JP2002003626A - Epoxy resin composition for impregnation of organic fiber base material and prepreg made of it, laminated plate and printed wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an epoxy resin composition that is suitable for a printed wiring board with organic fiber base material, does not cause increase of conductance-resistance of the through-hole conductor composed of copper, and secures flame-resistance and heat-resistance despite non-halogen. SOLUTION: The epoxy resin composition includes a bisphenol-F type-epoxy resin as a bi-functional epoxy resin, multi-functional (more than 3-functional) epoxy resin, phenolic novolak resin and phosphorus compound. The content of bisphenol-F type-epoxy resin and phosphorus in the resin solid content are 5-30 mass % and 1-2.6 mass %, respectively, but the content of phosphorus is preferably to be 2-2.6 mass %. A prepreg is prepared by impregnating the resin composition into an aramid-fiber non-woven-fabric base material and drying.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a flame-retardant epoxy resin composition for impregnating an organic fiber base material. In addition, the present invention relates to a prepreg, a laminate, a metal foil-clad laminate, and a printed wiring board using the epoxy resin composition.

[0002]

2. Description of the Related Art An epoxy resin printed wiring board to be incorporated in an electronic device is required to have safety such as being difficult to burn and difficult to spread. Therefore, a brominated epoxy resin or a bromine-added phenol novolak resin is used as a curing agent for the epoxy resin to impart flame retardancy.
However, when halogen-containing materials such as bromine and chlorine are used at high temperatures for a long time, there is a concern that halides may be dissociated.
When the halogen-containing material is incinerated, there is a concern that harmful halides are generated. In recent years, from the viewpoint of environmental safety, the direction of imparting non-halogen flame retardancy is changing.
Phosphorus compounds have attracted attention as flame retardants instead of halogen compounds. Most of the phosphorus compound is a phosphate ester compound having a low melting point (80 to 100 ° C.), so that it is easily thermally decomposed at a high temperature during combustion. The carbonized film of polyphosphoric acid generated by thermal decomposition shields the resin from oxygen and heat, thereby exhibiting a flame retardant effect. Further, as a flame retardant, in addition to the phosphorus compound, there is a resin containing nitrogen, and a technique for imparting flame retardancy without halogen by using a combination of phosphorus and nitrogen has been proposed.

[0003]

The printed wiring board and the multilayer printed wiring board are soldered at 270.degree.
Exposure to high temperatures in a moderate reflow process. If a large amount of a low-melting phosphorus compound is added in order to impart flame retardancy, the phosphorus compound is thermally decomposed in the above step, and blistering occurs at the interface between the printed wiring and the resin. Therefore, when a phosphorus compound is added to impart flame retardancy to a printed wiring board or a multilayer printed wiring board, it is also required that the addition does not cause a decrease in heat resistance. For printed wiring boards and multilayer printed wiring boards, those using glass fiber woven fabric or glass fiber nonwoven fabric as a base material of an insulating layer are often used, but it is difficult to add a small amount of a phosphorus compound to these. Flammability can be imparted. This is because there are many non-combustible glass fibers. However, an organic fiber-based epoxy resin printed wiring board requires special measures for a resin composition for imparting flame retardancy with no halogen, because the substrate itself is liable to burn.
When a conductor made of copper plating or copper paste is used to connect printed wiring between insulating layers by through holes or IVH, if a resin containing nitrogen atoms is added to the insulating layer, nitrogen It has been found that the conduction resistance of the through-hole and the IVH conductor increases due to the promotion of the moisture absorption and the oxidation reaction of copper by the atoms.

[0004] As described above, an organic fiber-based epoxy resin printed wiring board and a multilayer printed wiring board satisfy heat resistance even if flame retardancy can be imparted by using a halogen-free material.
It is not easy to avoid an increase in the conduction resistance of a through-hole made of copper or an IVH conductor. The problem to be solved by the present invention is to provide an organic compound which imparts flame retardancy with a non-halogen while restricting the amount of a phosphorus compound added, satisfies heat resistance, and avoids an increase in conduction resistance of through holes and IVH conductors. An object of the present invention is to provide an epoxy resin composition suitable for a fiber-based printed wiring board. Another object of the present invention is to provide a prepreg, a laminate or a metal foil-clad laminate, a printed wiring board or a multilayer printed wiring board of an organic fiber substrate to which the epoxy resin composition is applied.

[0005]

In order to solve the above problems, the epoxy resin composition for impregnating an organic fiber substrate according to the present invention contains substantially no resin containing a nitrogen atom. And it contains a bisphenol F type epoxy resin as a bifunctional epoxy resin, a trifunctional or higher polyfunctional epoxy resin, and further contains a phosphorus compound. The bisphenol F type epoxy resin content in the resin solid content is 5 to 30% by mass, and the phosphorus content in the resin solid content is 1 to 2.6% by mass, more preferably 2 to 2.6% by mass. I do.

[0006] The phosphorus compound produces a carbonized film of polyphosphoric acid by thermal decomposition, which exerts a flame-retardant effect by shielding the resin from oxygen and heat. In order to ensure heat resistance, the phosphorus content in the resin solid content is limited to a small amount as described above, and this alone is insufficient to ensure flame retardancy, so here, as a bifunctional epoxy resin, By combining a bisphenol F-type epoxy resin having a molecular structure with few side chains, the level of flame retardancy is improved. Even if the bisphenol F type epoxy resin content is low or high, the flame retardancy cannot be improved,
It is necessary to be within the above range. In the epoxy resin composition applied to the organic fiber base printed wiring board,
By adopting the above composition, good flame retardancy can be imparted for the first time without halogen, and further, a remarkable effect of avoiding an increase in conduction resistance of through holes and IVH conductors without lowering heat resistance. To play.

A prepreg according to the present invention is obtained by impregnating the above-mentioned epoxy resin composition into an organic fiber base material and drying the same, and a laminate is formed by heating and pressing a part or all of the prepreg layer. The metal foil-clad laminate is one in which a metal foil is integrated with the surface during the heating and pressing. Further, a printed wiring board according to the present invention includes an insulating layer formed by heating and pressing the prepreg layer.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION In the epoxy resin composition according to the present invention, selection of a trifunctional epoxy resin or a polyfunctional epoxy resin improves heat resistance. Bifunctional epoxy resin is
A bisphenol F type epoxy resin is selected instead of a frequently used bisphenol A type epoxy resin. A bisphenol S-type epoxy resin having a molecular structure with few side chains may be used in combination. Even if a bisphenol S-type epoxy resin is used instead of the bisphenol F-type epoxy resin, the flame retardancy is improved. Phenolic novolak resins act as curing agents for epoxy resins. A phenol novolak resin can be selected. Moreover, 2-ethyl 4-methylimidazole or the like is blended as a curing accelerator. The phosphorus compound which is a component of the resin composition is, for example, a phosphorus-based polyol, an addition-type phosphate ester that does not react with an epoxy resin, or a reactive phosphate ester that reacts with an epoxy resin. Since the reactive phosphate ester reacts with the epoxy resin and hinders the crosslinking reaction between the phenolic novolak resin as the curing agent and the epoxy resin, the addition type phosphate ester is preferably selected.

The epoxy resin composition according to the present invention can enhance flame retardancy by blending an inorganic compound powder such as aluminum hydroxide or magnesium hydroxide. However, care should be taken not to increase the blending amount. If the amount of the inorganic compound powder is large, the inorganic compound powder remains on the surface of the prepreg, and the adhesiveness at the interface between the metal foil (printed wiring) and the resin decreases. As long as the amount does not decrease the adhesiveness, it does not prevent blending of an inorganic compound powder such as aluminum hydroxide or magnesium hydroxide for imparting flame retardancy. The organic fiber base material impregnated with the epoxy resin composition is preferably a nonwoven fabric mainly composed of aromatic polyamide fibers. This nonwoven fabric is manufactured by forming fibers dispersed in water into a sheet. The resin binder in the form of an emulsion is sprayed on the paper-made nonwoven fabric and dried by heating to harden the resin binder, thereby obtaining a nonwoven fabric having sufficient strength. For printed wiring boards and multilayer printed wiring boards, it is required to improve the solder connection reliability of electronic components mounted by soldering. For this purpose, it is essential to reduce the thermal expansion of the insulating layer, and it is a preferable embodiment to select an aromatic polyamide fiber having a negative coefficient of thermal expansion as the organic fiber constituting the nonwoven fabric. The aromatic polyamide fibers are classified into para-based and meta-based. Preferably, the content of the para-based aromatic polyamide fiber in the fibers constituting the nonwoven fabric is set to 50% by mass or more. The selection of para aromatic polyamide fiber is more advantageous for lowering the thermal expansion,
This is because it has excellent moisture resistance. In order to impart further flame retardancy, it is also possible to select a wholly aromatic polyester (molten liquid crystal polymer) as the organic fiber base material.

The prepreg is produced by impregnating the above nonwoven fabric with the above epoxy composition and drying it. Printed wiring boards
First, a metal foil is superimposed on the prepreg layer, and these are heated and pressed to form a metal foil-clad laminate, and the metal foil is etched into a predetermined wiring pattern to be manufactured. A multilayer printed wiring board is manufactured by laminating a metal foil on the printed wiring board via a prepreg by heat and pressure molding, and etching the metal foil into a predetermined wiring pattern. Further, the number of wiring layers can be increased by laminating a metal foil on the surface via a prepreg and integrating them by heating and pressing, and etching the metal foil on the surface into a predetermined wiring pattern. In another method, a prepreg is interposed between a plurality of printed wiring boards, a metal foil is overlaid on the surface via the prepreg, these are integrated by heating and pressing, and the metal foil on the surface is etched into a predetermined wiring pattern. Process. The laminate and the printed wiring board may be configured by using a combination of the prepreg according to the present invention and another prepreg, for example, a glass fiber base material prepreg.

[0011]

Embodiments will be described below. Hereinafter, the printed wiring board is not specifically described, but the configuration and the manufacturing method are as described above, and thus the description is omitted. In order to confirm the flame retardancy and heat resistance of the insulating layer of the printed wiring board and the conduction resistance of the through-hole conductor of the printed wiring board, in the following example, for convenience, a copper foil of 18 μm thickness is provided on both sides where five prepregs are stacked. And a copper-clad laminate (0.5 mm thick) formed by heating and pressing was manufactured and subjected to a test.

Conventional Example 1 A para-aromatic polyamide fiber chop ("Technola" manufactured by Teijin Limited) was dispersed in water and formed into a sheet.
A resin binder comprising a mixture of a bisphenol A type epoxy resin and an isocyanate resin was sprayed in the form of an emulsion of an aqueous dispersion medium, and dried at 160 ° C. for 30 minutes to obtain a nonwoven fabric of 60 g / m ² . The adhesion amount of the resin binder is 8% by mass. Bisphenol A is used as an epoxy resin composition impregnated with the above nonwoven fabric as a base material.
Type epoxy resin ("Ep-8" manufactured by Yuka Shell Epoxy Co., Ltd.)
28 ") 31 parts by mass, trifunctional epoxy resin (Toto Kasei
20 parts by mass of "VG3101M80", 19 parts by mass of a phenol novolak resin ("LF-6161" manufactured by Dainippon Ink Co., Ltd.) as a curing agent and a brominated phenol novolak resin (manufactured by Bromochem Far East Co., Ltd.) "T
BBA ") 30 parts by mass, 2-ethyl 4 as a curing accelerator
A varnish was prepared by dissolving 0.2 parts by mass of methyl imidazole in 30 parts by mass of methyl ethyl ketone. The varnish was impregnated into the nonwoven fabric substrate and dried at 150 ° C. for 5 minutes to obtain a prepreg. The content of the resin is 52% by mass. Using the prepreg, the above-mentioned copper-clad laminate was manufactured. The molding conditions were as follows: temperature 170 ° C, pressure 4.9MPa
Under the conditions of the above for 60 minutes.

Examples 1 to 13 and Comparative Examples 1 to 4 Bisphenol F type epoxy resin ("Y" manufactured by Toto Kasei Co., Ltd.)
DF-170 "), trifunctional epoxy resin (Toto Kasei Co., Ltd.)
“VG3101M80”, phenol novolak resin (“TD-2090”, manufactured by Dainippon Ink and Chemicals, Inc.), and condensed phosphate ester (“PX-20” manufactured by Daihachi Chemical Industry Co., Ltd.)
0 "), 2-ethyl 4-methylimidazole was dissolved in methyl ethyl ketone, and the phosphorus content in the resin solid content was% by mass.
(P mass%) and bisphenol F type epoxy resin content mass% (bisF epoxy mass%) in the resin solid content are shown in Tables 1-2.
A varnish was prepared so as to have the respective compositions shown in (1). Otherwise, a copper-clad laminate was manufactured in the same manner as in Conventional Example 1.

[0014]

[Table 1]

[0015]

[Table 2]

Comparative Examples 5 to 7 Bisphenol F type epoxy resin ("Y" manufactured by Toto Kasei Co., Ltd.)
DF-170 "), trifunctional epoxy resin (Toto Kasei Co., Ltd.)
"VG3101M80", a phenol novolak resin ("TD-2090", manufactured by Dainippon Ink and Chemicals, Inc.), a melamine-modified phenol novolak resin ("LF-6161" manufactured by Dainippon Ink, Inc.), and a condensed phosphate ( "PX-200" manufactured by Daihachi Chemical Industry Co., Ltd.), 2-ethyl 4-methylimidazole was dissolved in methyl ethyl ketone, and the same amount of bisphenol F type epoxy resin and phosphoric acid ester as in Example 4 was used. % Nitrogen content in the
The varnish was prepared so that each of the varnishes had the composition shown in Table 3. Otherwise, a copper-clad laminate was manufactured in the same manner as in Conventional Example 1. This nitrogen content is based on the formulation of the melamine-modified phenol novolak resin.

[0017]

[Table 3]

Tables 4 to 6 show the results of evaluating the flame retardancy and the conduction resistance of the through-hole conductor processed by printed wiring for the copper-clad laminates of the above examples. Each characteristic shown in the table was evaluated as follows. The flame retardancy was measured by a residual flame time (sec) based on the UL-94 test method. For the conduction resistance of the through-hole conductor, prepare a test piece with a 2mm land diameter and a 0.4mm hole diameter through-hole plated with copper with a thickness of 25μm. Then, the conduction resistance of the through-hole conductor was measured.

[0019]

[Table 4]

[0020]

[Table 5]

[0021]

[Table 6]

From the controls of Examples 1 to 7 and Comparative Examples 1 and 2,
It can be understood that the flame retardancy can be secured by setting the phosphorus content in the resin solid content to 1 to 2.6% by mass. Further, in order to impart further flame retardancy, 2 to 2.6% by mass
Is preferable. Comparative Example 1 shows that the flame retardancy is insufficient when the phosphorus content is less than 1% by mass, and Comparative Example 2 lowers the heat resistance when the phosphorus content exceeds 2.6% by mass. Condensed phosphate ester (melting point 95 ° C)
Are released at the high temperature of the reflow device, thereby increasing the conduction resistance of the through-hole conductor. Further, from the comparison between Examples 8 to 13 and Comparative Examples 3 and 4, in order to ensure flame retardancy, it is essential that the bisphenol F type epoxy resin content in the resin solid content be 5 to 30% by mass. I can understand that. Further, Comparative Examples 5 to 7 increase the conduction resistance of the through-hole conductor even if the flame retardancy can be ensured by the nitrogen atom content. This indicates that ensuring the flame retardancy by blending is not appropriate. It is necessary not to mix a nitrogen atom-containing resin in the epoxy resin composition impregnated in the base material in order to manufacture the prepreg.

[0023]

As described above, by applying the epoxy resin composition according to the present invention to an organic fiber base material, it is possible to secure sufficient flame retardancy with no halogen and satisfy heat resistance. Thus, it is possible to provide a printed wiring board which does not cause an increase in conduction resistance of a through hole made of copper or an IVH conductor.

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Claims (8)

[Claims] An epoxy resin composition for impregnating an organic fiber base material, wherein bisphenol F is used as a bifunctional epoxy resin.
Epoxy resin, a polyfunctional epoxy resin having three or more functional groups, a phenolic novolak resin, and a phosphorus compound. The content of bisphenol F type epoxy resin in the resin solid content is 5 to 30% by mass. An epoxy resin composition for impregnating an organic fiber base material, wherein the phosphorus content in the solid content is 1 to 2.6% by mass. 2. The epoxy resin composition according to claim 1, wherein the content of phosphorus in the solid content of the resin is from 2 to 2.6% by mass. Composition. 3. A prepreg obtained by impregnating and drying an organic fiber base material with the epoxy resin composition according to claim 1. 4. The prepreg according to claim 3, wherein the organic fiber base material is a nonwoven fabric base material containing an aromatic polyamide fiber as a main component. 5. A laminate obtained by heating and pressing a part or all of the prepreg layer according to claim 3 or 4. 6. A metal foil-clad laminate in which a metal foil is integrated on at least one surface of the laminate according to claim 5. 7. A printed wiring board comprising an insulating layer formed by heating and pressing the prepreg layer according to claim 3 or 4. 8. The printed wiring board according to claim 7, wherein the through-hole conductor of the insulating layer is made of copper.