JPH09227699A - Production of prepreg - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the electric reliability of a base without leaving bubbles behind by impregnating the base with a specified primary solvent, then impregnating it with an epoxy resin varnish to conduct secondary impregnation, and drying the product by heating. SOLUTION: A base having a thickness of 200μm or below is impregnated with a solvent having a b.p. of 90 to 155 deg.C selected from among ketones, alcohols and aromatic hydrocarbons. Then the base is impregnated with an epoxy resin varnish containing 1 to 20 pts.wt. of a solvent having a b.p. of not below 150 deg.C selected from among amides, and then dried by heating at 150 to 180 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a prepreg used for manufacturing a printed wiring board.

[0002]

2. Description of the Related Art Conventionally, a laminated board used for manufacturing a printed wiring board is obtained by impregnating a base material such as glass cloth with a thermosetting resin varnish such as epoxy resin, followed by heating and drying to semi-cure. It is manufactured by producing a prepreg, stacking a required number of the prepregs, arranging metal foils such as copper foils on one side or both sides of the prepregs and laminating the foils, and heating and pressing to form the prepregs. Also,
The multilayer laminate, after forming a circuit by etching the metal foil on the surface of the metal foil-clad laminate obtained by the above method,
Manufactured by stacking the required number of prepregs similar to the above on the front and back of the laminated plate on which the circuit is formed, and arranging and laminating the metal foil on one side or both sides as necessary, and heating and pressing to perform molding. ing.

Since the resin varnish generally has a high viscosity, it is difficult for the resin varnish to be sufficiently impregnated into the inside of the substrate, and air bubbles are generally left in the prepreg. Therefore, when molding is performed, a laminated board is generally manufactured by a method in which pressure is applied to cause a resin to flow to remove air bubbles in a base material.

In the case of producing a prepreg using a resin varnish containing an epoxy resin, a hard-to-dissolve hardener such as dicyandiamide is used as a hardener in order to secure the storage stability of the prepreg and the heat resistance of the laminate. Is generally used. In the case of using a hardly soluble curing agent such as dicyandiamide, a resin varnish in which the epoxy resin and the curing agent are uniformly dissolved at a proper viscosity is obtained unless they are dissolved using a solvent having a boiling point of 150 ° C. or higher. In many cases, it is difficult to use a solvent having a boiling point of 150 ° C. or higher for the resin varnish.

With the high performance of printed wiring boards in recent years,
The plate thickness accuracy required for laminated plates is extremely high. Therefore, reduce the pressure when molding,
Methods for improving the plate thickness accuracy are being studied. But,
When the molding pressure is reduced, the flow rate of the resin is reduced and bubbles in the prepreg are less likely to escape during molding, and bubbles remain in the laminated board, and when the printed wiring board is manufactured using the laminated board, the bubbles There is a problem in that the plating solution may infiltrate into the to cause insulation failure and reduce the electrical reliability. Especially in the case of a multi-layered laminated plate, a difference in pressure applied to the prepreg between the portion with the metal foil and the portion without the metal foil occurs due to the formation of the circuit. Occurrence of residue is remarkable.

Therefore, as a method for removing bubbles in a prepreg, as shown in the section of the prior art of JP-A-6-107820, the base material is first impregnated with a low-viscosity solvent, and After removing the air bubbles, the resin varnish is further impregnated with the solvent, and the resin varnish is further impregnated by substituting the solvent with the solvent and the resin varnish with the solvent. Methods such as a solvent replacement method for permeating the particles to the surface and a vacuum impregnation method are being studied. However, even if the solvent substitution method (the method of first impregnating the base material with the solvent and then the second impregnation with the resin varnish) is used, the resin varnish may not sufficiently penetrate the details of the base material. When the laminated plate is manufactured by lowering the molding pressure, air bubbles may remain in the laminated plate, which may lower the electrical reliability.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and its object is to obtain a substrate having a boiling point of 150 ° C. or higher after primary impregnation with a solvent. Secondary impregnation of a solvent-containing epoxy resin-based resin varnish, which is a method for producing a prepreg produced by heating and drying, when a laminate is produced using the prepreg, even if molding is performed at a low pressure, It is an object of the present invention to provide a method for producing a prepreg that can obtain a laminated plate with less residual air bubbles.

[0008]

[Means for Solving the Problems] In order to solve the above problems, the inventors have conducted various studies, and as a result, the boiling point of the solvent to be primarily impregnated has been found to improve the penetration of the resin varnish to be secondly impregnated into the substrate. We found that it was one of the factors and solved the problem.

The method for producing a prepreg according to claim 1 of the present invention is a method in which a base material is first impregnated with a solvent, and then the base material containing the solvent contains an epoxy resin varnish containing a solvent having a boiling point of 150 ° C. or higher. In the method for producing a prepreg, which is produced by secondary impregnation with and then heating and drying, the boiling point of the solvent used for primary impregnation is 90 to 155 ° C.

A method for producing a prepreg according to a second aspect of the present invention is characterized in that, in the method for producing the prepreg according to the first aspect, the solvent used for the primary impregnation contains N, N-dimethylformamide.

The method for producing a prepreg according to claim 3 of the present invention is characterized in that, in the method for producing a prepreg according to claim 1 or 2, methoxypropanol is contained in the solvent used for the primary impregnation.

The method for producing a prepreg according to claim 4 of the present invention is the method for producing a prepreg according to any one of claims 1 to 3, wherein the solvent used for primary impregnation is:
It is characterized by containing methyl ethyl ketone.

A method for producing a prepreg according to a fifth aspect of the present invention is characterized in that, in the method for producing the prepreg according to any one of the first to fourth aspects, the base material is glass cloth.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The prepreg of the present invention is obtained by first impregnating a base material with a solvent, secondarily impregnating the base material with a resin varnish in a state of containing the solvent, and then heating and drying. This resin varnish contains at least epoxy resin,
A curing agent and a solvent having a boiling point of 150 ° C. or higher are contained, and if necessary, a curing accelerator, a filler and the like may be contained.

The solvent used for the primary impregnation has a boiling point of 90 to 1.
It is important that the temperature is 55 ° C, and more preferably 100
１５０150 ° C. When the boiling point is less than 90 ° C., when the resin varnish is secondarily impregnated and then dried by heating, the solvent is apt to evaporate rapidly, and the solvent and the second impregnated resin varnish are insufficiently evaporated. However, there are problems that the resin does not easily penetrate into the inside of the base material and that the surface of the prepreg is likely to have irregularities and the appearance thereof is deteriorated. On the other hand, when the temperature exceeds 155 ° C., the solvent evaporates slowly, and the solvent is likely to remain in the base material, which makes it difficult for the resin to permeate into the base material. When using a mixed solvent of a plurality of solvents for primary impregnation,
It is important that the boiling point of the solvent in the mixed state is within the range of 90 to 155 ° C.

The solvent used for the primary impregnation has a boiling point of 9
There is no particular limitation so long as it is in the range of 0 to 155 ° C., and amides such as N, N-dimethylformamide, alcohols such as methoxypropanol, ethers such as ethylene glycol monobutyl ether, and the like can be used. it can. These can also be used together. In addition, it is preferable to include N, N-dimethylformamide (boiling point 153 ° C.) and / or methoxypropanol (boiling point 120 ° C.) in the solvent because the boiling point of the solvent can be easily adjusted to a range of 90 to 155 ° C.

When these solvents are used in combination with a solvent having a boiling point of 90 to 155 ° C. and the boiling point of the mixed solvent is in the range of 90 to 155 ° C., the solvent having a boiling point of less than 90 ° C., such as acetone or methyl ethyl ketone, is used. The above ketones, alcohols such as methanol and ethanol, aromatic hydrocarbons such as benzene, and the like can also be used. In addition, when methyl ethyl ketone (boiling point 80 ° C.) is contained in the solvent, since methyl ethyl ketone has a low viscosity and a good impregnating property into the substrate, when the resin varnish is secondarily impregnated and then heat-dried, the resin will reach the inside of the substrate. It is preferable because it easily penetrates.

As the base material used in the prepreg of the present invention, inorganic fibers such as glass, organic fibers such as polyester, polyamide, polyacryl and polyimide, and woven cloth, nonwoven cloth, paper and the like of natural fibers such as cotton are used. be able to. In addition, inorganic fibers such as glass cloth are preferable because they have excellent heat resistance and moisture resistance. In addition, the thickness of the substrate is 200μ
When it is m or less, the effect of the present invention is easily obtained, which is preferable.

The present invention is limited to the case where the resin varnish used for the secondary impregnation contains a solvent having a boiling point of 150 ° C. or higher. As a solvent having a boiling point of 150 ° C or higher, N, N-
Examples thereof include amides such as dimethylformamide and N, N-dimethylacetamide. When a solvent having a boiling point of 150 ° C. or higher is used, even if a hardly soluble curing agent such as dicyandiamide or a slightly soluble epoxy resin is used, the epoxy resin and the curing agent have an appropriate viscosity, It is possible to obtain a resin varnish that is uniformly dissolved. When the solvent having a boiling point of 150 ° C. or higher is N, N-dimethylformamide, a resin varnish having a particularly suitable viscosity can be easily obtained, which is preferable. Incidentally, the resin varnish of the present invention,
The epoxy resin and the curing agent are not limited to a resin varnish that is uniformly dissolved with an appropriate viscosity, but a resin having a solid curing agent dispersed as long as it contains a solvent having a boiling point of 150 ° C. or higher. The present invention can be applied to the case of varnish and the like.

The resin varnish contains amides such as formamide, ethers such as ethylene glycol monomethyl ether, ketones such as acetone and methyl ethyl ketone, alcohols such as methanol and ethanol, which are solvents having a boiling point of less than 150 ° C. Aromatic hydrocarbons such as benzene and toluene can also be used together.

With respect to 100 parts by weight of the resin varnish,
The content of the solvent having a boiling point of 150 ° C. or higher is preferably 1 to 20 parts by weight. When the content is less than 1 part by weight, it becomes difficult to obtain a resin varnish which has an appropriate viscosity and is uniformly solubilized, and when it exceeds 20 parts by weight, the resin content of the prepreg is decreased, and the prepreg is used. When a laminate is manufactured, the heat resistance of the laminate may decrease.

The epoxy resin contained in the resin varnish may be any epoxy resin having two or more epoxy groups in one molecule, for example, bisphenol A type epoxy resin, bisphenol F type epoxy resin, Phenolic novolac type epoxy resin, bisphenol A novolac type epoxy resin, cresol novolac type epoxy resin, diaminodiphenylmethane type epoxy resin, and epoxy flame retarded by halogenating some hydrogen atoms in these epoxy resin structures. Examples of the resin include single substances, modified substances, and mixtures. Especially,
At least one epoxy resin selected from the group consisting of bisphenol A type epoxy resin, tetrabromobisphenol A type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, and bisphenol A novolac type epoxy resin. It is preferable that a laminated board having excellent electrical characteristics and physical characteristics and having a good balance between the two can be obtained. It should be noted that these resins may be used in combination of plural kinds.

The curing agent contained in the resin varnish is not particularly limited, and amide type curing agents such as dicyandiamide and aliphatic polyamide, amine type curing agents such as ammonia, triethylamine and diethylamine, phenol novolac resin, Cresol novolac resin, p
-Phenolic curing agents such as xylene-novolac resin, acid anhydrides, and the like. In addition, these can also be used together.

The curing accelerator that can be contained in the resin varnish is not particularly limited, but tertiary amines such as triethylenediamine and benzyldimethylamine, 2-methylimidazole and 2-ethyl-4-methyl. Examples include imidazoles such as imidazole and 2-phenylimidazole, organic phosphines such as tributylphosphine and triphenylphosphine, tetraphenylphosphonium tetraphenylborate, tetraphenylboron salts such as triphenylphosphine tetraphenylborate, and the like. A plurality of them can be used together.

The filler that can be contained in the resin varnish is not particularly limited, but inorganic powder fillers such as alumina, silica, calcium carbonate, talc, clay, barium sulfate and aluminum hydroxide, and glass. Examples thereof include fibrous fillers such as fibers, pulp fibers, aramid fibers, and ceramic fibers, and a plurality of these may be used in combination.

The prepreg of the present invention is obtained by first impregnating a base material with a solvent, secondarily impregnating the base material with a resin varnish in a state of containing the solvent, and then heating and drying. After impregnating the base material details by impregnating a solvent having a lower viscosity than the resin varnish, impregnating the resin varnish compatibilizes the primary impregnated solvent with the resin varnish, and when the solvent disappears by evaporation, The solvent is replaced with the resin varnish, and the resin varnish penetrates into the details of the substrate. The heating and drying conditions include heating and drying by appropriately setting the temperature and time according to the type of resin used, the curing agent, etc., but the heating and drying temperature is lower than the boiling point of the solvent used and the solvent. Is difficult to dry, and the resin varnish does not easily penetrate into the details of the substrate. Therefore, it is generally desirable to set the temperature to about 150 to 180 ° C.

[0027]

【Example】

(Example 1) As a solvent for primary impregnation, 10 parts by weight of N, N-dimethylformamide [manufactured by Mitsubishi Gas Chemical Co., Inc.] and 40 parts by weight of methoxypropanol [manufactured by Daicel Chemical Company],
A mixed solvent of 50 parts by weight of methyl ethyl ketone [manufactured by Idemitsu Oil Co., Ltd.] was used. The boiling point of this mixed solvent was 90 ° C.

As the resin varnish for secondary impregnation, a resin varnish consisting of the following two kinds of epoxy resins, two kinds of solvents, a curing agent and a curing accelerator was used. -Epoxy resin 1: Tetrabromobisphenol A type epoxy resin having an epoxy equivalent of 500 [Toto Kasei Co., Ltd., trade name YDB-500] as a solid content is 94 parts by weight.-Epoxy resin 2: Cresol having an epoxy equivalent of 220. 13 parts by weight of novolac type epoxy resin [Toto Kasei Co., Ltd., trade name YDCN-220] as a solid content ・ Curing agent: 2.8 parts by weight of dicyandiamide ・ Curing accelerator: 0 of 2-ethyl-4-methylimidazole .1 part by weight-Solvent 1: 55 parts by weight of N, N-dimethylformamide [manufactured by Mitsubishi Gas Chemical Co., Inc.]-Solvent 2: 50 parts of methyl ethyl ketone [manufactured by Idemitsu Petroleum]
0 parts by weight.

A glass cloth having a thickness of 0.19 mm [manufactured by Nitto Boseki Co., Ltd., product name 18W] was used as a substrate, impregnated with a solvent for primary impregnation, and then continuously impregnated with a resin varnish. Then, it was heated and dried at a maximum temperature of 180 ° C, the resin amount was 42% by weight and the gel time at 170 ° C was 1%.
A 10 second prepreg was prepared.

One prepreg obtained had a thickness of 3 on both outer sides.
After arranging and stacking 5 μm copper foil, this laminate is sandwiched between metal plates and molded under the conditions of a maximum temperature of 180 ° C., a pressure of 1 MPa and a time of 130 minutes, and a thickness of 0.2 mm and a size of 1
An m-square double-sided copper-clad laminate was obtained.

Example 2 As a solvent for primary impregnation, N,
A double-sided copper-clad laminate was obtained in the same manner as in Example 1 except that a mixed solvent of 50 parts by weight of N-dimethylformamide and 50 parts by weight of methoxypropanol was used. The boiling point of this mixed solvent was 130 ° C.

Example 3 As a solvent for primary impregnation, N,
A double-sided copper-clad laminate was obtained in the same manner as in Example 1 except that N-dimethylformamide (boiling point: 153 ° C) was used.

Comparative Example 1 As a solvent for primary impregnation, N,
A double-sided copper-clad laminate was obtained in the same manner as in Example 1 except that 5 parts by weight of N-dimethylformamide, 20 parts by weight of methoxypropanol, and 75 parts by weight of methyl ethyl ketone were used as a mixed solvent. The boiling point of this mixed solvent is 8
5 ° C.

(Comparative Example 2) As a solvent for primary impregnation, N,
A double-sided copper-clad laminate was obtained in the same manner as in Example 1 except that a mixed solvent of 50 parts by weight of N-dimethylformamide and 50 parts by weight of ethylene glycol monobutyl ether (boiling point 168 ° C) was used. The boiling point of this mixed solvent was 160 ° C.

Example 4 The same procedure as in Example 1 was carried out except that the prepreg having a resin amount of 50% by weight and a gel time of 120 seconds at 170 ° C. was prepared by changing the rate of secondary impregnation and heating and drying conditions. A prepreg was obtained (the boiling point of the solvent for primary impregnation was 90 ° C.).

The copper foil thickness is 70 μm, and the total thickness is 1.
A copper foil of a 1 mm double-sided copper-clad laminate [Matsushita Electric Works, Ltd., product name R1766] was etched to obtain an inner layer board having a circuit with an etching rate of 40%.

Next, the obtained prepregs are laminated on both sides of this inner layer board, and further, a thickness of 1 is formed on both outer sides thereof.
After arranging and stacking 8 μm copper foil, this laminate is sandwiched between metal plates, and molded under the conditions of a maximum temperature of 180 ° C., a pressure of 1 MPa and a time of 130 minutes, and a thickness of 1.5 mm and a size of 5
A 4-layer copper-clad laminate having a size of 0 cm was obtained.

Example 5 A prepreg was obtained in the same manner as in Example 4 except that the solvent (boiling point 130 ° C.) used in the primary impregnation of Example 2 was used for primary impregnation. Then, in the same manner as in Example 4, a 4-layer copper-clad laminate was obtained.

(Example 6) A prepreg was obtained in the same manner as in Example 4 except that the solvent (boiling point: 153 ° C) used in the primary impregnation of Example 3 was used for the primary impregnation. Then, in the same manner as in Example 4, a 4-layer copper-clad laminate was obtained.

(Example 7) Glass cloth having a thickness of 0.1 mm as a substrate [Nitto Boseki Co., Ltd., product name 116E]
A prepreg was obtained in the same manner as in Example 4 except that was used. (The boiling point of the solvent for primary impregnation is 90 ° C.) Then, a four-layer copper-clad laminate was obtained in the same manner as in Example 4 except that each two prepregs obtained were laminated on both sides of the inner layer plate.

Comparative Example 3 A prepreg was obtained in the same manner as in Example 4, except that the solvent used for the primary impregnation of Comparative Example 1 (boiling point: 85 ° C.) was used for the primary impregnation. Then, in the same manner as in Example 4, a 4-layer copper-clad laminate was obtained.

Comparative Example 4 A prepreg was obtained in the same manner as in Example 4, except that the solvent used for the primary impregnation of Comparative Example 2 (boiling point 160 ° C.) was used for the primary impregnation. Then, in the same manner as in Example 4, a 4-layer copper-clad laminate was obtained.

(Comparative Example 5) A glass cloth having a thickness of 0.1 mm as a substrate [Nitto Boseki Co., Ltd., product name 116E].
Was obtained, and a prepreg was obtained in the same manner as in Example 4 except that the solvent used for the primary impregnation of Comparative Example 1 (boiling point: 85 ° C.) was used for the primary impregnation. Then, a double-sided copper-clad laminate was obtained in the same manner as in Example 4 except that the two prepregs obtained were laminated on each side of the inner layer plate.

Reference Example A prepreg was obtained in the same manner as in Example 4 except that the base material was directly impregnated with the resin varnish without primary impregnation. Then, a 4-layer copper-clad laminate was obtained in the same manner as in Example 4 except that the pressure was increased to 3.9 MPa.

(Evaluation, Results) With respect to the double-sided copper-clad laminates obtained in Examples 1 to 3 and Comparative Examples 1 and 2, the formability was evaluated as an evaluation of residual air bubbles in the laminate. Also,
With respect to the 4-layer copper-clad laminates obtained in Examples 4 to 7, Comparative Examples 3 to 5, and Reference Example, the formability and the variation in plate thickness were evaluated. Formability is measured by measuring the size of the part that is discolored white due to the residual air bubbles in the laminate by measuring the length from the end face of the laminate after removing the entire surface of the copper foil by etching. The maximum value of each 5 plates was determined. The white discolored portion was generated at the end portion of the laminated plate and not at the central portion, and thus the length from the end surface of the laminated plate was used to judge whether the formability was good or bad. In addition, the thickness variation is measured with a micrometer at a total of 9 places, that is, the four corners of each of the five laminated plates, the central portions of the four sides, and the central portion of the laminated plate, and the difference between the maximum value and the minimum value is measured. It was considered as variation.

The results are shown in Tables 1 and 2, and it was confirmed that Examples 1 to 3 had better moldability than Comparative Examples 1 and 2. Further, Examples 4 to 7
Confirms that the moldability is better than Comparative Examples 3 to 5, and that the moldability is good even when compared with the Reference Examples in which a prepreg was produced without impregnation with a solvent and molded at high pressure. Was done. In addition, Examples 4 to 7 are compared with the reference example.
It was confirmed that the variation in plate thickness was good.

[0047]

[Table 1]

[0048]

[Table 2]

[0049]

The prepreg manufacturing method of the present invention comprises the steps of first impregnating a base material with a solvent having a boiling point of 90 to 155 ° C.,
Since the resin varnish containing the epoxy resin, the curing agent and the solvent is secondarily impregnated, the resin varnish easily penetrates into the inside of the base material, and when a laminated plate is manufactured using the prepreg, the molding is performed at a low pressure. It is possible to obtain a laminated plate with less residual air bubbles.

Claims (5)

[Claims] 1. A method comprising first impregnating a base material with a solvent, secondarily impregnating the base material containing the solvent with an epoxy resin varnish containing a solvent having a boiling point of 150 ° C. or higher, and then heating and drying. In the method for producing a prepreg, the boiling point of the solvent used for the primary impregnation is 90 to 155 ° C. 2. The solvent used for primary impregnation contains N, N-dimethylformamide.
A method for producing the described prepreg. 3. The method for producing a prepreg according to claim 1, wherein the solvent used for the primary impregnation contains methoxypropanol. 4. The method for producing a prepreg according to claim 1, wherein the solvent used for the primary impregnation contains methyl ethyl ketone. 5. The method for producing a prepreg according to claim 1, wherein the base material is glass cloth.