JPH0317857B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a method for producing prepreg for printed wiring boards. [Prior Art] As the density of printed wiring boards increases, the number of layers increases, the diameter of through holes becomes smaller, and materials for printed wiring boards with good drillability are required. In terms of drillability, the occurrence of smear impedes the conduction between the inner layer circuit copper and the through-hole plated copper, significantly impairing the through-hole reliability. In order to remove smear, printed wiring board manufacturers perform a hesmear removal process, but it uses concentrated sulfuric acid, hydrofluoric acid, chromium, etc., which poses a safety problem. Further, such treatment roughens the inner wall of the through hole, causing a reduction in the reliability of the through hole. The cause of smear is
This is said to be caused by resin softened by the frictional heat generated during drilling and adhering to the cross section of the inner layer circuit copper foil inside the through hole. Even when the conventionally used prepreg for printed wiring boards is sufficiently cured, the temperature at which it cures and fuses is low, at about 250°C. Generally, the drill temperature during drilling is 300℃.
Conventional cured prepreg resins for printed wiring boards (for example, dicyandiamide cured epoxy resins) soften and adhere to the cross section of the inner layer circuit copper foil, resulting in smear. Furthermore, when printed wiring boards are used with components mounted on them, temperatures can reach temperatures of over 100°C. Therefore, long-term heat resistance in air is required. When a laminate made using conventional prepreg for printed wiring boards is treated in a dryer at 170°C for a long time, it takes about 500 hours for the bending strength retention rate to decrease to 50% or less. It is. By making this time longer, the reliability when used with components mounted and energized is improved. As a resin system that satisfies the above requirements, there is an epoxy resin cured with a polyfunctional phenolic resin. When polyfunctional phenol-cured epoxy resin is applied to prepreg for printed wiring boards, the occurrence of smear during drill workability is reduced to less than half that of conventional products using dicyandiamide-cured epoxy resin, and long-term heat resistance and bending strength are maintained. The processing time at 170°C until the yield rate falls below 50% is 2 times longer than that of conventional products.
It will more than double. However, epoxy resins using polyfunctional phenolic resin as a curing agent have poorer adhesion to metals such as copper foil than conventional products. For example, the peel strength of a 35 μm thick copper foil with one side roughened is about 2 Kg/cm for conventional products, whereas the peel strength for products using polyfunctional phenol-cured epoxy resin is about 1 to 1.5 Kg/cm.
Kg/cm. In addition, when the metallic luster surface is subjected to roughening and oxidation treatment, the peel strength also decreases.
For example, the adhesion to the glossy surface of copper foil that has been treated in this way is approximately 1.5 kg/cm compared to the conventional product.
For products using polyfunctional phenol-cured epoxy resins, it is approximately 0.5 to 1 kg/cm. Furthermore, when we measured the peel strength of these specimens after immersing them in hydrochloric acid, we found that the peel strength of conventional products hardly decreased;
For products using polyfunctional phenol-cured epoxy resins, the value is halved. [Problems to be Solved by the Invention] The present invention has been made in view of the above circumstances, and provides printed wiring using a polyfunctional phenol-cured epoxy resin that has good drill workability and long-term atmospheric heat resistance. The purpose is to improve the adhesion of plate prepreg to metal. [Means for Solving the Problems] That is, the method for producing a prepreg for a printed wiring board of the present invention includes: (a) an epoxy resin (b) a multifunctional phenol (c) an inorganic acid salt of an aliphatic amine (d) coupling The method is characterized in that a base material is impregnated with a varnish containing a curing accelerator and (e) a curing accelerator as essential components, and then dried. The present invention will be explained in detail below. Any polyfunctional epoxy resin may be used as the epoxy resin (a), such as bisphenol A
type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, phenol novolak type epoxy resin, cresol novolak type epoxy resin, bisphenol A novolak type epoxy resin, bisphenol F type novolak type epoxy resin, alicyclic resin There are formula epoxy resins, glycidyl ester type epoxy resins, glycidylamine type epoxy resins, vidantoin type epoxy resins, isocyanurate type epoxy resins, aliphatic chain epoxy resins, and their halides and hydrogenated products. It is also possible to use several types in combination. The polyfunctional phenol resin (b) may be any resin as long as it has two or more functional groups in one molecule and can be polymerized with an epoxy resin, such as bisphenol A, bisphenol F, polyvinylphenol, or Examples include novolak resins such as phenol, cresol, alkylphenol, catechol, bisphenol A, and bisphenol F, and halogenated products of these phenolic resins.
Several types of these phenolic resins can also be used in combination. The blending amount is preferably in the range of 0.5 to 1.5 equivalents of phenolic hydroxyl group to epoxy group from the viewpoint of drill workability. (c) The aliphatic amine inorganic hydrochloric acid is necessary to improve the peel strength of copper foil, and examples of aliphatic amines include ethylamine, methylamine, ethylenediamine, and other aliphatic monovalent and polyvalent It is an amine. Examples of inorganic acids include hydrohalic acids such as hydrochloric acid and hydrobromic acid, as well as phosphoric acid, sulfuric acid, and sulfurous acid. Several types of these compounds can be used in combination. The blending amount is 0.1 per 100 parts by weight of epoxy resin.
The amount is preferably 10 parts by weight. If it is less than 0.1 part by weight, it has no effect on copper foil peeling strength, and 10
If the amount exceeds the weight part, drilling workability will be reduced. The coupling agent (d) is necessary to improve the peel strength of the copper foil, and can be significantly improved by using it in combination with an inorganic acid salt of an aliphatic amine. Silane coupling agents, titanate coupling agents, etc. are used. Silane coupling agents include γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, and N-β(aminoethyl)-γ-aminopropylmethoxysilane. , γ-mercaptopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-ureidopropyltriethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, N-vinylbenzyl-δ-
Aminopropyltriethoxysilane, etc.
In addition, any material may be used as long as it has a functional group that reacts with an epoxy group or a phenolic hydroxyl group, and also has a hydrolyzable alkoxy group. Titanate coupling agents include isopropyl triisostearoyl titanate, isopropyl tridodecylbenzenesulfonyl titanate, isopropyl tris(dioticle birophosphate) titanate, tetrapropyl bis(dioctyl phosphite) titanate, tetraoctyl bis(ditridecyl phosphite) Titanate, tetra(2,2-diallyloxymethyl-1-butyl)
Examples include bis(di-tridecyl) phosphite titanate, bis(dioctyl pyrophosphate) oxyacetate titanate, and bis(dioctyl pyrophosphate) ethylene titanate, and titanates with lower molecular weights may also be used. The blending amount of these coupling agents is preferably 0.1 to 10 parts by weight per 100 parts by weight of the epoxy resin. Less than this has no effect on copper foil peeling strength, and more than this has no effect on heat resistance and drilling workability. decreases. As the curing accelerator (e), imidazole compounds, organic phosphorus compounds, tertiary amines, quaternary ammonium salts, etc. are used, but imidazole compounds whose imino groups are masked with acrylonitrile, isocyanate, melamine acrylate, etc. By using this method, it is possible to obtain a prepreg that has storage stability that is more than twice that of conventional prepregs. The imidazole compounds used here include imidazole, 2-ethylimidazole, 2
-ethyl-4-methylimidazole, 2-phenylimidazole, 2-undecylimidazole,
1-benzyl-2-methylimidazole, 2-heptadecyl imidazole, 4,5-diphenylimidazole, 2-methylimidazoline, 2-phenylimizodalin, 2-undecylimidazoline, 2-heptadecylimidazoline, 2-isopropyl imidazole, 2,4-dimethylimidazole, 2-phenyl-4-methylimidazole,
2-ethylimidazoline, 2-isopropylimidazoline, 2,4-dimethylimidazoline, 2-
phenyl-4-methylimidazoline, etc.
Examples of masking agents include acrylonitrile, phenylene diisocyanate, triene diisocyanate, naphthalene diisocyanate, hexamethylene diisocyanate, methylene bisphenyl isocyanate, and melamine acrylate. Several types of these curing accelerators may be used in combination, and the blending amount is 0.01 parts by weight per 100 parts by weight of epoxy resin.
~5 parts by weight is preferred. If it is less than 0.01 part by weight, the promoting effect will be small, and if it is more than 5 parts by weight, storage stability will be poor. Further, a solvent is often used when impregnating a base material with a blended varnish. These solvents include acetone, methyl ethyl ketone, toluene,
xylene, methyl isobutyl ketone, ethyl acetate, ethylene glycol monomethyl ether,
Examples include N,N-dimethylformamide, N,N-dimethylacetamide, methanol, and ethanol, and several types of these may be used in combination. The varnish obtained by blending the above (a), (b), (c), (d) and (e) is mixed with glass cloth, glass non-woven fabric or paper, or a base material other than glass, and then dried in a drying oven for 80 minutes. Dry with a cloth containing ingredients in the range of ~200°C to obtain prepreg for printed wiring boards. Prepreg is heated and pressed to produce printed wiring boards or metal clad laminates (hereinafter referred to as MCL).
It is used for manufacturing. Drying here means removing the solvent if a solvent is used, or making it lose fluidity at room temperature if no solvent is used. [Examples] Examples of the present invention will be described below. Example 1 Brominated bisphenol A type epoxy resin (epoxy equivalent: 530) 80 parts by weight Phenol novolak type epoxy resin (epoxy equivalent: 200) 20 parts by weight Phenol novolak resin 30 parts by weight Ethylamine hydrochloride 2 parts by weight γ-glycidoxy resin Propyltrimethoxysilane
2 parts by weight 1-cyanoethyl-2-phenylimidazole
0.2 parts by weight The above compound was dissolved in methyl ethyl ketone to prepare a varnish with a nonvolatile content of 60%. 0.1mm of this varnish
After impregnating a thick glass cloth, the mixture was dried at 130°C for 5 minutes to obtain a prepreg. Example 2 In place of ethylamine hydrochloride in Example 1, 2 parts by weight of ethylenediamine dihydrochloride was blended. Example 3 In place of ethylamine hydrochloride in Example 1, 22 parts by weight of ethylamine hydrogen bromide was blended. Example 4 Instead of γ-glycidoxypropyltrimethoxysilane in Example 1, 1 part by weight of γ-mercaptopropylmethyldimethoxysilane was blended. Example 5 In place of γ-glycidoxypropyltrimethoxysilane in Example 1, 1 part by weight of tetraoctyl bis(ditridecylphosphite) titanate was blended. Comparative Example 1 Both ethylamine hydrochloride and γ-glycidoxypropyltrimethoxysilane in Example 1 were not blended. Comparative Example 2 Ethylamine hydrochloride in Example 1 was not blended. Comparative Example 3 γ-Glycidoxytrimethoxysilane in Example 1 was not blended. Comparative Example 4 In place of 1-cyanoethyl-2-phenylimidazole in Example 1, 2-phenylimidazole was blended. Comparative Example 5 In place of the phenol novolac resin in Example 1, 4 parts by weight of dicyandiamide was blended.
In addition to methyl ethyl ketone in Comparative Example 1, N,N-dimethylformamide was used as a solvent. Drying was carried out at 170°C for 5 minutes in addition to 130°C for 5 minutes. Three sheets of prepreg obtained in Examples 1 to 5 and Comparative Examples 1 to 5 and two sheets of 35 μm thick copper foil were heated at 170°C for 60 minutes.
A copper-clad laminate was produced under the conditions of 50 kg/cm ² and 50 kg/cm 2 .
After processing the inner layer circuit on the MCL, a 6-layer wiring board was fabricated using 3 MCL sheets and 6 prepreg sheets. Drill workability, air heat resistance, copper foil peeling strength, and soldering heat resistance were evaluated using this six-layer wiring board. The table also shows the results of evaluating the change in prepreg gel time over time in order to evaluate the storage stability of the prepreg.

【table】

〔Effect of the invention〕

The prepreg for printed wiring boards of the present invention has improved drilling workability for multilayer wiring boards, copper foil peeling strength, in-air heat resistance, and storage stability of the prepreg compared to conventional techniques.

Claims (1)

[Scope of Claims] 1. A varnish based on (a) an epoxy resin, (b) a multifunctional phenolic resin, (c) an inorganic acid salt of an aliphatic amine, (d) a coupling agent, and (e) a curing accelerator as essential components. A method for producing prepreg for printed wiring boards, which comprises impregnating the material and then drying it. 2. The method for producing a prepreg for a printed wiring board according to claim 1, wherein the curing accelerator is an imidazole compound with an imino group masked.