JPH04186789A - Printed wiring board - Google Patents

Abstract

PURPOSE:To remove the inferiority in bonding and slippage and prevent the occurrence of a warp by making the cloth of aromatic polyamide fibers a mat of short fibers, and using the epoxy resin, wherein a half quantity of aromatic polyamine is mixed. CONSTITUTION:First prepregs 5 and 6, which are obtained by impregnating the paper consisting of polyamide fibers with resin, are interposed between second prepregs 7 and 8, where the cloths consisting of glass fibers are impregnated with approximately the same resin, and metallic foils 1 and 2, respectively. Hereupon, the paper to make the first prepreg is made of polyamide fibers only. And this is one where the rate is made 50-65wt.% when denaturing the epoxy resin into polyamide as impregnation resin.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to printed wiring boards, particularly suitable for surface mounting;
The present invention also relates to a printed wiring board that can smoothly bond through-hole plating and metal foil.

Conventional technology Conventionally, laminates made by impregnating a paper base material or a glass cloth base material with resin and then laminating and molding the same are well known. There is a drawback that the temperature and humidity expansion coefficients do not match. Further, it is desirable that no warping occurs in order to stably place the parts and prevent slipping, but there is no satisfactory method in this regard.

Problems to be Solved by the Invention In the past, there was an example in which a flip chip was mounted on a laminate made using aromatic aramide cloth as a base material by matching the expansion coefficient. Due to this occurrence, there was a drawback that the flip-chip bonding was inaccurate. There were also problems with through-hole connections.

Means for Solving the Problems The present invention was carried out based on the above matters, and
At least, aromatic polyamide fiber cloth (long fibers) is made into a mat of short fibers with low elasticity (-5ppm/'11::
) was limited to the horizontal direction. As the resin that can be impregnated into this mat, an epoxy resin modified with about half of an aromatic polyamine is used.

In order to improve the elasticity in the thickness direction, a conventional glass cloth is used for the inner prepreg, and the above-mentioned mat is used for the outer prepreg.

Action At this time, as the resin for the internal prepreg, if the conventional dicyandiamide curing agent is used as a curing agent, it will not have good electrical conductivity with the outer layer prepreg, so it is better to use an impregnating resin that is approximately the same as the outer layer. We have found that results can be obtained. In order to make the expansion/contraction value in the thickness direction almost the same as that of conventional glass cloth, the ratio of the impregnated resin of the inner layer prepreg between the inner layer (glass cloth) and the outer layer (aramide mat) must be set to 50% by weight, for example. % to 75% by weight (preferably 55 to 65% by weight), the expansion/relaxation rate is changed and a stress buffering prepreg is obtained.

Example An embodiment will be explained below based on FIG. 1.

FIG. 1 shows a double-sided steel foil coated laminate with a thickness of 1.0!1111, which is used as a double-sided wiring board. The number of prepreg sheets is eight, and they are arranged diagonally on both sides with the thickness of the sheet as the center. In FIG. 1, 1.2 is a copper foil, 3 and 4 are outer layer prepregs, 9.10 is an inner layer prepreg, 5 and 6 are first buffer prepregs, and 7 and 8 are second buffer prepregs. The impregnating resins 1 to 8 were all epoxy, but polyester, polyimide, phenol, melamine, etc. can be freely selected. Table 1 shows the epoxy resin impregnation rate (weight percent) of each layer.

(Left below) Brominated bisphenol A type epoxy resin with 4 percent by weight of dicyandiamide as a curing agent (epoxy equivalent: 49
5 > 80 M parts, and FR-4 with an impregnated resin consisting of 20 parts by weight of a cresol novolak type epoxy resin (epoxy equivalent weight 23.5) When laminated with 8 layers of prepreg to a thickness of 0.95 mm Compared to the above, the overall engraving coefficient is improved by 20%, and the surface layer width is improved by 6.
The temperature is maintained at 9 to 7.2 ppm °C. Regarding the expansion/contraction rate in the thickness direction, when all the layers are composed of prepregs 1 and 2, the expansion/contraction rate in the thickness direction 8 is improved by about 20%, and 7
．． The value was almost the same as when all layers were configured with 8. The results are summarized in Table 2.

(Left below) Effects of the Invention As described above, it is possible to obtain a double-sided wiring board that has both a temperature elongation rate in the X-Y plane suitable for surface mounting and a temperature elongation rate in the Z-axis direction suitable for through holes. can. Possibly because the expansion/contraction values between the isomeric prepreg layers are kept to a small level, no adhesion failure or "slippage" occurs. Further, no warping was observed.

[Brief explanation of drawings]

In the figure, X and Y indicate the horizontal direction of the laminate. Further, Z indicates the thickness direction of the laminate. 1.2... Copper foil, 3, 4... Outer layer prepreg, 5.6... First buffer prepreg, 7.
8...Second buffer prepreg, 9,10...
...Inner layer prepreg.

Claims (2)

[Claims] (1) A first prepreg obtained by impregnating paper made of aromatic polyamide fiber with a resin and a second prepreg obtained by impregnating a cloth made of glass fiber with almost the same resin and a metal foil. A printed wiring board that is interposed between (2) The paper forming the first prepreg is formed only from aromatic polyamide fibers, and when the epoxy resin is modified with aromatic polyamide as the impregnating resin, the ratio is 50 to 50%.
The printed wiring board according to claim 1, characterized in that the content is 65% by weight.