JP7653340B2 - Resin film, conductive laminate, and circuit board - Google Patents

Description

The present invention relates to a resin film, a conductive laminate, and a circuit board that can improve adhesion, mechanical strength, etc., and reduce the dimensional shrinkage rate after etching.

In recent years, polyarylene ether ketone (PAEK) resin, a super engineering plastic, has been attracting attention. This polyarylene ether ketone resin is a thermoplastic crystalline resin that has excellent electrical insulation, heat resistance, chemical resistance, and the like. In view of these excellent properties, polyarylene ether ketone resin is used in the automotive, energy, and medical fields, and is also used in the manufacture of circuit boards made of flexible printed circuits (FPCs) and the like (see Patent Documents 1 and 2).

In the case of manufacturing a circuit board using such a polyarylene ether ketone resin, although not shown in the figure, a polyarylene ether ketone resin film is formed and prepared as a base substrate, copper foil that will become a circuit pattern is directly bonded to this polyarylene ether ketone resin film, a photoresist layer for etching is laminated on the exposed surface, processing holes are drilled at predetermined locations of this laminated intermediate, the photoresist layer is exposed to ultraviolet light, and developed to dissolve the photoresist layer in the unexposed parts, thereby revealing the circuit pattern. When forming a polyarylene ether ketone resin film, in addition to the polyarylene ether ketone resin, fluororesin, talc, mica, etc. are added to the forming material as necessary (see Patent Document 3).

Once the circuit pattern has been raised, the circuit pattern on the intermediate is etched and the photoresist layer is peeled off, the intermediate is washed and dried, a cover film is attached to most of the intermediate to form an insulating layer, and exposed terminal parts etc. are subjected to surface treatment such as plating. Once surface treatment such as plating has been applied to the intermediate in this way, the intermediate is shaped, an electrical check is made for the continuity of the circuit pattern, and a final inspection is carried out, and the circuit board can be manufactured.

JP 2021-042294 A JP 2007-051256 A JP 2016-29164 A

Conventional circuit boards are manufactured as described above, and by using a polyarylene ether ketone resin film, excellent electrical insulation, heat resistance, and chemical resistance can be obtained. However, there is a problem in that it is not easy to simultaneously improve the adhesion and mechanical strength of the polyarylene ether ketone resin film and reduce the dimensional shrinkage rate of the polyarylene ether ketone resin film after etching.

When talc is added to the molding material of the polyarylene ether ketone resin film to solve this problem, the dimensional shrinkage rate of the polyarylene ether ketone resin film after etching of the intermediate can be reduced, but this leads to a deterioration in adhesion. Furthermore, when mica is added to the molding material of the polyarylene ether ketone resin film, simple addition without any consideration of the mica's properties can result in a deterioration in tensile strength, making it difficult to improve mechanical strength.

The present invention has been made in consideration of the above, and aims to provide a resin film, a conductive laminate, and a circuit board that can simultaneously improve adhesion and mechanical strength while reducing the dimensional shrinkage rate after etching.

In order to solve the above problems, the present invention provides a resin film formed from a molding material containing at least a polyarylene ether ketone resin and mica,
The composition volume ratio of the molding material is 70 volume % or more and 95 volume % or less of polyarylene ether ketone resin, and 5 volume % or more and 30 volume % or less of mica,
The mica molding material is characterized in that the amount of mica particles having a particle diameter of 1 μm or more is 90% or more of the total mica particles, the amount of mica particles having a particle diameter of less than 1 μm is 0.1% to 10% of the total mica particles, the specific surface area of the mica particles is 4.0 ^m2 /g to 15 ^m2 /g , the median diameter D50 is 2.0 μm to 6.0 μm, the median diameter D90 is 5.0 μm to 9.2 μm, and the median diameter D95 is 6.0 μm to 10 μm .

The resin film preferably has a tensile strength of 75 N/mm ² or more and 125 N/mm ² or less, as measured in accordance with JIS K 7127:1999.
In addition, the resin film preferably has an adhesion to a double-sided copper-clad laminate of 7 N/cm or more and 10 N/cm or less, as measured with reference to JIS Z 0237:2009.
The composition volume ratio of the molding material is preferably 80 volume % or more and 95 volume % or less of polyarylene ether ketone resin and 5 volume % or more and 20 volume % or less of mica.
It is also preferable that the mica is synthetic mica.

In order to solve the above problems, the present invention is characterized in that a metal layer is laminated on at least one of both sides of the resin film described in any one of claims 1 to 5 .
In order to solve the above problems, the present invention is characterized in that it includes a resin film as defined in any one of claims 1 to 5 .

The resin film in the claims can be manufactured to a thickness of 10 μm or more and 350 μm or less by a known manufacturing method such as melt extrusion molding, calendar molding, or casting. When manufacturing a resin film by melt extrusion molding, the resin film can be manufactured by melt-kneading the molding material using an extrusion molding machine, extruding the resin film from the die of the extrusion molding machine, and cooling it. In addition, the circuit board includes at least a printed wiring board, a flexible board, a high-frequency circuit board, etc.

According to the present invention, since mica is used, it is possible to obtain excellent adhesion while maintaining the strength of the resin film. In addition, by specifying the composition volume ratio of the molding material and the range of the particle size distribution of mica, the amount of mica particles with a particle size of less than 1 μm is limited to 10% or less of the total mica particles, and mica particles with a median diameter D50 of 2.0 μm to 6.0 μm are used, so that it is possible to reduce the dimensional shrinkage rate of the resin film after etching to a range where the resin film is not damaged while maintaining excellent adhesion and mechanical strength.

According to the present invention, there is an effect that the adhesiveness and mechanical strength of the resin film can be improved. In particular, since the composition volume ratio of the molding material is 70% by volume or more and 95% by volume or less of polyarylene ether ketone resin and 5% by volume or more and 30% by volume or less of mica, it is possible to prevent deterioration of the dimensional shrinkage rate of the resin film after etching, and to prevent the adhesiveness of the resin film from decreasing and the resin film from becoming easily cracked. In addition, since the amount of mica particles having a particle size of less than 1 μm is 0.1% to 10% of the total mica particles, it is possible to reduce the dimensional shrinkage rate of the resin film after etching during the manufacture of the circuit board. In addition, since the specific surface area of the mica particles is 4.0 m ² /g to 15 m ² /g, it is possible to reduce the dimensional shrinkage rate of the resin film after etching during the manufacture of the circuit board.
In addition, since the median diameter is selected to grasp the diameter of the mica particles, rather than the average diameter or the most frequent diameter, it is suitable for grasping the representative value of the particle size distribution of the mica particles, and it is possible to facilitate the comparison of the particle size distribution of multiple samples. Furthermore, since the median diameter D50 of the mica particles is 2.0 μm or more and 6.0 μm or less, it is expected that the film formability of the resin film will be improved. Furthermore, since the median diameter D95 is 6.0 μm or more and 10 μm or less , it is expected that the mechanical strength of the resin film will be improved.

According to the invention described in claim 4 , the composition volume ratio of the molding material is 80 volume % or more and 95 volume % or less of polyarylene ether ketone resin, and 5 volume % or more and 20 volume % or less of mica, so that the strength of the base material of the resin film is improved and the adhesion is better.
According to the fifth aspect of the present invention , since the mica is synthetic mica, deterioration of dielectric properties due to moisture absorption can be suppressed and the dimensional stability of the resin film can be improved.

According to the invention described in claim 6 or 7 , the resin film described in any one of claims 1 to 5 is used, so that when manufacturing a circuit board, it is possible to simultaneously achieve improved adhesion and mechanical strength of the resin film and a reduced dimensional shrinkage rate of the resin film after etching.

FIG. 1 is an explanatory diagram illustrating an embodiment of a resin film according to the present invention. FIG. 2 is a perspective view illustrating a state in which a copper foil is laminated on the surface of a resin film in an embodiment of the resin film and the conductive laminate plate according to the present invention. 10 is a perspective view illustrating a state in which copper foil is laminated on both the front and back sides of a resin film in a second embodiment of the resin film and conductive laminate plate according to the present invention; FIG.

A preferred embodiment of the present invention will be described below with reference to the drawings. As shown in Figs. 1 and 2, the resin film 1 in this embodiment is a film formed from a molding material containing polyarylene ether ketone resin and mica with a specified particle size distribution range, and a thin metal layer 2 of copper is formed on one side to form a conductive laminate 4. This conductive laminate 4 is used as a circuit board that electrically connects active and passive elements, thereby contributing to the achievement of Goal 9 of the SDGs (the United Nations' international goals for sustainable development, consisting of 17 global goals and 169 targets (achievement criteria)) adopted at the United Nations Summit.

The molding material contains at least polyarylene ether ketone (PAEK) resin and mica, and optionally contains other resins and various fillers as necessary, to form the thin resin film 1 shown in Figure 1. The composition volume ratio of this molding material is preferably 5% to 30% by volume of mica when the polyarylene ether ketone resin is 70% to 95% by volume. When it is desired to improve the base material strength and adhesion of the resin film 1, it is preferable that the mica is 5% to 20% by volume when the polyarylene ether ketone resin is 80% to 95% by volume.

The reason why the composition volume ratio of mica is 5% to 30% by volume is that if it is less than 5% by volume, the dimensional shrinkage rate of the resin film 1 after etching deteriorates. On the other hand, if it exceeds 30% by volume, the adhesion of the resin film 1 decreases and the hardness of the resin film 1 increases more than necessary, making it more likely to crack.

The molding material, polyarylene ether ketone resin, is a thermoplastic crystalline resin consisting of arylene groups, ether groups, and carbonyl groups, and examples of such resins include those described in Patent Publication No. 5709878 and Patent Publication No. 5847522, or in the literature (Asahi Research Center Co., Ltd.: PEEK, a super engineering plastic growing in cutting-edge applications (Part 1)). It has a melting point of 300°C to 360°C and is excellent in electrical insulation, mechanical properties, heat resistance, chemical resistance, radiation resistance, hydrolysis resistance, low water absorption, and recyclability.

Specific examples of polyarylene ether ketone resins include polyether ether ketone (PEEK) resin, polyether ketone ketone (PEKK) resin, polyether ketone (PEK) resin, polyether ketone ether ketone ketone (PEKEKK) resin, etc. Among these, polyether ether ketone resin is the most suitable because it can obtain the optimal processing temperature for manufacturing the conductive laminate 4 and the circuit board, and is also inexpensively available.

Examples of polyether ether ketone resin products include Victrex's Victrex Powder series and Victrex Granules series, Daicel-Evonik's VestaKeep series, and Solvay Specialty Polymers' KetaSpire PEEK series. Examples of polyether ketone ketone resin products include Arkema's KEPSTAN series. Examples of polyether ketone resin products include Victrex's HT G22 and HT G45. Examples of polyether ketone ether ketone ketone resin products include Victrex's ST G45.

The polyarylene ether ketone resin may be used alone or in a mixture of two or more types, or may be a copolymer. The polyarylene ether ketone resin is usually used in a form suitable for molding, such as powder, granules, or pellets. There are no particular limitations on the method for producing the polyarylene ether ketone resin, but for example, the method described in the literature [Asahi Research Center Co., Ltd.: PEEK, a super engineering plastic growing in cutting-edge applications (Part 1)] is used.

Mica (also called mica) used as a molding material is classified into two types: synthetic mica (potassium tetrasilicon fluoromica, etc.) artificially produced using talc as the main raw material, and natural mica (muscovite, black mica, etc.) produced in nature. Synthetic mica is preferred because it suppresses deterioration of dielectric properties due to moisture absorption and contributes to the adhesion and dimensional stability of the resin film 1. Synthetic mica is classified into non-swelling, swelling, lipophilic, etc., but non-swelling mica, which has excellent heat resistance, is preferred. A specific example of a synthetic mica product is the Micromica MK series (product name: manufactured by Katakura Coop Agri Co., Ltd.).

The mica is composed of many mica particles of different particle sizes, with the amount of mica particles with a particle size of 1 μm or more, for example, an average particle size of 2 μm to 13 μm, being 80% or more of the total mica particles, and the amount of mica particles with a particle size of 1 μm or less being 20% or less of the total mica particles, preferably 0.1% to 20%, more preferably 10% or less, and particularly preferably 0.15% to 10%. This is because if the amount of mica particles with a particle size of 1 μm or less exceeds 20% of the total mica particles, it is not possible to reduce the dimensional shrinkage rate of the resin film 1 after etching during the manufacture of the circuit board.

To explain this point, since mica is a plate-like particle, it is believed that the more the mica particles are aligned parallel to the surface direction of the resin film 1, the less shrinkage there will be in the surface direction (because mica is an inorganic particle and shrinks less compared to resin). If the resin film 1 contains 20% or more mica with a particle size of 1 μm or less, it is presumed that the mica is difficult to align parallel to the surface direction of the resin film 1 when it is molded, resulting in a resin film 1 in which the mica is aligned in non-uniform directions (mica with a particle size of 1 μm or less is believed to be easily aligned at an angle, such as diagonally or perpendicularly, to the surface direction of the resin film 1).

On the other hand, if the amount of mica with a particle size of 1 μm or less is less than 20%, the resin film 1 will have a high amount of mica oriented in the surface direction of the resin film 1. After lamination with a metal such as copper foil, the shrinkage after etching is in the surface direction, so if the amount of mica with a particle size of 1 μm or less is 20% or less, the shrinkage rate is expected to be small.

The specific surface area of the mica particles is 3.0 m ^{2 /g or more, preferably 3.0 m 2} /g to 15 m 2 /g, more preferably 3.05 m ² /g to 15 m ² /g, even more preferably 4.00 ^{m 2} /g to 15 m ² /g, and particularly preferably 4.00 m ² /g to 9.71 ^{m 2 /} g, in order to reduce the dimensional shrinkage rate of the resin film 1 after etching during the manufacture of the circuit board. The specific surface area of the mica particles is 3.0 ^{m 2 /} g or more because if the specific surface area of the mica particles is less than 3.0 m ² /g, it will contain a large amount of aggregates or coarse particles. The specific surface area of the mica particles can be measured by a permeation method or various gas adsorption methods, but it is preferable to measure it in accordance with JIS Z 8830:2013.

The majority of the mica particles contain mica particles with a median diameter D50 of 2.0 μm or more and 10 μm or less in order to reduce the dimensional shrinkage rate after etching. The median diameter (central diameter) is selected rather than the average diameter or the most frequent diameter because it is suitable for grasping a representative value of the particle size distribution of mica particles and is convenient when comparing the size of the particle size distribution of multiple samples.

The median diameter D50 of the mica particles is optimally 2.0 μm to 10 μm, preferably 2.0 μm to 6.0 μm, more preferably 2.8 μm to 5.10 μm, in order to improve the film-forming properties of the resin film 1. The median diameter D10 is 2.6 μm or less, preferably 0.9 μm to 2.6 μm, more preferably 0.97 μm to 2.55 μm. The median diameter D90 is 9.20 μm or less, preferably 5.00 μm to 9.20 μm, more preferably 5.20 μm to 9.15 μm. Furthermore, from the viewpoint of improving the mechanical strength of the resin film 1, the median diameter D95 is optimally 16.2 μm or less, preferably 6.00 μm or more and 16.2 μm or less, more preferably 6.00 μm or more and 15 μm or less, and even more preferably 6.20 μm or more and 14.20 μm or less.

The resin film 1 is formed from such molding materials, and the molding method can be any of melt extrusion, calendar molding, casting, etc. However, when considering ease of handling and simplification of manufacturing equipment, melt extrusion is optimal. When manufacturing the resin film 1 using this melt extrusion method, the molding material is melt-kneaded using an extrusion molding machine, and the resin film 1 is extruded from the T-die of the extrusion molding machine and cooled, thereby producing a thin resin film 1.

The thickness of the produced resin film 1 is not particularly limited, but considering the strength, rigidity, productivity, and versatility as a base for a circuit board, it is optimal to have a thickness of 10 μm to 350 μm, preferably 10 μm to 250 μm, and more preferably 50 μm to 100 μm. The thickness of this resin film 1 can be measured using a dedicated micrometer, etc.

The copper of the metal layer 2 is made of a thin copper foil 3, specifically rolled copper foil or electrolytic copper foil, having a thickness of, for example, 1 μm to 50 μm, preferably 10 μm to 13 μm, and is laminated on the surface of the resin film 1 by a thermocompression method to form a circuit pattern, as shown in FIG. 2. Specific examples of copper foil 3 products include electrolytic copper foil TQ-M7VSP [product name: manufactured by Mitsui Mining & Smelting Co., Ltd.] and rolled copper foil HA-V2 type [product name: manufactured by JX Nippon Mining & Metals Corporation].

In the above, when the resin film 1 is manufactured, the prepared molding material is first fed into the raw material inlet of the melt extruder, preferably while supplying an inert gas, and the molding material is melt-kneaded in the melt extruder heated to a temperature below the thermal decomposition temperature. From the viewpoint of dispersibility and workability, it is preferable that the molding material is prepared by adding mica to molten polyarylene ether ketone and melt-kneading the two. The melt extruder is not particularly limited, but may be, for example, a single-screw extruder, a twin-screw extruder, or a triple-screw extruder.

After the molding materials are melted and kneaded in a melt extrusion molding machine, a strip-shaped resin film 1 is continuously extruded from a T-die at the tip of the melt extrusion molding machine, and this resin film 1 is wound in sequence around multiple cooling rolls, a pair of pressure rolls, a tension roll, and a winding core of a winding machine, and cooled by sliding it against multiple cooling rolls. Both sides of the resin film 1 are cut with a slit blade to adjust the appearance, and then the resin film 1 is wound in sequence around the winding core of the winding machine to form the original roll of resin film 1, and the resin film 1 can be manufactured.

From experimental results, the tensile strength of the produced resin film 1 is preferably 75 N/mm ² or more and 125 N/mm ² or less, and more preferably 80 N/mm ² or more and 120 N/mm ² or less. The tensile strength of this resin film 1 can be measured in accordance with, for example, JIS K 7127:1999.

From experimental results, the dielectric loss tangent of the resin film 1 at a frequency of about 28 GHz is 0.0020 or more, preferably 0.0040 to 0.0080, and more preferably 0.0044 to 0.0075. The dielectric loss tangent of this resin film 1 is not particularly limited, but can be measured by the Fabry-Perot method using an open-type interferometer, a method for determining the relative dielectric constant and dielectric loss tangent at high frequencies by the cavity resonator perturbation method, a three-terminal measurement method using a mutual induction bridge circuit, etc. Among these, the Fabry-Perot method and the cavity resonator perturbation method, which have excellent high resolution, are the most suitable.

Next, when manufacturing the conductive laminate 4 using the resin film 1, by laminating conductive copper on the surface of the resin film 1, it is possible to manufacture the conductive laminate 4, which is a copper-clad laminate that serves as an intermediate for the circuit board. There is no particular limitation on the copper lamination method, but examples include (1) a method of laminating the resin film 1 and the copper foil 3 by heat fusion, (2) a method of laminating the copper foil 3 by adhering it to the resin film 1 with an adhesive, (3) a method of laminating the copper foil 3 by vapor deposition on the resin film 1, and (4) a method of sputtering copper onto the resin film 1.

Method (1) is a method in which the resin film 1 and the copper foil 3 are directly stacked and sandwiched between a press molding machine or rolls, and heated and pressurized at or near the melting point of the polyarylene ether ketone resin to heat-seal the copper foil 3 to the resin film 1. When carrying out this method, fine irregularities can be formed on the opposing surfaces of the resin film 1 or the copper foil 3 to improve the fusion strength. In addition, the surface of the resin film 1 or the copper foil 3 can be treated by corona irradiation treatment, ultraviolet irradiation treatment, plasma irradiation treatment, flame irradiation treatment, itro irradiation treatment, oxidation treatment, hairline processing, sand mud processing, etc. Furthermore, the surface of the resin film 1 or the copper foil 3 can also be treated with a silane coupling agent, a silane agent, a titanate-based coupling agent, or an aluminate-based coupling agent.

Method (2) is a method in which an adhesive such as an epoxy resin adhesive, a urethane resin adhesive, an acrylic resin adhesive, a melamine resin adhesive, a phenol resin adhesive, a silicone resin adhesive, a polyimide resin adhesive, or a polystyrene resin adhesive is placed between the resin film 1 and the copper foil 3, and the resin film 1 and the copper foil 3 are then sandwiched in a press molding machine or between rolls, and then heated and pressed to form the copper foil 3 on the resin film 1.

As described above, the surfaces of the resin film 1 and the copper foil 3 can be formed with fine irregularities in order to improve the adhesive strength. The surfaces of the resin film 1 and the copper foil 3 may also be treated with corona irradiation treatment, ultraviolet irradiation treatment, plasma irradiation treatment, flame irradiation treatment, itro irradiation treatment, oxidation treatment, hairline processing, sand mud processing, etc. As described above, the surfaces of the resin film 1 and the copper foil 3 may also be treated with a silane coupling agent, a silane agent, a titanate-based coupling agent, or an aluminate-based coupling agent.

In the case of methods (3) and (4), copper can be laminated by using a dedicated vapor deposition or sputtering device. Among these methods (3) and (4), the vapor deposition method (3) can be used to easily obtain a high-frequency circuit board for the fifth generation mobile communication system. In addition, the sputtering method (4) can be used to use various metals as the metal layer 2, and high adhesion strength can be obtained.

Next, when manufacturing a circuit board such as a flexible board using the conductive laminate 4, which is a copper-clad laminate, a photoresist layer for etching is laminated on the exposed surface of the conductive laminate 4, holes for processing are drilled at predetermined locations on the conductive laminate 4, the photoresist layer is exposed to ultraviolet light, and developed to dissolve the photoresist layer in the unexposed areas and reveal the circuit pattern. Once the circuit pattern has been revealed in this way, the circuit pattern on the conductive laminate 4 is etched to peel off the photoresist layer, the conductive laminate 4 is washed and dried at a temperature of 150°C to 160°C, a cover film is attached to most of the conductive laminate 4 to form an insulating layer, and exposed terminal parts, etc. are subjected to surface treatment such as plating.

Then, the conductive laminate 4 is contoured, the continuity of the circuit pattern is electrically checked, reinforcing material is crimped onto the conductive laminate 4, components are mounted, and a final inspection is carried out to manufacture the circuit board.

Experimental results show that the dimensional shrinkage rate of the resin film 1 after etching of the conductive laminate 4 or the circuit board is 0.03% to 0.20%, preferably 0.04% to 0.18%. This dimensional shrinkage rate can be determined in accordance with JIS C 6481:1996 by measuring the dimensions of the resin film 1 in the extrusion direction and width direction before and after etching using a two-dimensional side length measuring machine.

From experimental results, the adhesion of the resin film 1 to the conductive laminate 4 or the circuit board is 7 N/cm or more, preferably 7 N/cm to 10 N/cm, and more preferably 7.2 N/cm to 9.2 N/cm. The adhesion of the resin film 1 can be measured by cutting a test piece in which copper is laminated onto the resin film 1, and using this test piece to perform a peel test with reference to JIS Z 0237:2009 (Test method for adhesive tapes and adhesive sheets).

As described above, mica, which has excellent adhesion to metals, is used instead of talc, so that excellent adhesion can be obtained while maintaining the strength of the base material, the resin film 1. In addition, the composition volume ratio of the molding material and the range of the mica particle size distribution are specified, and the amount of mica particles with a particle size of 1 μm or less is set to 20% or less of the total mica particles, and mica particles with a median diameter D50 of 2.0 μm to 10 μm are used, so that the dimensional shrinkage rate of the resin film 1 after etching can be reduced to a range where the resin film 1 is not damaged during the manufacture of the circuit board while maintaining excellent adhesion and mechanical strength.

3 shows a second embodiment of the present invention, in which a thin metal layer 2, a copper foil 3, is laminated on both sides of a resin film 1 to form a conductive laminate 4, which is used to manufacture a circuit board. The other parts are the same as those of the above embodiment, so a description thereof will be omitted.
The present embodiment is expected to provide the same advantageous effects as the above-described embodiment, and it is clear that the present embodiment can be of great use in the manufacture of double-sided circuit boards in which complex circuits can be formed by crossing wiring.

In the above embodiment, the resin film 1 is used for a circuit board, but the present invention is not limited to this and may be used for other purposes, such as audio equipment. In the above embodiment, the copper foil 3 is laminated as the metal layer 2 by thermal fusion, but the present invention is not limited to this. For example, the metal layer 2 may be laminated by thermal fusion of gold, silver, chromium, aluminum, nickel alloy, tin, etc.

Examples of the resin film and the conductive laminate plate according to the present invention will be described below together with comparative examples.
A molding material was prepared using polyarylene ether ketone resin and mica or talc, and the prepared molding material was melt extruded to produce 16 types of resin films used in Examples 1 to 10 and Comparative Examples 1 to 7 with a film width of 530 mm (see Tables 1 and 2). As the polyarylene ether ketone resin of the molding material, a polyether ether ketone (PEEK) resin having a melting point of 341°C and a glass transition temperature of 147°C (manufactured by Victrex: product name Victrex Granules series 450G), or a polyether ketone ketone (PEKK) resin having a melting point of 360°C and a glass transition temperature of 165°C (manufactured by Arkema: product name KEPSTAN series 8002) was used.

As the mica for the molding material, eight types of synthetic mica shown in Tables 3 and 4 (manufactured by Katakura Coop Agri Co., Ltd.: product name Micromica MK series) or natural mica with a median diameter D50 of 4.38 μm (Yamaguchi Mica Co., Ltd.: product name SJ-005) were used. The eight types of synthetic mica were firstly synthetic mica 1, which was MK-100DS (manufactured by Katakura Coop Agri Co., Ltd.: product name) with a median diameter D50 of 2.85 μm, and synthetic mica 2, which was MK-100PDS (manufactured by Katakura Coop Agri Co., Ltd.: product name) with a median diameter D50 of 4.67 μm. For synthetic mica 3, MK-100P (manufactured by Katakura Coop Agri Co., Ltd.: product name) was pulverized by a high-pressure dry jet mill to obtain synthetic mica 3 with a median diameter D50 of 5.01 μm.

Synthetic mica 4 was MK-100PGDS (product name, manufactured by Katakura Co-op Agri Co., Ltd.) with a median diameter D50 of 3.36 μm. Synthetic mica 5 was made by feeding MK-200 (product name, manufactured by Katakura Co-op Agri Co., Ltd.) into a dry classifier and removing mica particles with a particle size of more than 40 μm to obtain synthetic mica 5 with a median diameter D50 of 5.1 μm.

Synthetic mica 6 was FGMK80DS (product name, manufactured by Katakura Co-op Agri Co., Ltd.) with a median diameter D50 of 1.4 μm. Synthetic mica 7 was made by pulverizing synthetic mica 1 with a high-pressure dry jet mill to obtain synthetic mica 7 with a median diameter D50 of 2.2 μm. Synthetic mica 8 was MK-300 (product name, manufactured by Katakura Co-op Agri Co., Ltd.) with a median diameter D50 of 11.72 μm.

Synthetic mica 6 and 7 are for comparison, in which mica particles with a particle size of 1 μm or less account for more than 20% of the total mica particles. Synthetic mica 8 is for comparison, in which the amount of mica particles with a particle size of 1 μm or less accounts for 0% and contains mica particles with a median diameter D50 of more than 10 μm. In addition, when mica is not used as a molding material, talc with a median diameter D50 of 5 μm shown in Table 4 (Nippon Talc Co., Ltd.: Product name Micro Ace Series SJ-005) was used instead for comparison.

The composition volume ratios were calculated assuming that the specific gravity of the polyarylene ether ketone resin was 1.3 and that of the mica was 2.7. 45 parts by mass of mica was added to 100 parts by mass of polyarylene ether ketone resin, so the volume of the polyarylene ether ketone resin was 76.9 and that of the mica was 16.7, calculated from their respective specific gravities. Therefore, the composition volume ratios within a total volume of 100% were 82.1% by volume for the polyarylene ether ketone resin and 17.9% by volume for the mica.

The particle size distribution of mica and talc was measured in accordance with JIS Z 8825:2013. Water was used as the dispersion liquid, and the volume distribution was evaluated by laser diffraction/scattering using a particle size distribution measuring device (manufactured by Microtrac-Bell Co., Ltd.: product name: MT3300EXII), and the results are summarized in Tables 3 and 4. The specific surface area of mica and talc was measured in accordance with JIS Z 8830:2013.

When preparing the molding material, polyarylene ether ketone resin was fed into a hopper, which was the first feed port located near the base of the screws of a co-rotating twin-screw extruder (φ25 mm, L/D=41, product name TEX25αIII, manufactured by Japan Steel Works, Ltd.). Mica or talc was forcibly fed into the co-rotating twin-screw extruder through the second feed port of the side feeder located immediately next to the vent port open to atmospheric pressure.

Polyarylene ether ketone resin was added, and mica or talc was forcibly added. The mixture was then melt-kneaded under the following conditions: barrel temperature of 200°C to 380°C, screw speed of 350 rpm, and output per hour of 7.2 kg/hr in a co-rotating twin-screw extruder. The mixture was then extruded into strands, and the strands were air-cooled to solidify, then cut into pellets to prepare the molding material.

When melt extrusion molding a resin film, the molding material was set in a φ40 mm single screw extruder equipped with a T-die and melt-kneaded, and this melt-kneaded molding material was continuously extruded from the T-die of the single screw extruder, and then cooled with a metal roll, which was a cooling roll at 230°C, to produce a resin film of a specified thickness. Here, the temperature of the φ40 mm single screw extruder was adjusted to 360°C to 400°C, the temperature of the T-die to 400°C, and the temperature of the connecting pipe connecting the single screw extruder and the T-die to 400°C.

Example 1
First, a resin film having a thickness of 100 μm was melt-extruded from a molding material containing polyether ether ketone resin and synthetic mica 1. As shown in Table 1, the composition volume ratio of the molding material was 82.1 volume % of polyether ether ketone resin and 17.9 volume % of synthetic mica 1.

After the resin film was melt-extruded in this way, the resin film and the prepared copper foil were cut to 320 mm x 320 mm and directly laminated together, sandwiched between 1 mm thick SUS plates, and thermocompressed for 5 minutes at a surface pressure of 4 MPa using a heat press machine with a heat plate set to 350°C, before being removed to produce a conductive laminate that is a double-sided copper-clad laminate. The copper foil used was 12 μm thick TQ-M7VSP [product name: manufactured by Mitsui Mining & Smelting Co., Ltd.].

Next, the dimensional shrinkage rate and adhesion of the resin film after etching of the conductive laminate, which is a copper-clad laminate, were measured, and then the tensile strength, dielectric tangent at a frequency of about 28 GHz, and cracking tendency were measured using the resin film from which all the copper foil of the conductive laminate had been removed, and the results were reported in Table 5 and evaluated.

Dimensional shrinkage of resin film after etching The dimensional shrinkage of the resin film after etching was measured in accordance with JIS C 6481: 1996. First, the conductive laminate was cut to a size of 300 mm (extrusion direction) × 300 mm (width direction), holes were drilled at four ends of this conductive laminate, and the length of the conductive laminate before etching was measured by the distance between the centers of the holes in the extrusion direction and width direction. After that, the laminated copper foil was removed with an aqueous iron chloride solution, and the length of the resin film was measured at the same portion as previously measured.

A two-dimensional length measuring machine (product name: VMH600, manufactured by Mino Group) was used to measure the dimensions. The target value for the dimensional shrinkage rate of the resin film after etching was less than 0.2%, with a shrinkage rate of 0.2% or more being evaluated as poor (X), shrinkage rates of less than 0.2% to greater than 0.15% being normal (△), shrinkage rates of less than 0.15% to greater than 0.1% being good (○), and shrinkage rates of 0.1% or less being extremely good (◎).

Adhesion of resin film in conductive laminate Regarding the adhesion of the resin film in the conductive laminate, the conductive laminate was cut into a test specimen having a width of 25 mm, and the conductive laminate was fixed to a support and the copper foil was fixed to a pulling jig at a peel speed of 0.3 mm/min and a peel angle of 180°, and the adhesion strength (adhesion) was measured by measuring the peel strength when the copper foil was pulled from the conductive laminate, with reference to JIS Z 0237: 2009. The peeling surfaces in each Example and Comparative Example were all base material failure between the resin films.

Tensile strength of resin film The tensile strength of the resin film was evaluated by the maximum tensile strength at 23°C using the resin film after removing the copper foil by etching. The tensile strength was measured in the extrusion direction and width direction (perpendicular to the extrusion direction) of the resin film. The measurement was performed in accordance with JIS K 7127, at a pulling speed of 50 mm/min and a temperature of 23°C. The measured tensile strength was evaluated by indicating that 90 N/mm2 or ^more was good strength ○, and that 80 N/ ^mm2 or more and less than 90 N/ ^mm2 was normal strength △.

Dielectric Loss Tangent of Resin Film The dielectric loss tangent of the resin film was measured using an electronic measuring instrument (product name: Compact USB Vector Network Analyzer MS46122B: manufactured by Anritsu Corporation) by the Fabry-Perot method, which is a type of open resonator method, at a frequency of around 28 GHz, at 23°C x 50 RH%, in a normal state and after immersion in water for 24 hours.

Specifically, the resin film from which the copper foil had been removed by dissolving it in an aqueous iron chloride solution was cut to 100 x 100 mm, and the cut test pieces were left in a constant temperature and humidity room at 23°C ± 2°C and 50 ± 10% RH for at least 10 hours, after which the value measured using the Fabry-Perot method was taken as the dielectric tangent before immersion in water. For measurements 24 hours after immersion in water, the test pieces whose dielectric properties had been measured before immersion were immersed in ion-exchanged water for 24 hours, then removed, the water adhering to the surface of the resin film was wiped off with paper, and the pieces were left in an environment of 23 ± 2°C and 50 ± 10% RH for 5 minutes, after which measurements were made using the Fabry-Perot method. All measurements before and after 24 hours of immersion in water were performed in an environment of 23 ± 2°C and 50 ± 10% RH.

The resonator used was an open-type resonator (product name: Fabry-Perot resonator, Model No. DPS03, manufactured by Keycom). For the measurement, a conductive laminate was placed on the sample stage of the open-type resonator jig, and a vector network analyzer was used to perform the measurement using the Fabry-Perot method, which is a type of open-type resonator method. Specifically, the dielectric loss tangent was measured using a resonance method that utilizes the difference in resonance frequency between a state in which the conductive laminate was not placed on the sample stage and a state in which the conductive laminate was placed on the sample stage. The specific frequency used for the measurement was 28 GHz. The target value for the dielectric loss tangent tan δ after 24 hours of water immersion was less than 0.0080, and a good value was 0.0075 or less.

-Crackability of resin film The crackability of the resin film was evaluated by the MIT test according to JIS P 8115. Specifically, using an MIT folding endurance tester, a test piece of the resin film was repeatedly folded in the width direction with a load of 4.9 N and a bending clamp R of 0.8 mm, and while pulling the test piece with a predetermined load, the test piece was folded left and right at 135° at a speed of 175 times/min, and continued until the test piece broke, and the folding endurance was measured from the number of times of folding until the test piece broke. The number of times of folding was based on 30 times, and when it was 30 times or more, it was evaluated as ○, which means good crackability, and when it was less than 30 times, it was evaluated as ×, which means poor crackability.

Example 2
Basically, the procedure was the same as in Example 1, but a resin film having a thickness of 100 μm was melt extrusion molded from a molding material containing polyether ether ketone resin and synthetic mica 2. As shown in Table 1, the composition volume ratio of the molding material was 82.1 volume % polyether ether ketone resin and 17.9 volume % synthetic mica 2.

Otherwise, a conductive laminate was prepared in the same manner as in Example 1, and the dimensional shrinkage rate, adhesion, tensile strength, dielectric tangent at a frequency of about 28 GHz, and cracking tendency of the resin film after etching of the dried conductive laminate were measured and evaluated, as shown in Table 5.

Example 3
Basically, the procedure was the same as in Example 1, but a resin film having a thickness of 100 μm was melt extrusion molded from a molding material containing polyether ether ketone resin and synthetic mica 3. As shown in Table 1, the composition volume ratio of the molding material was 82.1 volume % polyether ether ketone resin and 17.9 volume % synthetic mica 3.

Otherwise, a conductive laminate was prepared in the same manner as in Example 1, and the dimensional shrinkage rate, adhesion, tensile strength, dielectric tangent at a frequency of about 28 GHz, and cracking tendency of the resin film after etching of the dried conductive laminate were measured and evaluated, as shown in Table 5.

Example 4
Basically, the procedure was the same as in Example 1, but a resin film having a thickness of 100 μm was melt extrusion molded from a molding material containing polyether ether ketone resin and synthetic mica 4. As shown in Table 1, the composition volume ratio of the molding material was 82.1 volume % polyether ether ketone resin and 17.9 volume % synthetic mica 4.

Otherwise, a conductive laminate was prepared in the same manner as in Example 1, and the dimensional shrinkage rate, adhesion, tensile strength, dielectric tangent at a frequency of about 28 GHz, and cracking tendency of the resin film after etching of the dried conductive laminate were measured and evaluated, as shown in Table 5.

Example 5
The melt extrusion molding was performed in the same manner as in Example 4, except that the thickness of the resin film was changed to 50 μm. A conductive laminate was produced in the same manner as in Example 1, and the dimensional shrinkage rate, adhesion, tensile strength, dielectric loss tangent at a frequency of about 28 GHz, and cracking tendency of the resin film after etching of the dried conductive laminate were measured and evaluated, as shown in Table 5.

Example 6
Basically, the same as in Example 1, a resin film having a thickness of 100 μm was melt extrusion molded from a molding material containing polyether ketone ketone resin and synthetic mica 4. As shown in Table 1, the composition volume ratio of the molding material was 82.1 volume % of polyether ketone ketone resin and 17.9 volume % of synthetic mica 4.

After the resin film was melt-extruded, the resin film and the prepared copper foil were cut to 320 mm x 320 mm and directly laminated together, sandwiched between 1 mm thick SUS plates, and thermocompressed for 5 minutes at a surface pressure of 4 MPa using a heat press machine with a heat plate set to 370°C, before being removed to produce a conductive laminate that is a double-sided copper-clad laminate. The rest of the experiment was the same as in Example 1, and the dimensional shrinkage rate, adhesion, tensile strength, dielectric loss tangent at a frequency of around 28 GHz, and cracking tendency of the resin film after etching of the dried conductive laminate were measured and evaluated, as shown in Table 5.

Example 7
The procedure was basically the same as in Example 1, but a resin film having a thickness of 100 μm was melt extrusion molded from a molding material containing polyether ether ketone resin and synthetic mica 4. As shown in Table 1, the composition volume ratio of the molding material was changed to 76.2 volume % of polyether ether ketone resin and 23.8 volume % of synthetic mica 4.

Otherwise, a conductive laminate was prepared in the same manner as in Example 1, and the dimensional shrinkage rate, adhesion, tensile strength, dielectric tangent at a frequency of about 28 GHz, and cracking tendency of the resin film after etching of the dried conductive laminate were measured and evaluated, as shown in Table 5.

Example 8
The procedure was basically the same as in Example 1, but a resin film having a thickness of 100 μm was melt extrusion molded from a molding material containing polyether ether ketone resin and synthetic mica 4. As shown in Table 1, the composition volume ratio of the molding material was changed to 88.9 volume % of polyether ether ketone resin and 11.1 volume % of synthetic mica 4.

Otherwise, a conductive laminate was prepared in the same manner as in Example 1, and the dimensional shrinkage rate, adhesion, tensile strength, dielectric tangent at a frequency of about 28 GHz, and cracking tendency of the resin film after etching of the dried conductive laminate were measured and evaluated, as shown in Table 5.

Example 9
The procedure was basically the same as in Example 1, but a resin film having a thickness of 100 μm was melt extrusion molded from a molding material containing polyether ether ketone resin and synthetic mica 5. As shown in Table 1, the composition volume ratio of the molding material was changed to 82.1 volume % of polyether ether ketone resin and 17.9 volume % of synthetic mica 5.

Otherwise, a conductive laminate was prepared in the same manner as in Example 1, and the dimensional shrinkage rate, adhesion, tensile strength, dielectric tangent at a frequency of about 28 GHz, and cracking tendency of the resin film after etching of the dried conductive laminate were measured and evaluated, as shown in Table 6.

Example 10
The process was basically the same as in Example 1, but a resin film having a thickness of 100 μm was melt-extruded from a molding material containing polyether ether ketone resin and natural mica. As shown in Table 1, the composition volume ratio of the molding material was 82.1 volume % polyether ether ketone resin and 17.9 volume % natural mica.

Otherwise, a conductive laminate was prepared in the same manner as in Example 1, and the dimensional shrinkage rate, adhesion, tensile strength, dielectric tangent at a frequency of about 28 GHz, and cracking tendency of the resin film after etching of the dried conductive laminate were measured and evaluated, as shown in Table 6.

Comparative Example 1
The procedure was basically the same as in Example 1, but a resin film having a thickness of 100 μm was melt extrusion molded from a molding material containing polyether ether ketone resin and synthetic mica 6. As shown in Table 2, the composition volume ratio of the molding material was changed to 82.1 volume % of polyether ether ketone resin and 17.9 volume % of synthetic mica 6.

Otherwise, a conductive laminate was prepared in the same manner as in Example 1, and the dimensional shrinkage rate, adhesion, tensile strength, dielectric tangent at a frequency of about 28 GHz, and cracking tendency of the resin film after etching of the dried conductive laminate were measured and evaluated, as shown in Table 6.

Comparative Example 2
The procedure was basically the same as in Comparative Example 1, but a resin film having a thickness of 100 μm was melt extrusion molded from a molding material containing polyether ether ketone resin and synthetic mica 6. As shown in Table 2, the composition volume ratio of the molding material was changed to 76.2 volume % of polyether ether ketone resin and 23.8 volume % of synthetic mica 6.

Otherwise, a conductive laminate was prepared in the same manner as in Comparative Example 1, and the dimensional shrinkage rate, adhesion, tensile strength, dielectric tangent at a frequency of about 28 GHz, and cracking tendency of the resin film after etching of the dried conductive laminate were measured and evaluated, and the results are shown in Table 6.

Comparative Example 3
The procedure was basically the same as in Comparative Example 1, but a resin film having a thickness of 100 μm was melt extrusion molded from a molding material containing polyether ether ketone resin and synthetic mica 7. As shown in Table 2, the composition volume ratio of the molding material was changed to 82.1 volume % of polyether ether ketone resin and 17.9 volume % of synthetic mica 7.

Otherwise, a conductive laminate was prepared in the same manner as in Comparative Example 1, and the dimensional shrinkage rate, adhesion, tensile strength, dielectric tangent at a frequency of about 28 GHz, and cracking tendency of the resin film after etching of the dried conductive laminate were measured and evaluated, and the results are shown in Table 6.

Comparative Example 4
The procedure was basically the same as in Comparative Example 1, but a resin film having a thickness of 100 μm was melt extrusion molded from a molding material containing polyether ether ketone resin and synthetic mica 8. As shown in Table 2, the composition volume ratio of the molding material was changed to 82.1 volume % of polyether ether ketone resin and 17.9 volume % of synthetic mica 8.

Otherwise, a conductive laminate was prepared in the same manner as in Comparative Example 1, and the dimensional shrinkage rate, adhesion, tensile strength, dielectric tangent at a frequency of about 28 GHz, and cracking tendency of the resin film after etching of the dried conductive laminate were measured and evaluated, and the results are shown in Table 6.

Comparative Example 5
The procedure was basically the same as in Comparative Example 1, but a resin film having a thickness of 100 μm was melt extrusion molded from a molding material containing polyether ether ketone resin and talc outside the scope of the present invention. As shown in Table 2, the composition volume ratio of the molding material was changed to 82.1 volume % of polyether ether ketone resin and 17.9 volume % of talc.

Otherwise, a conductive laminate was prepared in the same manner as in Comparative Example 1, and the dimensional shrinkage rate, adhesion, tensile strength, dielectric tangent at a frequency of about 28 GHz, and cracking tendency of the resin film after etching of the dried conductive laminate were measured and evaluated, and the results are shown in Table 6.

Comparative Example 6
The procedure was basically the same as in Comparative Example 1, but a resin film having a thickness of 100 μm was melt extrusion molded from a molding material containing polyether ether ketone resin and synthetic mica 4. As shown in Table 2, the composition volume ratio of the molding material was changed to 67.9 volume % of polyether ether ketone resin, which is outside the range of the present invention, and 32.1 volume % of synthetic mica 4.

Otherwise, a conductive laminate was prepared in the same manner as in Comparative Example 1, and the dimensional shrinkage rate, adhesion, tensile strength, dielectric tangent at a frequency of about 28 GHz, and cracking tendency of the resin film after etching of the dried conductive laminate were measured and evaluated, and the results are shown in Table 6.

Comparative Example 7
The composition volume ratio of the molding material in Comparative Example 7 was changed to 96 volume % of polyether ether ketone resin, which is outside the range of the present invention, and 4 volume % of synthetic mica 4, as shown in Table 2.

Otherwise, a conductive laminate was prepared in the same manner as in Comparative Example 1, and the dimensional shrinkage rate, adhesion, tensile strength, dielectric tangent at a frequency of about 28 GHz, and cracking tendency of the resin film after etching of the dried conductive laminate were measured and evaluated, and the results are shown in Table 6.

〔evaluation〕
In each example, good results were obtained in terms of the dimensional shrinkage rate, adhesion, tensile strength, dielectric loss tangent at a frequency of about 28 GHz, and cracking tendency of the resin film after etching. In the cases of Examples 3, 9, and 10, the tensile strength was slightly reduced, but the value was not problematic in practical use. From these results, it is presumed that by manufacturing a circuit board using the resin film or conductive laminate of the examples, it is possible to simultaneously achieve improved adhesion and mechanical strength of the resin film and reduced dimensional shrinkage rate of the resin film after etching.

In contrast, in the case of each comparative example, good results could not be obtained with respect to the dimensional shrinkage rate of the resin film after etching, adhesion, tensile strength, dielectric loss tangent at a frequency of about 28 GHz, and cracking tendency. In particular, in the case of comparative examples 2, 5, and 6, serious problems occurred with cracking tendency, so it is presumed that serious doubts will arise about the practicality of manufacturing circuit boards using the resin films and conductive laminates of the comparative examples.

The resin film, conductive laminate, and circuit board of the present invention are used in fields such as information and communications and automotive equipment.

1 Resin film 2 Metal layer 3 Copper foil 4 Conductive laminate

Claims (7)

A resin film formed from a molding material containing at least a polyarylene ether ketone resin and mica,
The composition volume ratio of the molding material is 70 volume % or more and 95 volume % or less of polyarylene ether ketone resin, and 5 volume % or more and 30 volume % or less of mica,
The mica molding material contains mica particles having a particle size of 1 μm or more that account for 90% or more of the total mica particles, and mica particles having a particle size of less than 1 μm that account for 0.1% to 10% of the total mica particles, and the mica particles have a specific surface area of 4.0 ^m2 /g to 15 ^m2 /g, a median diameter D50 of 2.0 μm to 6.0 μm, a median diameter D90 of 5.0 μm to 9.2 μm, and a median diameter D95 of 6.0 μm to 10 μm . The resin film according to claim 1, which has a tensile strength measured in accordance with JIS K 7127:1999 of 75 N/mm ² or more and 125 N/mm ² or less. The resin film according to claim 1 or 2, wherein the adhesion to a double-sided copper-clad laminate measured with reference to JIS Z 0237:2009 is 7 N/cm or more and 10 N/cm or less. The resin film according to claim 1, 2, or 3, in which the composition volume ratio of the molding material is 80% by volume or more and 95% by volume or less of polyarylene ether ketone resin and 5% by volume or more and 20% by volume or less of mica. The resin film according to any one of claims 1 to 4, in which the mica is synthetic mica. A conductive laminate comprising a resin film according to any one of claims 1 to 5, and a metal layer laminated on at least one of the two surfaces. A circuit board comprising the resin film described in any one of claims 1 to 5.

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