JPH11181124A - Prepreg - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a prepreg with a good impregnating property of a resin, being satisfactory for both prevention of dusting therefrom and a glass transition temperature of a laminate. SOLUTION: This prepreg is prepared by impregnating into a sheet-shaped base an epoxy resin composition comprising as essential components a straight- chain epoxy resin bifunctional at its terminal having an epoxy equivalent of 165-300, an epoxy resin of a straight-chain brominated epoxy resin bifunctional at its terminal having an epoxy equivalent of 1,500-4,500, and an epoxy resin composition having three or more functionalities, dicyandiamide as a curing agent at a level of 1-4 pts.wt. relative to 100 pts.wt. of its epoxy resin and a catalyst at a dicyandiamide/catalyst weight ratio of 20-50, and drying it. The dispersion index of the molecular weight distribution of the total epoxy resins is preferably 4.0 or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a prepreg which generates extremely small particles of resin powder and the like, and eliminates the need for a heat remelting treatment of a prepreg which has been conventionally performed to prevent dust generation. The present invention relates to a prepreg in which prevention of dust generation from a prepreg and glass transition temperature of a laminate are compatible with each other, which has been hardly reconciled with less occurrence during subsequent handling.

[0002]

2. Description of the Related Art Epoxy resin laminates for printed circuits are:
Generally, one or more prepregs obtained by applying and drying an epoxy resin on a fiber base material are laminated, and a metal foil is laminated on the upper surface thereof, followed by heat and pressure molding. Also,
The method of manufacturing a multilayer printed wiring board is such that at least one prepreg obtained by applying and drying an epoxy resin to a fiber base material is laminated on an inner layer circuit board having both sides or one side subjected to circuit processing and black processing, and a metal foil on the upper surface. Are superimposed on each other and heated and pressed. The epoxy resin used for the prepreg is usually a small amount of a terminal bifunctional linear brominated or non-brominated epoxy resin having an epoxy equivalent of about 350 to 800, and a small amount of a novolak type epoxy resin for improving heat resistance and chemical resistance. (About 5 to 30% by weight based on the entire epoxy resin). Epoxy resin with such a composition has good properties as a printed circuit board. However, during the cutting and drilling of the prepreg, and during the handling of the prepreg in the process up to multilayer molding (prepreg alignment, overlapping, etc.) ) Easily generates resin powder.

In the formation of a printed wiring board, resin powder generated from a cut portion of a prepreg or the like enters a space between a metal mirror plate and a metal foil in a heating / pressing step or a preceding laminating step, and is formed as it is. Then, the resin powder acts in the same manner as an etching resist in an etching step for forming a circuit pattern in a later step, causing insulation failure of the circuit pattern and the like. So far, by heating and remelting the resin and the resin powder in the portion of the prepreg where the resin powder is likely to be generated or where the resin powder is attached, the generation of the resin powder from the prepreg,
Spattering was prevented. However, this process requires extra equipment and man-hours, and furthermore, even if the powder on the surface is eliminated by heat melting, powder is generated again in handling up to multi-layer molding. A prepreg that does not generate resin powder from the prepreg even if the remelting step is unnecessary has been desired.

[0004]

SUMMARY OF THE INVENTION In order to solve the problem that resin powder from a prepreg enters between a metal mirror plate and a metal foil during lamination molding, the present inventor has proposed a composition of an epoxy resin impregnated in a prepreg. As a result of intensive studies, the present invention has been accomplished. The conventional method can significantly reduce the resin powder generated from the prepreg in the steps of cutting, bending, drilling, and the like, and also during the handling during the lamination with the prepreg or copper foil, thereby allowing the prepreg to be reheated. The melting step can be eliminated,
The glass transition temperature is much lower than that of the current NEMA standard FR-4, and it has been desired to develop a method for producing a prepreg that achieves both of these characteristics. In the present invention,
The generation of resin powder from the prepreg can be prevented, and a prepreg equivalent to that of the current FR-4 can be obtained when the laminate is used as a laminate.

[0005]

According to the present invention, an epoxy resin having an epoxy equivalent of 165 to 4500 and a terminally bifunctional linear brominated or non-brominated epoxy resin and a trifunctional or higher functional epoxy resin are used as essential components. 1.5 to 4 parts by weight of dicyandiamide as a curing agent is mixed with 100 parts by weight of epoxy resin, and an epoxy resin composition in which the ratio of dicyandiamide / catalyst is 20 or more and less than 50 is impregnated into a sheet-like substrate and dried. A prepreg having a molecular weight distribution of the epoxy resin in the obtained prepreg having a dispersity index of 4.0 or more, preferably the epoxy equivalent of 16
An epoxy resin having an epoxy equivalent of 16
A bifunctional terminal linear epoxy resin having 5 to 300,
A prepreg comprising a brominated epoxy resin having a bifunctional terminal straight chain having an epoxy equivalent of 1500 to 4500,
Further, the present invention relates to a laminated plate obtained by laminating one or more of these prepregs and heating and pressing.

A bifunctional terminal epoxy resin having an epoxy equivalent of 165 to 4500 and a trifunctional or higher functional epoxy resin are used as essential components, and the dispersity index of the molecular weight distribution of all epoxy resins is 4.0 or more. This makes it possible to prevent both the generation of resin powder from the prepreg and the glass transition temperature (Tg) of the laminate. Furthermore, by blending 1.5 to 4 parts by weight of dicyandiamide as a curing agent with respect to 100 parts by weight of the epoxy resin and blending the catalyst at a weight ratio of dicyandiamide / catalyst of 20 to 50, resin powder generation from the prepreg is reduced. And the flow during molding is improved. Therefore, good moldability such as filling of through holes when forming a multilayer printed circuit board is obtained.

The epoxy resin having an epoxy equivalent of 165 to 4500 is preferably an epoxy equivalent of 165 to 3500.
A bifunctional linear epoxy resin having a terminal of 00 and a bifunctional linear brominated epoxy resin having an epoxy equivalent of 1500 to 4500 are used. The epoxy equivalent 16
Epoxy resins of 5 to 300 are usually those not subjected to bromination. To this, the brominated epoxy resin having an epoxy equivalent of 1500 or more and 4500 or less is added, and the bromine content in all epoxy resins is about 20% by weight (resin,
The appropriate amount varies depending on the type of the curing agent, the thickness of the laminated plate, and the like) so as to obtain NEMAFR-4 grade flame resistance. Alternatively, a non-brominated epoxy equivalent of 1500
４4500 epoxy resin can be used, and the bromination content can be adjusted by blending highly brominated epoxy resin or tetrabromobisphenol A. In this way, it is sufficient that bromine is contained in a necessary amount when all resin solids are blended. Of course, it can be used in combination with a flame retardant other than bromine. By using each of the epoxy resins in an amount of 50 to 100% by weight of the total epoxy resin excluding the curing agent and the catalyst, it is possible to obtain a formulation in which the dispersity index of the epoxy resin molecular weight is increased.

Although the viscosity of the coating varnish can be easily reduced by adding a large amount of a low molecular weight epoxy resin, the molecular weight increases by heating during drying after coating on the base material. It is necessary to determine the mixing ratio of the resin and the application conditions. When a large amount of a high molecular weight epoxy resin is blended, not only does the viscosity of the varnish increase, but also the dispersity index does not increase. In the present invention, in order to increase the glass transition temperature (Tg) and improve the heat resistance of the laminate, a trifunctional or higher epoxy resin is blended. Examples of such an epoxy resin include a polyglycidylamine type epoxy resin and a novolak type epoxy resin. The epoxy resin thus obtained is preferably mixed with a curing agent and a catalyst, and preferably has a dispersity index of 4 or more indicating a molecular weight distribution of the resin,
The obtained prepreg has good resin impregnating property, improves the glass transition temperature (Tg) of the laminate, and generates very little dust such as resin powder. Therefore, it is particularly suitable as a prepreg for a multilayer printed wiring board. I have. If the dispersity index is less than 4,
The effect of preventing the generation of the resin powder from the prepreg may be insufficient.

An object of the present invention is to eliminate the need for thermal remelting of the impregnated resin of the prepreg in order to prevent the resin powder from scattering, as described in the section of the problem to be solved by the invention. The object of the present invention is to provide a method for producing a prepreg which can prevent generation of resin powder during handling in a laminating step for the prepreg. That is, by combining a relatively high molecular weight terminal bifunctional linear high molecular weight epoxy resin with a low molecular weight epoxy resin having a good balance of properties other than the generation of resin powder, the resin powder from the epoxy resin impregnated prepreg which is B-staged The generation of resin powder from the prepreg and the improvement of the glass transition temperature of the laminated board can be achieved at the same time by compounding a trifunctional or higher epoxy resin which is effective for improving the glass transition temperature. Was achieved. Further, by blending 1 to 4 parts by weight of dicyandiamide as a curing agent with respect to 100 parts by weight of the epoxy resin, and blending the catalyst at a dicyandiamide / catalyst ratio of 20 to less than 50, the generation of resin powder from the prepreg is reduced, In addition, the flow during molding is improved.

Hereinafter, the present invention will be described in detail. As the epoxy resin, a low dusting property of the prepreg is obtained, and in order to eliminate the need for re-melting treatment of the prepreg, the dispersity index of the molecular weight distribution of all epoxy resins is set to 4.0 or more, and the epoxy equivalent is 165 to 4000. Is used. Typically, a bifunctional linear epoxy resin obtained by reacting a bifunctional phenol such as bisphenol A with epihalohydrin and a terminal bifunctional obtained by an alternating copolymerization reaction of a bifunctional epoxy resin and a bifunctional phenol There are linear epoxy resins and the like, and these can be used in combination of several types. For example, bisphenol A type epoxy resin, bisphenol F type epoxy resin, tetrabromobisphenol A type epoxy resin,
Propylene oxide bisphenol A type epoxy resin, bisphenol S type epoxy resin, biphenyl type epoxy resin, 2,6-naphthol type diglycidyl ether polymer, bisphenol A type epoxy resin and tetrabromobisphenol A copolymer, bisphenol F type epoxy resin And tetrabromobisphenol A copolymer,
Examples thereof include a bisphenol S-type epoxy resin and a tetrabromobisphenol A copolymer. For flame retardancy,
The brominated epoxy resin can be used.

The epoxy resin having three or more functional groups used in the present invention will be described. Such an epoxy resin is effective in increasing the glass transition temperature (Tg) and improving the heat resistance of the laminate, and among them, the polyglycidylamine type epoxy resin has high heat resistance, and In the state of the reaction rate in the state of the prepreg (B stage), the structure does not become rigid and does not promote the generation of resin powder.
The reactivity is considered to be about the same as that of the bisphenol A type epoxy resin, and it is not too sensitive to subtle changes in drying conditions. As a polyglycidylamine type epoxy resin, for example, Epicoat 630 and Epicoat 604 made of Yuka Shell Epoxy,
Sumitomo Chemical's ELM-100, ELM-120, ELM
-434, and the like. On the other hand, the novolak-type epoxy resin has improved heat resistance, chemical resistance, solvent resistance and the like. However, this resin cures faster than bisphenol A type epoxy resin, has a high crosslinking density, and has a brittle property, so that the prepreg may not be in a favorable direction with respect to powder dusting. Attention must be paid to the drying conditions and the like. As a novolak type epoxy resin, for example, Epicoat 180S75 and Epicoat 154 made of Yuka Shell Epoxy or ES made by Sumitomo Chemical
CN-220HH and Epicron 6 manufactured by Dainippon Ink.
73, Epicron 770, Epicron 865 and the like.

Reference will be made to the molecular weight of the epoxy resin. Considering the low dusting property of the prepreg that has not been subjected to the remelting treatment, the higher the molecular weight, the better, but the curability tends to decrease. Although there are some differences depending on the basic skeleton of the epoxy resin and the type of curing agent, this tendency is basically the same. In a printed wiring board using an epoxy resin, the low dusting property of a prepreg required for practical use is determined by an average epoxy equivalent of 1
In the case of using 500 epoxy resins, it was a practically minimum level. In addition, depending on the bromine content, in the case of an epoxy resin having an average epoxy equivalent of 4500 or more, the dusting property is at a sufficiently low level, but the heat distortion temperature decreases,
Necessary heat resistance is not exhibited. This is because the distance between the bridging points is too large and the number of bridging points is reduced.

The amount of the terminal bifunctional linear epoxy resin having an epoxy equivalent of 300 or less is 20 to 20% of the total epoxy resin.
Preferably it is 75% by weight. If the amount is less than 20% by weight, the features of the epoxy resin such as the impregnation property and the multilayer moldability as described above cannot be sufficiently exhibited. If the content exceeds 75% by weight, the generation of resin powder when prepreg is formed increases. Preferably it is 30 to 60% by weight. The compounding amount of the terminal bifunctional linear epoxy resin having an epoxy equivalent of 1500 to 4500 is 20 to
Preferably it is 75% by weight. If the amount is less than 20% by weight, the features of the epoxy resin such as the prevention of generation of resin powder as described above cannot be sufficiently exhibited. If it exceeds 75% by weight, impregnating properties and multilayer moldability will be reduced. Preferably it is 30 to 60% by weight. 3
It is sufficient that the compounding amount of the functional or higher epoxy resin is 5 to 20% by weight based on the total epoxy resin.
Costs rise.

As a curing agent, dicyandiamide is used. The blending amount of dicyandiamide and the blending ratio with the catalyst will be described. An appropriate curability can be obtained by mixing the dicyandiamide in an amount equivalent to 0.5 to 1.5 times the epoxy resin in an equivalent ratio. By making the ratio of the amount of the curing agent to the amount of the catalyst 20 to 50 times, it is possible to prepare a prepreg having characteristics capable of forming a multilayer, and the obtained prepreg has good curability and resin powder. Outbreaks have been further improved. If it is less than 20 times (the amount of catalyst is large), the curability is sufficient, but the generation of resin powder is relatively large, and if it is more than 50 times (the amount of catalyst is small), the generation of resin powder is sufficiently improved. Sex is reduced.

The curing accelerator will be described. The type of the curing accelerator is not particularly limited, but an imidazole-based curing accelerator and a phosphine-based curing accelerator are preferably used. Many imidazole-based curing accelerators particularly have a high glass transition temperature, and include 2-methylimidazole, 2-ethyl-4-methylimidazole,
2-phenylimidazole, 2-phenyl-4-methylimidazole, 2,4′-diamino-6- [2′-ethyl-4′-methylimidazolyl- (1 ′)] ethyl-s
-Triazine, 2-methylimidazole / isocyanuric acid adduct, 2-methylimidazole / trimellitic acid adduct and the like, and phosphine-based curing accelerators include triphenylphosphine and triphenylphosphine phenol salt. In order to improve heat resistance, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 2-undecylimidazole, 1-cyanoethyl-
2-undecylimidazole or 2,4-diamino-6
It is preferable to use-{2'-undecylimidazolyl- (1 ')} ethyl-s-triazine each alone or in combination. The amount of the curing catalyst based on 100 parts by weight of the epoxy resin is preferably 0.04 to 0.2 parts by weight. If the addition amount exceeds 0.2 parts by weight, the curing is too fast, and the moldability (such as the ability to fill through holes during multilayer molding) decreases.
There is a case that the resin powder dropping property from the prepreg is also reduced.
On the other hand, if the addition amount is less than 0.04 parts by weight, the curing property and heat resistance become insufficient due to insufficient curing, and the adhesiveness also decreases.

Further, if necessary, a silane coupling agent can be added for the purpose of imparting adhesion to an inorganic substance such as a metal foil or glass cloth. For example, as the coupling agent, a silane coupling agent,
Titanate-based coupling agents, aluminum chelate-based coupling agents, and the like can be used. For example, chloropropyltrimethoxysilane, vinyltrichlorosilane, γ-glycidoxypropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, N -Β- (aminoethyl) -γ-aminopropyltrimethoxysilane, γ-ureidopropyltriethoxysilane, isopropyltriisostearoyl titanate, isopropyltrimethacrylate titanate, isopropyltri (dioctylphyrophosphate) titanate, isopropylisostearoyldi ( 4-aminobenzoyl) titanate and the like. The compounding amount is preferably 0.1 to 2.0 parts by weight based on 100 parts by weight of the epoxy resin. If the amount is less than 0.1 part by weight, the effect of improving the peel strength with an inorganic substance such as a metal foil or a glass cloth is insufficient, and even if the amount exceeds 2.0 parts by weight, no further improvement is observed. Particularly, an unreacted portion may be generated, which may hinder curing.

Further, if necessary, an antifoaming agent can be blended as a surface tension adjusting agent for improving the appearance characteristics of the prepreg (without repelling, craters, voids, etc.). As the defoaming agent, a non-silicone type (acrylic) type is preferable because the slip characteristics are improved. The amount of the defoamer is preferably 0.1 to 2.0 parts by weight based on 100 parts by weight of the epoxy resin. When the amount is less than 0.1 part by weight, the effect of the compounding is small, and when the amount is more than 2.0 parts by weight, the gel time of the varnish is shortened. Within this range, a sufficient effect of improving appearance characteristics is exhibited.

When the epoxy resin composition is applied to a fiber substrate, the viscosity is usually adjusted with a solvent. As the solvent, acetone, methyl ethyl ketin, toluene, xylene, ethylene glycol monoethyl ether and its acetate compound, propylene glycol monoethyl ether and its acetate, dimethylformamide,
Methyl diglycol, ethyl diglycol, methanol, ethanol and the like can be mentioned.

As a coating method, any method can be used as long as it is a method of impregnating the substrate with an epoxy resin varnish containing an organic solvent. In any of the methods, since there is an optimum viscosity required for impregnation, it is necessary to adjust the type and the amount of the reactive diluent and the solvent depending on the application method.

The cured state of the resin of the prepreg will be described. The cured state is generally A, which is a completely uncured state.
It can be divided into a stage state, a B-stage state which is a semi-cured state, a gel state which has been further cured, and a C-stage state which is a completely cured state. The epoxy resin of the prepreg obtained according to the present invention is usually in the B-stage state, but handling is particularly facilitated by keeping it in a tack-free state.

By using the prepreg obtained according to the present invention for a printed wiring board, it is possible to eliminate the need for a process for reducing dust generation by heating and re-melting the prepreg, which was conventionally required during lamination molding or multilayer molding. . Therefore,
Reduction of man-hours spent on prepreg quality control and reduction of production cost by going through the prepreg remelting process are achieved.Furthermore, by not remelting the prepreg, the local gel time of the prepreg may be shortened. Absent. Furthermore, when there is a re-cutting or drilling of the cut size, even if the prepreg is once made low dusting by re-melting, it is necessary to repeat the same process, and the quality control is also duplicated and complicated, but such In such a case, the prepreg of the present invention does not require the above-described redundant quality control.
In addition, the prepreg of the present invention reduces the generation of resin powder by the resin composition, so that it has the same effect as the prepreg obtained by the conventional hot-melting method, as well as the prepreg lamination process during molding. Resin powder that is erroneously generated during handling can be significantly reduced. Therefore, it is more useful for manufacturing a high-density wiring board than before.

[0022]

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

(Example 1) Glass woven fabric base material thickness 0.1 m
The surface of a glass epoxy double-sided copper-clad laminate with a copper foil thickness of 35 μm is polished and soft-etched to remove rust-preventive treatment. After that, a circuit pattern having 100 circular recesses having a diameter of 10 mm is formed by etching, and black-treated. The process was performed to obtain an inner printed circuit board.

50 parts by weight of a bisphenol A type epoxy resin (Epiclon EXA3399: epoxy equivalent 4330) was dissolved in 50 parts by weight of methyl ethyl ketone (MEK). 40 parts by weight of a bisphenol A type epoxy resin (Epicoat 828: epoxy equivalent 190) and a polyfunctional polyglycidylamine type epoxy resin (Epicoat 6)
30: Epoxy equivalent 100) was mixed with 10 parts by weight, and dicyandiamide was added and dissolved as a curing agent in an amount (3.74 parts by weight) at which the amine equivalent became 0.55 times the epoxy equivalent ratio of the epoxy resin. did. Furthermore, 0.2 parts by weight of 2-ethyl-4-methylimidazole as a curing accelerator and 0.1 of an acrylic defoamer (BYK-361) are used.
After adding parts by weight, they were mixed in a mixing tank. Further, M
The viscosity was adjusted by EK to obtain an epoxy resin varnish for impregnation.

A glass woven fabric was impregnated with the epoxy resin varnish and dried to obtain a prepreg (thickness: 180 μm). This prepreg is laminated one by one on the inner layer printed circuit board, and a copper foil having a thickness of 18 μm is laminated on both sides thereof one by one.
The molded body was heated and pressed at 70 ° C. for 150 minutes including heating and cooling to obtain a multilayer printed wiring board (the time during which the temperature of the molded body was 160 ° C. or higher was 60 minutes or longer). The amount of resin powder generated for the prepreg was measured, and the glass transition temperature and solder heat resistance after moisture absorption were evaluated as characteristics of the multilayer printed wiring board. Table 1 shows the results. It can be seen that the amount of resin powder generated from the prepreg is extremely small, and the glass transition temperature of the laminate is 140 ° C. or higher, which is equivalent to the current FR-4 product.

(Examples 2 to 4) A multilayer printed wiring board was prepared in the same manner as in Example 1 except that the composition of the varnish was changed as shown in Table 1, and the characteristics were evaluated. Table 1 shows the compositions and evaluation results. As in Example 1, the amount of resin powder generated from the prepreg was small, and the glass transition temperature of the laminate was 140 ° C. or higher. (Comparative Examples 1 to 4) A multilayer printed wiring board was prepared in the same manner as in Example 1 except that the composition of the varnish was changed as shown in Table 1, and the characteristics were evaluated. Table 1 shows the compositions and evaluation results. Comparative Examples 1 and 2 and Comparative Example 3
And No. 4 have the same resin formulation, but the dispersity index of the molecular weight distribution is changed by changing the drying conditions at the time of preparing the prepreg. In Comparative Examples 2 and 4, the drying conditions are severe and the curing reaction of the resin is progressing.

[0030]

[Table 1]

(Measurement method) Generated amount of resin powder: Measured in a state where eight prepregs each having a fixed size (100 mm square) were piled up, and determined as a weight before treatment. This is vertically gripped on a table and dropped 20 times from a height of 15 mm.
Divided by pre-treatment weight. 2. Glass transition temperature (Tg): By viscoelasticity method. The peak value of tan δ was determined at a heating rate of 3 ° C./min. 3. Hole-filling property during multilayer molding: The entire surface copper foil was etched, the inner layer circuit was visually observed, and the percentage of voids out of 100 recesses was determined. 4. Solder heat resistance after moisture absorption: 20 test pieces (50 × 50
mm) was etched only on one side of the copper foil and subjected to a moisture absorption treatment at 100 ° C. for 4 hours, then floated on a solder at 260 ° C. for 120 seconds, and observed for swelling.

[0032]

As is clear from the above embodiments, the prepreg of the present invention can be used as a laminate when the prepreg of the present invention is used.
The glass transition temperature equivalent to that of No. 4 is maintained, and the generation of resin powder is extremely small when cutting the prepreg or the like, and molding defects in lamination molding or multilayer molding with this resin powder can be substantially eliminated. Therefore, the heat remelting treatment of the prepreg, which has been conventionally required, can be eliminated, and the manufacturing process of the printed circuit board can be shortened.

Claims (3)

[Claims] 1. An epoxy resin having an epoxy equivalent of 165 to 4500 and a bifunctional terminal epoxy resin and a trifunctional or higher epoxy resin are used as essential components, and dicyandiamide is used as a curing agent in an amount of 1 to 100 parts by weight of the epoxy resin. An epoxy resin composition containing 4 parts by weight of a dicyandiamide / catalyst in a weight ratio of 20 to 50 is impregnated into a sheet-like substrate and dried, and the molecular weight distribution of the epoxy resin in the prepreg has a dispersity index. Is not less than 4.0. 2. A bifunctional linear epoxy resin having an epoxy equivalent of 165 to 4500 is an epoxy resin having an epoxy equivalent of 165
The prepreg according to claim 1, comprising a bifunctional linear epoxy resin having an epoxy equivalent of from 300 to 300 and a bifunctional linear brominated epoxy resin having an epoxy equivalent of 1500 to 4500. 3. A laminated plate obtained by laminating one or more prepregs according to claim 1 or 2 and heating and pressing.