JP2003113222A - Epoxy resin composition for impregnating into organic fiber substrate and prepreg, laminate and printed circuit board using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a new epoxy resin composition which can be combined with organic fiber substrates to form insulated layers that allow printed circuits to hold excellent adhesive forces and heat resistance. SOLUTION: This epoxy resin composition which is impregnated into organic fiber substrates to form insulated layers is characterized by comprising (a) a trifunctional epoxy resin, (b) a cresol novolak epoxy resin, and (c) a urethane structure-containing bifunctional epoxy resin, wherein a compounded weight ratio (a)/ (b) is 90/10 to 50/50, and the content of the component (c) in the solid resin is 5 to 30 wt.%. The organic fiber substrate to be impregnated with the epoxy resin composition is preferably a non-woven fabric form prepared by binding fibers containing poly-p-phenylene terephthalamide fibers as a main component with fibers obtained by fibrillating poly-m-phenylene isophthalamide fibers.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an epoxy resin composition for impregnating an organic fiber base material. The present invention also relates to a prepreg, a laminated board or a metal foil-clad laminated board, and a printed wiring board to which the epoxy resin composition is applied.

[0002]

2. Description of the Related Art As electronic devices have become smaller and lighter and have a higher density, it has become mainstream to mount electronic components on a printed wiring board by a surface mounting method. Most of the insulating layers constituting the printed wiring board are insulating layers made of a combination of glass fiber woven cloth and epoxy resin. When mounting electronic components on a printed wiring board, it is necessary to match the thermal expansion coefficients of the electronic components and the printed wiring board as much as possible. The difference in the thermal expansion coefficient between the two is large, and there is a concern that cracks may occur in the solder connection portion of the electronic component due to the cooling / heating cycle after mounting. From such a viewpoint, an insulating layer in which an aramid fiber nonwoven fabric having a negative thermal expansion coefficient and an epoxy resin are combined has attracted attention as an insulating layer of a printed wiring board.

[0003]

Due to the miniaturization of electronic devices and electronic parts and the resulting thinning of printed wiring patterns, the adhesiveness between the printed wiring (copper foil) and the insulating layer is required more than ever. Has become. However, the adhesiveness between an insulating layer obtained by impregnating an organic fiber base material such as an aramid fiber non-woven fabric with an epoxy resin and a copper foil is not sufficient when the printed wiring pattern is thinned. Also, due to environmental considerations, attention has been paid to component mounting using lead-free solder, the reflow temperature becomes higher when lead-free solder is used, and the heat resistance of printed wiring boards and multilayer printed wiring boards is higher than ever. Has been required by.

The problem to be solved by the present invention is to apply a new epoxy resin composition to an insulating layer formed by a combination of an organic fiber base material and an epoxy resin so as to maintain excellent adhesion and heat resistance to printed wiring. It is to let.

[0005]

In order to solve the above problems, an epoxy resin composition for impregnating an organic fiber base material according to the present invention comprises (a) a trifunctional epoxy resin and (b) a phenolic novolac type epoxy. It includes a resin and (c) a bifunctional epoxy resin containing a urethane structure. And the above (a)
And the blending mass ratio (a) / (b) of (b) is 90/10
50/50, the content of (c) in the resin solids is 5
It is characterized by being ˜30% by mass. Prepreg is
An organic fiber base material is impregnated with the above-mentioned epoxy resin composition and dried to form. This prepreg layer is heat-pressed as a part or the whole of the prepreg layer to form a laminated plate. In the heat and pressure molding, a metal foil is integrated on one side or both sides as necessary to form a metal foil-clad laminate. The printed wiring board is provided with an insulating layer formed by heating and pressing the prepreg layer.

We have focused on the urethane structure in order to improve the adhesion between the printed wiring (copper foil) and the insulating layer. It is believed that the urethane structure causes a chemical secondary bond between an isocyanate group contained in the urethane structure and a surface containing active hydrogen, for example, the surface of a copper foil due to its high polarity and reactivity. Further, since the urethane structure easily has a hydrogen bond, it has excellent mechanical and physical adhesive strength and chemical adhesive strength (Keiji Iwata, "Polyurethane Resin," pages 230-2.
31 pages, published by Nikkan Kogyo Shimbun in 1969). Further, it is easy to modify the bifunctional epoxy resin with a urethane resin, and the epoxy resin containing such a urethane structure is used as an adhesive.

(C) An epoxy resin composition according to the present invention in which a bifunctional epoxy resin containing a urethane structure is mixed in a resin solid content in an amount of 5% by mass or more is obtained by combining the insulating layer to which the resin composition is applied and the printed wiring. The adhesive strength can be increased. However, since (c) has a long molecular straight chain and has many methyl groups, it is easily burned. Therefore, (c) is blended so that the content in the resin solid content is 30% by mass or less. Limiting only to the problem of flammability, this problem can be easily solved by blending Br-containing compounds together. However, when a large amount of Br-containing resin is blended for imparting flame retardancy, Br gas is likely to be generated when the printed wiring board is exposed to a high temperature such as during solder reflow, which is not environmentally preferable. In order to impart flame retardancy while suppressing the blending of the Br-containing resin, the content of (c) in the resin solid content is suppressed to 30% by mass or less. Further, in (c), the epoxy groups are present only at both ends.
If a large amount of such an epoxy resin is blended, the cross-linking density of the resin cured product will be low and the heat resistance will decrease. From this point as well, the content of (c) in the resin solid content is 3%.
It is 0 mass% or less.

Furthermore, in the epoxy resin composition according to the present invention, the compounding mass ratio of (a) trifunctional epoxy resin and (b) phenolic novolac type epoxy resin (a) /
The reason for limiting (b) to 90/10 to 50/50 is as follows. That is, by blending (b),
As compared with the case where a bifunctional epoxy resin such as a bisphenol A type epoxy resin or a bisphenol F type epoxy resin is used instead of this, the cross-linking density of the resin cured product is increased, so that the heat resistance is improved. However, since (b) contains a large amount of methyl groups, blending in a large amount should be avoided from the viewpoint of flame retardancy, and the above-mentioned limitation is imposed.

In the epoxy resin composition applied to the organic fiber-based printed wiring board, the compounding composition as described above (particularly the compounding of a bifunctional epoxy resin containing a urethane structure)
Only then, the adhesiveness between the printed wiring and the insulating layer is improved, and the heat resistance is maintained.

When an aramid fiber non-woven fabric is selected as the organic fiber base material that is impregnated with the above epoxy resin composition to form a prepreg, the aramid fiber non-woven fabric is poly-m.
-A non-woven fabric form in which fibers having poly-p-phenylene terephthalamide fiber as a main component are bound by fibrillated fibers of phenylene isophthalamide fiber is preferable.

A thermosetting resin binder such as an epoxy resin may be applied as a means for binding the fibers to each other to form the non-woven fabric. In this case, due to the influence of the thermosetting resin binder, the flame retardant resin is used. It becomes difficult to impart sex.
As described above, poly-m is used as a means for binding fibers together.
-By applying fibrillated phenylene isophthalamide fibers, it is advantageous to impart flame retardancy as compared with the case where a thermosetting resin binder is applied.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The epoxy resin composition according to the present invention is not particularly limited to the kind of (a) phenolic novolac type epoxy resin, and may be cresol novolac type epoxy resin, phenol novolac type epoxy resin or the like. You can choose. The phenol novolac type epoxy resin is advantageous in that it has less methyl groups than the cresol novolac type epoxy resin and thus imparts flame retardancy. As the curing agent for the epoxy resin, phenolic novolac resin can be selected. Also, as a curing accelerator,
2-Ethyl 4-methylimidazole or the like is added.

The prepreg is produced by impregnating the organic fiber base material with the epoxy composition according to the present invention and heating and drying. The printed wiring board, first, a metal foil is laminated on the layer of the prepreg, and these are heat-pressed to form a metal foil-clad laminate,
It is manufactured by etching a metal foil into a predetermined wiring pattern. The multilayer printed wiring board is manufactured by stacking a metal foil on the printed wiring board via a prepreg to integrate them by heat and pressure molding, and etching the metal foil into a predetermined wiring pattern. Further, it is possible to increase the number of wiring layers by stacking a metal foil on the surface via a prepreg and integrating them by heat and pressure molding, and etching the metal foil 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 heat and pressure molding, and the surface metal foil is etched into a predetermined wiring pattern. To process. The laminated board 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.

[0014]

EXAMPLES Examples will be described below. Although the printed wiring board is not specifically described below, its configuration and manufacturing method are as described above, and thus the description thereof is omitted. In order to confirm the printed wiring peeling strength and heat resistance of the printed wiring board, and the flame retardancy of the insulating layer, in the following example, for the sake of convenience, 1 is placed on each side of 5 prepregs.
A copper-clad laminate (0.5 mm thick) in which a copper foil having a thickness of 8 μm was placed and heat-pressed was manufactured and subjected to a test.

Conventional Example As an organic fiber base material, an aramid fiber non-woven fabric made by paper-making 95% by mass of poly-p-phenylene terephthalamide fiber chop and 5% by mass of fibrillated fiber of poly-m-phenylene isophthalamide fiber. (Unit mass 72g /
m ² ) is used. As an epoxy resin composition impregnated therein, a trifunctional epoxy resin (“VG3 manufactured by Toto Kasei Co., Ltd.”
101M80 ") 25 parts by mass, cresol novolac type epoxy resin (" YDCN704EK7 "manufactured by Tohto Kasei Co., Ltd.)
5 "), 25 parts by mass, 20 parts by mass of phenol novolak resin (" LF-6161 "manufactured by Dainippon Ink and Chemicals, Inc.) as a curing agent, and brominated bisphenol A (" TBBA ", Br manufactured by Bromochem Far East Co., Ltd.). Rate: 58% by mass)
30 parts by mass and 0.02 parts by mass of 2-ethyl 4-methylimidazole as a curing accelerator were dissolved in 30 parts by mass of methyl ethyl ketone to prepare a varnish. Br in resin solids
The content rate is 17.4% by mass. The nonwoven fabric was impregnated with this varnish and dried at 150 ° C. for 5 minutes to obtain a prepreg. The resin content of the prepreg is 53% by mass. The copper-clad laminate described above was manufactured using the prepreg. The molding conditions are heating and pressure molding for 60 minutes at a temperature of 170 ° C. and a pressure of 4.9 MPa.

Examples 1 to 11 and Comparative Examples 1 to 4 (a) Trifunctional epoxy resin ("VG31" manufactured by Tohto Kasei Co., Ltd.)
01M80 ”) (b) Cresol novolac type epoxy resin (Tohto Kasei
(YDCN704EK75 manufactured by Co., Ltd.) (c) Urethane-modified epoxy resin as a bifunctional epoxy resin containing a urethane structure (“XAC415 manufactured by Asahi Chiba Co., Ltd.”)
1 ”) Phenol novolac resin (Dainippon Ink and Co., Ltd.“ LF
-6161 ") Brominated bisphenol A (Bromochem Far yeast
"TBBA" manufactured by Co., Ltd.) with a Br content of 1 in the resin solid content.
The compounding mass ratio (a) / (b) of (a) and (b) and the content rate of (c) in the resin solid content at 5 mass% (less than the conventional example) are shown in Tables 1 and 2. Varnishes were prepared so as to have the respective formulations shown in. A copper clad laminate was manufactured in the same manner as in Conventional Example 1 except that these varnishes were used.

[0017]

[Table 1]

[0018]

[Table 2]

Comparative Examples 5 to 10 (a) Trifunctional epoxy resin ("VG31" manufactured by Tohto Kasei Co., Ltd.)
01M80 ”) (b) Cresol novolac type epoxy resin (Tohto Kasei
(YDCN704EK75 manufactured by KK) (c ') Bisphenol A type epoxy resin as a bifunctional epoxy resin ("Ep-" manufactured by Japan Epoxy Resins Co., Ltd.)
828 ”) Phenol novolac resin (Dainippon Ink and Co., Ltd.“ LF
-6161 ") Brominated bisphenol A (Bromochem Far yeast
"TBBA" manufactured by Co., Ltd.) with a Br content of 1 in the resin solid content.
The compounding mass ratio (a) of the above (a) and (b) at 5 mass%.
The varnish was adjusted so that / (b) and the content of (c ') in the resin solids were in the respective formulations shown in Table 3. A copper clad laminate was manufactured in the same manner as in Conventional Example 1 except that these varnishes were used.

[0020]

[Table 3]

Examples 12 to 17 Poly-p was used as the base material to be impregnated with the epoxy resin composition.
-A phenylene terephthalamide fiber chop was made into a paper, a thermosetting resin binder was sprayed onto this paper and dried by heating to form a nonwoven fabric (unit mass 72 g / m ² , thermosetting resin binder adhesion amount 8% by mass). ). The thermosetting resin binder is an epoxy resin emulsion (“V coat A” manufactured by Dainippon Ink and Chemicals, Inc.) and a blocked isocyanate resin (“CR-60B” manufactured by Dainippon Ink and Chemicals, Inc.) as a curing agent. With 10 parts by mass of epoxy resin and 1 part by mass of block isocyanate resin.
It is what Example 1 for the above aramid fiber nonwoven fabric
Applying the epoxy resin composition in ~ 6 respectively,
A copper clad laminate was manufactured in the same manner as in Conventional Example 1 except for the above.

With respect to the copper-clad laminates of the above examples, the evaluation results of copper foil peel strength, heat resistance, and flame retardancy are shown in Tables 4 to 4.
The results are shown in Table 7. Each property shown in the table was evaluated as follows. The copper foil peeling strength was measured based on JIS. For heat resistance, prepare a copper clad laminate of 250 x 250 mm size as a sample, leave it in a constant temperature / humidity bath at 85 ° C-85% RH for 48 hours, then take it out and float it in a solder bath at 280 ° C to leave it on the surface. The time (minutes) until blistering occurred was measured. For flame retardancy, the afterflame time (seconds) was measured based on the UL-94 test method.

[0023]

[Table 4]

[0024]

[Table 5]

[0025]

[Table 6]

[0026]

[Table 7]

From the control of the conventional example, Examples 1 to 6 and Comparative examples 1 and 2, the content of (c) in the resin solid content is set to 5 to 30 mass% to increase the copper foil peeling strength. I can understand that. Comparative Example 1 shows that the copper foil peeling strength is small when the content of (c) is less than 5% by mass.
Indicates that the flame retardancy is insufficient when the content of (c) exceeds 30 mass%.

Further, the conventional example, Examples 7 to 11 and Comparative example 3
From the controls of ~ 4, it can be understood that (a) / (b) is required to be in the range of 90/10 to 50/50 in order to secure flame retardancy and heat resistance.

From the comparisons of Examples 1 to 6 and Comparative Examples 5 to 11, the copper foil peeling strengths when the bifunctional epoxy resin containing the urethane structure and the bifunctional epoxy resin not containing the urethane structure were blended were measured. I can understand the difference again.

From the comparison between Examples 1 to 6 and Examples 12 to 17, it can be seen that there is no difference in the copper foil peel strength and heat resistance, but there is a difference in flame retardancy due to the difference in selection of the aramid nonwoven fabric. It can be understood. A higher level of flame retardancy can be secured by not selecting a thermosetting resin-resin binder as a means for binding fibers to each other to form a nonwoven fabric.

[0031]

As described above, with respect to the organic fiber base material,
By applying the epoxy resin composition according to the present invention, the printed wiring (copper foil) is excellent in adhesive strength and heat resistance,
A printed wiring board that retains flame retardancy can be provided.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Shigeru Kurumaya             2-8-7 Nihonbashihonmachi, Chuo-ku, Tokyo             Inside Shin-Kobe Electric Machinery Co., Ltd. (72) Inventor Hirokazu Goto             2-8-7 Nihonbashihonmachi, Chuo-ku, Tokyo             Inside Shin-Kobe Electric Machinery Co., Ltd. F-term (reference) 4F072 AA01 AA04 AB06 AB29 AD23                       AD27 AD30 AG03 AH21 AL09                       AL13                 4J036 AA01 AA04 AA06 AF06 AJ17                       DC40 FB07 JA08

Claims (5)

[Claims] 1. An epoxy resin composition for impregnating an organic fiber substrate, comprising: (a) a trifunctional epoxy resin, (b) a phenolic novolac type epoxy resin, and (c) a bifunctional epoxy containing a urethane structure. Resin, and the compounding mass ratio (a) / (b) of (a) and (b) is 9
The epoxy resin composition for impregnating an organic fiber base material, which has a content of (c) in the resin solid content of 5/10 to 50/50. 2. A prepreg obtained by impregnating the following organic fiber base material with the epoxy resin composition according to claim 1 and drying. An organic fiber substrate in the form of a non-woven fabric, in which a fiber containing poly-p-phenylene terephthalamide fiber as a main component is bound by a fiber obtained by fibrillating poly-m-phenylene isophthalamide fiber. 3. A laminate comprising the prepreg layer according to claim 2 and a part of or the whole of the prepreg layer, which is heated and pressed. 4. A metal foil-clad laminate in which a metal foil is integrated on at least one surface of the laminate according to claim 3. 5. A printed wiring board comprising an insulating layer formed by heating and pressing the layer of the prepreg according to claim 2.