preferably one that is incompatible with other components contained in the matrix resin composition after curing. Preferably, the flame retardant is incompatible with the low-molecular-weight PPE and/or crosslinking agent in the matrix resin composition after curing. Examples of flame retardants include inorganic flame retardants such as antimony trioxide, aluminum hydroxide, magnesium hydroxide, and zinc borate; aromatic bromine compounds such as hexabromobenzene, decabromodiphenylethane, 4,4-dibromobiphenyl, and ethylene bistetrabromophthalimide; and phosphorus-based flame retardants such as resorcinol bis-diphenyl phosphate and resorcinol bis-dixylenyl phosphate. These flame retardants may be used alone or in combination of two or more. Among these, decabromodiphenylethane is preferred as the flame retardant from the viewpoint of achieving a low dielectric constant and a low dielectric dissipation factor when the matrix resin composition is cured.

The amount of flame retardant is not particularly limited, but from the perspective of maintaining flame retardancy at UL Standard 94V-0 level, it is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and even more preferably 15 parts by mass or more per 100 parts by mass of the total of low-molecular-weight PPE and crosslinking agent. Furthermore, from the perspective of maintaining low dielectric constant and dielectric dissipation factor of the resulting cured product, the amount of flame retardant is preferably 50 parts by mass or less, more preferably 45 parts by mass or less, and even more preferably 40 parts by mass or less.

(f) Silica Filler The matrix resin composition may contain a silica filler. Both natural and synthetic silica can be used as the silica filler, including fused silica, amorphous silica, aerosil, and hollow silica. A spherical silica filler with an average particle size of 0.1 to 2 μm is preferred. An average particle size of 0.1 to 2 μm provides good dispersibility in the matrix resin and excellent dimensional stability (warpage) of the substrate. Furthermore, an average particle size of 2 μm or less provides excellent impregnation of the matrix resin into the PPE resin composition fibers. The content of the silica filler in the matrix resin composition is preferably 10 to 50% by mass, 10 to 45% by mass, or 10 to 40% by mass, which facilitates high dispersibility and provides excellent elastic modulus and dimensional stability (warpage) of the substrate. Furthermore, the silica filler may be surface-treated using a silane coupling agent or the like.

In addition to the above components, the matrix resin composition may further contain additives such as heat stabilizers, antioxidants, UV absorbers, surfactants, and lubricants.

(g) Solvent The matrix resin composition can be made into a matrix resin composition varnish containing a solvent in order to obtain suitable fluidity when impregnating an organic fiber cloth. In the prepreg production process, after impregnating the organic fiber cloth with the matrix resin composition varnish, it is preferable to dry and remove the solvent using a hot air dryer or the like. The solid components in the matrix resin composition may be dissolved or dispersed in the varnish. The amount of solvent may be adjusted as appropriate so that the fluidity of the matrix resin composition varnish falls within a suitable range. For example, the amount of solvent in the matrix resin composition varnish may be 20% by mass to 80% by mass, 30% by mass to 70% by mass, or 40% by mass to 60% by mass.

From the viewpoint of the solubility of the components in the matrix resin composition, preferred solvents are aromatic compounds such as toluene and xylene, methyl ethyl ketone, cyclopentanone, cyclohexanone, and chloroform. These solvents may be used alone or in combination of two or more.

From the viewpoint of favorably dissolving the low-molecular-weight PPE in the solvent and ensuring favorable fluidity of the matrix resin composition varnish even at room temperature, aromatic compounds such as toluene are preferred as the solvent. For example, toluene-methyl ethyl ketone mixed solvents, toluene-cyclohexanone mixed solvents, and toluene-cyclopentanone mixed solvents are preferred. Furthermore, since the matrix resin composition dissolves favorably in such solvents even when toluene is used alone, and therefore has excellent impregnation properties into the substrate, toluene alone is also preferred as the solvent.

<Metal-clad laminate>
The metal-clad laminate of the present disclosure includes a laminate of the present disclosure and a metal foil laminated on the surface layer thereof. By incorporating the laminate of the present disclosure, the metal-clad laminate of the present disclosure has excellent dielectric constant, dielectric loss tangent, and dielectric constant uniformity, as well as a low thermal expansion coefficient and high heat resistance. The metal foil can be laminated on the surface of the first resin layer constituting the surface layer and/or between the first resin layers. It may be laminated between the first resin layer constituting the surface layer and the second resin layer constituting the core layer, or it may be laminated between the second resin layers constituting the core layer. In the metal-clad laminate, the first resin layer and the second resin layer form an insulating layer, and the insulating layer may be formed from a single first resin layer or a single second resin layer, or from two or more first resin layers and/or a single second resin layer.

Figure 5 is a schematic diagram showing a cross section of a metal-clad laminate of the present disclosure. In Figure 5, the metal-clad laminate (200) has a core layer (10) consisting of five first resin layers (1), and a surface layer (20) consisting of two second resin layers laminated on both sides of the core layer (10). The metal-clad laminate (200) has copper foil (3) laminated on its surface, and also has copper foil (3) laminated between the first resin layer constituting the surface layer and the second resin layer constituting the core layer, and between the second resin layers constituting the core layer.

Copper, aluminum, and other materials can be used as the metal foil. There are no particular restrictions on the metal foil used here, as long as it is a material used in printed wiring boards, but known copper foils such as rolled copper foil and electrolytic copper foil are preferred. The thickness of the metal foil (conductor layer) is also not particularly limited, but is preferably 1 μm to 70 μm, and more preferably 1.5 μm to 35 μm.

The molding method and molding conditions for the metal-clad laminate are not particularly limited, and general techniques and conditions for printed wiring board laminates and multilayer boards can be applied. For example, a multi-stage press, a multi-stage vacuum press, a continuous molding machine, an autoclave molding machine, etc. can be used to mold the metal-clad laminate. Furthermore, in molding the metal-clad laminate, the temperature is generally 100°C to 300°C, the pressure is 2 kgf/cm ² to 100 kgf/cm ² , and the heating time is generally in the range of 0.05 hours to 5 hours. Furthermore, post-curing can be performed at a temperature of 150°C to 300°C, if necessary. It is also possible to form a multilayer board by combining the above-mentioned prepreg with a separately prepared wiring board for the inner layer and laminating and molding it.

The surface layer may be laminated using a build-up method. Here, "build-up" refers to the process of laminating prepregs and/or metal-clad laminates, and repeatedly performing processes such as drilling and wiring on each layer to create a multilayer printed wiring board. By laminating surface layers with highly uniform dielectric constants using a build-up method and then performing fine wiring processing, it is possible to reduce the difference in electrical signal delay between each fine wiring, enabling electronic components to be mounted at a high density.

More specifically, prepregs and/or metal-clad laminates can be used as build-up materials for printed wiring boards. In printed wiring boards formed using prepregs, the hardened layers of the prepregs form the insulating layers. Furthermore, in printed wiring boards formed using metal-clad laminates, the hardened layers of the prepregs form the insulating layers.

When using prepreg as a build-up material, a metal-clad laminate can be produced using the prepreg, and then a printed wiring board can be obtained by a build-up method. Alternatively, when using the prepreg as a material for a multilayer printed wiring board, as described below, the prepreg can be used directly as the build-up material.

When using prepreg as a build-up material, the prepreg is surface-treated using standard methods, and a wiring pattern (conductor layer) is formed on the surface of the insulating layer by plating, resulting in a printed wiring board.

When using a metal-clad laminate as a build-up material, a printed wiring board can be obtained by etching the metal foil of the metal-clad laminate using standard methods, then surface-treating the layer made of prepreg (insulating layer), and forming a wiring pattern (conductor layer) on the surface of the insulating layer by plating.

In either case, various other processes (e.g., drilling processes to form via holes, through holes, etc.) may be added for each layer as needed.

<Printed wiring board>
A printed wiring board is a metal-clad laminate from which a portion of the metal foil has been removed. A printed wiring board can typically be formed by a method of pressurizing and heat-molding using the above-described prepreg. Examples of cloth include the same organic fiber cloths as those described above for the prepreg. By incorporating the laminate of the present disclosure, the printed wiring board has excellent dielectric constant, dielectric loss tangent, and dielectric constant uniformity, as well as a low thermal expansion coefficient and high heat resistance.

Examples of the present disclosure are described in detail below. However, the present disclosure is not limited to these examples.

<Measurement and evaluation methods>
(1) Number Average Molecular Weight The number average molecular weight of the PPE and the weight average molecular weight of the thermoplastic resin were determined by gel permeation chromatography (GPC) by comparing with the elution time of standard polystyrene of known molecular weight. Specifically, after preparing a measurement sample with a sample concentration of 0.2 w/vol% (solvent: chloroform), the measurement was performed using a measurement device HLC-8220GPC (manufactured by Tosoh Corporation), a column: Shodex GPC KF-405L HQ x 3 (manufactured by Showa Denko K.K.), an eluent: chloroform, an injection amount: 20 μL, a flow rate: 0.3 mL/min, a column temperature: 40°C, and a detector: RI.

(2) Diameter of Single Yarn Images of the cross sections of 100 randomly selected filaments were taken using a scanning electron microscope (Hitachi Science Systems, Ltd. SEMEDX3 Type N), and the diameters were measured and the average value was calculated.

(3) Weave Density in Warp and Weft Directions of Cloth Measured in both the warp and weft directions according to JIS R3420.

(4) Opening ratio of cloth A 100 mm wide (approximately 4 inch wide) square was cut from the center of the cloth roll, and the total warp width (i.e., the total width of the warp threads in the entire 100 mm × 100 mm cloth) and the total weft width (i.e., the total width of the weft threads in the entire 100 mm × 100 mm cloth) were measured in the surface morphology image of the cloth taken under an optical microscope, and the average values of each of the warp and weft threads were calculated. Based on this average value and the weave density of the warp and weft threads calculated above, the opening ratio was calculated according to the following formula.
Opening rate = (25.4 mm ÷ warp density - warp width mm) × (25.4 mm ÷ weft density - weft width mm) ÷ ((25.4 mm ÷ warp density) × (25.4 mm ÷ weft density))

(5) Thickness of cloth: Measured in accordance with JIS R3420.

(6) Heat Resistance Laminates were produced by laminating prepregs in the structure shown in Table 1, vacuum pressing them under conditions of a pressure of 5 kg/ ^cm2 while heating from room temperature at a temperature increase rate of 3°C/min, and when the temperature reached 130°C, vacuum pressing them under conditions of a pressure of 40 kg/ ^cm2 while heating at a temperature increase rate of 3°C/min, and when the temperature reached 200°C, vacuum pressing them under conditions of a pressure of 40 kg/ ^cm2 for 60 minutes while maintaining the temperature at 200°C. The laminates were cut into 50 mm x 50 mm pieces, and five pieces were placed in a pressure cooker at 121°C saturated vapor pressure for 10 hours, removed, wiped to remove surface moisture, and then immersed in a solder bath at 288°C for 20 seconds to evaluate the swelling of the laminates.
◎: No blister at all ○: One blister occurred △: Two or more blister occurred ×: Three or more blister occurred

(7) Dielectric constant and dielectric loss tangent of the surface layer (electrical properties, 10 GHz)
As in the heat resistance evaluation (6) above, laminates were prepared by stacking eight prepregs shown in Table 1 for the surface layer (b) in Examples 1 to 8 and Comparative Examples 1 and 2, and by stacking eight prepregs shown in Table 1 for the core layer (a) in Comparative Example 3, and the dielectric constant and dielectric loss tangent at 10 GHz were measured by the cavity resonance method. Measurements were performed using a network analyzer (N5230A, manufactured by Agilent Technologies) and a cavity resonator (Cavity Resonator CP series) manufactured by Kanto Electronics Application Development Co., Ltd.

(8) Dielectric constant uniformity of the surface layer (local variation in dielectric constant)
Laminates were prepared in the same manner as in (6) Heat Resistance Evaluation and (7) Surface Layer Dielectric Constant and Dielectric Loss Tangent Evaluation, except that a single prepreg was used. The laminates were embedded in resin, and the cross sections were machined and polished. Cross-sectional images were taken with a scanning electron microscope (Hitachi Science Systems, Ltd., SEMEDX3 Type N) over a continuous measurement width of 25 mm. The resulting cross-sectional images were analyzed, and the fiber loading (as the total area of the fiber portion within the field of view) and matrix resin composition loading (as the total area of the resin portion within the field of view) were measured for each unit width of 50 μm. The ratio of fiber loading/matrix resin composition loading was then calculated. The dielectric constant per unit width was then calculated using the calculated ratio of fiber loading/matrix resin composition loading for each unit width, the dielectric constant of the fiber, and the dielectric constant of the matrix resin composition. The standard deviation of the dielectric constant across the unit width was taken as the local dielectric constant variation.

(9) Amount of warpage of substrate As in the above (6) Evaluation of heat resistance, a laminate was prepared by laminating a core layer (a) and a surface layer (b) in the structure shown in Table 1, and four 50 mm square samples were randomly cut out, and the amount of warpage at each of the four corners of each sample (the larger one on the front or back) was measured with a vernier caliper. The average value of the four corners was calculated and used as the amount of warpage of the substrate.

(10) Thermal Expansion Coefficient The thermal expansion coefficient was measured by the TMA method (thermo-mechanical analysis). Similar to the heat resistance evaluation (6) above, a laminate was prepared by laminating a core layer (a) and a surface layer (b) to the structure shown in Table 1 to obtain the desired structure. The resulting laminate was cut into 5 mm squares, the thickness was measured, and the cross-sectional area of the specimen was calculated. A load of 40 g/ ^cm² was applied to the test specimen, and the specimen was heated at a heating rate of 10°C/min to measure the change in length. The specimen was heated from 25°C to 300°C, and the change in length in the temperature range of 50°C to 100°C was divided by the length of the test specimen, and then further divided by 50 to obtain the thermal expansion coefficient. Alternatively, a laminate having the desired layer structure may be prepared by polishing some of the layers of the laminate.

<Examples 1 to 8, Comparative Examples 1 to 3>
Preparation of PPE composition for organic fiber cloth:
PPE, sPS, LCP, and SEBS (styrene-ethylene-butadiene-styrene copolymer) having number average molecular weights (Mn) shown in Table 1 were melt-kneaded at 350°C in a twin-screw extruder in the blending ratios (by mass) shown in Table 1 to obtain PPE compositions.

Preparation of organic fiber cloth:
The PPE composition was extruded through a spinneret in a melt spinning machine and spun to produce a multifilament. The diameter of the single yarn was 20 μm, and the multifilament consisted of 50 single yarns.

Next, the multifilament was woven, physically processed, desizing, surface treated, and opened to produce an organic fiber cloth with a warp and weft density of 30 threads/inch, a thickness of 50 μm, and an opening ratio of 20%.

Glass cloth:
The glass cloth used was low dielectric glass cloth L2116 (weave density 60×58/inch, thickness 95 μm, opening ratio 5%).

Preparation of matrix resin composition:
[material]
The following materials were used:
(Low molecular weight PPE)
- Terminal methacrylic group-modified PPE (product name "SA9000", manufactured by Sabic Innovative Plastics, Mn: 2756, number of terminal functional groups per molecule: 2)
(Crosslinking agent)
・RICON100 (manufactured by CRAY VALLEY, weight average molecular weight: 4500)
TAIC (manufactured by Mitsubishi Chemical Corporation, molecular weight: 249.7)
(organic peroxide)
Bis(1-tert-butylperoxy-1-methylethyl)benzene (product name "Perbutyl P", manufactured by NOF Corporation)
(thermoplastic resin)
Hydrogenated styrene-based thermoplastic resin (SEBS) (product name "Tuftec H1051", manufactured by Asahi Kasei Corporation, weight average molecular weight (Mw): 49,000, styrene unit content: 30% by mass)
(Flame retardant)
Decabromodiphenylethane (product name "SAYTEX 8010", manufactured by Albemarle)
(Other ingredients)
Epoxy resin: cresol novolac epoxy resin (product name "N680-75M", manufactured by Dainippon Ink and Chemicals Co., Ltd.)
- Hardener: dicyandiamide (DICY)

Preparation of matrix resin composition varnish:
Each material was weighed in advance, and a 50:50 toluene/methyl ethyl ketone mixed solvent was placed in a container. While stirring with a mixer, each material was added and mixed for 5 hours or more to prepare a 50% by mass matrix resin composition varnish.

Preparation of first prepreg and second prepreg:
The cloth was impregnated with the resin composition varnish at a constant tension of about 100 N/m, scraped off with a slit, and dried at 120° C. for 3 minutes to prepare a prepreg.

Preparation of laminates:
Prepregs were prepared by preparing cloth using the materials described above and organic fibers having the compositions shown in Table 1 for eight core layers and eight surface layers, and then impregnating the cloth with varnish. The compositions and evaluation results are shown in Table 1.

<Examples 9 to 15, Comparative Examples 4 to 6>
The following computer simulations were performed to simulate the performance of laminates with various numbers of core and surface layers, pre-cure coefficients of thermal expansion (CTE), and post-cure coefficients of thermal expansion (CTE).

Computer simulation software:
The simulation software used was Abaqus 2018, a finite element analysis software.
1. Layer structure The layer structure of the model is the same as the cross-sectional structure of the multilayer structure shown in Figure 6. That is, it is a laminated structure in which surface layers (20) are laminated on both sides of a core layer (10). The "number of layers" refers to the total number of layers. For example, if the number of core layers is 8 and the number of surface layers is 8, this means that surface layers each consisting of four second resin layers are disposed on both sides of a core layer consisting of eight first resin layers.
2. Model The structure shown in Figure 6 was modeled. A two-dimensional mesh was created with the laminate length set to 4 mm and thickness set to 1.6 mm, the copper foil (3) on the laminate and on the substrate located on the laminate set to 0.68 mm and thickness set to 0.025 mm, and the substrate (4) located on the laminate set to 4 mm and thickness set to 1 mm. The solder formed a circle with a diameter of 0.68 mm, and the center line of the circle was cut symmetrically at positions 0.205 mm above and below and 0.41 mm high to create a model and mesh.
3. Thermal Expansion Coefficient The thermal expansion coefficient of the laminate was set as shown in Table 2. The other thermal expansion coefficients were set as follows: copper foil: 17 ppm/°C, substrate located on the laminate: 12 ppm/°C, and solder: 23 ppm/°C.
4. Temperature cycle The temperature load was set to apply three cycles of uniform temperature rise and fall to the entire model. The temperature was set to -55°C to 125°C and held for 5 minutes. The temperature rise and fall times were set to 10 minutes, excluding the start and end.

Simulation results:
Thermal stress analysis was performed on each member of each example and comparative example, and the inelastic strain in the solder joint was calculated. Furthermore, the number of cycles until failure was simulated based on the fatigue life diagram described in Non-Patent Document 1, and the results were evaluated according to the following criteria. The results are shown in "Temperature Cycle Test" in Table 2.
○ The number of repeated breakages is 1E+5 times or more. △ The number of repeated breakages is 5E+4 times or more but less than 1E+5 times. × The number of repeated breakages is less than 5E+4 times.

The "thermal expansion coefficient as laminate" in Table 2 was calculated as follows.
In the third temperature cycle, the change in length of the model in the temperature range of 50° C. to 100° C. was divided by the length of the model, and then divided by 50 to obtain the thermal expansion coefficient.

The "electrical signal delay in the surface layer" in Table 2 was simulated and evaluated as follows.
Computer simulation software:
The simulation software used was Ansys HFSS, which is finite element analysis software.
1. Layer structure The layer structure of the model is the same as the cross-sectional structure of the multilayer structure shown in Figure 7. That is, it is a laminated structure in which surface layers (20) are laminated on both sides of a core layer (10). The "number of layers" refers to the total number of layers. For example, if the number of core layers is 8 and the number of surface layers is 8, this means that surface layers each consisting of four second resin layers are disposed on both sides of a core layer consisting of eight first resin layers.
2. Model The structure shown in Figure 7 was modeled. The laminate had a length of 3.68 mm, a depth of 7.36 mm, and a thickness of 1.6 mm, and copper foil (3) was placed between the second and third layers from the surface of the laminate. Two copper foils (3) measuring 0.27 mm in length, 7.36 mm in depth, and 0.018 mm in thickness were placed on the laminate. The copper foils were placed at positions where the warp and weft threads of the cloth overlap, resulting in a high cloth filling rate, and at positions where the resin filling rate between the weaves of the cloth is high, and a three-dimensional model and mesh were created.
3. Dielectric Constant The dielectric constants of the matrix resin, glass cloth and organic fiber cloth in the laminate were set as shown in Table 2.
4. Calculation method for electrical signal delay difference A 10 GHz high-frequency signal was applied to the two copper foil wirings of the above model, and the delay time when the signal propagated was measured. The electrical signal delay difference was calculated from the delay time difference between the wirings.

Simulation results:
Simulations were performed on each member of each example and comparative example, and the electrical signal delay difference was calculated and evaluated according to the following evaluation criteria. The results are shown in Table 2 under "Electrical signal delay in surface layer."
○ Signal delay time is less than 0.25 psec/inch × Signal delay time is 0.25 psec/inch or more

1 First resin layer 2 Second resin layer 3 Copper foil 4 Substrate 10 Core layer 20 Surface layer 100 Laminate 200 Metal-clad laminate

Claims (19)

a core layer including at least one first resin layer in which a glass fiber cloth is impregnated or coated with a first matrix resin;
a surface layer laminated on one or both sides of the core layer and including at least one second resin layer in which a second matrix resin is impregnated or coated into an organic fiber cloth,
A laminate, wherein the second resin layer has a thermal expansion coefficient in a planar direction greater than the thermal expansion coefficient in a planar direction of the first resin layer. The thermal expansion coefficient of the first resin layer in the planar direction is 3 ppm/°C or more and less than 20 ppm/°C, and the thermal expansion coefficient of the second resin layer in the planar direction is 18 ppm/°C or more and 200 ppm/°C or less. The laminate according to claim 1. The laminate according to claim 1 or 2, wherein the surface layers are laminated on both sides of the core layer. The laminate according to any one of claims 1 to 3, wherein the fibers of the organic fiber cloth are fibers composed of a resin composition containing polyphenylene ether. The laminate according to claim 4, wherein the polyphenylene ether-containing resin composition comprises, based on the total mass of the resin composition, 5% to 95% by mass of polyphenylene ether and 5% to 95% by mass of at least one selected from liquid crystal polyester and syndiotactic polystyrene. The thermal expansion coefficient in the planar direction of the first resin layer is 3 ppm / ° C. or more and less than 20 ppm / ° C., and the thermal expansion coefficient in the planar direction of the second resin layer is 20 ppm / ° C. or more and 150 ppm / ° C. or less. The laminate according to any one of claims 1 to 5. The laminate according to any one of claims 1 to 6, wherein the core layer comprises two or more continuous first resin layers. The laminate described in any one of claims 1 to 7, wherein the number of layers of the first resin layer included in the core layer is greater than the number of layers of the second resin layer included in the surface layer. The laminate described in any one of claims 1 to 8, wherein the dielectric constant of the second matrix resin contained in the surface layer is 2.0 or more and 3.0 or less, and the dielectric constant of the organic fiber cloth is 2.0 or more and 3.0 or less. A metal-clad laminate comprising the laminate according to any one of claims 1 to 9 and a metal foil laminated on the surface layer of the laminate. a step of laminating at least one first prepreg obtained by impregnating or coating a glass fiber cloth with a first matrix resin and at least one second prepreg obtained by impregnating or coating an organic fiber cloth with a second matrix resin to prepare a prepreg laminate comprising a core layer including the at least one first prepreg and surface layers including the at least one second prepreg laminated on one or both sides of the core layer;
curing the first matrix resin and the second matrix resin;
A method for manufacturing a laminate, comprising:
A method for manufacturing a laminate, wherein the second prepreg has a larger thermal expansion coefficient in a planar direction than the first prepreg. The method according to claim 11, wherein the thermal expansion coefficient of the first prepreg in the planar direction is 3 ppm/°C or more and less than 20 ppm/°C, and the thermal expansion coefficient of the second prepreg in the planar direction is 18 ppm/°C or more and 200 ppm/°C or less. The method of claim 11 or 12, wherein the surface layers are laminated on both sides of the core layer. The method according to any one of claims 11 to 13, wherein the fibers of the organic fiber cloth are fibers composed of a resin composition containing polyphenylene ether. The method of claim 14, wherein the polyphenylene ether-containing resin composition comprises, based on the total mass of the resin composition, 5% to 95% by mass of polyphenylene ether and 5% to 95% by mass of at least one selected from liquid crystal polyester and syndiotactic polystyrene. The thermal expansion coefficient in the planar direction of the first prepreg is 3 ppm/°C or more and less than 20 ppm/°C, and the thermal expansion coefficient in the planar direction of the second prepreg is 20 ppm/°C or more and 150 ppm/°C or less. The method according to any one of claims 11 to 15. The method according to any one of claims 11 to 16, wherein two or more layers of the first prepreg are laminated continuously on the core layer. The method described in any one of claims 11 to 17, wherein the number of layers of the first prepreg laminated on the core layer is greater than the number of layers of the second prepreg laminated on the surface layer. The method according to any one of claims 11 to 18, wherein the dielectric constant of the second matrix resin contained in the surface layer is 2.0 or more and 3.0 or less, and the dielectric constant of the organic fiber cloth is 2.0 or more and 3.0 or less.