JPH0747637B2 - Curable resin composition - Google Patents

Description

Detailed Description of the Invention [Industrial applications]

The present invention relates to a curable resin composition used for producing a laminated board used as a printed wiring board.

2. Description of the Related Art In recent years, frequencies used in the fields of electronic industry, communication, computers and the like have been shifted to high frequency regions such as MHz and GHz. In the resin that constitutes the laminated board that is the substrate of the printed wiring board used in such a high frequency region, the dielectric constant is small in order to shorten the signal propagation delay, and the power loss is also small. It is desirable that the dielectric loss tangent be smaller. Therefore, tetrafluoroethylene resin (Teflon) or polyphenylene oxide (PPO), which has a low dielectric constant and dielectric loss tangent, is used.
Attempts have been made to form a laminated plate using a resin such as.

[Problems to be Solved by the Invention]

However, when making laminated boards using these resins, the glass transition temperature (Tg) is low at about 180 to 200 ° C and the heat resistance is insufficient, and the reliability of through holes such as smearing during through hole processing is improved. There is a problem in that it cannot be formed on a multilayer printed wiring board because it cannot be obtained at a high cost. The present invention has been made in view of the above points, it is possible to maintain excellent electrical characteristics and high heat resistance, in addition to increase the impact resistance cracks during drilling of the laminate The purpose is to prevent the reliability of through-hole plating from being lowered.

[Means for Solving the Problems]

The present invention comprises a prepolymer prepared by reacting a polyfunctional cyanate ester compound and a polyhydric phenol in an equivalent ratio of 10: 1 to 1: 1 as a main component, and further has a cyanate group and a phenol group in the molecule. It is a mixture of aromatic cyanate ester and phenol. The present invention will be described in detail below. As a polyfunctional cyanate ester compound, Japanese Patent Publication No.
No. 28, the general formula is shown by (N≡C—O—Ar) x—R (where Ar is an aromatic group and R is a C ₀ -C ₂₀ aliphatic group). Any material may be used without particular limitation, but in general, those having a bisphenol A skeleton, a bisphenol F skeleton, a biphenol skeleton, or the like can be easily obtained. For example, the following can be listed as preferable ones. The polyfunctional cyanate ester compound may be a monomeric compound as described above, or may be in a prepolymer state. In the case of prepolymers, the molecular weight is 5000 or less if it is expressed by weight average molecular weight (M _W ), 2000 or less if it is expressed by number average molecular weight (M _N ) (all are compared with polystyrene standard by GPC (gel permeation chromatography)) It is preferable to use the one of (measured in step 1). If the molecular weight is higher than this range, problems may occur in the impregnation property into the base material or the flowability at the time of laminate molding may deteriorate, so a lower molecular weight is used. Therefore, cyanate ester resins (polytriazine, cyanate resins) obtained from the above cyanate ester compounds
Has a low dielectric constant (approximately ε2.78) and a low dielectric loss tangent (tanδ
It has excellent electrical characteristics such as around 0.003) and high heat resistance (glass transition temperature Tg250 or higher, oven heat resistance 300 ℃).
It has excellent characteristics as a resin that constitutes an insulating substrate of a printed wiring board. However, when the cyanate ester compound is cured alone, the cyanate forms a triazine ring and has a structure having heat resistance, but since the crosslink density is very high, the impact resistance of the cured resin is weak. Therefore, when a laminated board is made of a cyanate ester resin obtained by curing a cyanate ester compound, the inner wall of the through hole may be cracked during drilling to make a through hole when processing a printed wiring board. However, there is a problem that the reliability of through-hole plating is deteriorated because the plating solution for through-hole plating penetrates from these cracks and the insulation between the through-hole plating and the inner layer circuit of the printed wiring board cannot be ensured. Therefore, in order to modify the cyanate ester resin, various epoxy resins, maleimide resins and prepolymers with diamine, which have been variously studied so far, and butadiene resin, polyesterimide resin, epoxy ester of acrylic acid and methacrylic acid, have been prepared. , Mixing with resins having a phenolic hydroxyl group, etc. is considered, but in the case of prepolymerization or mixing with a high molecular weight material, the wettability or impregnability with respect to the base material decreases with an increase in the molecular weight, As a result, the resulting laminate has poor moisture resistance and chemical resistance, and is not practical. Therefore, in the present invention, in order to improve impact resistance when the cyanate ester compound is cured alone, polyhydric phenols are blended with the cyanate ester compound and reacted to form a prepolymer. Was found to be effective and was completed. The polyhydric phenols can be used without particular limitation as long as they are represented by (HO) x-Ar (x is a positive integer, Ar is aromatic). However, it is not preferable that the ortho position of the OH group has a bulky substituent group exceeding the methyl group. When the preferred ones are listed as polyhydric phenols, Etc., and one or more of these can be selected and used. Of course, it is not limited thereto, and it may have a substituent containing no active hydrogen other than the phenolic hydroxyl group, such as a group having a CH ₃ group or a C ₂ H ₅ group. When the cyanate ester compound and the polyhydric phenol are reacted to obtain a prepolymer, the cyanate ester compound and the polyhydric phenol are mixed in an equivalent ratio of —O—C≡N / —OH of 10/1 to 1 Blended in the range of / 1, 30 at 80-150 ℃
It can be carried out by heating for minutes to 600 minutes. If the amount of polyhydric phenols is less than this range, the effect of reacting the polyhydric phenols is insufficient, and if the amount of polyhydric phenols is more than this range, the electrical conductivity of the cured resin of the cyanate ester compound is low. There is a possibility that the characteristics and heat resistance may be adversely affected. The prepolymer of the cyanate ester compound thus obtained and the polyhydric phenol can be used as it is. However, in the present invention, aromatic cyanic acid containing a cyanate group and a phenol group in the molecule is further used. ester·
Phenol is blended and used as a mixture or as a prepolymer by reacting. The aromatic cyanate ester / phenol containing a cyanate group and a phenol group in the molecule can be obtained by adjusting the equivalent ratio of the charges when the polyhydric phenol and the cyanogen halide are reacted. That is, an aromatic cyanate ester compound (monomer or prepolymer) that can be used in the present invention is obtained by reacting a polyhydric phenol with a cyanogen halide as disclosed in JP-B No. 41-1928. It can be synthesized, but by adjusting the charging of polyhydric phenols and cyanogen halide so that the equivalent ratio of —OH / Cl—C≡N is greater than 1 in this reaction, a cyanate group is formed in the molecule. An aromatic cyanate ester / phenol containing a phenol group can be obtained. −OH / Cl−
The equivalent ratio of C≡N is preferably in the range of 2/1 to 3/1. By changing the type of polyhydric phenol to be reacted, various aromatic cyanate ester / phenols can be obtained, and all of them can be used in the present invention. Among them, the following are listed as preferable ones. be able to. In the present invention, if necessary, a flame retardant may be added to enhance flame retardancy. As the flame retardant, a brominated polycarbonate oligomer, tetrabromobisphenol A, a brominated phenol novolac resin, or the like can be used alone or in combination of two or more. The blending amount of the flame retardant is preferably 5 to 20%, more preferably 10 to 15% by weight of Br based on the total solid content of the resin. According to the UL standard, 5% or more is required to obtain the level of 94V-1, and 10% or more is required to obtain the level of 94V-0. However, if the blending amount of the flame retardant is increased, the performance of the cyanate ester resin is improved. Since there is a possibility that the deterioration of (1) will occur, it is preferable to set in this range. As a reaction catalyst for polymerizing a cyanate ester compound, imidazoles, tertiary amines, zinc octylate,
Organic metal salts such as organic cobalt salts such as cobalt naphthenate and cobalt octylate, Lewis bases and the like can be used, and organic cobalt salts are particularly preferable. The amount of the reaction catalyst is not particularly limited, for example, in the case of using an organic cobalt salt, it is common to add in the range of 10 to 700 ppm as the weight cost of cobalt ion relative to the weight of the cyanate ester compound. It is preferable to adjust the gel time of the desired varnish according to the drying temperature of the solvent used in the preparation. Then, a varnish is prepared by dissolving a prepolymer of a cyanate ester compound and a polyhydric phenol, or a mixture or reaction product of this and an aromatic cyanate ester / phenol, a flame retardant, and a reaction catalyst in an organic solvent. Prepare. The organic solvent is not particularly limited as long as it dissolves these and does not adversely affect the reaction, such as aromatic hydrocarbons, alcohols and ketones. For example, toluene, aceone, methyl ethyl ketone (MEK), dimethylformamide (DMF), dimethylacetamide (DMAc), methyl cellosolve, etc. may be used alone or in combination of two or more. The concentration of varnish is generally adjusted so that the solid content is 50 to 70% by weight. However, when preparing the prepreg, the base material is not particularly limited, but it is common to use a woven or non-woven fabric of glass fiber, and the base material is impregnated with varnish and dried by heating. To do. The amount of varnish impregnated into the substrate is preferably set so that the ratio of the solid content to the substrate is 45% by weight or more. The level of the dielectric constant is affected by the resin content, and when the substrate is made of E-glass cloth, the dielectric constant is 45% by weight or more when impregnated.
A value of 4.0 or less can be achieved, and when the substrate is formed of a D glass cloth, a dielectric constant of 3.5 or less can be achieved by impregnation of 45% by weight or more. The heating and drying conditions for preparing the prepreg are affected by the amount of the reaction catalyst compounded, but for example, when the heating temperature is 160 ° C, the heating time is 3
The stroke gel time of the desired prepreg can be obtained by setting the time to about 10 minutes. The stroke gel time of the prepreg varies depending on molding conditions and the like, but is generally about 2 to 10 minutes at 170 ° C. Then, a plurality of prepregs thus prepared are stacked, further metal foils such as copper foils are stacked on both upper and lower surfaces or one side, and by heat-press molding, the cyanate ester compound in the prepreg is polymerized and cured. A double-sided metal foil-clad or single-sided metal foil-clad laminate can be prepared by laminating and adhering metal foils on both sides or one side of an insulating substrate to be constructed. At this time, since the cyanate ester compound is used in the state of the prepolymer reacted with the polyhydric phenols, the crosslink density can be relaxed as compared with the case where the cyanate ester compound is cured alone, The shrinkage at the time of curing can be reduced and the flexibility of the polymerized cured product of the cyanate ester compound can be increased. An inner layer printed wiring board can be made by forming a circuit by etching the metal foil of the thus-prepared laminated board, and the inner layer printed wiring board can be stacked with a plurality of the above prepregs and at the same time. By stacking metal foil on the outer layer and heat-pressing it, you can create a multilayer printed wiring board.
The molding conditions are generally set such that the heating temperature is 170 ° C. to 230 ° C., the maximum pressure is about 30 to 40 kg / cm ² , and the time is about 90 to 120 minutes. Then, a through hole is further drilled to form a circuit by etching the outermost metal foil and the like, and a through hole plating is applied to finish the multilayer printed wiring board. At the time of this drilling, since the flexibility of the polymerized cured product of the cyanate ester compound is increased by the polyhydric phenols, it is possible to perform the drilling without fear of cracks, and therefore, when performing through-hole plating, etc. It is possible to prevent the plating solution from penetrating from the inner wall of the through hole and lowering the insulation reliability between the through hole plating and the inner layer circuit.

【Example】

Hereinafter, the present invention will be described in detail with reference to examples. Example 60 parts by weight of the cyanate ester represented by the following formula, Add 10 parts by weight of a polyhydric phenol represented by the following formula, Both monomers were reacted at 110 ° C. for 60 minutes. It was confirmed by GPC analysis that a part of each monomer reacted and dimerized into a prepolymer. To what was diluted by adding MEK to 70 parts by weight of this prepolymer, was added 30 parts by weight of what is shown in the following formula as an aromatic cyanate ester / phenol having a cyanate group and a phenolic hydroxyl group, MEK was further added to this so that the solid content became 70% by weight, and 250 pt of cobalt naphthenate was used as a reaction catalyst.
A varnish was prepared by adding pm. 2116 type E glass cloth base material (made by Nitto Boseki Co., Ltd.)
116E) so that the solid content is 48% by weight,
A prepreg was prepared by heating and drying at 150 ° C. for 4 minutes. Next, stack 8 sheets of this prepreg on both sides
After laminating 70μ thick double-sided roughened copper foil, molding temperature 170 ℃, molding pressure 40kg / cm ² and condition for 90 minutes, and further after molding in an electric oven at 210 ℃ for 90 minutes. It was cured to obtain a 0.8 mm-thick double-sided copper-clad laminate. Comparative Example To 50 parts by weight of the same cyanate ester as in Example, 50 parts by weight of bismaleimide resin (Kelimide 601 manufactured by Rhone Poulenc Co., Ltd.) was added, reacted at 110 ° C. for 60 minutes, and 50 ppm of cobalt naphthenate was added as a reaction catalyst. Then, 40 parts by weight of MEK was further added to prepare a varnish. Thereafter, a prepreg was prepared in the same manner as in the example, and a 0.8 mm-thick double-sided copper-clad laminate was obtained. The electrical properties (dielectric constant), moisture resistance (moisture absorption rate), and drill workability of the laminated plates of Examples and Comparative Examples obtained as described above were measured, and the results are shown in the following table. In the following table, the dielectric constant and moisture absorption rate were measured based on JIS C 6481. In addition, the drill workability is to drill a through hole by using a drill bit of 0.9 mmφ for a laminated plate, and under the conditions of a rotation speed of 40,000 rpm and a feed rate of 50 μ / rev per one rotation, a through hole is cut. It was evaluated by observing with a microscope whether cracks occurred. As can be seen from the results in the table, in the examples in which the cyanic acid ester compound was reacted with the polyhydric phenols and used, the moisture resistance was good and the wettability and impregnability to the substrate were improved. It is also confirmed that the drill workability is very good and the impact resistance of the resin is modified.

【The invention's effect】

As described above, in the present invention, the polyfunctional cyanate ester compound is used as a prepolymer reacted with the polyhydric phenol in an equivalent ratio of 10: 1 to 1: 1. The impact resistance can be enhanced by improving the flexibility of the cyanate ester resin without lowering the properties and impregnability. Further, since the aromatic cyanate ester / phenol having a cyanate group and a phenol group in the molecule is blended, the flame retardancy of the resin can be enhanced.

Claims (2)

[Claims] 1. A prepolymer obtained by reacting a polyfunctional cyanate ester compound and a polyhydric phenol in an equivalent ratio of 10: 1 to 1: 1 is contained, and a cyanate group and a phenol group are contained in the molecule. A curable resin composition comprising an aromatic cyanate ester / phenol contained therein. 2. The curable resin composition according to claim 1, wherein the polyfunctional cyanate ester compound is a monomer or a prepolymer having a weight average molecular weight of 5000 or less and a number average molecular weight of 2000 or less.