JPH0892393A - Production of prepreg - Google Patents

Abstract

PURPOSE: To obtain prepreg for multi-layer printed circuit boards with the forming time shortened and the surface smoothness improved by impregnating the fiber base material with a resin composition containing an epoxy resin, a polyfunctional phenol and guanide and drying them. CONSTITUTION: The fiber base material, for example, a glass fiber woven fabric, is impregnated with an epoxy resin composition formulated with (A) 1 equivalent amount of an epoxy resin bearing 2 or more epoxy groups such as bisphenol-A epoxy resin, (B) 0.5-1.2 equivalent amount of polyfunctional phenol such as novolak resin, (C) 0.03-0.5 equivalent amount of a guanide such as 1,3-diphenyl- guanidine and (D) 0.02-0.4 equivalent amount of dicyandiamide, and dried to give this prepreg which is to be used in copper laminates, multi-layer printed circuit boards and other laminates for electric purposes with formation time shortened.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a prepreg used for electrical laminates such as copper clad laminates and multilayer printed wiring boards, and more particularly to a method for producing a prepreg for shortening the time required for forming the laminate.

[0002]

2. Description of the Related Art Conventionally, electrical laminates such as copper-clad laminates are made by impregnating glass fiber or paper with thermosetting resin such as epoxy resin or phenol resin to form prepregs. It is manufactured by stacking, laminating metal foils such as copper foils if necessary, and heating and pressurizing this. Further, the multilayer prepreg wiring board, a circuit is formed on the surface of the laminate obtained by the above method as an inner layer circuit board, usually prepreg and a metal foil are stacked on both sides,
It is manufactured by heat and pressure molding. These laminates are
In recent years, the tendency toward high-density mounting and high integration of printed wiring boards has increased, and the demands for various characteristics such as workability, heat resistance, and moldability have become more sophisticated and multifaceted. Among them, regarding moldability, it is strongly desired that the molding time can be shortened without deteriorating other properties.
Therefore, shortening the curing time of the resin used for the prepreg has been studied. For example, in the case of an epoxy resin, various combinations of a curing agent and a curing accelerator have been proposed.

[0003]

However, although the molding time can be shortened to some extent in any of the formulations,
This is not sufficient, and if it is attempted to further shorten the molding time, disadvantages such as heat resistance and deterioration of electrical characteristics after high humidity treatment will appear. As a result of various studies on the forming technology for laminated plates, the present inventors have succeeded in achieving a shortening of the forming time, which was insufficient with the conventional technology, without deteriorating other properties. .

[0004]

The present invention provides a varnish made of an epoxy resin composition containing (a) an epoxy resin having two or more epoxy groups, (b) a polyfunctional phenol, and (c) a guanide compound. The present invention relates to a method for producing a prepreg, which comprises impregnating and drying a fiber base material.

In the present invention, as the epoxy resin (a) having two or more epoxy groups, any epoxy resin conventionally used for electrical insulation can be used. For example, bisphenol A type epoxy resin, bisphenol F type epoxy resin. Resin, bisphenol S type epoxy resin, phenol novolac type epoxy resin, orthocresol novolac type epoxy resin, isocyanurate type epoxy resin, trifunctional or tetrafunctional glycidylamine type epoxy resin, epoxy resin having a biphenyl skeleton (biphenyl type Epoxy resin), an epoxy resin having a naphthalene skeleton, an epoxy resin having a cyclopentadiene skeleton, an epoxy resin having a limonene skeleton, and the like. These may be used alone or in combination of several kinds. Among such epoxy resins, epoxy resins having two epoxy groups such as bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin and biphenyl type epoxy resin have few voids in the prepreg. This is preferable.

Furthermore, in order to impart flame retardancy, the above epoxy resin is blended with a brominated product, and the above epoxy resin and epoxy tetrabromobisphenol A are blended.
And co-condensing bisphenol A, blending the above epoxy resin with epoxy tetrabromobisphenol A and bisphenol A, blending the above epoxy resin with tetrabromobisphenol A, or
Any method such as blending the above-mentioned epoxy resin with brominated epoxyphenol novolac is possible.

In the process of manufacturing a prepreg, an epoxy resin composition is usually dissolved in a solvent, impregnated in a glass cloth, and the solvent content is evaporated at a temperature of about 150 ° C. to 170 ° C. to obtain a B-stage state. However, when the melt viscosity of the epoxy resin after solvent evaporation is high, there is a drawback that voids tend to remain between the strands of the glass cloth. In the prepreg with shortened curing time of the present invention, the greatest feature is that the time to final curing is shortened as compared with the conventional prepreg. Therefore, if voids remain in the prepreg, lamination after curing It has the drawback that it easily remains in the board. As a result of various studies on epoxy resins, it was found that lowering the melt viscosity at the drying temperature of the prepreg is effective in reducing voids. Considering other characteristics, it is preferable that the bifunctional epoxy resin is contained in an amount of 10 to 50% by weight relative to the total epoxy resin. If it is less than 10%, the effect of lowering the viscosity is small, and if it exceeds 50%, the crosslink density of the cured product tends to be low, and the glass transition temperature tends to be low. Further, the degree of polymerization of the bifunctional epoxy resin is preferably such that the number of n indicating the degree of polymerization is in the range of n = 0 to 2. When n = 2 is exceeded, the molecular weight becomes large and the effect of lowering the viscosity tends to be small.

Among these bifunctional epoxy resins, the biphenyl type epoxy resin is most suitable for the prepreg of the present invention. This is because the biphenyl skeleton in the molecule has a high orientation in terms of molecular structure and high crystallinity, and thus has a feature that melt viscosity is particularly low.

Next, the polyfunctional phenol corresponds to a novolac resin obtained by condensing a phenol compound having one or more phenolic hydroxyl groups in the molecule with formaldehyde under an acidic catalyst. Examples of the phenol compound include phenol, o-cresol, p-cresol, pt-butylphenol, α-naphthol, β-naphthol, bisphenol A and bisphenol F. As a polyfunctional phenol, in addition to the novolak resin obtained by reacting these phenol compounds with formaldehyde, a novolak resin modified with a terpene compound, dicyclopentadiene, polybutadiene, alkylbenzene, or naphthalene is used for improving heat resistance and electrical characteristics. Is preferred. In addition, drying oil modified novolak resin,
Cashew oil-modified novolak resin can also be used.

Specific examples of the above modified novolak resin include the following. The terpene-modified novolac resin is YLH-4 manufactured by Yuka Shell Epoxy Co., Ltd.
02, dicyclopentadiene modified novolak resin is DC-100LL manufactured by Sanyo Kokusaku Pulp Co., Ltd., paraxylene modified novolac resin is XL-225L manufactured by Mitsui Toatsu Co., Ltd.
Examples of L and polybutadiene-modified novolac resins include PP-700 manufactured by Nippon Oil Co., Ltd.

The guanide compound generally means a compound having a guanidine structure, and includes 1,3-diphenylguanidine, di-orthotolylguanidine, 1-orthotolyldiguanide, α-2,5-dimethylguanide, α,
ω-diphenyldiguanide, 5-hydroxynaphthyl-
1-diguanide, phenyldiguanide, α, α'-bisguanylguanididinodiphenyl ether, p-chlorophenyldiguanide, α-benzyldiguanide, α, ω
-Dimethyldiguanide, α, α'-hexamethylenebis [ω- (p-chlorophenol)] diguanide, o-tolyldiguanide zinc salt, diphenyldiguanide iron salt, phenyldiguanide copper salt, diguanide nickel Salt, ethylenebisdiguanide hydrochloride, lauryldiguanide hydrochloride,
Examples thereof include phenyldiguanide oxalate, mono-substituted or di-substituted alkyl-modified phenyl diguanide, and the like.

The advantage of these guanide compounds is that they generate a great amount of heat when they react with an epoxy group to open the epoxy ring. Therefore, the reaction is remarkably accelerated in the reaction system in which the addition polymerization is caused with the epoxy resin by heating. When the reaction of the epoxy resin was examined by a scanning calorimeter, the prepreg in the system in which no guanide compound was present, for example, FR-4 prepreg having an epoxy resin, an aromatic polyamine and dicyandiamide as a composition, had a resin content of 1 m.
20-40 mJ per gram, the amount of heat generated during the reaction is small, the reaction initiation temperature is about 150 ° C, and the reaction activation temperature is about 1
As high as 70 ° C. That is, it is suggested that the reaction is difficult to proceed in the temperature rising process at the time of press molding, and that a larger amount of heat needs to be supplied until complete curing. On the other hand, in the system of epoxy resin, polyfunctional phenol, and guanide compound, 60 to 140 mJ per 1 mg of resin has a large amount of heat generation during the reaction, and the reaction initiation temperature is about 130 ° C and the reaction activation temperature is low at about 150 ° C. . That is, it means that the curing reaction occurs at a lower temperature in the temperature rising process during press molding, the reaction is further promoted by heat generation, and the curing reaction is completed in a short time.

Dicyandiamide is preferably added in order to impart good adhesion to the copper foil.

The blending amount will be mentioned. The blending amount of the polyfunctional phenol is determined in relation to the glass transition temperature. That is, when the compounding amount is less than 0.5 equivalent with respect to 1 equivalent of the epoxy resin, the glass transition temperature is low and the effect of adding the polyfunctional phenol is not sufficiently observed. When the amount added is further increased, the glass transition temperature is almost the highest at 1.0 equivalent, and the glass transition temperature level does not change up to 1.2 equivalent. When the amount is further increased, the glass transition temperature starts to gradually decrease. Therefore, it is suitable to mix it in the range of 0.5 to 1.2 equivalents. The equivalent amount of the guanide compound is calculated assuming that all the amines contained in one molecule of the guanide compound are involved in the crosslinking reaction. When the equivalent amount of the guanide compound is 0.03 equivalent or less, the calorific value is small,
Sufficient fast curability cannot be obtained, and when an amount exceeding 0.5 equivalent is blended, the amount of moisture absorption increases, and the solder heat resistance tends to decrease. Therefore, the compounding amount of 0.03 to 0.5 equivalent is appropriate. The blending amount of dicyandiamide is determined in consideration of the adhesiveness to the copper foil and the solder heat resistance when absorbing moisture. That is, 0.02 per 1 equivalent of epoxy resin
If the blending amount is less than the equivalent amount, the addition effect is small from the viewpoint of improving the adhesion to the copper foil, and the O. When the compounding amount exceeds 4 equivalents, the amount of moisture absorption increases, which is likely to cause deterioration of solder heat resistance after moisture absorption treatment, which is an advantage of polyfunctional phenol, and also causes deterioration of storage stability.

There are no particular restrictions on the composition other than these. For example, to increase the adhesion with glass fiber,
For the purpose of adding a coupling agent exemplified by epoxysilane or aminosilane, or for further improving the plate thickness accuracy,
It is possible to add a polybutadiene rubber, a nitrile rubber, a nitrile butadiene rubber, or a carboxylic acid-modified, amine-modified, or epoxy-modified product thereof. In addition, there is no particular limitation on the addition of an imidazole compound, an adduct imidazole, a microencapsulation curing accelerator, a phosphine-based accelerator, an amine-based accelerator, or the like for adjusting the gel time of the prepreg or imparting further rapid curing property.

[0016]

The prepreg obtained according to the present invention is fast-curing, so that the heating and pressurizing time of the laminated plate can be greatly shortened. In the case of an epoxy resin laminated plate, it has become possible to shorten the molding time, which normally takes 120 to 200 minutes by one lamination molding, to about 40 to 60 minutes. As a result, manufacturing costs are significantly reduced,
The man-hours for quality control and inventory control will also be greatly reduced. In addition, it is possible to significantly reduce the molding time when molding the multilayer printed wiring board.

Further, in the production of a multilayer printed wiring board, by applying an undercoating agent to the inner layer circuit board in advance, the resin flow is smaller than that in the case of using a conventional prepreg. The accuracy is good, the surface smoothness of the outer layer surface is high due to the effect of embedding the undercoat agent, and it is possible to form a fine pattern circuit.

[0018]

EXAMPLES The present invention will be described in detail below based on examples.

Example 1 A glass fiber woven fabric was impregnated with an epoxy resin composition composed of an epoxy resin having a composition ratio shown in Table 1, a polyfunctional phenol and 1-orthotolyldiguanide, and dried to obtain an epoxy resin composition. A prepreg having a thickness of 180 μm and a resin content of 42% was obtained. When the number of voids between strands in the prepreg was evaluated by a microscope, it was 6 and it was confirmed that there was no problem in practical use. Regarding the evaluation of voids, a method was adopted in which the prepreg was magnified 50 times with a microscope and the number of voids present at each intersection of the warp and the weft was counted. When the conventional FR-4 prepreg is cured under normal conditions, if the number of voids is 15 or less, it does not remain in the laminated plate after the molding press at all, but the rapid-curing prepreg of the present invention will be described later in a short time. When curing with, it is necessary to keep the number of voids within 10. Six of these prepregs and 18 μm thick copper foil were laid on both sides and pressure was 150 kg / cm ^{2 with} a laminating press.
And pressurize to room temperature, and start heating from room temperature.
Molding was carried out at a maximum attainable temperature of 170 ° C. The time required to reach the maximum temperature was about 10 minutes.

Regarding the heating time required for molding, the relationship between the press heating time and the glass transition temperature was investigated, and the glass transition temperature (± 3 ° C.) was almost equal to the glass transition temperature of the prepreg in 140 minutes of heating time. The heating time required was the heating time required for molding. Therefore, the heating time required for molding is the sum of the temperature rising time from room temperature to the highest temperature and the holding time at the highest temperature. The viscoelastic method was used for the glass transition temperature. As a result, the heating time required for molding was 40 minutes, and Table 1 shows the characteristics of the laminated plate during the heating time.

Here, regarding the preservability of the prepreg,
The prepreg was stored in a temperature / humidity atmosphere of 25 ° C. and 60%, and molded every two weeks under the above-mentioned molding conditions, and the etching appearance was compared with the initial appearance and judged. When the life of the prepreg has passed, voids will remain, so it is possible to make a sufficient judgment by checking the appearance as a simple method.

Example 2 A glass fiber woven fabric was impregnated with an epoxy resin composition composed of an epoxy resin having a composition ratio shown in Table 1, a polyfunctional phenol, dicyandiamide and 1-orthotolyldiguanide, and dried. 180 μm
A prepreg having a thickness and a resin content of 42% was obtained. Six of these prepregs and 18 μm thick copper foil were laid on both sides of the prepreg, and a pressure of 150 kg / cm ² was applied by a laminating press and heating was started from room temperature. Molded. The time required to reach the maximum temperature was about 10 minutes, and the heating time required for molding was 40 minutes. Table 1 shows the characteristics of the laminated plate during the heating time.

Example 3 A glass fiber woven fabric was impregnated with an epoxy resin composition composed of an epoxy resin having a composition ratio shown in Table 1, a polyfunctional phenol and p-chlorophenyldiguanide and dried to obtain 180 μm. Thickness, resin content 42%
I got a prepreg of. 6 pieces of this prepreg and 18 μm thick copper foil are laid on both sides of the prepreg, and a pressure of 150 k is applied by a laminating press.
The pressure was increased to g / cm ² , heating was started from room temperature, and molding was performed at a temperature rising rate of about 18 ° C./minute and a maximum attainable temperature of 170 ° C. It took about 10 minutes to reach the maximum temperature,
The heating time required for molding was 40 minutes. Table 1 shows the characteristics of the laminated plate during the heating time.

Example 4 A glass fiber woven fabric was impregnated with an epoxy resin composition composed of an epoxy resin, a polyfunctional phenol and 1-orthotolyldiguanide and dried to give a thickness of 180 μm and a resin content of 42%. I got a prepreg of.
Six pieces of this prepreg and 18 μm thick copper foil were laid on both sides of the prepreg, and a pressure of 150 kg / cm ² was applied by a laminating press.
Heating was started from room temperature, and molding was performed at a temperature rising rate of about 18 ° C./min and a maximum reached temperature of 170 ° C. The time required to reach the maximum temperature was about 10 minutes, and the heating time required for molding was 60 minutes. Table 1 shows the characteristics of the laminated plate during the heating time.

Comparative Example 1 A glass fiber woven fabric was impregnated with an epoxy resin composition composed of only an epoxy resin, an aromatic polyamine and dicyandiamide, and dried to obtain 1
A prepreg having a thickness of 80 μm and a resin content of 42% was obtained. Six of these prepregs and 18 μm thick copper foil were laid on both sides of the prepreg, and a pressure of 150 kg / cm ² was applied by a laminating press.
Molding was performed at 70 ° C. It took about 10 minutes to reach the maximum temperature, and the heating time required for molding was 12 minutes.
It was 0 minutes. Table 1 shows the characteristics of the laminated plate during the heating time.

[0026]

[Table 1]

[0027]

As described above, since the prepreg obtained by the method of the present invention is fast-curing, the time required for molding the electrical laminate can be greatly shortened. Further, also in the molding of a multilayer printed wiring board, the molding time can be shortened by using it as an interlayer insulating material. In particular, by applying an undercoating agent to the surface of the inner layer circuit board, not only the molding time is shortened, but also the thickness accuracy of the obtained board is good, and a multilayer printed wiring board having excellent surface smoothness is obtained. be able to.

Claims (6)

[Claims] 1. A fiber substrate is impregnated with a varnish comprising (a) an epoxy resin having two or more epoxy groups, (b) a polyfunctional phenol, and (c) an epoxy resin composition containing a guanide compound, and dried. A method for producing a prepreg, characterized by: 2. The epoxy resin composition has an equivalent ratio of 0.5 to 1.2 of polyfunctional phenol (b) to 1 equivalent of epoxy resin having two or more epoxy groups (a).
The method for producing a prepreg according to claim 1, wherein the guanide compound (c) is equivalent to 0.03 to 0.5 equivalent. 3. A varnish made of an epoxy resin composition containing (a) an epoxy resin having two or more epoxy groups, (b) a polyfunctional phenol, (c) a guanide compound, and (d) dicyandiamide is used as a fiber base material. A method for producing a prepreg, which comprises impregnating and drying the prepreg. 4. The epoxy resin composition has an equivalent ratio of 0.5 to 1.2 of polyfunctional phenol (b) per equivalent of (a) epoxy resin having two or more epoxy groups.
The method for producing a prepreg according to claim 1, wherein the equivalent is (c) guanide compound 0.03 to 0.5 equivalent, and (d) dicyandiamide is 0.02 to 0.4 equivalent. 5. Epoxy resin, 10 to 50% by weight
The prepreg manufacturing method according to claim 1, wherein the is an epoxy resin having two epoxy groups. 6. The method for producing a prepreg according to claim 5, wherein the epoxy resin having two epoxy groups is an epoxy resin having a biphenyl skeleton.