JP2011105916A - Prepreg, multilayer printed wiring board, and flexible printed wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a prepreg which excels in adhesiveness and circuit embedding property while restraining flow of resin and prevents the generation of dust when it is processed, and is also excellent in yield, and to provide printed wiring boards. <P>SOLUTION: The prepreg is obtained by impregnating a fibrous base material with a varnish containing an epoxy resin composition and drying the resulting base material. The epoxy resin composition contains, as essential components, (A) an epoxy resin (except (B) the urethane-modified epoxy resin), (B) the urethane-modified epoxy resin, (C) an epoxy resin curing agent, and (D) a curing accelerator, wherein the total amount of the components (A) to (D) is 100 pts.mass, and the blending amount of the component (B) is 15-90 pts.mass in the total amount of the components (A) to (D). Multilayer printed wiring boards and flexible printed wiring boards each using the prepreg are also provided. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a prepreg used as a material for a printed wiring board, in which a fiber base material is impregnated with an epoxy resin composition and dried, and a multilayer printed wiring board and a flexible printed wiring board.

In recent years, printed wiring boards are required to be thinned with high-density mounting. Accordingly, flexible wiring boards and flex-rigid wiring boards have been adopted. In addition, the use of flex-rigid wiring boards having interlayer connection vias is increasing.
Problems in the flex-rigid wiring board in which interlayer connection vias are formed will be briefly described with reference to the drawings. FIG. 1 is a schematic diagram showing a procedure for bonding a rigid wiring board on a flexible wiring board with a prepreg and a cross-sectional shape. FIG. 2 is a schematic diagram showing a procedure for a build-up type flex-rigid wiring and a cross-sectional shape.

First, as shown in FIG. 1A, the wiring pattern 2 is formed on the front and back of the base film 1, and then the coverlay 3 is laminated on the front and back of the base film 1 to protect the wiring pattern 2. By doing so, the flexible wiring board 4 shown in FIG. 1B is obtained.
Next, as shown in FIG. 1 (c), a prepreg (insulating adhesive layer) 5 that penetrates a portion corresponding to a bent portion 10 that can be bent later on the front and back of the flexible wiring board 4, and on one side. The rigid substrate 7 on which the wiring pattern 2 is formed is sequentially arranged, and is integrally formed by heating and pressure lamination.
Next, as shown in FIG.1 (d), the through hole 9 is formed in a desired position.
Further, as shown in FIG. 1 (e), the outer layer wiring pattern 2 is formed by a general subtractive method, and then the solder resist 11 for protecting the outer layer wiring pattern 2 is formed. By doing so, a flex-rigid wiring board having a bent portion 10 is obtained. Here, FIG. 3 is an enlarged view around the interlayer connection via A. FIG.

On the other hand, in the manufacturing method of the build-up type flex-rigid wiring, as shown in FIG. 2 (c), instead of the rigid substrate 7, the copper foil 12 and the prepreg 5 are laminated and then shown in FIG. 2 (d). As shown in FIG. 2E, the interlayer connection via processing is performed, the interlayer connection via 6 is plated, and the circuit pattern is formed as shown in FIG. 2E. Here, FIG. 4 is an enlarged view around the interlayer connection via B formed in this way.
The flex-rigid wiring board manufacturing method is as described above. However, if the resin flow of the prepreg 5 used as an adhesive sheet is large, the resin of the prepreg 5 flows into the bent portion 10 and the resin flow. Since the portion 8 is formed, there is a problem that the flexibility is lowered.

Therefore, a prepreg obtained by impregnating a glass substrate with a resin having a viscosity of 10,000 to 50,000 poise and semi-cured (see Patent Document 1) or a prepreg containing a rubber in a resin composition (see Patent Documents 2 and 3). The technique which aims at suppression of the resin flow to the bending part 10 by laminating | stacking using is disclosed.
Here, in prepregs and multilayer wiring boards obtained by impregnating and drying an epoxy resin composition on a fiber base material, a number of proposals have been made to adjust various characteristics using a plurality of different types of epoxy resins (for example, patents). References 4-11).

JP-A-7-176836 JP 2005-213352 A JP 2007-326929 A JP 7-196769 A Japanese Patent Laid-Open No. 2001-151991 WO2002 / 006399 Publication JP 2006-28274 A JP 2006-182991 A JP 2008-88400 A JP 2008-291056 A JP 2009-212097 A

However, when a flexible wiring board and a rigid wiring board are bonded using a prepreg as described in Patent Documents 1 to 3, even if the resin flow to the bent portion is suppressed, the embeddability in the wiring pattern is improved. It was not enough. In particular, as shown in FIGS. 3 and 4, it is required to improve the resin embedding property in the portion where the inner layer circuit is thickened by plating.
Furthermore, in the process of the build-up type printed wiring board as shown in FIG. 2, since the interlayer connection via is formed in the cured prepreg, the chemical resistance is insufficient.
In addition, the combination of a plurality of epoxy resins described in Patent Documents 4 to 11 can be used from the opening portion of the prepreg end face without deteriorating circuit embedding property, dust generation during processing, solder reflow heat resistance and storage stability. The resin flow could not be suppressed.
The present invention was made to eliminate the above-mentioned drawbacks, while suppressing the resin flow from the opening end face of the prepreg, while being excellent in adhesiveness, circuit embedding property and storage stability, and at the time of processing An object of the present invention is to provide a prepreg, a multilayer printed wiring board and a flexible printed wiring board which prevent dust generation and have a good yield.

That is, the present invention is a prepreg obtained by impregnating and drying the following (1) a varnish containing an epoxy resin composition on a fiber substrate, wherein the epoxy resin composition is (A) an epoxy resin [provided that (B) A prepreg [components (A) to (D)] containing, as essential components, (B) urethane-modified epoxy resin, (C) epoxy resin curing agent, and (D) curing accelerator The total amount of component (B) in the total amount is 15 to 90 parts by mass],
(2) The prepreg according to (1) above, wherein the amount of the epoxy resin as the component (A) is 5 to 80 parts by mass in 100 parts by mass of the components (A) to (D),
(3) The prepreg as described in (1) or (2) above, wherein the semi-cured epoxy resin composition has a minimum melt viscosity of 5000 to 35000 Pa · s at 50 ° C. to 180 ° C.,
(4) The prepreg according to any one of the above (1) to (3), wherein the epoxy resin of the component (A) is a naphthalene type epoxy resin and / or a biphenyl skeleton type epoxy resin,
(5) The prepreg according to any one of (1) to (4), wherein the fiber base material is a glass cloth,
(6) A multilayer printed wiring board in which an insulating layer is formed by the prepreg according to any one of (1) to (5) above, and (7) the prepreg according to any one of (1) to (5) above Provided is a flexible printed wiring board bonded.

  By using a specific amount of urethane-modified epoxy resin in combination with other epoxy resins, resin flow from the opening end face of the prepreg is prevented, and a prepreg with excellent circuit embedding, solder reflow heat resistance, and storage stability is obtained. Can do.

FIG. 5 is a schematic diagram showing a procedure for laminating each layer and a cross-sectional shape in a flex-rigid wiring board in which a rigid wiring board is bonded to a flexible wiring board by a prepreg. In a build-up type flex-rigid wiring board, it is a schematic diagram which shows the procedure of laminating | stacking each layer, and the shape of a cross section. FIG. 2 is an enlarged view around an interlayer connection via A in the flex-rigid wiring board of FIG. 1. FIG. 3 is an enlarged view around an interlayer connection via B in the build-up type flex-rigid wiring board of FIG. 2.

Hereinafter, the present invention will be described in detail.
In the epoxy resin composition used in the prepreg of the present invention, the epoxy resin of component (A) (excluding the urethane-modified epoxy resin of component (B) described later) has a molecular weight of less than 20,000 and is 2 per molecule. The epoxy resin which has the above epoxy groups is mentioned. In addition, the molecular weight as used in the field of this invention is a weight average molecular weight of standard polystyrene conversion measured by GPC.
As the epoxy resin of component (A), a glycidyl ether type epoxy resin is preferably used, and more specifically, a naphthalene type polyfunctional epoxy resin, a biphenyl skeleton type epoxy resin, a bisphenol A type epoxy resin, a bisphenol F type epoxy resin. Resin, novolac type epoxy resin, etc. are mentioned, These can be used individually or in mixture of 2 or more types. The epoxy resin as the component (A) includes glycidyl ether-based modified epoxy resins. As the modified epoxy resin, for example, a BT resin (bismaleimide / triazine resin) modified epoxy resin or the like can be used. Among these, naphthalene type polyfunctional epoxy resin and biphenyl skeleton type epoxy resin are preferable. These epoxy resins can use a commercial item as it is.
As a commercial item of a naphthalene type polyfunctional epoxy resin, for example, manufactured by DIC Corporation, Epicron HP-4032 (epoxy equivalent 150), HP-4700 (epoxy equivalent 160), Epicron HP-4032D (epoxy equivalent 141), Epicron HP-4032H (epoxy equivalent 250), Epicron EXA4750 (epoxy equivalent 182), Epicron EXA4700 (epoxy equivalent 163), etc. can be mentioned.
Moreover, as a commercial item of a biphenyl frame | skeleton type epoxy resin, Nippon Kayaku Co., Ltd. product, NC-3000H (epoxy equivalent 290), Yuka Shell Epoxy Co., Ltd. product, Epicoat (trademark) Epicoat YX4000 (epoxy), for example Equivalent 180-192), the same YX-4000H (epoxy equivalent 195), the oil-made shell epoxy Co., Ltd. product, YL6121 (epoxy equivalent 175), etc. can be mentioned.
As commercial products of bisphenol A type epoxy resin, Epicoat 825 (epoxy equivalent 172 to 178), Epicoat 828 (epoxy equivalent 184 to 194), Epicoat 834 (epoxy equivalent 230 to 270), Epicoat 1001 (epoxy equivalent 450 to 500) Epicoat 1002 (epoxy equivalent 600-700), Epicoat 1003 (epoxy equivalent 670-770), Epicoat 1004 (epoxy equivalent 875-975), Epicoat 1007 (epoxy equivalent 1750-2200), Epicoat 1009 (epoxy equivalent 2400-3300) , Epicoat 1010 (epoxy equivalent 3000-5000) [The above, made by Yuka Shell Epoxy Co., Ltd.], Epototo YD-128 (Epoxy equivalent 184-194), Epototo YD-011 Epoxy equivalent 450-500), epototo YD-014 (epoxy equivalent 900-1000), epototo YD-017 (epoxy equivalent 1750-2100), epototo YD-019 (epoxy equivalent 2400-3000), epototo YD-022 (epoxy equivalent) 4000-6000), [above, manufactured by Tohto Kasei Co., Ltd.], Epicron 840 (epoxy equivalent 180-190), Epicron 850 (epoxy equivalent 184-194), Epicron 1050 (epoxy equivalent 450-500), Epicron 3050 (epoxy) Equivalent 740-860), Epicron HM-101 (epoxy equivalent 3200-3900) [manufactured by DIC Corporation], Sumiepoxy ELA-128 (epoxy equivalent 184-194) [manufactured by Sumitomo Chemical Co., Ltd.], DER331 ( D Carboxymethyl eq 182-192) [Dow Chemical Co.] and the like.
As commercial products of bisphenol F type epoxy resin, Epicoat 806 (epoxy equivalent 160 to 170), Epicoat 807 (epoxy equivalent 160 to 175), Epicoat E4002P (epoxy equivalent 610), Epicoat E4003P (epoxy equivalent 800), Epicoat E4004P ( Epoxy equivalent 930), Epicoat E4007P (Epoxy equivalent 2060), Epicoat E4009P (Epoxy equivalent 3030), Epicoat E4010P (Epoxy equivalent 4400) [above, manufactured by Yuka Shell Epoxy Co., Ltd.], Epicron 830 [Epoxy equivalents 165 to 180, DIC Corporation], Epototo YDF-2001 (epoxy equivalents 450-500), Epototo YDF-2004 (epoxy equivalents 900-1000) [above, manufactured by Toto Kasei Co., Ltd. And the like.
Commercially available products of novolak type epoxy resins include Epicoat 152 (epoxy equivalents 172 to 179), Epicoat 154 (epoxy equivalents 176 to 181) [manufactured by Yuka Shell Epoxy Co., Ltd.], DER438 (epoxy equivalents 176 to 181). [Manufactured by Dow Chemical Co., Ltd.], Araldite EPN1138 (epoxy equivalents 176 to 181) (manufactured by Ciba), Araldite EPN1139 (epoxy equivalents 172 to 179) [manufactured by Ciba), Epototo YCPN-702 (epoxy equivalents 200 to 230) [Toto Kasei Co., Ltd.], BREN-105 (epoxy equivalents 262 to 278) [Nippon Kayaku Co., Ltd.] and the like.

(A) The compounding quantity of the epoxy resin of a component is 5-80 mass parts in 100 mass parts of resin compositions [(A)-(D) component], and it is more preferable that it is 10-70 mass parts.
If the blending amount of the component (A) is 5 parts by mass or more, good circuit embedding properties and adhesiveness will be exhibited, and reflow heat resistance will be good. On the other hand, if it is 80 parts by mass or less, the resin flow from the end face of the prepreg at the time of molding can be suppressed, and since the dust generation is good, the yield in the manufacturing process is not reduced.

The urethane-modified epoxy resin (B) used in the prepreg of the present invention refers to a resin in which a urethane bond is introduced into the epoxy resin skeleton. The method for producing this urethane-modified epoxy resin is not particularly limited, and the hydroxyl group of the compound having both an epoxy group and a hydroxyl group in the molecule is reacted with the isocyanate group of the urethane prepolymer to form a urethane bond in the epoxy resin. The method to introduce | transduce etc. can be mentioned.
The urethane prepolymer is a polymer obtained by reacting a polyisocyanate compound that can be represented by a general formula such as U- (NCO) _m and a polyhydroxy compound that can be represented by a general formula such as R- (OH) _n. Say. Here, U and R are each a hydrocarbon chain, a polyether chain, a polyester chain, etc., but are not necessarily limited to these. m and n are each an integer of 2 or more.
For example, examples of the polyisocyanate compound include compounds having two or more isocyanate groups such as tolylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, and methylene diphenyl diisocyanate.
Examples of the polyhydroxy compound include compounds having two or more hydroxyl groups such as polyether polyol, polyester polyol, castor oil derivative, polytetramethylene glycol, and lactone polyol.

The urethane-modified epoxy resin as component (B) can be obtained by reacting the urethane prepolymer obtained as described above with the hydroxyl group of the compound having both an epoxy group and a hydroxyl group in the molecule.
For example, a linear urethane-modified epoxy resin is obtained by reacting a urethane prepolymer with a hydroxyl group such as glycidol or an epoxy-containing resol; and a branched urethane-modified epoxy resin is a hydroxyl group such as a bisphenol-type epoxy resin. What reacted with the urethane prepolymer; As an acrylic urethane modified epoxy resin, what reacted the hydroxyl group of hydroxy (meth) acrylate and the urethane prepolymer can be mentioned.
Examples of commercially available urethane-modified epoxy resins as described above include, for example, Adeka Resin EPU series manufactured by ADEKA Corporation (product numbers EPU-6, EPU-15, EPU-16A, EPU-16B, EPU-17T-6, EPU-4-75X, EPU-75X, EPU-86, EPU-73, EPU-78, EPU-11) and Epicron TSR series (Epicron TSR-243, Epicron TSR-250-80BX) manufactured by DIC be able to.

(B) The compounding quantity of the urethane-modified epoxy resin of a component is 15-90 mass parts in 100 mass parts of resin compositions, and it is more preferable that it is 20-85 mass parts.
If the blending amount is 15 parts by mass or more, good circuit embedding and adhesiveness are exhibited, and reflow heat resistance is good. On the other hand, when the amount is 90 parts by mass or less, the resin flow from the end face of the prepreg at the time of molding is suppressed, and since the dust generation is good, the yield in the manufacturing process is not reduced.

As the curing agent of the component (C) used in the prepreg of the present invention, known ones used as a curing agent for epoxy resins can be used.
Specifically, aliphatic amine curing agents such as diethylenetriamine, tetraethylenetetramine, and tetraethylenepentamine, alicyclic amine curing agents such as isophoronediamine, and aromatic amines such as diaminodiphenylmethane, diaminodiphenylsulfone, and phenylenediamine Type curing agent, acid anhydride type curing agent such as phthalic anhydride, pyromellitic anhydride, trimellitic anhydride, hexahydrophthalic anhydride, 2-methylimidazole, 2-ethyl-4-methylimidazole, 1-cyanoethyl-2-ethyl Examples include imidazole compounds such as -4-methylimidazole, dicyandiamide, boron trifluoride amine complex salts, borofluorides such as tin borofluoride and zinc borofluoride, and octylates such as tin octylate and zinc octylate. , Preferably aliphatic amine curing agent, aromatic amine Agent, an imidazole compound, dicyandiamide, 硼弗 products, and octylate, aromatic amine curing agent is a dicyandiamide, and imidazole compounds. One of these curing agents may be used alone, or two or more thereof may be used in combination.

The amount of component (C) is determined in consideration of the epoxy equivalents of components (A) and (B), the cured state of the adhesive composition, the balance of properties, etc., and is generally determined by components (A) and (B). It is 0.1-40 mass parts with respect to 100 mass parts, and it is more preferable that it is 0.5-30 mass parts.
If the blending amount is 0.1 parts by mass or more, good life characteristics and warpage, and an improvement in handling properties are exhibited, the epoxy resin is sufficiently cured, and solder heat resistance and solvent resistance are improved. . On the other hand, in the case of 40 parts by mass or less, the composition is sufficiently cured and reliability such as solder heat resistance is not impaired.

In the present invention, the curing accelerator of component (D) is used. Examples of the curing accelerator include tertiary amines used as curing accelerators for ordinary epoxy resins, imidazole compounds such as 2-ethyl-4-imidazole and 1-benzyl-2-methylimidazole, aromatic amines, and trifluoride. Examples thereof include boron complex compounds and triphenylphosphine. A boron trifluoride complex compound is preferable. As the boron trifluoride complex compound, boron trifluoride monomethylamine complex, boron trifluoride piperidine complex, boron trifluoride triethanolamine complex, boron trifluoride benzylamine complex, boron trifluoride imidazole complex, etc. Can be mentioned. These curing accelerators can be used alone or in combination of two or more.
The blending amount of the (D) curing accelerator used in the present invention is in the range of 0.01 to 5 parts by mass with respect to 100 parts by mass of the (A) component and the (B) component epoxy resin. Is preferred.

The adhesive composition in the prepreg of the present invention contains the above-described components (A) to (D) as essential components. However, as long as it does not contradict the purpose of the present invention, an elastomer, an inorganic filler, and a deterioration are added as necessary. An inhibitor or the like can be added and blended.
Elastomers include acrylonitrile-butadiene rubber (NBR), carboxyl group-containing NBR, styrene-butadiene rubber (SBR), styrene-butadiene-styrene copolymer (SBS), partially hydrogenated products and epoxidized products of SBS (ESBS). It is preferable to use carboxyl group-containing NBR.
By adding an elastomer, appropriate elasticity can be imparted to the rigid portion of the multilayer printed wiring board or the flexible printed wiring board.
Examples of inorganic fillers include aluminum hydroxide, titanium oxide, calcium carbonate, and silica. Among them, excellent dimensional stability is imparted, and connection reliability of multilayer printed wiring boards and flexible printed wiring boards is improved. It is preferable to use aluminum hydroxide from the viewpoint that it can be formed.
Examples of the degradation inhibitor include hindered amine ultraviolet degradation inhibitors, phenol thermal degradation inhibitors, hindered phenol antioxidants, phosphoric acid stabilizers, sulfur antioxidants, and the like.
Furthermore, cyclophosphazene oligomer, chain amide phosphazene oligomer, chain anilide phosphazene oligomer, chain propoxyphosphazene oligomer, chain phenoxyphosphazene oligomer, cyclic amide phosphazene oligomer, cyclic anilide phosphazene oligomer, cyclic propoxyphosphazene oligomer, cyclic phenoxyphosphazene Polymer-type flame retardants such as oligomers, cyclic aminophenoxyphosphazene oligomers, and cyclic hydroxyphenoxyphosphazene oligomers can also be added.
The epoxy resin composition described above is diluted with a suitable organic solvent such as methyl ethyl ketone, toluene, acetone, ethyl cellosolve, methyl cellosolve, and cyclohexanone to form a resin solution (varnish) in which an inorganic filler is dispersed. The prepreg of the present invention can be produced by impregnating and drying the fiber base material.
The concentration of the varnish is preferably adjusted so that the total amount of the resin component and the inorganic filler is 40 to 70% by mass. When the concentration is less than 40% by mass, it is difficult to impregnate the fiber base with the necessary amount of resin. Conversely, when the concentration exceeds 70% by mass, the viscosity is too high and the fiber base is impregnated. May be significantly reduced.
The minimum melt viscosity at 50 ° C. to 180 ° C. of the semi-cured epoxy resin composition after impregnating the varnish into the fiber base material is preferably 5000 to 35000 Pa · s.
When the viscosity is 5000 Pa · s or more, the flow of resin from the prepreg end face opening can be suppressed, and when it is 35000 Pa · s or less, the fiber base material is sufficiently impregnated and the circuit is embedded. It becomes an epoxy resin composition having excellent properties.
In addition, the semi-cured epoxy resin composition is a prepreg in a state called a B stage by drying (substantially free of solvent) for about 3 to 15 minutes at a temperature of about 120 to 190 ° C. Of the resin composition.

Examples of the fiber base material used in the present invention include inorganic fiber base materials such as glass cloth and glass mat, and organic fiber base materials such as aromatic polyamide fiber, cellulose fiber, and polyester fiber. Can be used as a mixture.
Among them, the glass substrate is preferably a glass cloth, and the glass cloth can be used without any particular limitation, but a plain weave E glass cloth defined in IPC-EG-140 is used. It is preferable that the thickness of 30 to 50 μm, such as 1080 type and 1037 type, is particularly preferable for flex rigid wiring board applications where prepreg thinness is required.
The prepreg of the present invention is a fiber base material impregnated with a varnish containing an epoxy resin composition, and the thickness thereof is a little thicker than the thickness of the fiber base material. Therefore, the prepreg of the present invention preferably has a thickness of 30 to 60 μm.
It is preferable to adjust the impregnation amount of the epoxy resin composition (in which the organic solvent is removed from the varnish) to the fiber base so that it is 50 to 80% by mass in the total amount of both.

As described above, a semi-cured prepreg called a B stage can be prepared by impregnating a fiber base material with varnish and drying it at a temperature of about 120 to 190 ° C. for about 3 to 15 minutes.
A metal foil-clad laminate can be obtained by stacking one or a predetermined number of such prepregs, and stacking a metal foil such as a copper foil on one surface or both surfaces, followed by heating and pressing. The molding conditions at this time are generally preferably a molding temperature of 150 to 300 ° C., a molding pressure of 20 to 70 kg / cm ² , and a molding time of 10 to 60 minutes. Moreover, a metal foil-clad laminate can be obtained by preliminarily stacking the required number of prepregs and heating and press-molding, and then stacking the metal foil on one side or both sides of the resulting laminate and heating and pressing again. It can also be manufactured. A multilayer printed wiring board or a flexible printed wiring board can be obtained by printing the metal foil on the surface of the metal foil-clad laminate to form a circuit.
More specifically, using this prepreg as an insulating layer, the wiring pattern 2 is formed on the base film 1 and the both sides of the flexible wiring board 4 covered with the coverlay 3 as shown in FIG. 1 or FIG. In addition, a multilayer printed wiring board or a flexible printed wiring board with few resin flow portions 8 can be produced by laminating rigid wiring boards and performing through-hole plating.

EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to these Examples.

[Example 1]
(Preparation of prepreg)
As an epoxy resin of component (A), naphthalene type polyfunctional epoxy resin [manufactured by DIC Corporation, trade name: HP-4700, epoxy equivalent 160] 31.3 parts by mass, urethane modified epoxy resin of component (B) [ADEKA Product name: Adeka Resin EPU-4, epoxy equivalent 800] 31.3 parts by mass, dicyandiamide [Japan Epoxy Resin Co., Ltd., product name: DICY-7] as an epoxy resin curing agent of component (C) 2.5 parts by mass, an imidazole-based curing agent (trade name: C11Z-A, manufactured by Shikoku Kasei Co., Ltd.) as a curing accelerator for component (D), 0.3 parts by mass, as an elastomer for imparting appropriate elasticity Carboxyl group-containing acrylonitrile butadiene rubber [manufactured by JSR Corporation, trade name: Nipol 1072] with methyl ethyl ketone and a solid content of 20 mass 7.2 parts by mass of the material dissolved so as to become, 17.5 parts by mass of aluminum hydroxide (made by Showa Denko KK, trade name: H-421) as a flame retardant, and cyclophosphazene oligomer as a flame retardant [ 10.0 parts by mass of Otsuka Chemical Co., Ltd., trade name: SPB-100, melting point 100 ° C.] was dissolved and diluted in a mixed solvent of methyl ethyl ketone / toluene = 6/4 to prepare a varnish. This varnish was impregnated into a 30 μm-thick glass cloth (trade name: A106 / AS891AW, manufactured by Asahi Sebel Co., Ltd.) and dried at 180 ° C. for 3 minutes. A prepreg containing an epoxy resin composition was prepared.

(Production of flex-rigid board)
After circuit formation of both sides of a flexible double-sided copper-clad board [trade name: TLF-W-521MH, manufactured by Kyocera Chemical Co., Ltd.], a coverlay film [trade name: TFA-560AGM-, manufactured by Kyocera Chemical Co., Ltd.] is formed on both sides. 1225] was laminated and heated and pressed for 1 hour under the conditions of 160 ° C. and 4 MPa by hot pressing to obtain a flexible wiring board for the inner layer.
Separately, a circuit is formed on one side of a glass epoxy double-sided copper-clad laminate (product name: TLC-W-551, manufactured by Kyocera Chemical Co., Ltd.) having a thickness of 0.1 mm and a copper foil of 35 μm, and a rigid wiring board for outer layers Got.
The prepreg was aligned with the circuit forming surface of the outer layer rigid wiring board, and the inner layer flexible wiring board was positioned and temporarily fixed.
Thereafter, heat press bonding was performed for 1 hour under the conditions of 160 ° C. and 2.5 MPa by hot pressing to produce a flex-rigid substrate, and the properties of the prepreg were evaluated by the following methods. The results are shown in Table 1.

(Evaluation methods)
<Viscosity>
Using a flow tester (manufactured by Shimadzu Corporation, CFT-500 type), the varnish prepared in each example was started temperature 50 ° C., end temperature 180 ° C., temperature rising rate 5 ° C./min, load 400 N, die length. The minimum melt viscosity of the epoxy resin composition in a semi-cured state was measured under the condition of (L) / die diameter (D) = 10 mm / 1 mm (in Table 1, referred to as the minimum melt viscosity).
<Tensile modulus>
Using EXSTER6000 DMA, manufactured by Seiko Instruments Inc., the sample from which the copper foil was removed was cut into 5 mm × 30 mm, and the tensile modulus at 1 Hz from room temperature to 250 ° C. was measured at a heating rate of 5 ° C./min. did.
<Resin flow from the opening>
In Examples or Comparative Examples, the resin flow from the end face of the prepreg opening through the portion corresponding to the bent portion to the surface of the flexible wiring board exposed as the bent portion (8 in FIG. 1) is 100 times larger. Measured with a microscope and judged according to the following criteria.
○: Less than 0.5 mm Δ: 0.5 mm or more, less than 1 mm ×: 1 mm or more <Circuitability>
The outer layer side copper foil of the flex-rigid substrate was subjected to front etching, and the case where the resin was completely filled in the 50 μm conductor gap was visually evaluated as ◯, and the case where the filling was insufficient or a void could be confirmed was evaluated as x.
<Dust generation>
The maximum length (mm) of the resin whitening portion from the punched end after press punching was measured using a predetermined punching jig (Bik type), and less than 1 mm was judged as ◯, and 1 mm or more was judged as ×.
<Adhesiveness>
The adhesive strength (N / cm) in the 90 ° direction between the prepreg and the polyimide film was measured in the same manner as in JIS C5016 8.1 conductor peel strength (Measurement Method A).
<Reflow heat resistance>
The flex-rigid substrate is subjected to pretreatment of baking treatment (125 ° C., 4 hours) and humidification treatment (40 ° C., humidity 90%, 96 hours), and reflow treatment (preheating temperature 180 ° C., 100 seconds, reflow temperature 250 ° C. , 30 seconds, peak temperature 260 ° C.), the substrate having no abnormality such as blistering was evaluated as ◯, and the one having blistering was evaluated as ×.
<Storage stability>
Stack 50 sheets of prepregs cut to 300 x 500 mm, apply a load of 19.6 N under an environment of 20 ° C, and leave for 1 day. If there is no resin adhesion (blocking) between the prepregs, The case where there was adhesion (blocking) was evaluated as x.

[Examples 2 to 7]
A prepreg was prepared in the same manner as in Example 1 with the blending composition as shown in Table 1, then a flex-rigid substrate was prepared, the properties of the prepreg were evaluated, and the results are shown in Table 1.

[Comparative Examples 1-5]
A prepreg was prepared in the same manner as in Example 1 with the blending composition as shown in Table 1, then a flex-rigid substrate was prepared, the properties of the prepreg were evaluated, and the results are shown in Table 1.
Materials other than the above used in Examples 2 to 7 and Comparative Examples 1 to 5 are as follows.
(A) Epoxy resin: biphenyl skeleton type epoxy resin (trade name: NC-3000H, epoxy equivalent 290) manufactured by Nippon Kayaku Co., Ltd.
(A) Epoxy resin: bisphenol A type epoxy resin manufactured by Japan Epoxy Resin Co., Ltd. (trade name: Epicoat 1001, epoxy equivalent 470)
(B) Epoxy resin: Urethane-modified epoxy resin manufactured by ADEKA Corporation, Adeka Resin EPU-11 (trade name, epoxy equivalent 225)

From the results shown in Table 1, in Comparative Examples 1 and 2 in which the amount of component (B) is zero or small, the viscosity in a semi-cured state is too high, and the resin flow from the prepreg end face opening, dust generation, and adhesion In Comparative Example 3 in which the amount of component (B) is large, it is confirmed that the circuit embedding property, the reflow heat resistance and the storage stability are poor.

1: Base film 2: Wiring pattern 3: Coverlay 4: Flexible wiring board 5: Prepreg 6: Interlayer connection via 7: Rigid wiring board 8: Resin flow part 9: Through hole plating 10: Bending part 11: Solder resist 12: Copper foil 13: Plating

Claims (7)

  A prepreg formed by impregnating and drying a varnish containing an epoxy resin composition on a fiber base material, wherein the epoxy resin composition is (A) an epoxy resin (except for the urethane-modified epoxy resin (B)), ( B) A prepreg comprising urethane-modified epoxy resin, (C) epoxy resin curing agent and (D) curing accelerator as essential components [total amount of components (A) to (D) is 100 parts by mass, The blending amount of the component (B) in the total amount is 15 to 90 parts by mass].   The prepreg according to claim 1, wherein the amount of the epoxy resin (A) is 5 to 80 parts by mass in 100 parts by mass of the components (A) to (D).   The prepreg according to claim 1 or 2, wherein the semi-cured epoxy resin composition has a minimum melt viscosity of 5000 to 35000 Pa · s at 50 ° C to 180 ° C.   The prepreg according to any one of claims 1 to 3, wherein the epoxy resin of the component (A) is a naphthalene type epoxy resin and / or a biphenyl skeleton type epoxy resin.   The prepreg according to any one of claims 1 to 4, wherein the fiber base material is a glass cloth.   A multilayer printed wiring board in which an insulating layer is formed by the prepreg according to claim 1.   A flexible printed wiring board bonded by the prepreg according to claim 1.