JPH08165332A - Production of prepreg - Google Patents

Abstract

PURPOSE: To decrease the molding cycle time of a prepreg by using a varnish made from a resin compsn. prepd. by compounding an epoxy resin mixture contg. a specific trisphenol epoxy resin with a polyhydric phenol and a guanide compd. CONSTITUTION: A polyepoxy resin (e.g. a bisphenol A epoxy resin) is mixed with 10-50 equivalent % trisphenol epoxy resin repesented by the formula. 1 equivalent of the resulting mixture is compounded with 0.5-1.2 equivalents of a curative (e.g. a polyhydric phenol), 0.03-0.5 equivalent of a guanide compd. (e.g. 1-orthotolyldiguanide), 0.05-0.4 equivalent of dicyandiamide, and if necessary other additives to give a quickly curing epoxy resin compsn., which is dissolved in a solvent to give a varnish. A glass fabric is impregnated with the varnish and dried to give a prepreg. Several sheets of the prepreg and copper foils placed on both sides thereof are pressed under heating for 40-60-min with a press to give a laminate.

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 which require heat resistance, and particularly for shortening the time required for forming the laminate. The present invention relates to a method for manufacturing a prepreg.

[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. In particular, regarding resins having high heat resistance, the glass transition temperature of the cured product is high, but the reaction to the final curing is slow, and it is currently difficult to shorten the molding time. 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. In the method for producing a prepreg in which a fiber base material is impregnated and dried, the production of a prepreg in which 10 to 50% of the epoxy resin is an epoxy resin having three epoxy groups (hereinafter referred to as trisphenol type epoxy resin) in an equivalent ratio It is about the method.

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), naphthalene type epoxy resin,
Examples thereof include an epoxy resin having a cyclopentadiene skeleton and an epoxy resin having a limonene skeleton. These may be used alone or in combination of several kinds.
Among such epoxy resins, in the present invention, the trisphenol type epoxy resin is preferable from the viewpoints of good curability, excellent heat resistance of the cured product, small linear expansion coefficient, and excellent dimensional stability. It is a thing.

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. In the present invention, a trisphenol type epoxy resin is used as the epoxy resin having a low melt viscosity. Considering other characteristics,
This epoxy resin is preferably contained in an equivalent ratio of 10 to 50% with respect to the total epoxy resin. 10
If it is less than%, the effect of lowering the viscosity and improving the heat resistance is small,
Even if it exceeds 50%, the properties of the cured product do not largely change, and the cost is often high. Further, this trisphenol type epoxy resin has, for example, the following chemical formula, but is not limited thereto. However, the smaller the epoxy equivalent, the better for lowering the viscosity and high heat resistance, and the epoxy equivalent is preferably 300 or less.

[0008]

Embedded image

Since the trisphenol type epoxy resin has three epoxy groups in the molecule, a resin having a small molecular weight (a resin having a small epoxy equivalent) has a high crosslink density after curing, and therefore, a glass. High transition temperature and excellent heat resistance. Further, since the molecular structure is relatively constant, it has a feature of low melt viscosity. For this reason,
It is possible to reduce voids remaining in the prepreg and further reduce defects due to voids in the laminated plate after molding.

Next, the polyfunctional phenol corresponds to a novolak 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. The following may be mentioned as specific examples of the modified novolac resin. The terpene modified novolac resin is YLH-402 manufactured by Yuka Shell Epoxy Co., Ltd., the dicyclopentadiene modified novolac resin is DC-100LL manufactured by Sanyo Kokusaku Pulp Co., Ltd., and the paraxylene modified novolac resin is XL-manufactured by Mitsui Toatsu Co., Ltd. 225LL, polybutadiene modified novolak resin is PP- manufactured by Nippon Oil Co., Ltd.
It is 700 mag.

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 large amount of heat when they react with an epoxy group to open the epoxy ring. Therefore, in a reaction system in which an epoxy resin and an addition polymerization are caused by heating, the reaction does not occur. Remarkably promoted. In the present invention, shortening of the molding time is achieved by utilizing this feature. When the reaction of the epoxy resin was examined by a scanning calorimeter, 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 20 to 40 mJ per 1 mg of the resin. The heat generation during the reaction is small, the reaction initiation temperature is about 150 ° C, and the reaction activation temperature is about 170 ° 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 per 1 mg of resin.
The amount of heat generated during the reaction with mJ is large, the reaction initiation temperature is about 130 ° C, and the reaction activation temperature is about 150 ° C. That is,
This means that a 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 ends 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.

The trisphenol type epoxy resin used in the present invention has a feature that it is particularly excellent in heat resistance as described above. In general, when a thermosetting resin is made to be fast curable, non-uniform curing occurs, and heat resistance and properties after water absorption are often deteriorated. In the epoxy resin composition according to the present invention, polyfunctional phenol is used as a curing agent,
In this case, it was found that the reaction between the epoxy resin, particularly the trisphenol type epoxy resin and the polyfunctional phenol was uniform and the crosslink density was relatively high. Therefore, despite being quick-curing, the main thermal characteristics as a circuit board such as heat resistance and solder heat resistance after water absorption treatment are excellent. Further, since the melt viscosity is low, the number of voids remaining in the prepreg is small. Therefore, even when the molding time is shortened, defects due to voids in the laminated plate after molding can be further reduced.

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 small as compared with the case of using a conventional prepreg, so that the board thickness is reduced. 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.

[0019]

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. 6 prepregs and 1 on each side
8μm thick copper foils are stacked and pressure is 30kg /
Pressurize to cm ² , start heating from room temperature, heating rate about 18
Molding was carried out at a maximum reaching 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 having a composition ratio shown in Table 1, a multifunctional phenol, dicyandiamide and 1-orthotolyldiguanide, and dried. 180 μm
A prepreg having a thickness and a resin content of 42% was obtained. Six pieces of this prepreg and 18 μm thick copper foil were overlaid on both sides of the prepreg, and pressure was applied to the pressure of 30 kg / cm ² with a laminating press, heating was started from room temperature, and the temperature rising rate was about 18 ° C./minute and the maximum reached temperature was 170 ° C. 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 the pressure is 30 kg by a laminating press.
/ Cm ² and pressurize to start heating from room temperature.
Molding was performed at 8 ° 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 40 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 an epoxy resin containing no trisphenol type epoxy resin, a polyfunctional phenol and 1-orthotolyldiguanide, and dried to give a dry treatment. , 18
A prepreg having a thickness of 0 μm and a resin content of 42% was obtained. Six of these prepregs and 18 μm thick copper foil were overlaid on both sides of the prepreg, pressure was applied to 30 kg / cm ² with a laminating press, heating was started from room temperature, temperature rising rate was about 18 ° C./min, and maximum reached temperature was 170.
Molding was performed at ° 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 2 A glass fiber woven fabric was impregnated with an epoxy resin composition containing only an epoxy resin containing no trisphenol type epoxy resin, an aromatic polyamine and dicyandiamide and dried to obtain 180 μm.
A prepreg having a thickness and a resin content of 42% was obtained. Six pieces of this prepreg and 18 μm thick copper foil were overlaid on both sides of the prepreg, and pressure was applied to the pressure of 30 kg / cm ² with a laminating press, heating was started from room temperature, and the temperature rising rate was about 18 ° C./minute and the maximum reached temperature was 170 ° C. Molded. The time required to reach the maximum temperature was about 10 minutes, and the heating time required for molding was 120 minutes. Table 1 shows the characteristics of the laminated plate during the heating time.

(Comparative Example 3) A glass fiber woven fabric was impregnated with an epoxy resin composition containing a trisphenol type epoxy resin, a polyfunctional phenol, dicyandiamide, and 2-methylimidazole as a curing accelerator, and dried. Processed, 180μm thick, 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 the pressure is 30 kg by a laminating press.
/ Cm ² and pressurize to start heating from room temperature.
Molding was performed at 8 ° 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 120 minutes. Table 1 shows the characteristics of the laminated plate during the heating time.

[0028]

[Table 1]

[0029]

As described above, the prepreg obtained by the method of the present invention has very few remaining voids and is quick-curing, so that the time required for molding an electrical laminate is significantly reduced. Can be shortened to 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.

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Claims (5)

[Claims] 1. A prepreg obtained by impregnating and drying a varnish composed of an epoxy resin having (a) an epoxy resin having two or more epoxy groups, (b) a polyfunctional phenol, and (c) a guanide compound on a fiber base material. Of the epoxy resin, in an equivalent ratio of 10 to 50.
% Is an epoxy resin having three epoxy groups, and a method for producing a prepreg. 2. The epoxy resin composition, wherein the equivalent ratio is 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 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. In the method for producing a prepreg, which comprises impregnating and drying the same, 10 to 50% of the epoxy resin is an epoxy resin having three epoxy groups in an equivalent ratio. 4. The epoxy resin composition, wherein the equivalent ratio is 0.5 to 1.2 of polyfunctional phenol (b) per equivalent of (a) epoxy resin having two or more epoxy groups.
Equivalent amount, (c) guanide compound 0.03 to 0.5 amount,
The method for producing a prepreg according to claim 3, wherein (d) dicyandiamide is 0.02 to 0.4 equivalent. 5. The method for producing a prepreg according to claim 1, wherein the epoxy resin having three epoxy groups is one or more epoxy resins represented by the following chemical formula. Embedded image