JPH10266055A - Resin fiber nonwoven fabric for electrical insulation, its production and laminated board and prepreg - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce the subject nonwoven fabric resistant to the warpage and twist caused by the heat generated in the surface mounting of a leadless chip part while suppressing the deformation of a substrate in forming by bonding resin fibers resistant to thermal softening with a prescribed amount of a specific resin binder. SOLUTION: This nonwoven fabric is composed of resin fibers essentially free from heat-softening tendency such as poly-p-phenylene 3,4'-diphenyl ether terephthalamide fibers bonded with each other with a resin binder having a glass transition temperature of >=200 deg.C. The amount of applied resin binder is 5-25 wt.%. The electrically insulating resin fiber nonwoven fabric has a bulk density of >=0.55 g/cc and is preferably used as a prepreg.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin fiber nonwoven fabric for electrical insulation and a method for producing the same. Also,
The present invention relates to a prepreg and a laminate using the nonwoven fabric as a base material. The nonwoven fabric substrate prepreg and the laminate are suitable as an insulating layer of a printed wiring board on which chip components such as resistors and ICs are surface-mounted.

[0002]

2. Description of the Related Art In recent years, the surface mounting method has become the mainstream for mounting electronic components on printed wiring boards which are incorporated and used in electronic devices in view of reduction in size and weight and increase in density of electronic devices. Therefore, the electronic component is a leadless chip component. The printed wiring board was manufactured by performing circuit processing on the metal foil of the metal foil-clad laminate by etching, and the laminate was formed by heating and pressing a sheet-like fiber base material impregnated with a thermosetting resin. Things.

[0003] When a leadless chip component is surface-mounted on a printed wiring board by soldering, it is necessary to prevent the occurrence of cracks due to cooling and heating cycles in the solder connection portion during long-term use. From such a viewpoint, a laminated board used as an insulating layer of a printed wiring board includes:
It is required that the thermal expansion coefficient in the plane direction be close to the thermal expansion coefficient of the leadless chip component (2 to 7 × 10 ⁻⁶ / ° C.), and aromatic polyamide fibers (polyp) having a negative thermal expansion coefficient are required. -Phenylene terephthalamide fiber or poly-p
A laminate or a metal foil-clad laminate based on a nonwoven fabric made of phenylene phenyl ether terephthalamide fiber) has been studied. The nonwoven fabric has a structure in which aromatic polyamide short fibers are bound with an epoxy resin binder having a glass transition temperature of about 110 ° C.

[0004]

The elastic modulus of the above-mentioned aromatic polyamide fiber nonwoven fabric rapidly decreases in a temperature range exceeding the glass transition temperature (110 ° C.) of the epoxy resin binder. In the process of impregnating the non-woven fabric with a thermosetting resin (matrix resin) to produce a laminate by heating and pressing, the temperature range in which the matrix resin melts and flows is 80 to 140 ° C. Therefore, the aromatic polyamide fiber nonwoven fabric whose elastic modulus has decreased in such a temperature range is likely to be deformed unevenly due to the influence of the flow of the matrix resin and the molding pressure. This deformation causes warpage and torsion of the printed wiring board. Further, since the step of surface mounting the leadless chip component on the printed wiring board by soldering is performed by a reflow device, the printed wiring board receives heat of 200 ° C. or more. The insulating layer made of the aromatic polyamide fiber nonwoven fabric as a base material does not uniformly expand and contract, but exhibits a non-uniform behavior of partially expanding and contracting under the influence of the orientation of the fiber. This also causes the printed wiring board to warp and twist.

[0005] The problem to be solved by the present invention is to suppress the deformation of the base material during molding in a laminate made of a nonwoven fabric made of a heat-resistant resin fiber such as an aromatic polyamide fiber. Another object of the present invention is to suppress warpage and twisting caused by heat when a leadless chip component is surface-mounted. An object of the present invention is to provide a resin fiber nonwoven fabric for electrical insulation used for such a laminate.

[0006]

In order to solve the above-mentioned problems, a resin fiber non-woven fabric for electrical insulation according to the present invention has a glass transition temperature of 200.degree.
It is configured by binding with the resin binder described above (measured by the TMA method). When the amount of the resin binder attached is 5 to 2
5% by weight. The resin fiber which does not substantially heat soften is preferably a para-type aromatic polyamide fiber, for example, a poly p-phenylene terephthalamide fiber or a poly p-phenylene phenyl ether terephthalamide fiber. Other examples include aromatic polymer fibers containing a hetero ring. The heterocycle-containing aromatic polymer has a chemical structure in which an amino bond of an aromatic polyamide is replaced with a heterocycle, and is poly (p-phenylenebenzobisthiazole) or poly (p-phenylenebenzobisoxazole). These fibers are used in the form of short fibers.

[0007] The nonwoven fabric in which the high heat-resistant resin fibers are bound together by the high heat-resistant resin binder has a small temperature dependence of the elastic modulus. That is, this nonwoven fabric has a small decrease in the elastic modulus in the range of the melting temperature of the matrix resin at the time of forming the laminate, and is hardly affected by the flow and pressure of the matrix resin. As a result, non-uniform deformation of the nonwoven fabric which causes warpage and twist is reduced, and warpage and twist of the laminated board are suppressed. When a high heat-resistant resin binder having a glass transition temperature of 200 ° C. or higher is used, if the amount of adhesion is less than 5% by weight, the bonding strength between fibers is weak, and the strength of the nonwoven fabric is insufficient. Further, such a high heat-resistant resin binder reduces the moisture-resistant insulation property of the laminate when the amount of adhesion thereof increases, and increases the thermal expansion coefficient (linear expansion coefficient) in the planar direction of the laminate. Be careful not to. Suitably up to 25% by weight.

[0008] The above resin fiber non-woven fabric is obtained by binding the fibers with a resin binder having a glass transition temperature of 200 ° C or higher.
Further, it is preferable to manufacture by thermal compression at a temperature higher than the glass transition temperature. The heat compression is performed by, for example, a hot roll or the like.
The glass transition temperature of the resin binder can be further increased by promoting the curing of the high heat-resistant resin binder having a temperature of not less than ° C. If the amount of the resin binder adhered is large, the resin binder adheres to a hot roll or the like or breaks the nonwoven fabric during thermal compression. Therefore, from such a viewpoint, the amount of the resin binder adhered is set to 25% by weight or less. There is a need.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The resin fiber non-woven fabric for electrical insulation according to the present invention comprises a para-type aromatic polyamide fiber or a hetero ring-containing aromatic polymer fiber (all short fibers) as a resin fiber which does not substantially heat-soften. It is dispersed in water, laid on a wire mesh (papermaking), sprayed with a resin binder solution having a glass transition temperature of 200 ° C. or higher, and dried by heating to produce the product. The resin binder is cured by heating and drying, and the fibers are bound together. Basically, in this state, the glass transition temperature of the resin binder is 200 ° C. or higher. However, even if the glass transition temperature has not reached 200 ° C., the resin binder can be selected by the heat compression manufacturing method described below. , 200 ° C. or higher. The resin binder having a glass transition temperature of 200 ° C. or higher is made of an epoxy resin, a polyimide resin, or the like. In the examples described later, the following binder was used. That is, a trifunctional epoxy resin (“VG31 made by Mitsui Petrochemical”
01 ", 100 parts by weight of glycidylated trisphenylol methane type) and 11.6 parts by weight of triethylenetetramine, 48 parts by weight of acetone were added, mixed well, and reacted at room temperature for 8 hours with stirring. Thereafter, 1004 parts by weight of a 10% acetic acid aqueous solution was added to prepare a water-soluble epoxy resin binder. The glass transition temperature of the cured resin binder was 200 ° C. as measured by the TMA method.

[0010] The amount of resin binder adhering to the nonwoven fabric is
Considering the strength of the nonwoven fabric and the moisture-resistant insulation of the laminate,
Preferably it is 10 to 20% by weight. Further, when the bulk density of the nonwoven fabric is 0.55 g / cc or more, the number of binding points between fibers by the resin binder increases, which is preferable. The bulk density of the nonwoven fabric in which the fibers are bound with a resin binder having a glass transition temperature of 200 ° C. or higher can be adjusted to a temperature higher than the glass transition temperature, for example, 210 to 350 ° C., to achieve the above bulk density. In order to further promote the curing of the resin binder having a glass transition temperature of 200 ° C. or higher, it is necessary to set the temperature of the thermal compression to 210 ° C. or higher. Depending on the glass transition temperature of the resin binder before the thermal compression, a higher heat may be applied. Set the compression temperature. On the other hand, when the temperature of thermal compression is 350
If the temperature exceeds ℃, the resin binder will be compressed
The thickness of the non-woven fabric is uneven because the non-woven fabric breaks due to fusion to the non-woven fabric, or the non-woven fabric surface becomes uneven, so the thickness is adjusted appropriately. When heat compression is performed by a hot roll, the linear pressure at which the hot roll contacts the nonwoven fabric is preferably 150 to 250 kg / cm. However, it is not limited to this. When the thermal compression is performed using a hot roll, the transfer speed of the nonwoven fabric is set at 10 to make the nonwoven fabric obtain a predetermined amount of heat from the hot roll.
m / min or less is desirable. However, it is not limited to this.

When the nonwoven fabric is formed by mixing thermoplastic resin fibers (short fibers) having a softening temperature of 220 ° C. or higher as the second fibers, the second fibers are softened or melted when the nonwoven fabric is thermally compressed as described above. As a result, the nonwoven fabric is entangled or fused with the resin fiber that does not substantially soften, and the temperature dependence of the elastic modulus of the nonwoven fabric can be further reduced. The second fiber is preferably a meta-type aromatic polyamide fiber,
For example, poly m-phenylene isophthalamide fiber. Other examples include polyester fibers typified by polyethylene terephthalate fiber and polybutylene terephthalate, and nylon fibers typified by 6 nylon and 66 nylon.

The laminate is manufactured by heating and pressing a layer of the nonwoven fabric impregnated with a thermosetting resin. At this time, the metal foil can be formed integrally with the metal foil on the surface. As the thermosetting resin, an epoxy resin, a phenol resin, a urea resin, a polyimide, a polyester, or the like can be appropriately used. As the metal foil, a copper foil, an aluminum foil, a nichrome foil, or the like can be appropriately used. The prepreg obtained by impregnating and drying the nonwoven fabric with a thermosetting resin is used not only for the production of the laminate, but also as an insulating layer of a multilayer printed wiring board by a build-up method or the like.

[0013]

【Example】

Examples 1 to 17 and Comparative Examples 1 to 3 Poly-p-phenylene 3,4'-diphenyl ether terephthalamide staple fibers ("Technola" manufactured by Teijin Ltd., resin fibers that are not substantially heat-softened) were prepared and had a glass transition temperature of 200.
(The condition of heating and drying after spraying the resin binder solution is 220 ° C. and 5 ° C.)
Min) to obtain a nonwoven fabric having a unit weight of 60 g / m ² . The adhesion amounts of the resin binder are as shown in Tables 1 and 2. Also,
Among the nonwoven fabrics of the respective examples, some of the nonwoven fabrics were thermally compressed with a hot roll under the conditions shown in the same table to further advance the curing of the epoxy resin binder. Each of the resin fiber nonwoven fabrics was impregnated with a brominated bisphenol A type epoxy resin varnish and dried to prepare a resin fiber nonwoven fabric prepreg having a resin adhesion amount of 50% by weight. Five ply of the prepared prepregs were stacked, and a copper foil having a thickness of 18 μm was placed on both sides of the prepreg, and a 0.5 mm-thick copper-clad laminate was obtained by heating and pressing.

Conventional Example Paper-made poly p-phenylene 3,4'-diphenylether terephthalamide short fiber ("Technola" manufactured by Teijin Ltd., a resin fiber which does not substantially heat soften) has a glass transition temperature of 110.
(The condition for heating and drying after spraying the resin binder solution is 5 ° C at 130 ° C.)
Min) to obtain a nonwoven fabric having a unit weight of 60 g / m ² . The adhesion amount of the resin binder is 15% by weight. The resin fiber nonwoven fabric was impregnated with a brominated bisphenol A type epoxy resin varnish and dried to prepare a resin fiber nonwoven fabric prepreg having a resin adhesion amount of 50% by weight. Five ply of the prepared prepregs were stacked, and a copper foil having a thickness of 18 μm was placed on both sides of the prepreg, and a 0.5 mm-thick copper-clad laminate was obtained by heating and pressing.

Examples 18 to 34, Comparative Examples 4 to 6 Short fibers of polyp-phenylene 3,4'-diphenylether terephthalamide ("Technola" manufactured by Teijin, resin fibers which are not substantially heat-softened) and polym -A nonwoven fabric made of phenylene isophthalamide short fibers ("CONEX" manufactured by Teijin, softening temperature: 280 ° C, second fiber) is bound with an epoxy resin binder having a glass transition temperature of 200 ° C (after spraying the resin binder solution). The heating and drying conditions are 220 ° C
To obtain a nonwoven fabric having a unit weight of 60 g / m ² (the compounding weight ratio of the resin fiber which does not substantially soften and the second fiber is 8).
5:15). The adhesion amounts of the resin binder are as shown in Tables 3 and 4. Further, among the nonwoven fabrics of the respective examples, some of the nonwoven fabrics were thermally compressed with a hot roll under the conditions shown in the same table to further advance the curing of the epoxy resin binder. Further, among these, the non-woven fabric which is thermally compressed by setting the roll temperature to 300 ° C. and 350 ° C. has a configuration in which the second fiber is softened or melted, so that the second fiber is entangled or fused with the fiber which is not substantially thermally softened. became. The second fibers are also fused together.
Each of the above resin fiber non-woven fabrics has a brominated bisphenol A
Impregnated with epoxy resin varnish and dried.
A resin fiber nonwoven fabric prepreg of weight% was prepared. Five ply of the prepared prepregs were stacked, and a copper foil having a thickness of 18 μm was placed on both sides thereof, and a copper-clad laminate having a thickness of 0.5 mm was obtained by heating and pressing.

The properties of the resin fiber non-woven fabric obtained in Examples 1 to 34, Comparative Examples 1 to 6, and the conventional example, that is, the glass transition temperature (Tg) of the resin binder and the bulk density of the non-woven fabric,
The solvent wet strength is also shown in Tables 1, 2, 3, and 4.
The solvent wet strength is a value obtained by measuring the tensile strength when a central portion of a nonwoven fabric cut into a width of 15 mm and a length of 100 mm is wetted with methyl ethyl ketone and pulled in the length direction to break.

[0017]

[Table 1]

[0018]

[Table 2]

[0019]

[Table 3]

[0020]

[Table 4]

Examples 1 to 34, Comparative Examples 1 to 6, and the warp size, coefficient of linear thermal expansion, moisture resistance, and thickness accuracy of copper-clad laminates based on the resin fiber nonwoven fabric obtained in the conventional examples. Are shown in Table 5, Table 6, Table 7, and Table 8. Each characteristic was measured as follows. Warpage size: A sample is placed on a flat surface, and the amount of lifting from the flat surface is measured at the four corners of the front and back, and the maximum value is defined as the warpage (n = 10). The warpage of the copper-clad laminate after molding (indicated as "after molding" in the table) is 500 mm x 5
Measured with a sample of 00mm size. Warpage is less than 3 mm: ○ 3 mm or more: The ratio of ×× is 10% or less: △ After processing the copper-clad laminate into a printed wiring board and performing a reflow treatment at a maximum temperature of 230 ° C. for surface mounting of components (see “ The back) is measured on a 50 mm x 70 mm sample. Warpage is less than 2 mm: ○ 2 mm or more: The ratio of XX is 10% or less: Δ Moisture resistance insulation property: The insulation resistance of the laminate after 6 hours of pressure cooker was measured. Linear thermal expansion coefficient: heating rate 10 ° C / min, load 2g, 30 ~
The coefficient of linear thermal expansion of the laminate at 80 ° C. in the nonwoven fabric vertical direction was measured. Plate thickness accuracy: Measure the plate thickness at the center 5 points and the end 5 points of the laminated plate after molding. Variation is ± 0.015 or less: ○ ± 0.030 or less: Δ Exceeds ± 0.03: ×

[0022]

[Table 5]

[0023]

[Table 6]

[0024]

[Table 7]

[0025]

[Table 8]

[0026]

As is clear from Tables 5 to 8, the resin fiber nonwoven fabric according to the present invention contributes to suppressing the warpage and twisting of a laminate made of the same. Glass transition temperature 2
10-20% by weight
The above-mentioned nonwoven fabric contributes to keeping the moisture-resistant insulation properties of the laminate using the base material at a high level and not increasing the thermal expansion coefficient of the laminate in the planar direction. further,
The nonwoven fabric having a bulk density of 0.55 g / cc or more contributes to improving the thickness accuracy of the laminate. When the resin fiber nonwoven fabric according to the present invention is thermally compressed at a temperature equal to or higher than the glass transition temperature of the resin binder, the glass transition temperature of the resin binder is further increased. (Example 1
7 and Examples 7, 11, and 15 in which the amount of resin binder attached is the same as in Example 17). A nonwoven fabric in which thermoplastic fibers having a softening temperature of 220 ° C. or higher are mixed as the second fibers, and the second fibers are heat-sealed to resin fibers that are not substantially heat-softened, the bonding between the fibers is more reliably achieved. This further contributes to suppressing warpage and twisting of the laminate.

Claims (14)

[Claims] 1. An electric machine wherein resin fibers which are not substantially heat-softened are bound with a resin binder having a glass transition temperature of 200 ° C. or higher, and the adhesion amount of the resin binder is 5 to 25% by weight. Resin fiber non-woven fabric for insulation. 2. A resin fiber which does not substantially heat soften is a para-type aromatic polyamide fiber.
The resin fiber nonwoven fabric for electrical insulation according to the above. 3. The para-type aromatic polyamide fiber is poly-p-
3. The resin insulating nonwoven fabric according to claim 2, wherein the nonwoven fabric is phenylene 3,4'-diphenylether terephthalamide fiber. 4. The non-woven resin fiber fabric for electrical insulation according to claim 1, further comprising a thermoplastic resin fiber having a softening temperature of 220 ° C. or higher as the second fiber. 5. The resin-fiber non-woven fabric for electrical insulation according to claim 4, wherein the second fiber is heat-sealed to a resin fiber which does not substantially heat-soften. 6. The non-woven resin fiber fabric for electrical insulation according to claim 4, wherein the second fiber is a meta-type aromatic polyamide fiber. 7. The method according to claim 7, wherein the meta-type aromatic polyamide fiber is poly-m-
The resin insulating nonwoven fabric according to claim 6, wherein the nonwoven fabric is phenylene isophthalamide fiber. 8. The resin-fiber non-woven fabric for electrical insulation according to claim 1, wherein the amount of the resin binder attached is 10 to 20% by weight. 9. The resin-fiber non-woven fabric for electrical insulation according to claim 1, wherein the bulk density is 0.55 g / cc or more. 10. A nonwoven fabric (resin binder adhering amount: 5 to 25% by weight) in which resin fibers that are not substantially thermally softened are bonded with a resin binder having a glass transition temperature of 200 ° C. or higher at a temperature higher than the glass transition temperature. A method for producing a resin-fiber nonwoven fabric for electrical insulation, comprising thermally compressing. 11. The method for producing a resin nonwoven fabric for electrical insulation according to claim 10, wherein a nonwoven fabric containing a thermoplastic resin fiber having a softening temperature of 220 ° C. or higher as the second fiber is thermally compressed. 12. The method for producing a resin nonwoven fabric for electrical insulation according to claim 11, wherein the second fibers are heat-sealed to the resin fibers that are not substantially thermally softened by thermal compression. 13. A laminate obtained by heating and pressing a sheet-like fiber base material impregnated with a thermosetting resin, wherein the sheet-like base material is the resin fiber nonwoven fabric according to any one of claims 1 to 9. A laminated plate characterized by the above. 14. A prepreg obtained by impregnating and drying a thermosetting resin in a sheet fiber base material, wherein the sheet base material is the resin fiber nonwoven fabric according to any one of claims 1 to 9. .