JPH0362993A - Phenol resin one side metal foil pasted laminated plate - Google Patents

Abstract

PURPOSE:To suppress generation of a curve and a twist as a printed circuit board by making an elongation percentage of a kraft paper base material of a layer adjacent to a metal foil larger than the elongation percentage of the other kraft paper base material which is a main layer. CONSTITUTION:A phenol resin one side metal foil pasted laminated plate uses kraft paper as a base material to be impregnated with phenol resin. And, an elongation percentage of the kraft paper base material of a neighboring layer 2 adjacent to the metal foil is made larger than the elongation percentage of the other kraft paper base material which is a main layer 3. Further, the kraft paper base material as the main layer 3 may use that having a basis weight of 200 to 250g/m<2> so as to reduce the number of sheets for lamination for being made a lamination plate having the prescribed thickness. Further, the elongation percentage of the kraft paper base material of a large elongation percentage of the neighboring layer 2 is desirably to be in the range of 1.2 to 1.5%. That is that the kraft paper base material having a large elongation percentage of the neighboring layer 2 of the metal foil 1 suppresses thermal shrinkage of a coat to suppress a curve and a twist keeping the balance with the substrate shrinkage.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a phenolic resin single-sided metal foil laminate for printed circuit boards. In particular, the present invention relates to a single-sided metal foil-covered laminate suitable for printed circuit boards which are subjected to heat treatment after being undercoated for insulation, such as when forming a carbon resistance circuit.

BACKGROUND OF THE INVENTION Phenolic resin steel clad laminates are widely used for printed circuit boards in the consumer electronics field. As electronic components have become more sophisticated and denser in recent years, demands for suppressing warpage and twisting during the circuit board manufacturing process have become increasingly strict.

In particular, single-sided printed circuit boards are susceptible to twisting due to their asymmetric structure in the thickness direction. For example, when a carbon resistance circuit is further formed after a circuit is formed by etching, an undercoat is applied to the circuit surface of the copper foil for insulation, and heat treatment is performed at a high temperature during the carbon printing and curing process. This heat treatment causes warping and twisting of the board, causing problems during the circuit board manufacturing process and parts assembly process. Furthermore, it is difficult to cope with higher density.

Conventionally, in order to reduce the occurrence of warping and twisting in the above process, a resin with small shrinkage when heated is used as the phenolic resin, and a combination of kraft paper and linter paper is used as the base material to be impregnated with the phenolic resin. We are responding.

Problems to be Solved by the Invention However, as long as a phenolic resin that is an additional wire mold is used, it is difficult to obtain a phenolic resin with low dimensional shrinkage through modification. Furthermore, when used in combination with linter paper, whose dimensional change behavior is completely different from that of kraft paper, more twisting tends to occur.

An object of the present invention is to provide a phenolic resin single-sided metal foil-clad laminate that can suppress the occurrence of warping and twisting as a printed circuit board. In particular, a single-sided metal foil-covered laminate suitable for printed circuit boards that involve heat treatment in the manufacturing process of printed circuit boards, where the heat treatment is performed after applying an insulating coat to the surface of the circuit board. The goal is to provide the following.

Means for Solving the Problems The phenolic resin single-sided metal foil-clad υ laminate according to the present invention has the following features:
Kraft paper is used as the base material to be impregnated with phenolic resin. As shown in FIG. 1, the elongation rate of the kraft paper base material of the adjacent layer 2 that is in contact with the metal foil 1 is made larger than the elongation rate of the other kraft paper base material that is the main layer 3. .

In addition, the kraft paper base material of the main layer 3 has a basis weight of 200 to 25
o 9/rrt may be used to reduce the number of stacked sheets to obtain a laminate of a predetermined thickness. Furthermore, the elongation rate of the kraft paper base material having a large elongation rate of the adjacent layer 2 is preferably in the range of 1.2 to 1.5%. Here, the elongation rate is measured according to JIS-P-8132-1976.

A single-sided printed circuit board obtained by processing a phenol resin single-sided metal foil-clad laminate has an asymmetrical structure in the thickness direction, and therefore warps and twists occur during heat treatment. and,
When a circuit surface is coated with an insulating coating and then subjected to heat treatment, as in the case of forming a carbon resistor by printing, significant warping and twisting occur.

That is, the phenolic resin of the substrate shrinks due to heat treatment, but the resin applied to the circuit surface for coating shows even more remarkable heat shrinkage. As a result, the circuit surface side becomes concave. Also, the difference in shrinkage between the circuit side and the opposite side causes twisting.

In the single-sided metal foil-clad laminate according to the present invention, the kraft paper base material with a high elongation rate in the layer adjacent to the metal foil suppresses the thermal shrinkage of the coat, balances the amount of shrinkage of the substrate, and prevents warping and twisting. suppress.

When the elongation rate of kraft paper, which has a high elongation rate, decreases by more than 1.2, the effect of suppressing warpage and twisting decreases, and as it increases to 1.51, the opposite warpage (the circuit side becomes convex) occurs. ).

The cause of torsion is the strain remaining between the base material layers during lamination molding, but by using paper with a high basis weight, fewer layers are required to obtain a laminate of the same thickness. As a result, since the number of interlayers is reduced, the amount of residual strain during molding is reduced, and twisting can be suppressed.

Example The present invention will be described in detail.

Example 1 Tsubo 1k135 f! h", a kraft paper base material with an elongation rate of 1.2 is impregnated with tung oil-modified phenolic resin and dried to form a resin gold [
A 48% prepreg was obtained (prepreg A).

A kraft paper base material with a tsubo fk of 135.9/7& and an elongation rate of 0.7% was impregnated with a tung oil-modified phenolic resin and dried to obtain a prepreg with a resin content of 48% (prepreg B).

4 plies of prepreg B, 1 ply of prepreg A, and 35 μ thick steel foil coated with adhesive were stacked in this order, and heated and pressed at a temperature of 160'C and a pressure of 100 kg/i for 60 minutes to form a sheet of 1.0 mm. A thick single-sided steel laminate was obtained.

Example 2 Tsubo i 250. A kraft paper base material with @/ffl and elongation rate of 0.7% was impregnated with tung oil-modified phenolic resin and dried to obtain Gripreg with resin gold of 1149% (Prepreg C).

2 plies of Gripreg C, 1 ply of prepreg A of Example 1
A ply and a 35 μm thick copper foil coated with an adhesive were stacked in this order, and under the same molding conditions as in Example 1, a single-sided steel-clad υ laminate with a thickness of 1.0 steel was obtained.

Comparative Example 1 5 plies of Gripreg A obtained in Example 1 were stacked with 35μ thick copper foil coated with adhesive, and 1.0 mm thick single-sided copper-clad laminate was made under the same molding conditions as Example 1. Got the board.

Comparative Example 2 Basis weight 135. ! 7/c! , linter paper with an elongation rate of 0.7% was impregnated with tung oil-modified phenolic resin and dried to a resin content of 4.
A 9% prepreg was obtained (prepreg D).

Example 20 2 plies of prepreg B, 1 prepreg D1, and a 35 μ thick copper foil coated with adhesive were stacked in this order to form a 1.0 mm thick single-sided steel-clad laminate under the same molding conditions as in Example 1. I got it.

Each of the above single-sided steel laminates is 300 x 200
An undercoat was applied to the circuit surface, a carbon resistor was formed by printing, the carbon resistor was hardened by heat treatment, and the outer shape was punched out. Figure 3 shows the change in warpage over time at this time. Further, FIG. 4 shows a comparison of twist after the punching. To twist, hold one corner of the printed circuit board on a flat surface.
It is indicated by the maximum value of the amount of lifting of other edges.

Note that if the circuit surface is not coated for insulation, or if the coat is coated after heat treatment in a furnace, the heat shrinkage of the substrate on the side without the circuit increases, so special measures are required. The single-sided metal foil-clad laminate according to the present invention is effective for use in single-sided printed circuit boards where the circuit surface is coated and then heat treated.

Effects of the Invention As mentioned above, the phenolic resin single-sided metal foil-clad 9-laminate according to the present invention is used for single-sided printed circuit boards that require heat treatment in the manufacturing process, and can suppress warpage and twisting to a minimum in the above-mentioned applications in particular. This makes it possible to prevent troubles caused by warpage and twisting of the circuit board during the component mounting process on the circuit board. In addition, by suppressing warpage and twisting, it becomes possible to support high-density fine patterns of circuits.

[Brief explanation of drawings]

4 is a curve diagram showing changes in warpage over time during the printed circuit board manufacturing process, and FIG. 4 is a comparison diagram of torsion after heat treatment. 1 is the metal foil, 2 is the adjacent layer, and 3 is the main layer.

Claims (3)

[Claims] 1. In a single-sided metal foil-covered laminate in which a metal foil is placed on one surface of a phenol resin-impregnated kraft paper base layer and integrally laminated, the elongation rate is mainly that of the kraft paper base layer in the layer adjacent to the metal foil. A phenolic resin single-sided metal foil-clad laminate characterized by having a higher elongation rate than other kraft paper base materials. 2. The basis weight of the kraft paper base material that does not touch the metal foil is 200~
The phenolic resin single-sided metal foil laminate according to claim 1, which has a high basis weight of 250 g/m^2. 3. The elongation rate of the kraft paper base material, which has a high elongation rate, is 1.2.
The phenolic resin single-sided metal foil-clad laminate according to claim 1 or 2, wherein the phenol resin content is in the range of 1.5%.