JP2006036869A - Prepreg, laminate and printed wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a prepreg comprised of an epoxy resin composition having an inorganic filler highly charged without worsening the moldability and workability, to provide a laminate and to provide a printed-wiring board. <P>SOLUTION: The prepreg is prepared by forming a coated film of the inorganic filler on a sheet-like fiber substrate in advance and impregnating the epoxy resin composition containing an epoxy resin and a curing agent to the sheet-like fiber substrate to make a prepreg in a semi-cured state. Finally, the laminate is obtained. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a laminated board or printed wiring board having high thermal conductivity, and a prepreg used for constituting them.

  In recent years, with the reduction in size and weight of various electrical and electronic equipment products, laminated boards for printed wiring boards incorporated therein are also required to have various characteristics. In particular, when used in high-density mounting equipment such as personal computers and engine rooms of automobiles, the laminated board is exposed to a high temperature due to heat generated by the mounting parts or surrounding parts, which causes deterioration of the resin and deterioration of the functions of the mounting parts. There is a worry to cause.

  On the other hand, in a highly electronic vehicle control system, the influence of the reliability of electronic control devices on the reliability of the entire vehicle is significant. In general, durability and operating characteristics of electronic devices and units are affected by the usage environment. In the case of automobiles, the main heat source is the heat generated by engine heat, friction of the automatic transmission and brake system. In particular, the conditions in the engine room during climbing in high temperature weather or in a traffic jam are severely harsh conditions. When a printed wiring board is mounted directly in the engine room, it is a big problem how to withstand the high temperature conditions and how to release the heat.

  In addition, the performance of the mounted component itself is steadily improving, and the amount of heat generation is rapidly increasing. In order to cope with such a situation, there is an increasing demand for a technology for improving the heat dissipation of the laminate.

As a means for solving the above problems, there is a proposal of adopting the following laminated board as a printed wiring board.
(1) A metal-based laminate (Patent Document 1) in which a metal plate is insulated and coated with a resin composition to which an inorganic filler is added.
(2) A metal base laminate (Patent Document 2) in which an insulating adhesive sheet made of an epoxy resin is attached to a metal plate.
(3) A laminated plate obtained by heating and press-molding a prepreg layer obtained by impregnating an epoxy resin varnish into a sheet-like fiber base material in which aluminum nitride is introduced and heating and drying (Patent Document 3).
Each of the above-mentioned laminated plates is one in which heat dissipation is improved by using a metal plate or inorganic ceramic having good thermal conductivity. Therefore, the processability is inferior compared to a conventional laminate, that is, a laminate obtained by heat-pressing a layer of a prepreg obtained by impregnating a sheet-like fiber base material with a thermosetting resin varnish and drying by heating, In the case of using a metal plate, there is a problem that consideration must be given separately to insulation.

  On the other hand, in order to increase the thermal conductivity of conventional laminates, a general method is to add an inorganic filler such as alumina or silica to the resin. However, in order to add an inorganic filler to the resin, the inorganic filler is usually mixed with the resin varnish. Then, since the viscosity of the resin varnish increases remarkably, the resin varnish is applied to the sheet-like fiber substrate. Impregnation workability and moldability of prepreg deteriorate. Therefore, the present condition is that a large amount of inorganic filler cannot be added.

Japanese Patent Laid-Open No. 06-216484 Japanese Patent Laid-Open No. 08-167775 JP 2000-015746 A

  The problem to be solved by the present invention is to provide a laminated board or printed wiring board having high thermal conductivity by being highly filled with an inorganic filler, and to provide a prepreg for that purpose.

The gist of the present invention for achieving the above-mentioned problems is as follows.
The prepreg for electrical insulation according to the present invention is characterized in that an epoxy resin is held on a sheet-like fiber base material on which a film of an electrically insulating inorganic filler is formed. The electrically insulating inorganic filler is preferably made of an electrically insulating inorganic material having a thermal conductivity of 1 W / m · K or more.

  The laminate according to the present invention is obtained by heat-pressing the prepreg as a whole layer or a part of the prepreg layer integrally laminated. The printed wiring board according to the present invention includes an insulating layer formed by heating and pressing the prepreg layer.

  In the prepreg according to the present invention, since the inorganic filler film is formed on the sheet-like fiber base material in advance, even if the epoxy resin composition filled with a large amount of the inorganic filler is not held on the sheet-like fiber base material, the result is obtained. As a prepreg highly filled with inorganic filler. A cured product obtained by heating and pressing such a prepreg has high thermal conductivity, and contributes to the realization of a highly heat-conductive laminate or printed wiring board.

  Moreover, since the inorganic filler film is formed on the sheet-like fiber base material, the mechanical strength of the insulating layer is good, and the thermal characteristics are excellent. It is suitable for printed wiring boards for automobile equipment expected to be used in a high temperature atmosphere, and high-density mounting printed wiring boards such as personal computers.

  In the present invention, it is important to form an inorganic filler film on the surface of the sheet-like fiber substrate in advance for the purpose of highly filling the inorganic filler. The inorganic filler may be an electrically insulating inorganic material such as boron nitride, aluminum nitride, alumina, silica, magnesium oxide, and aluminum hydroxide, but is preferably a material having a thermal conductivity of 1 W / m · K or more. is there. The method for forming the film is, for example, means for thermally spraying the inorganic filler onto the sheet-like fiber base material. When a film is formed by thermal spraying, the particle size of the inorganic filler is preferably 1 μm or more. When the particle size is small, it is difficult to form a uniform film when the inorganic filler is melted at a high temperature and sprayed onto the sheet-like fiber substrate.

  In the present invention, the epoxy resin is preferably a biphenyl-containing epoxy resin. As the biphenyl-containing epoxy resin, any epoxy resin monomer having a biphenyl skeleton or a biphenyl derivative skeleton and having two or more epoxy groups in one molecule can be used. Particularly preferred is a biphenyl-containing epoxy resin monomer having the following chemical structural formula (Formula 1). This is because when this resin is used, the heat dissipation effect of the laminate is further increased.

  As the curing agent to be used, a curing agent conventionally used for advancing the curing reaction of the epoxy resin monomer can be used. Preferably, in order to obtain an epoxy resin cured product having a higher glass transition temperature and higher physical strength, it is preferable to have a rigid structure and a large number of reaction points that increase the crosslinking density. For example, amine compounds and derivatives thereof, acid anhydrides, imidazoles and derivatives thereof, and the like. Examples of the amine curing agent include compounds such as 4,4′-diaminodiphenylsulfone, 1,5-diaminonaphthalene, 4,4′-diaminodiphenylmethane, and derivatives thereof. Two or more kinds of these curing agents may be used in combination.

  Moreover, the hardening accelerator conventionally used in order to advance the polycondensation reaction of an epoxy resin monomer and a hardening | curing agent can be used for a hardening accelerator. Examples thereof include triphenylphosphine, imidazole and derivatives thereof, tertiary amine compounds and derivatives thereof.

  The epoxy resin composition containing the epoxy resin monomer, the curing agent, and the curing accelerator may contain a flame retardant, a diluent, a plasticizer, a coupling agent, and the like as necessary. Moreover, a solvent can be used as needed when impregnating this epoxy resin composition in the sheet-like fiber base material in which the membrane | film | coat of the inorganic filler was formed, and drying and manufacturing a prepreg. Use of these solvents does not affect the properties of the cured product.

  Furthermore, the epoxy resin composition may contain a metal oxide, hydroxide, inorganic ceramic, or other filler. For example, inorganic powder fillers such as boron nitride, aluminum nitride, silicon nitride, silicon carbide, titanium nitride, zinc oxide, tungsten carbide, alumina, magnesium oxide, silica, aluminum hydroxide, glass fiber, pulp fiber, synthetic fiber, ceramics Fibrous fillers such as fibers, colorants and the like can be added. Preferably, it is selected from boron nitride, aluminum nitride, silicon nitride, silicon carbide, titanium nitride, zinc oxide, tungsten carbide, alumina, and magnesium oxide. The shape of the filler may be any of powder (bulk shape, spherical shape), short fiber, long fiber and the like.

  The prepreg according to the present invention is obtained by impregnating the above epoxy resin composition into a sheet-like fiber base material (woven fabric or nonwoven fabric composed of glass fibers or organic fibers) on which an inorganic filler film is formed, and drying by heating. An epoxy resin is in a semi-cured state. The laminate is formed by heating and pressing the prepreg as a whole layer or a part of the prepreg layer, and copper foil or the like on one side or both sides by the heating and pressing as necessary. Bond metal foils together. Furthermore, the printed wiring board is provided with an insulating layer formed by heating and press-molding the prepreg layer, and has a single-sided printed wiring board, a double-sided printed wiring board, and further, a printed wiring on the inner layer and the surface layer. It is a multilayer printed wiring board.

  Examples of the present invention will be described below, and the present invention will be described in detail. In the following examples and comparative examples, “part” means “part by mass”. Moreover, this invention is not limited to a present Example, unless it deviates from the summary.

Examples 1-3
In advance, boron nitride with a mean particle size of 4 μm (thermal conductivity: 60 W / m · K, manufactured by Denki Kagaku Kogyo) is sprayed onto a glass fiber woven fabric with a thickness of 0.2 mm, and a boron nitride film is coated on the surface of the glass fiber woven fabric. Formed. At this time, the thickness of the film was set to three types: 5 μm (Example 1), 8 μm (Example 2), and 10 μm (Example 3).
As an epoxy resin component, 100 parts of biphenyl-containing epoxy resin (“YL6121H” manufactured by Japan Epoxy Resin, epoxy equivalent of 175) was dissolved in 100 parts of methyl ethyl ketone (manufactured by Wako Pure Chemical Industries) at 100 ° C. and returned to room temperature.
Next, 21 parts of 1,5-diaminonaphthalene (“1,5-DAN” manufactured by Wako Pure Chemical Industries, Ltd., amine equivalent 40) as a curing agent is dissolved in 100 parts of methyl ethyl ketone (manufactured by Wako Pure Chemical Industries) at 100 ° C. , Returned to room temperature.
These resin solution and curing agent solution were mixed and stirred to obtain a uniform epoxy resin varnish. “YL6121H” is an epoxy resin monomer having R = —CH ₃ , n = 0.1 and an epoxy resin monomer having R = —H, n = 0.1 in the chemical structural formula (formula 1), etc. It is an epoxy resin monomer contained in moles.
The epoxy resin varnish was impregnated into each glass fiber woven fabric having a different boron nitride film thickness and dried by heating to obtain a prepreg. The four prepregs were stacked and formed by heating and pressurizing for 90 minutes under conditions of a temperature of 175 ° C. and a pressure of 4 MPa to obtain a laminate having a thickness of 0.8 mm.

About Examples 1-3, the measurement result of the prepreg preparation availability and the glass transition temperature, storage elastic modulus, and thermal conductivity of the laminate is shown together in Table 1 together with the composition of the epoxy resin composition.
The glass transition temperature and the storage elastic modulus were obtained by cutting out a plate sample of 5 mm × 30 mm from the above laminate and measuring the dynamic viscoelasticity. These measurements used a dynamic viscoelasticity measuring device (DMA) and conformed to JIS-C-6481 5.17.2.
The thermal conductivity was measured at room temperature in accordance with the probe method by cutting out a plate sample of 50 mm × 120 mm from the above laminate.

  In the laminated plates of Examples 1 to 3, although there is no significant difference in the glass transition temperature, the thermal conductivity and the storage elastic modulus increase as the boron nitride film thickness increases.

Example 4
In the epoxy resin varnish used in Example 3, 69 parts of boron nitride (manufactured by Denki Kagaku Kogyo Co., Ltd.) having an average particle size of 4 μm was blended as a filler to prepare an epoxy resin varnish, and this varnish was used. Except for the above, a prepreg and a laminate were produced in the same manner as in Example 3.
This laminated plate has a greatly improved thermal conductivity of 7.2 W / m · K.

Examples 5 and 6
The filler sprayed on the glass fiber woven fabric is changed to magnesium oxide (thermal conductivity: 30 W / m · K, Example 5) and silica (thermal conductivity: 1.3 W / m · K, Example 6). Thereafter, a prepreg and a laminate were produced in the same manner as in Example 3.

Example 7
Instead of using the epoxy resin “YL6121H”, a bisphenol A type epoxy resin (“Ep828” manufactured by Japan Epoxy Resin, epoxy equivalent 185) was used instead, and prepregs and laminates were obtained in the same manner as in Example 3. It was.
As a result of cutting out a plate-like sample of 50 mm × 120 mm from this laminated plate and measuring the thermal conductivity, it was 1.0 W / m · K and a value lower than that when “YL6121H” was used.

Example 8
Instead of using “1,5-DAN” as the curing agent, instead of 62 parts of a liquid phenol novolac resin (“YLH987” manufactured by Japan Epoxy Resin, hydroxyl equivalent weight 116), the same as in Example 3 was used. Thus, a prepreg and a laminate were obtained.
A plate-like sample of 50 mm × 120 mm was cut out from this laminate and the thermal conductivity was measured. As a result, it was 1.7 W / m · K, but the glass transition temperature was reduced to 145 ° C. and the storage elastic modulus was reduced to 11 MPa.

Comparative Example 1
A prepreg and a laminate were obtained in the same manner as in Example 4 except that a raw glass fiber woven fabric not sprayed with boron nitride was used.
A 50 mm × 120 mm plate-like sample was cut out from this laminate and the thermal conductivity was measured. As a result, it was 0.7 W / m · K.

Comparative Example 2
In Comparative Example 1, when 183 parts of boron nitride having an average particle diameter of 4 μm was added as a filler to the epoxy resin varnish, the viscosity of the varnish became too high to be used for the production of the prepreg.

Claims (4)

  A prepreg for electrical insulation in which an epoxy resin is held on a sheet-like fiber base material on which a film of an electrically insulating inorganic filler is formed.   The prepreg according to claim 1, wherein the electrically insulating inorganic filler is made of an electrically insulating inorganic material having a thermal conductivity of 1 W / m · K or more.   A laminate obtained by heat-pressing the prepreg according to claim 1 or 2 as all or a part of the prepreg layer.   A printed wiring board comprising an insulating layer formed by heating and press-molding the prepreg layer according to claim 1.