JP2015108154A - Epoxy resin composition for printed wiring board, prepreg for printed wiring board using the epoxy resin composition for printed wiring board, and metal-clad laminate for printed wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an epoxy resin composition excellent in dielectric characteristics, which can be equipped with high heat resistance while maintaining fire retardancy.SOLUTION: An epoxy resin composition is used which is characterized by containing (A) an epoxy compound having a number average molecular weight of 1000 or less, at least two epoxy groups in one molecule, and no halogen atom, (B) a polyphenylene ether having a number average molecular weight of 5000 or less, (C) a cyanate ester compound, (D) an organometallic salt, and (E) a phosphorus-based flame retardant.

Description

  The present invention relates to an epoxy resin composition that is preferably used as an insulating material for a printed wiring board. Specifically, the epoxy resin composition preferably used for producing a printed wiring board having excellent heat resistance, and the epoxy resin composition are used. The present invention relates to prepregs and metal-clad laminates.

  In recent years, electronic devices used in the field of information and communication have been increasing in capacity and speed of signals, and there is a demand for printed wiring boards that have good high-frequency characteristics and can cope with a higher number of layers due to an increase in the number of wires. .

  In a printed wiring board used for such an electronic device, a low dielectric constant (ε) and a low dielectric loss tangent (tan δ) are required in order to maintain reliability in a high frequency region from the MHz band to the GHz band. Conventionally, as a printed wiring board having such electrical characteristics, one using a thermosetting resin composition in which polyphenylene ether (PPE) is blended with an epoxy resin is used for its insulating layer. Such a thermosetting resin composition exhibits a dielectric property superior to that of a normal epoxy resin composition, but other expensive high-frequency substrate materials such as PTFE, BT resin, polyimide resin, etc. There was a problem that heat resistance was low.

  In order to improve such low heat resistance, the following Patent Documents 1 and 2 include an epoxy resin containing a specific epoxy compound, a low molecular weight phenol-modified polyphenylene ether, and a cyanate compound as essential components. A composition is disclosed. Such an epoxy resin composition has high heat resistance and also has excellent dielectric properties.

  In addition to the above dielectric properties and heat resistance, the epoxy resin composition used for the insulating layer of the printed wiring board is also required to have high flame resistance. In order to impart flame retardancy to such an epoxy resin composition, a method of blending a predetermined amount of a brominated epoxy compound as an epoxy resin component has been widely used (for example, Patent Documents 1 to 4).

Japanese Patent Laid-Open No. 10-265669 JP 20007763 A JP-A-9-227659 JP-A-11-302529

  An epoxy resin composition containing an epoxy compound, a low molecular weight-modified phenol-modified polyphenylene ether, and a cyanate compound as essential components, which is known in the past, has excellent dielectric properties but still has heat resistance, but is still for other high-frequency substrates. It was insufficient compared with the material.

  In the epoxy resin composition containing an epoxy compound, a low molecular weight phenol-modified polyphenylene ether, and a cyanate compound as essential components, the present invention can provide high heat resistance while maintaining flame retardancy. An object is to provide an excellent epoxy resin composition.

  As a result of investigations for improving heat resistance in an epoxy resin composition containing an epoxy compound, a low molecular weight phenol-modified polyphenylene ether, and a cyanate compound as essential components, the present inventors have obtained an epoxy resin composition. When using brominated epoxy compounds and cyanate compounds commonly used for flame retardants, the heat resistance decreases, but without using brominated epoxy compounds, the heat resistance is greatly improved. I found out. As a result of further investigation, when a halogenated epoxy compound such as a brominated epoxy compound or a halogen-based flame retardant is used for the purpose of making the epoxy resin composition flame retardant, the halogenated epoxy compound at a high temperature is used. The present inventors have obtained some findings that the resin is considered to be thermally deteriorated due to the decomposition of the cyanate skeleton by halogen ions (or halogen radicals) generated by the elimination of. From this knowledge, the present invention has been completed.

  That is, the epoxy resin composition of the present invention comprises (A) an epoxy compound having a number average molecular weight of 1000 or less and having at least two epoxy groups in one molecule and containing no halogen atom, and (B) a number average molecular weight of 5000. It contains the following polyphenylene ether, (C) cyanate ester compound, (D) organometallic salt, and (E) phosphorus flame retardant. When a halogenated epoxy compound such as a brominated epoxy compound is used for the purpose of making the epoxy resin composition flame-retardant, the cured product is decomposed by the detached halogen, although the flame retardancy can be maintained. However, as in the present invention, instead of using a halogenated epoxy compound, by using a phosphorus flame retardant (E), decomposition of a cured product due to halogen desorption at high temperatures is suppressed. Therefore, flame retardance and high heat resistance can be maintained.

  As the phosphorous flame retardant (E) as described above, a phosphazene compound having a phosphazene skeleton is preferably used because of its excellent electrical characteristics and heat resistance.

  The epoxy compound (A) includes at least one epoxy compound selected from a dicyclopentadiene type epoxy compound, a bisphenol F type epoxy compound, a bisphenol A type epoxy compound, and a biphenyl type epoxy compound. ) Is preferably used from the viewpoint of good compatibility with it.

  The polyphenylene ether (B) is preferably obtained by redistributing a polyphenylene ether having a number average molecular weight of 10,000 to 30,000 in a solvent in the presence of a phenolic compound and a radical initiator. . Since such a polyphenylene ether has hydroxyl groups derived from a phenolic compound that contributes to curing at both ends of the molecular chain, it can maintain higher heat resistance.

  Moreover, the prepreg of the present invention is obtained by impregnating a fibrous base material with the epoxy resin composition and curing it.

  In addition, the metal-clad laminate of the present invention is obtained by laminating a metal foil on the prepreg and heating and pressing.

  ADVANTAGE OF THE INVENTION According to this invention, the resin composition preferably used for manufacture of a printed wiring board etc. which is excellent in heat resistance and a flame retardance, and has the outstanding dielectric characteristic is obtained.

  Hereinafter, embodiments of the present invention will be described.

  The type of the epoxy compound which does not contain a halogen atom having a number average molecular weight (A) of 1000 or less and having at least two epoxy groups in one molecule is not particularly limited. Specific examples thereof include a dicyclopentadiene type epoxy compound, a bisphenol A type epoxy compound, a bisphenol F type epoxy compound, a phenol novolac type epoxy compound, a naphthalene type epoxy compound, and a biphenyl type epoxy compound. These may be used alone or in combination of two or more. Among these, dicyclopentadiene type epoxy compounds, bisphenol F type epoxy compounds, bisphenol A type epoxy compounds and biphenyl type epoxy compounds are preferably used from the viewpoint of good compatibility with polyphenylene ether. In addition, although it is preferable not to contain a halogenated epoxy compound in an epoxy resin composition, as long as the effect of this invention is not impaired, you may add as needed.

  The blending ratio of the epoxy compound (A) is 20 to 60% by mass, and further 40 to 50% by mass with respect to the total amount of the components (A) to (C). It is preferable from the viewpoint that excellent mechanical and electrical properties can be maintained.

  Even if the polyphenylene ether (B) having a number average molecular weight of 5000 or less used in the present invention is obtained by a polymerization reaction, PPE having a high molecular weight (specifically, a number average molecular weight of about 10,000 to 30,000) is converted to toluene. It may be obtained by heating in the presence of a phenolic compound and a radical initiator in a solvent such as a redistribution reaction.

  In addition, since the polyphenylene ether obtained by the said redistribution reaction has the hydroxyl group derived from the phenol type compound which contributes to hardening at both ends of a molecular chain, it is preferable from the point which can maintain still higher heat resistance. Moreover, the polyphenylene ether obtained by polymerization is preferable from the point of showing excellent fluidity.

  The number average molecular weight of the polyphenylene ether (B) is 5000 or less, preferably 2000 to 4000. When the number average molecular weight exceeds 5,000, the fluidity is deteriorated and the reactivity with the epoxy group of the epoxy compound is lowered, so that the curing reaction takes a long time or is not taken into the curing system and is not reacted. As a result, the glass transition temperature decreases and sufficient heat resistance cannot be expected.

  The molecular weight of the polyphenylene ether (B) can be adjusted by adjusting the blending amount of the phenolic compound used in the redistribution reaction. That is, the greater the amount of the phenolic compound, the lower the molecular weight.

  As the high molecular weight PPE subjected to the above redistribution reaction, commercially available products such as commercial products can be used, and typical examples thereof include poly (2,6-dimethyl-1,4-phenylene ether). . In addition, the phenolic compound used in the redistribution reaction is not particularly limited. For example, a polyfunctional phenol having two or more phenolic hydroxyl groups in the molecule such as bisphenol A, phenol novolak, cresol novolak, and the like. System compounds are preferably used. These may be used alone or in combination of two or more.

  As the blending ratio of the polyphenylene ether (B), 20 to 60% by mass, and further 20 to 40% by mass in the total amount of the components (A) to (C) are sufficiently imparted with excellent dielectric properties. It is preferable because it can be performed.

  The (C) cyanate ester compound used in the present invention is not particularly limited as long as it is a compound having two or more cyanate groups in one molecule. Specific examples thereof include 2,2-bis (4-cyanatophenyl) propane, bis (3,5-dimethyl-4-cyanatophenyl) methane, and 2,2-bis (4-cyanatophenyl). An ethane etc. or derivatives thereof, aromatic cyanate ester compounds, etc. are mentioned. These may be used alone or in combination of two or more.

  The cyanate ester compound (C) is a component that acts as a curing agent for the epoxy resin and forms a rigid skeleton. This gives a high glass transition point (Tg). Moreover, since the viscosity is low, the high fluidity of the resin varnish obtained can be maintained.

  In addition, cyanate ester compound (C) self-polymerizes also in cyanate ester compounds by presence of organometallic salt (D). In this self-polymerization reaction, cyanate groups react with each other to form a triazine ring, whereby the polymerization reaction proceeds. Such a self-polymerization reaction also contributes to an improvement in heat resistance.

  The blending ratio of the cyanate ester compound (C) is 20 to 60% by mass, and further 20 to 40% by mass in the total amount of the components (A) to (C), and sufficient heat resistance is obtained. Moreover, it is preferable from the point that the impregnation property with respect to the base material is excellent and crystals do not easily precipitate in the resin varnish.

  The organometallic salt (D) used in the present invention is a catalyst that promotes the reaction of the epoxy compound (A) and the polyphenylene ether (B) with the cyanate ester compound (C) that is a curing agent. Examples include organic metal salts such as Zn, Cu and Fe of organic acids such as octanoic acid, stearic acid, acetylacetonate, naphthenic acid and salicylic acid. These may be used alone or in combination of two or more. Among these, zinc octoate is particularly preferably used because higher heat resistance can be obtained.

  The blending ratio of the organometallic salt (D) is not particularly limited, but is preferably about 0.005 to 5 parts by mass with respect to 100 parts by mass of the total amount of the components (A) to (C).

  Further, the epoxy resin composition of the present invention may further contain a curing catalyst such as a tertiary amine such as triethylamine or triethanolamine, or an imidazole such as 2-ethyl-4-imidazole or 4-methylimidazole. Good.

  The phosphorus flame retardant (E) used in the present invention is not particularly limited as long as it is a known phosphorus flame retardant containing a phosphorus atom. Conventionally, as a prescription for making an epoxy resin composition flame retardant, a method of blending a brominated epoxy compound or a halogen flame retardant such as brominated polystyrene has been generally used. When such a halogen-containing compound is blended, the halogen is eliminated at a high temperature to generate a halogen ion (or halogen radical). The halogen ions and the like thus generated are considered to have an action of decomposing the resin skeleton of the cured product cured with the cyanate ester compound (C). Therefore, in the epoxy resin composition of the present invention, by using a phosphorus-based flame retardant containing no halogen atom as the flame retardant, the decomposition of the resin skeleton is suppressed, and the heat resistance of the resulting cured product is maintained. it is conceivable that.

  Specific examples of such phosphorus flame retardant (E) include, for example, phosphate compounds such as triphenyl phosphate, tricresyl phosphate, xylenyl diphenyl phosphate, cresyl diphenyl phosphate, cyclic or Examples thereof include chain phosphazene compounds, condensed phosphate ester compounds, cyclic phosphate ester compounds, and derivatives thereof. These may be used alone or in combination of two or more. Among these, phosphazene compounds are preferably used because they are excellent in electrical characteristics and heat resistance.

  As a compounding quantity of the said phosphorus flame retardant (E), the ratio that a phosphorus atom density | concentration will be about 1-3 mass% in the resin component (namely, component except an inorganic component) in the hardened | cured material obtained. It is preferable to contain.

  An inorganic filler may be added to the epoxy resin composition of the present invention as necessary for the purpose of increasing the dimensional stability during heating or increasing the flame retardancy.

  Specific examples of the inorganic filler include silica, alumina, talc, aluminum hydroxide, magnesium hydroxide, titanium oxide, mica, aluminum borate, barium sulfate, calcium carbonate, and the like.

  The blending ratio of the inorganic filler is 10 to 100 parts by mass, more preferably 20 to 50 parts by mass with respect to 100 parts by mass of the total amount of the components (A) to (C). This is preferable from the viewpoint of improving the dimensional stability without lowering the adhesion to the foil.

  In the epoxy resin composition of the present invention, as long as the effects of the present invention are not impaired, other components that are blended in the normal epoxy resin composition as necessary, for example, a heat stabilizer, an antistatic agent, an ultraviolet absorber, You may mix | blend a flame retardant, dye, a pigment, a lubricant, etc.

  In the epoxy resin composition of the present invention, it is preferable that any of the components (A) to (C), which are resin components, is dissolved in a resin varnish. Such a resin varnish is prepared as follows, for example.

  Predetermined amounts of (A) an epoxy compound and (C) a cyanate ester compound are dissolved in a resin solution of polyphenylene ether (B) having a number average molecular weight of 5000 or less, obtained by redistributing high molecular weight PPE in toluene. Let At this time, heating may be performed as necessary. Moreover, in the case of melt | dissolution, it is preferable to use what melt | dissolves in solvents, such as toluene, at normal temperature as an epoxy compound (A) and a cyanate ester compound (C) from the point which does not produce a precipitate etc. in a resin varnish.

  Furthermore, when adding an inorganic filler as required, it is dispersed using a ball mill, a bead mill, a planetary mixer, a roll mill or the like until a predetermined dispersion state is obtained.

  Then, an organic metal salt (D), a phosphorus flame retardant (E), and the like are further added to the resin varnish in which the components (A) to (C) are dissolved, and the mixture is stirred to be uniform. In this way, a resin varnish is prepared.

  Examples of the method for producing the prepreg include a method of impregnating a fibrous base material with the resin varnish and then drying.

  Examples of the fibrous base material include glass cloth, aramid cloth, polyester cloth, glass nonwoven fabric, aramid nonwoven fabric, polyester nonwoven fabric, pulp paper, linter paper and the like. When a glass cloth is used, a laminate having excellent mechanical strength can be obtained, and a flat glass processed glass cloth is particularly preferable. The flattening can be performed, for example, by continuously pressing the glass cloth with a press roll with an appropriate pressure and compressing the yarn flatly. In addition, as a thickness of a base material, the thing of 0.04-0.3 mm can generally be used.

  Impregnation is performed by dipping or coating. Impregnation can be repeated a plurality of times as necessary.In this case, the impregnation can be repeated using a plurality of solutions having different compositions and concentrations, and finally the desired composition and resin amount can be adjusted. is there.

  The base material impregnated with the resin varnish is heated at a desired heating condition, for example, 80 to 170 ° C. for 1 to 10 minutes, whereby a semi-cured (B stage) prepreg is obtained.

  As a method of producing a metal-clad laminate using a prepreg, one or a plurality of the prepregs are stacked, and a metal foil such as a copper foil is stacked on both upper and lower surfaces or one surface thereof, and this is heated and pressed. By stacking and integrating, a double-sided metal foil-clad or single-sided metal foil-clad laminate can be produced. The heating and pressing conditions can be appropriately set depending on the thickness of the laminated board to be produced, the type of the resin composition of the prepreg, etc. For example, the temperature is 190 to 210 ° C., the pressure is 3.5 to 4.0 Pa, and the time Can be 120 to 150 minutes.

  In the epoxy resin composition of the present invention, the phenolic hydroxyl group at the terminal of the polyphenylene ether (B) reacts with the epoxy group of the epoxy compound (A) in the curing reaction, and further, they and the cyanate ester compound (C). React with each other to form a strong cross-linked structure. The cured product of the cyanate ester compound (C) has excellent electrical characteristics and heat resistance. In addition, as an epoxy compound (A), an epoxy compound containing no halogen atom is used, and in order to impart flame retardancy, a phosphoric flame retardant (E) is used. Sex can be imparted.

  Then, by forming a circuit by etching the metal foil on the surface of the laminate thus produced, a printed wiring board having a conductor pattern as a circuit on the surface of the laminate can be obtained. . The printed wiring board thus obtained has excellent dielectric properties and has high heat resistance and flame retardancy.

  The present invention will be described more specifically with reference to the following examples. However, the scope of the present invention is not limited to these examples.

(Production Example 1: Production of a solution of polyphenylene ether (PPE1) having a number average molecular weight of 2500 obtained by polymerization)
SA120 (PPE with a number average molecular weight of 2500) manufactured by Nippon GE Plastics Co., Ltd. was dissolved in toluene at 90 ° C. to prepare a polyphenylene ether (PPE1) solution with a number average molecular weight of 2500 (solid content concentration: 28% by mass). .

(Production Example 2: Production of a solution of polyphenylene ether (PPE2) having a number average molecular weight of 2500 by redistribution reaction)
250 g of toluene was put in a 2000 ml flask equipped with a stirrer and a stirring blade. While controlling the flask at an internal temperature of 90 ° C., 90 g of high molecular weight PPE (PPE having a number average molecular weight of 25000 (“Noryl 640-111” manufactured by GE Plastics Japan)), 7 g of bisphenol A, and 7 g of benzoyl peroxide were added. The mixture was stirred and reacted for 2 hours to prepare a polyphenylene ether (PPE2) solution having a number average molecular weight of 2500 (solid content concentration: 28% by mass), where the number average molecular weight was determined by gel permeation chromatography ( It is a value in terms of styrene measured by GPC).

(Production Example 3: Production of polyphenylene ether (PPE3) solution having a number average molecular weight of 4000)
A solution of polyphenylene ether (PPE3) having a number average molecular weight of 4000 (solid content concentration: 28% by mass) is reacted in the same manner as in Production Example 2 except that 3.6 g of bisphenol A and 3.6 g of benzoyl peroxide are used. Was prepared.

(Production Example 4: Production of a solution of polyphenylene ether (PPE4) having a number average molecular weight of 25,000 obtained by polymerization)
High molecular weight PPE (PPE having a number average molecular weight of 25000 (“Noryl 640-111” manufactured by GE Plastics Co., Ltd.)) was dissolved in toluene at 90 ° C. to obtain a solution of polyphenylene ether (PPE4) having a number average molecular weight of 25000 (PPE4). A solid content concentration of 28% by mass) was prepared.

(Examples 1 and 2 , Reference Examples 1 to 9 , Comparative Examples 1 to 5)
First, the raw materials used in this example are shown together.

<Epoxy compound>
・ Epicron HP7200 (Dainippon Ink & Chemicals, Inc.) which is a dicyclopentadiene type epoxy compound and has a number average molecular weight (Mn) of 550
-Bisphenol F-type epoxy compound, Mn350 Epicron 830S (Dainippon Ink Chemical Co., Ltd.)
-Tetrabromobisphenol A type epoxy compound, Mn800 Epicron 153 (Dainippon Ink Chemical Co., Ltd.)
-Bisphenol A type epoxy compound, Mn 1500 Epicron 3050 (Dainippon Ink Chemical Co., Ltd.)
<Cyanate ester compound>
2,2-bis (4-cyanatophenyl) propane (Bandy made by Lonza Japan)
-Cyanate ester compound represented by the following formula (1) (XU366 manufactured by Huntsman Japan)

<Flame retardants>
Phosphazene flame retardant having a phosphorus content of 13% by mass (SPB-100 manufactured by Otsuka Chemical Co., Ltd.)
Aromatic condensed phosphate ester flame retardant having a phosphorus content of 9% by mass (PX-200 manufactured by Daihachi Chemical Co., Ltd.)
-Phosphate ester flame retardant having a phosphorus content of 17% by mass (FR-500 manufactured by Lonza Japan)
Phosphazene flame retardant having a phosphorus content of 10% by mass (FPC-3033 manufactured by Fushimi Pharmaceutical Co., Ltd.)
-Brominated polystyrene (SAYTEX HP-7010 manufactured by Albemarle Japan)
<Curing catalyst>
・ Zinc octoate (Dainippon Ink & Chemicals, Inc., zinc concentration 18%)
2-ethyl-4-methylimidazole (2E4MZ) (manufactured by Shikoku Kasei Co., Ltd.)
<Inorganic filler>
・ Spherical silica (SiO ₂ ) SO25R (manufactured by Admatex)
[Preparation of resin varnish]
The toluene solution of polyphenylene ether was heated to 90 ° C., and the epoxy compound and the cyanate ester compound were added so as to have the blending ratio shown in Table 1, followed by stirring for 30 minutes for complete dissolution. Further, a curing catalyst, a flame retardant, and an inorganic filler were added and dispersed with a ball mill to obtain a resin varnish.

  Next, the obtained resin varnish was impregnated into glass cloth (“WEA116E” manufactured by Nitto Boseki Co., Ltd.), and then heated and dried at 150 ° C. for 3 to 5 minutes to obtain a prepreg.

  Next, 6 sheets of the obtained prepregs were stacked and laminated, and copper foils (F2-WS 18 μm manufactured by Furukawa Circuit Foil Co., Ltd.) were disposed on both outer layers, respectively, under conditions of a temperature of 220 ° C. and a pressure of 3 MPa. By heating and pressing for 2 hours, a copper-clad laminate having a thickness of 0.75 mm was obtained.

The following evaluation was performed using the obtained prepreg and copper clad laminate.
<Evaluation of fluidity of prepreg>
A core material having a length of 150 mm, a width of 100 mm, and a thickness of 0.8 mm, in which 1000 communicating holes having a hole diameter of 0.3 mm were formed at a pitch of 2 mm, was prepared. And the obtained prepreg and copper foil were laminated | stacked in that order on the single side | surface of the said core material, and only copper foil was laminated | stacked on the other single side | surface. And the said laminated body was shape | molded with the hot press on the conditions of 220 degreeC x 2 hours, and a pressure of 3 MPa. Then, the number of completely filled holes out of 1000 holes was counted, and the ratio was obtained.

<Heat-resistant>
In accordance with the standard of JIS C 6481, the copper-clad laminate cut out to a predetermined size was left in a thermostat set at a predetermined temperature for 1 hour and then taken out. And the processed test piece was observed visually and the highest temperature when the swelling did not generate | occur | produce was calculated | required.

<Flame retardance>
The flame retardancy of the copper clad laminate cut out to a predetermined size was determined by performing a combustion test according to the UL 94 combustion test method.

<Dielectric properties>
According to the standard of JIS C 6481, the dielectric constant and dielectric loss tangent at 1 MHz were obtained.

<Coefficient of thermal expansion (CTE)>
The thermal expansion coefficient in the Z-axis direction was determined according to the standard of JIS C 6481. The measurement conditions were a temperature increase rate of 5 ° C./min and a temperature range of 75 to 125 ° C.

From Table 1, the copper-clad laminates obtained by using the epoxy resin compositions of Examples 1 and 2 and Reference Examples 1 to 9 according to the present invention all have a heat resistance of 260 ° C. or higher, and are difficult. The flammability was also V-0. Further, when Reference Example 3 using PPE obtained by redistribution reaction is compared with Reference Example 1 using PPE obtained by polymerization, Reference Example 3 using PPE by redistribution reaction is more heat resistant. Was expensive. On the other hand, the prepreg of Comparative Example 1 using high molecular weight PPE had low fluidity and low heat resistance. The copper clad laminates of Comparative Example 2 using a bromine-containing epoxy compound and Comparative Example 5 using brominated polystyrene also had low heat resistance. Further, Comparative Example 4 using only imidazole as a curing catalyst also had low heat resistance.

Claims (5)

(A) a number average molecular weight of 1000 or less having at least two epoxy groups in one molecule, an epoxy compound containing no halogen atom, (B) a number average molecular weight of 5000 or less of the polyphenylene ether, (C) sheet Aneto An ester compound, (D) an organic metal salt, and (E) a phosphate ester compound as a phosphorus flame retardant,
The blending ratio of the component (A), the component (B), the component (C), and the component (D) is 20 with respect to 100 parts by mass of the total amount of the components (A) to (C). The epoxy resin composition for printed wiring boards, which is ˜60 parts by mass, 20 to 60 parts by mass, 20 to 60 parts by mass, and 0.005 to 5 parts by mass.   The epoxy resin composition for printed wiring boards according to claim 1, wherein the blending ratio of the component (E) is such that the phosphorus atom concentration is 1 to 3% by mass in the total amount of the resin component.   The print according to claim 1 or 2, wherein the epoxy compound is at least one epoxy compound selected from a dicyclopentadiene type epoxy compound, a bisphenol F type epoxy compound, a bisphenol A type epoxy compound, and a biphenyl type epoxy compound. Epoxy resin composition for wiring boards.   A printed wiring board prepreg obtained by impregnating a fibrous base material with the epoxy resin composition for a printed wiring board according to any one of claims 1 to 3 and curing it.   A metal-clad laminate for a printed wiring board, obtained by laminating a metal foil on the prepreg for a printed wiring board according to claim 4 and heating and pressing.