JPH0263821A - Laminated plate - Google Patents

Abstract

PURPOSE:To allow the thermal expansion coefficient of a surface layer to approach the thermal expansion coefficient of chip parts and to reduce dimensional contraction at a time for working a distributing board by making the sheetlike base material of a middle layer of glass fiber woven fabric and making the sheetlike base material of the surface layer of para-amide fiber nonwoven fabric. CONSTITUTION:A prepreg A is manufactured by impregnating para-amide fiber nonwoven fabric with bisphenol type epoxy resin and drying it. On the other hand, a prepreg B is manufactured by impregnating glass fiber woven fabric with the same epoxy resin and drying it. A middle layer 6 is formed of the prepreg B and the surface layers 5 are formed by arranging the prepreg A on both surfaces of the middle layer. Furthermore a copper clad laminated plate 4 is produced by arranging the electrolytic thick copper foils on both surfaces of this constituted material and thereafter heating and pressurizing the copper foils. When the chip parts are placed thereon and connected with solder, the thermal expansion coefficient of the surface layers 5 is regulated to value approximate to the thermal expansion coefficient of the chip parts 1 and therefore reliability of a solder joining part is largely improved. Further the middle layer 6 is small in dimensional contraction and made high in rigidity and the dimensional contraction of the surface layers 5 is sufficiently suppressed and thereby the laminated plate small in dimensional contraction as a whole is produced.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a laminate suitable as a printed wiring board for surface mounting of chip components such as resistors and ICs.

BACKGROUND OF THE INVENTION In recent years, as electronic devices have become smaller, lighter, and more dense, electronic components used in these devices have rapidly shifted from leaded components to chip components. As for the mounting method, surface mounting on a printed wiring board is becoming mainstream. Against this background, the following strict characteristics have been required for copper-clad laminates, which are the material for printed wiring boards.

This will be explained with reference to the reference explanatory diagram of FIG. 2 together with the problem when mounting chip components on a boat. If the coefficient of thermal expansion of the chip component 1 and the coefficient of thermal expansion of the substrate 4 of the printed wiring board, for example, an epoxy resin-glass nonwoven base material laminate, are significantly different,
The solder joint 3 connecting the chip component 1 and the copper circuit 2 cracks due to loads such as cooling and heating cycles, making it unusable for practical use. The thermal expansion coefficient of commercially available chip components such as tC and transistors is 2 to 7 x 10-b/'C, while the substrate 4 on which the chip is mounted is 17
x20xlO-b/''C, making it difficult to ensure the reliability of the solder joint 3.A copper-clad laminate using a para-aramid fiber nonwoven base material instead of the glass nonwoven base material has been proposed. The coefficient of linear expansion of this material is close to that of the chip.However, because the dimensional shrinkage during heat treatment is greater than that of conventional copper-clad laminates, dimensional accuracy becomes a problem when processing wiring board circuits. It turns out that there is a danger.

Problems to be Solved by the Invention The present invention improves the above-mentioned drawbacks of thermal expansion coefficient and dimensional shrinkage, and provides a chip component with excellent surface mount reliability and small dimensional shrinkage during wiring board processing. The purpose of the present invention is to provide a copper-clad laminate suitable for surface mounting.

Means for Solving the Problems In order to achieve the above objects, the present invention provides a laminate in which a sheet-like base material is impregnated with a bisphenol-type epoxy resin composition or a polyfunctional epoxy resin composition and then laminated and molded. As shown in the figure, the sheet-like base material of the center layer 6 is made of glass fiber woven fabric, and the sheet-like base material of the surface layer 5 is made of para-amino acid fiber nonwoven fabric.

Operation The present invention has the above features, so that when a chip component is mounted and soldered as explained in FIG. 2, the coefficient of thermal expansion of the surface layer 5 becomes a value close to that of the chip component. , it is possible to greatly improve the reliability of solder joints during cooling and heating cycles. This effect can be achieved by incorporating an inorganic filler into the resin of the surface layer 5.
The coefficient of thermal expansion becomes a more approximate value and can be increased.

In addition, the heat received in the wiring board circuit processing process causes the laminate to release strain during laminate molding and shrink after curing the resin. Since the para-amide fiber nonwoven base material of the surface layer 5 has low rigidity against compressive stress, these forces cannot be suppressed, and there is a risk that the dimensional shrinkage of the laminate will increase.
In the present invention, since a glass fiber woven fabric with high rigidity against compressive stress is used for the center layer 6, the center layer 6 has small dimensional shrinkage and high rigidity, and the dimensional shrinkage of the surface layer 5 is sufficiently suppressed. The result is a laminate with small dimensional shrinkage as a whole.

Furthermore, containing an inorganic filler in the resin of the surface layer 5 reduces the amount of resin in the surface layer 5, which results in a decrease in the amount of post-curing shrinkage, leading to suppression of dimensional shrinkage of the laminate.

EXAMPLE In carrying out the present invention, commercially available bisphenol type epoxy resin-dicyandiamide cured type, glycidylamine type epoxy resin-dicyandiamide cured type, etc. can be used as the epoxy resin. Para-aramid fiber nonwoven fabric is
A hese made of low thermal expansion wind fibers such as commercially available polybalaf ζ nylene terephthalamide can be used. The amount of epoxy resin attached to the para-aramid fiber nonwoven base material is such that the thermal expansion coefficient of the surface layer approximates that of the chip component (5~
It is desirable to adjust it to 40 to 70% by weight on 10XIO-6/'C). Also, SiO□, MgO, AI□0
．． 3 grade inorganic filler to epoxy resin at a ratio of 5 to 30
By adding a large amount of resin to reduce the substantial amount of resin in the surface layer, it is possible to obtain a layer with an even lower coefficient of thermal expansion and to reduce the amount of heat shrinkage.

Furthermore, the glass fiber woven fabric is one that is commonly used for electrical insulation and is not particularly limited. A commercially available 18 μm or 35 μm electrolytic copper foil can be used as the copper foil to be integrally attached to the laminate during lamination molding.

The thickness and number of para-aramid fiber nonwoven fabrics and glass fiber woven fabrics used are adjusted so that the thickness of the layer-molded laminate is 5 to 50% of the thickness of the center layer and surface layer. Better to adjust. If the thickness of the central layer exceeds 50%, the thermal expansion coefficient of the central layer (usually 15-20
10-6/'C) has a large influence on the surface layer, and the solder connection reliability when chip components are mounted becomes low.

On the other hand, if the thickness is less than 5%, dimensional shrinkage of the surface layer due to heat received during wiring board circuit processing cannot be sufficiently suppressed.

Example 1 Dicyandiamide as a hardening agent and 4- as a hardening accelerator were added to rose type aramid fiber nonwoven fabric (tsubo 1:60g/rrr).
A prepreg (A) having a resin content of 55% by weight was prepared by impregnating and drying a bisphenol type epoxy resin containing methyl 2-ethylimidazole. On the other hand, a 40% by weight prepreg (B) was prepared by impregnating a glass fiber woven fabric with the same epoxy resin and drying it. The prepreg (B) 1 ply was used as the center layer, and 4 pieces of the prepreg (A) were placed on both surfaces of the prepreg (A), and after 35 μm thick electrolytic copper was electrolytically placed on both surfaces of the structure (Surface N), this sandwiched between mirror plates and heated at a temperature of 160°C and a pressure of 60kg/c.
1. After heating and pressurizing for a while. A copper-clad laminate of own thickness was manufactured.

Example 2 To the epoxy resin in Example 1, an inorganic filler (trade name: Satenton, Kagaya Kaolin Repair) consisting of a mixed system of 5iOz and Al2O was added in an amount of 20% (by weight) based on the solid resin. The epoxy resin composition was adjusted. This was impregnated into the rose type aramid fiber nonwoven fabric of Example 1 and dried to produce a prepreg (C) containing an inorganic filler and having a resin content of 58% by weight. One ply of the prepreg (B) of Example 1 was used as the center layer, and the prepreg (C) was arranged at four plies on both surfaces thereof (surface layer), and a stretched laminate thereof was obtained.

Example 3 Para-aramid fiber nonwoven fabric (tsubo ff160g/rrf)
Then, (D) was prepared using dicyandiamide as a curing agent and 4-methyl-2-ethylimidazole as a curing accelerator. On the other hand, a glass fiber woven fabric was impregnated with the same epoxy resin and dried to produce a prepreg (E) having a resin content of 40% by weight. One ply of the prepreg (E) was used as the center layer, and the prepreg (D) was arranged on both surfaces of the prepreg (D) at 4 ply as a surface layer), and after 35 μm thick electrolytic copper was electrolytically arranged on both surfaces of the structure, Example 1.0 under the same molding conditions as 1.
A copper-clad laminate with a thickness of mm was obtained.

Comparative Example 1 After stacking 10 plies of the prepreg (A) produced in Example 1 and electrolytically disposing 35 μm thick electrolytic copper on both surfaces, a 1.0 mm thick copper clad laminate was produced under the same molding conditions as Example 1. I got it.

Comparative Example 2 The prepreg (C) produced in Example 2 was
After 4 layers and 35 μm thick electrolytic copper whistles were placed on both surfaces, a 1.0 mm thick copper clad laminate was obtained under the same molding conditions as in Example 1.

Comparative Example 3 Five prepregs (B) prepared in Example 1 were stacked and 35 μm thick electrolytic copper was placed on both surfaces, and then
A copper-clad laminate having a thickness of 1.0 mm was obtained under the same molding conditions as in Example 1.

Table 1 shows the properties of the copper-clad laminates of Examples 1 to 3 and Comparative Examples 1 to 3.

Effects of the Invention As described above, the laminate according to the present invention uses a glass fiber woven fabric with high rigidity as the base material of the center layer and a para-aramid fiber nonwoven fabric as the base material of the surface layer. The coefficient of expansion is brought close to that of the chip component to be mounted, resulting in excellent surface mounting reliability of the chip component, and has the excellent effect of suppressing dimensional shrinkage due to heating to a small level. These effects become even more remarkable by incorporating an inorganic filler into the resin of the surface layer.

In addition, since the surface layer uses aramid fiber nonwoven fabric,
The surface roughness is smaller than when using glass fiber woven fabric, making it suitable for high-density packaging circuits.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a laminate according to the present invention, and FIG. 2 is an explanatory diagram of a printed wiring board on which chip components are mounted. 5 is the surface layer, 6 is the central layer Fig. 1 Fig. 2

Claims (1)

[Scope of Claims] 1. In a laminate formed by impregnating a bisphenol-type epoxy resin composition into a sheet-like base material and laminating it, the center layer sheet-like base material is a glass fiber woven fabric and the surface layer sheet-like base material A laminate made of para-aramid fiber nonwoven fabric. 2. The laminate according to claim 1, wherein the resin of the surface layer contains an inorganic filler. 3. The laminate according to claim 1 or 2, wherein the thickness of the central layer is 5 to 50% of the total thickness. 4. The laminate according to any one of claims 1 to 3, wherein the bisphenol type epoxy resin is a polyfunctional epoxy resin.