JPH11279375A - Resin composition for printed wiring board and printed wiring board using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a resin composition for printed wiring board which shows a high glass transition temperature and an excellent dielectric property, restrains generation of a metal migration and has high reliability of electric insulation without sacrificing heat resistance, adhesion, fire resistance or the like, and a printed wiring board using the same. SOLUTION: A resin composition for printed wiring board contains (A) 100 pts.wt. of a cyanate compound having not less than 2 isocyanate groups in a molecule, (B) 50-250 pts.wt. of an epoxy compound, (C) 0.1-5 pts.wt. of a hardening accelerator and (D) 0.1-20 pts.wt. of an antioxidant. The printed wiring board is obtained by impregnating the resin composition as a varnish in a substrate, drying thereof to obtain a pre-preg, laminating metal foil on one side or both sides of at least one pre-preg and forming thereof under heat and pressure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a high glass transition temperature (Tg), dielectric properties, heat and moisture resistance, insulation reliability, and the like.
The present invention relates to a resin composition for a printed wiring board having excellent flame resistance and a printed wiring board using the same.

[0002]

2. Description of the Related Art In recent years, an advanced information society in which a computer and a communication device are integrated has been developed. Due to the downsizing of computers, small systems are required to have the same processing capacity as conventional large machines. In addition, miniaturization, weight reduction, and high performance of information terminal devices typified by mobile phones, personal computers, and the like, which are rapidly spreading, are being promoted. The density of printed wiring boards mounted thereon has been increased and the thickness thereof has been reduced, and high heat resistance and high insulation reliability have been required. Further, in order to cope with an increase in signal speed and an increase in frequency, a material having a low relative dielectric constant and a low dielectric loss tangent is required. In order to respond to such demands, in a printed wiring board using an epoxy resin composition, a method of curing a polyfunctional epoxy resin with dicyandiamide, a method of curing with a polyfunctional phenol resin, and the like are performed as a method of improving heat resistance. ing. Further, the following proposals have been made for the purpose of improving the dielectric properties of epoxy resins. For example, an epoxy resin may be a poly-4-methyl-1-pentene disclosed in JP-A-60-135425, a phenol-added butadiene polymer disclosed in JP-A-61-126162, or an epoxy resin. There is a method of reacting with a polybutadiene modified with a terminal carboxy group described in JP-A-62-187736, a propargyl etherified aromatic hydrocarbon described in JP-A-4-13717, and the like. Further, as disclosed in JP-A-57-83090, hollow particles are mixed in a resin layer.
Japanese Patent Application Laid-Open No. Hei 4-24 / 2004, which uses an aromatic polyamide fiber as a base material described in Japanese Patent Application Laid-Open No. 3-84040 in which a fluororesin powder disclosed in Japanese Patent Application Laid-Open No.
No. 986, there is a method in which a glass cloth base fluororesin prepreg and a glass cloth base epoxy resin prepreg are stacked and used.

On the other hand, resin materials such as cyanate ester resins and BT resins (bismaleimide-triazine resins) have also been proposed as resin materials having both high heat resistance and low dielectric properties other than epoxy resin-based materials. However, these have the drawback that they have high water absorption and are inferior in adhesiveness, heat resistance when absorbing moisture, and the like.

Therefore, cyanate ester resins and BT
(Bismaleimide-triazine) In order to improve the above-mentioned disadvantages of the resin, glycidyl etherified product of phenol novolac shown in JP-A-63-54419 and phenols added in JP-A-2-214471 are disclosed. Epoxy resins such as glycidyl etherified dicyclopentadiene polymer, glycidyl etherified bisphenol A disclosed in JP-A-3-84040, and brominated phenol novolak disclosed in JP-A-2-286723. There is a method in which an epoxy resin such as glycidyl ether is used in combination.

[0005]

However, Japanese Patent Application Laid-Open Nos. 60-135425 and 61-126162 disclose the method.
Polymers such as poly-4-methyl-1-pentene, phenol-added butadiene polymer, polybutadiene modified with a terminal carboxy group, and epoxy resins as disclosed in JP-A-62-187736 and JP-A-62-187736. Has a problem that the inherent heat resistance of the epoxy resin is impaired, although the dielectric constant is lowered. Also, the method of reacting with propargyl etherified aromatic hydrocarbons disclosed in Japanese Patent Application Laid-Open No. Hei 4-13717 has a problem that the heat resistance is high but the cost is extremely high because a special resin is used. Was.

Further, a method of mixing hollow particles in a resin layer, a method of blending a fluororesin powder, a method of blending a fluororesin powder, and a method disclosed in JP-A-57-83090 and JP-A-2-203594. No. 84040 and JP-A-4-24-2
In the method using an aromatic polyamide fiber on a substrate as described in JP-A-4986 or the method using a glass cloth substrate with a fluororesin prepreg laminated thereon, the dielectric constant of the laminated plate is low, but the conventional glass cloth is used. There was a problem that the mechanical properties were lower than that of the base epoxy resin laminate.

Further, the dicyandiamide curing system has a drawback that the hygroscopicity becomes high, and it is difficult to satisfy the high insulation reliability for semiconductor package applications. In particular, the occurrence of metal migration (electrolytic corrosion) in which a metal constituting wiring, a circuit pattern, or an electrode moves on or in an insulating material due to the action of a potential difference in a high-humidity environment on or in the insulating material. It has become a very big problem. In addition, in the case of the polyfunctional phenol-cured resin, the cured resin becomes rigid, and minute cracks are likely to occur during drilling of through holes, and there is concern that metal migration may occur from these minute cracks. I can't satisfy her.

Further, in the method disclosed in JP-A-3-84040, in which an epoxy resin is blended with a cyanate ester resin, the adhesiveness is improved, but the water absorption rate is reduced and the heat resistance during moisture absorption is improved. Has no significant effect. In the method using an epoxy resin as disclosed in JP-A-63-54419, a decrease in Tg can be suppressed to some extent, and the heat resistance at the time of moisture absorption and the adhesion to metal can be improved, but the water absorption rate is low. However, there is a drawback that it increases, and no significant effect is seen in improving workability. In the method using an epoxy resin as disclosed in Japanese Patent Application Laid-Open No. 2-214741, the water absorption, the processability, and the heat resistance during moisture absorption are improved, but the problem that the adhesion to metal deteriorates. is there. Also, JP-A-2-286723
In the glycidyl etherified product of brominated phenol novolak disclosed in Japanese Patent Application Laid-Open Publication No. H10-209, there is a problem that the processability, the heat resistance during moisture absorption and the flame resistance can be added, but the water absorption deteriorates.

The present invention has a high glass transition temperature, excellent dielectric properties, and suppresses the occurrence of metal migration without impairing properties such as heat resistance, adhesion, and flame resistance.
An object of the present invention is to provide a resin composition for a printed wiring board which maintains high insulation reliability and a printed wiring board using the same.

[0010]

The present invention relates to (A) a cyanate compound containing two or more cyanato groups in one molecule, (B) an epoxy resin, (C) a curing accelerator and (D) a curing accelerator.
It is a resin composition for printed wiring boards containing an antioxidant.

The present invention also relates to (A) 100 to 100 parts by weight of a cyanate compound containing two or more cyanato groups per molecule, (B) 50 to 250 parts by weight of an epoxy resin,
It is a preferable resin composition for printed wiring boards containing (C) 0.1 to 5 parts by weight of a curing accelerator and (D) 0.1 to 20 parts by weight of an antioxidant. Further, the present invention provides a method for producing a cyanate compound comprising (A) a cyanate compound containing two or more cyanato groups in one molecule, comprising 2,2-bis (4-cyanatephenyl) propane or a prepolymer containing this prepolymer as a main component. A compound, (B) the epoxy resin contains a brominated bisphenol A type epoxy resin as a main component, and (C) a curing accelerator is an organic metal salt or an organic metal of iron, copper, zinc, cobalt, nickel, manganese, or tin. The printed wiring board, wherein the complex and the imidazole compound are used in combination, and (D) the antioxidant contains one or more selected from a phenolic antioxidant and a sulfur organic compound antioxidant. It is a resin composition for use.

The present invention also provides a varnish of the above-described resin composition for a printed wiring board, impregnation of a substrate, and drying, and laminating at least one or more prepregs, and laminating a metal foil on one or both surfaces thereof. It is a printed wiring board obtained by heating and pressing.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The (A) cyanate compound containing two or more cyanato groups in one molecule used in the resin composition for a printed wiring board of the present invention is not particularly limited, but is preferably 2 , 2-bis (4-cyanatephenyl)
It is particularly preferable to use propane or a cyanate compound containing this prepolymer as a main component, in terms of productivity, handleability, cost, and the like.

The monomer (A) of a cyanate compound having two or more cyanato groups in the molecule has high crystallinity, and when these monomers are varnished with a solvent, the varnish may vary depending on the solid concentration. May be recrystallized. Therefore, it is preferable to use the above-mentioned cyanate compound monomer in the form of a prepolymer.

The epoxy resin (B) used in the resin composition for a printed wiring board of the present invention is not particularly limited as long as it is an epoxy resin having two or more epoxy groups in one molecule. Specifically, a mixture of at least one or more selected from a bisphenol A type epoxy resin, a phenol novolak type epoxy resin, a cresol type epoxy resin, a biphenyl type epoxy resin, and a phenol salicylaldehyde novolak type epoxy resin can be used. Further, it is preferable to blend a brominated bisphenol A type epoxy resin or a brominated phenol novolak type epoxy resin in order to secure the flame resistance as a printed wiring board, and the amount of the bromine is 10% by weight or more based on the whole resin. It is preferable to mix them. In addition, it is preferable to incorporate a brominated bisphenol A type epoxy resin from the viewpoint of dielectric properties.

The amount of the epoxy resin (B) used in the resin composition for printed wiring boards of the present invention is not particularly limited, but (A) cyanates containing two or more cyanate groups in one molecule. It is preferable that the epoxy resin (B) is 50 to 250 parts by weight based on 100 parts by weight of the compound. If the amount is less than 50 parts by weight, heat resistance at the time of moisture absorption tends to be deteriorated, and if it exceeds 250 parts by weight, the dielectric properties are deteriorated and the glass transition temperature (Tg) is undesirably lowered.

The curing accelerator (C) used in the resin composition for a printed wiring board of the present invention accelerates the curing reaction of the cyanate group of the cyanate compound (A) containing two or more cyanato groups in one molecule. A compound having a catalytic function,
It is preferable to use (B) a compound having a catalytic function of accelerating the curing reaction of the glycidyl group of the epoxy resin. Specifically, (A) a compound having a catalytic function of accelerating the curing reaction of a cyanate group of a cyanate compound containing two or more cyanato groups in one molecule,
Examples include organometallic salts or organometallic complexes of iron, copper, zinc, cobalt, nickel, manganese, and tin. The compounding amount is preferably 0.2 to 2 parts by weight based on 100 parts by weight of the cyanate compound (A) containing two or more cyanato groups in one molecule. Examples of the compound (B) having a catalytic function of accelerating the curing reaction of the glycidyl group of the epoxy resin include alkali metal compounds, alkaline earth metal compounds, imidazole compounds, organic phosphorus compounds, secondary amines and tertiary amines. And a quaternary ammonium salt. An imidazole compound is most preferable as a glycidyl group catalytic function, and therefore it is preferable to use it. The compounding amount is preferably 0.1 to 2 parts by weight based on 100 parts by weight of the epoxy resin. The sum of the amount of the compound having a catalytic function of accelerating the curing reaction of the cyanate group of the cyanate compound and the amount of the curing accelerator which is the compound having the catalytic function of accelerating the curing reaction of the glycidyl group of the epoxy resin is 0.1 to 5 It is preferable to use parts by weight. If the amount is less than 0.1 part by weight, the catalyst function is inferior and the curing time becomes longer. On the other hand, when the amount exceeds 5 parts by weight, the storage stability of the varnish or prepreg becomes poor.

As the (D) antioxidant used in the resin composition for a printed wiring board of the present invention, a phenolic antioxidant and a sulfur organic compound antioxidant are used. Specific examples of phenolic antioxidants include pyrogallol,
Monophenols such as butylated hydroxyanisole and 2,6-di-t-butyl-4-methylphenol, and 2,2′-methylene-bis- (4-methyl-6-t-butylphenol), 4,4 ′ Bisphenols such as -thiobis- (3-methyl-6-t-butylphenol) and 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl)
Benzene, tetrakis- [methylene-3- (3'-5 '
-Di-t-butyl-4'-hydroxyphenyl) propionate] methane. Among the phenolic antioxidants, bisphenol-based antioxidants are particularly preferred in terms of effect. Specific examples of the sulfur organic compound antioxidant include dilauryl thiodipropionate, distearyl thiodipropionate, and the like. Some of these antioxidants may be used in combination. The antioxidant (D) of the present invention comprises (A) a cyanate compound 100 having two or more cyanate groups in one molecule.
It is preferable to mix 0.1 to 20 parts by weight with respect to parts by weight. If the amount is less than 0.1 part by weight, no improvement in insulating properties is observed, and if it exceeds 20 parts by weight, the insulating properties tend to decrease.

In the resin composition for a printed wiring board of the present invention, a filler and other additives can be blended as required. As the filler to be blended as necessary, usually, an inorganic filler is suitably used, specifically, fused silica, glass, alumina, zircon, calcium silicate, calcium carbonate, silicon nitride, boron nitride, beryllia, Zirconia, potassium titanate, aluminum silicate, magnesium silicate and the like can be mentioned, and these are used in the form of powder or sphere. Also, whiskers, single crystal fibers, glass fibers, inorganic and organic hollow fillers and the like can be blended.

The resin composition for a printed wiring board of the present invention can be subjected to the production of a printed wiring board excellent in dielectric properties, heat resistance and insulation reliability by heating and curing. That is, first, a prepreg is prepared by dissolving the resin composition for a printed wiring board of the present invention in a solvent to form a varnish once, impregnating a substrate such as a glass cloth, and drying. Then, the prepreg can be made into a printed wiring board (metal-clad laminate) by heating and press-molding an arbitrary number of the prepregs and a metal foil on one or both upper and lower surfaces thereof, and forming a circuit thereon. A printed wiring board is obtained.

When the resin composition for a printed wiring board of the present invention is varnished, the solvent is not particularly limited, but ketones, aromatic hydrocarbons, esters, amides, alcohols and the like are used. . Specifically, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone and the like are used as ketone solvents, toluene and xylene are used as aromatic hydrocarbon solvents, and methoxyethyl acetate, ethoxyethyl acetate and butoxy are used as ester solvents. Ethyl acetate, ethyl acetate and the like, and N-methylpyrrolidone, N, N-dimethylformamide, N-methylformamide, N, N
-Dimethylacetamide and the like, alcohol-based solvents such as methanol, ethanol, ethylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol, propylene glycol Monomethyl ether, dipropylene glycol monomethyl ether, propylene glycol monopropyl ether, dipropylene glycol monopropyl ether and the like can be mentioned. These solvents may be used alone or in combination of two or more. The copper foil used in the present invention is generally used for a laminated board in the range of 5 to 200.
μm can be used. Also, nickel, nickel-
Phosphorus, nickel-tin alloy, nickel-iron alloy, lead, lead-tin alloy, etc. are used as the intermediate layer, and 0.5 to 15 μm
A composite foil having a three-layer structure provided with a copper layer of m and a copper layer of 10 to 300 μm or a composite foil of aluminum and a copper foil can be used. Usually the molding temperature is 150-180
C., optionally in the range of 130 to 200 ° C., and the pressure is usually in the range of 1 to 6 MPa, sometimes in the range of 0.5 to 20 MPa,
It is appropriately selected according to the thickness of the target laminated plate. After the completion of molding, post-curing may be performed.

In a general epoxy resin curing reaction, a highly polar hydroxyl group is generated with the opening of the epoxy group.
There is a limit to lowering the dielectric constant. In addition, when a special curing agent represented by a hydrocarbon polymer such as phenol-added polybutadiene is used, the inherent heat resistance of the epoxy resin is impaired, and the glass transition is lower than when cured with a polyfunctional phenol resin or the like. There are problems such as low temperature and high cost. On the other hand, a cured product of a cyanate ester resin having a low-polarity, rigid and symmetric triazine skeleton has a low dielectric constant, a low dielectric loss tangent, and a high glass transition temperature, but has problems such as adhesiveness and heat resistance when absorbing moisture. There is. To solve this problem, a resin composition using a cyanate ester resin and an epoxy resin based on a conventional bisphenol A, brominated bisphenol A, or phenol-added dicyclopentadiene polymer can be used to increase the water absorption rate and adhere to metals. Problems such as sex occur. The resin composition for a printed wiring board of the present invention has a higher glass transition temperature and dielectric properties as compared with a conventional epoxy resin-based resin composition for a printed wiring board or a resin composition using the above-described cyanate ester resin and epoxy resin in combination. A resin composition for printed wiring boards that excels in heat resistance, flame resistance, and uses phenolic antioxidants and sulfur organic compound antioxidants to suppress the occurrence of metal migration and have high electrical insulation reliability. An article and a printed wiring board using the same can be obtained.

[0023]

EXAMPLES The present invention will be described below in detail with reference to examples, but the present invention is not limited to these examples.

Example 1 (A) As a cyanate compound containing two or more cyanato groups in one molecule, a prepolymer of 2,2-bis (4-cyanatophenyl) propane (ArocyB-30,
(B) As epoxy resin, bisphenol A type epoxy resin (DER331L, Dow Chemical Japan Co., Ltd.) and brominated bisphenol A type epoxy resin (ESB400T, product manufactured by Sumitomo Chemical Co., Ltd.) Was dissolved in methyl ethyl ketone at the compounding amounts shown in Table 1, (C) cobalt naphthenate and 2-methylimidazole (2MZ) as curing accelerators, and (D) pyrogallol as an antioxidant were compounded according to Table 1. A 70% by weight resin composition varnish for printed wiring boards was prepared.

Example 2 In Example 1, the bisphenol A type epoxy resin was replaced with a cresol novolak type epoxy resin (ESCN-195-3, trade name, manufactured by Sumitomo Chemical Co., Ltd.) with the compounding amount shown in Table 1. In Example 1, cobalt naphthenate was dissolved in zinc naphthenate, 2-methylimidazole was 2-ethyl-4-methylimidazole, and pyrogallol was 4,
A resin composition varnish for printed wiring boards was prepared in the same manner as in Example 1, except that 4'-thiobis- (3-methyl-6-t-butylphenol) was used instead of 4'-thiobis- (3-methyl-6-t-butylphenol).

(Example 3) In Example 1, the bisphenol A type epoxy resin was replaced with phenol salicylaldehyde novolak type epoxy resin (E1032, trade name of Yuka Shell Epoxy Co., Ltd.) and the amount of methyl ethyl ketone was as shown in Table 1. And a resin composition varnish for printed wiring boards was prepared in the same manner as in Example 1 except that sulfur organic compound antioxidant dilauryl thiodipropionate was used as an antioxidant.

Example 4 In Example 1, only the brominated bisphenol A type epoxy resin was used as the epoxy resin.
Was dissolved in methyl ethyl ketone in the amount shown in
In the above, cobalt naphthenate is converted to zinc naphthenate,
Same as Example 1 except that methylimidazole was replaced with 2-ethyl-4-methylimidazole and pyrogallol was replaced with 4,4'-thiobis- (3-methyl-6-t-butylphenol) according to Table 1. A resin composition varnish for a printed wiring board was prepared.

(Comparative Example 1) A resin composition varnish for printed wiring boards was prepared in the same manner as in Example 1 except that pyrogallol was not used.

(Comparative Example 2) In Example 1, the bisphenol A type epoxy resin as the epoxy resin, the brominated bisphenol A type epoxy resin, and the curing accelerator 2MZ were not blended, and instead of the curing accelerator cobalt naphthenate. Using zinc naphthenate to dissolve in methyl ethyl ketone in the amounts shown in Table 1 and adding 4,4′-thiobis- (3-methyl-6-t-butylphenol) instead of pyrogallol as an antioxidant. In the same manner as in Example 1, a resin composition varnish for a printed wiring board was prepared.

Comparative Example 3 Equivalent amount of a brominated bisphenol A type epoxy resin (ESB400T, trade name, manufactured by Sumitomo Chemical Co., Ltd.) as an epoxy resin, and a phenol novolak resin (HP850N, trade name of Hitachi Chemical Co., Ltd.) as a curing agent. It was blended at a ratio of 1: 1 and dissolved in methyl ethyl ketone, and 2-methylimidazole and dilaurylthiodipropionate were blended according to Table 1 to prepare a resin composition varnish for a printed wiring board having a nonvolatile content of 70% by weight. .

The varnishes of Examples 1 to 4 and Comparative Examples 1 to 3 were impregnated into a 0.2 mm-thick glass cloth (basis weight: 210 g / m ² ) and dried at 160 ° C. for 5 minutes to obtain a prepreg. Four prepregs and 18 μm thick copper foil are laminated on top and bottom,
Press forming was performed at 70 ° C. and 2.45 MPa for 1 hour to produce a printed wiring board (copper-clad laminate). Only the copper-clad laminate of Comparative Example 2 was further post-cured in a dryer at 200 ° C. for 2 hours. Next, after removing the copper of the copper-clad laminate by etching, the glass transition temperature (Tg), relative dielectric constant,
Solder heat resistance, electric corrosion resistance, and flame resistance were evaluated. In addition, the evaluation method was performed as follows. Glass transition temperature (Tg): measured by thermomechanical analysis (TMA method). Relative permittivity: Evaluated by a broadband dielectric property measuring device (gap change method) manufactured by Neumann. Solder heat resistance: After a test piece was subjected to a moisture absorption treatment at 121 ° C. and 0.22 MPa for 3 hours by a pressure cooker tester, the test piece was immersed in a solder bath at 260 ° C. for 20 seconds, and the state of the test piece was visually observed.ミ indicates no measling, Δ indicates measling, and × indicates blistering. Electrolytic corrosion resistance: The insulation resistance of 400 holes was measured with time for each sample using a test pattern in which the wall spacing between through holes was 350 μm. Test conditions are 85 ° C, 90%
The measurement was performed by applying a voltage of 100 V in an RH atmosphere, and the time until the occurrence of conduction breakdown was measured. Flame resistance: Evaluated according to the UL94 vertical test method. Table 1 shows the evaluation results.

[0032]

[Table 1]

As shown in Table 1, Comparative Example 1 is a laminated plate containing no antioxidant, and the number of days until the continuity breakdown, which is the evaluation result of the corrosion resistance, is 280 days. Inferior. Comparative Example 2 is a case in which no epoxy resin is blended, and is inferior in flame resistance and solder heat resistance. Comparative Example 3 is a laminate using no cyanate ester resin, but has a high relative dielectric constant. In contrast to these comparative examples, (A) a cyanate compound containing two or more cyanato groups in one molecule of the invention, (B) an epoxy resin,
The resin composition for a printed wiring board using (C) a curing accelerator and (D) an antioxidant in a predetermined amount is a glass transition temperature (T
g), the specific permittivity, heat resistance, electrolytic corrosion resistance, and flame resistance are excellent.

[0034]

Industrial Applicability The resin composition for printed wiring boards of the present invention and printed wiring boards using the same are excellent in glass transition temperature (Tg), dielectric properties, heat resistance, flame resistance, and corrosion resistance. And high heat resistance, excellent dielectric properties, high insulation reliability, high heat resistance, etc., and are suitable as resins for printed wiring boards and multilayer laminates.

Continued on the front page (72) Inventor Michitoshi Arata 1500 Oji Ogawa, Shimodate City, Ibaraki Pref.Hitachi Kasei Kogyo Co., Ltd. Inside

Claims (7)

[Claims] (A) a cyanate compound containing two or more cyanato groups in one molecule, (B) an epoxy resin,
A resin composition for a printed wiring board, comprising (C) a curing accelerator and (D) an antioxidant. 2. (A) 50 to 250 parts by weight of an epoxy resin, (C) 0 to 100 parts by weight of a cyanate compound containing two or more cyanato groups in one molecule, and (C) a curing accelerator in an amount of 100 parts by weight. 0.1 to 5 parts by weight, 0.1% of (D) antioxidant
2. The resin composition for a printed wiring board according to claim 1, comprising about 20 parts by weight. 3. 3. The method according to claim 1, wherein (A) the cyanate compound having two or more cyanato groups in one molecule is mainly composed of 2,2-bis (4-cyanatophenyl) propane or a prepolymer thereof. The resin composition for a printed wiring board according to claim 2. 4. The resin composition for a printed wiring board according to claim 1, wherein (B) the epoxy resin mainly comprises a brominated bisphenol A type epoxy resin. 5. The method according to claim 1, wherein (C) the curing accelerator is a combination of an organic metal salt or an organic metal complex of iron, copper, zinc, cobalt, nickel, manganese or tin and an imidazole compound. The resin composition for a printed wiring board according to any one of the above. 6. The printed wiring according to claim 1, wherein (D) the antioxidant is at least one selected from a phenolic antioxidant and a sulfur organic compound antioxidant. A resin composition for boards. 7. A varnish comprising the resin composition for a printed wiring board according to any one of claims 1 to 6, and at least one prepreg obtained by impregnating and drying a substrate and using one or more of the prepregs. A printed wiring board obtained by laminating metal foils on both sides and molding under heat and pressure.