JPH0513957A - Printed wiring board - Google Patents

Abstract

PURPOSE:To enable a printed wiring board to absorb residual stress by a groove so as to be protected against warpage even if the board is subjected to hot pressing by a method wherein a groove is provided to an inner board or an outer board. CONSTITUTION:An inner board 4 of a copper plated laminated board is etched for the formation of a circuit pattern 7, and a groove 11 is formed on the part of the board 4 where a copper foil is not provided. On the other hand, outer boards 2 and 3 formed of insulating boards plated with copper foils are laminated on the inner board 4 through the intermediary of adhesive agents 12 and 13, and the adhesive agents 12 and 13 are cured by hot pressing to form the boards into one piece. The copper foils of the outer boards 2 and 3 are etched into circuit patterns 5 and 6 for the formation of a printed wiring board 1. As mentioned above, as the groove 11 is provided to the inner board 4, residual stress induced by the expansion coefficient difference between the boards 2, 3, and 4 owing to the difference between the copper residues on their surfaces is absorbed by the groove 11, so that the board 1 can be protected against warpage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printed wiring board.

[0002]

2. Description of the Related Art FIG. 3 is a sectional view of a conventional printed wiring board. In the figure, 1 is a printed wiring board, 2 and 3 are outer layer boards constituting the printed wiring board 1, 4 is an inner layer board sandwiched between the outer layer boards 2 and 3, and 5 and 6 are formed on the outer layer boards 2 and 3. The circuit pattern 7 is a circuit pattern formed on the inner layer plate 4.

The printed wiring board 1 is manufactured as follows. First, an inner layer plate 4 made of a copper clad laminate in which copper foil is stretched on both sides of an insulating substrate such as a glass fiber / epoxy resin composite material is etched to form a circuit pattern 7. Then, a prepreg and a copper foil to be the outer layer plates 2 and 3 are laminated on both sides thereof and cured by hot pressing to form a copper clad multilayer substrate having the outer layer plates 2 and 3. After that, the copper foils on both sides are etched to form the circuit patterns 5 and 6, and the printed wiring board 1 is manufactured.

[0004]

However, in the conventional printed wiring board as described above, the circuit patterns 5, 6 formed on the front and back surfaces of the outer layer boards 2, 3 and the inner layer board 4, respectively.
Since there is a difference in the copper remaining rate of 7, when laminating prepregs and hot pressing, internal stress remains due to the difference in expansion coefficient,
There was a problem that warpage occurred.

The present invention has been made in order to solve the above problems, and an object thereof is to obtain a printed wiring board in which warpage is unlikely to occur even when hot pressing is performed.

[0006]

The printed wiring board according to the present invention is a printed wiring board in which an inner layer board and an outer layer board having circuit patterns are laminated, and grooves are formed in the inner layer board or the outer layer board.

[0007]

The printed wiring board of the present invention is manufactured by forming a circuit pattern on an inner layer board, laminating it with an outer layer board and a copper foil to form a copper clad laminated board, and etching this to form a circuit pattern. However, when laminating, grooves are formed in the inner layer plate or the outer layer plate, and the layers are laminated and cured by heating and pressing to be integrated.

When there is a difference in copper residual ratio between the inner layer plate and the outer layer plate, internal stress remains due to the difference in expansion coefficient when hot-pressed, but when a groove is formed, the residual stress is absorbed by the groove,
The occurrence of sleds is reduced.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows the printed wiring board of the embodiment at A- in FIG.
2 is a plan view, and the same reference numerals as those in FIG. 3 indicate the same or corresponding portions. Reference numeral 11 is a groove formed in the inner layer plate 4, and 12 and 13 are adhesives for joining the outer layer plates 2 and 3 and the inner layer plate 4 together. A plurality of grooves 11 are provided so as to extend in the width direction.

The above printed wiring board 1 is manufactured as follows. First, the inner layer plate 4 made of a copper clad laminate similar to the conventional one is etched to form a circuit pattern 7,
Grooves 11 are formed in the portions where the circuit pattern 7 is not present. On the other hand, the outer layer plates 2 and 3 in which a copper foil is stretched on one surface of the insulating substrate are attached to the adhesive 1
It is laminated on the inner layer plate 4 via 2 and 13, and the adhesives 12 and 13 are hardened and integrated by hot pressing. Then, the copper foils of the outer layer plates 2 and 3 are etched to form the circuit patterns 5 and 6.
And the printed wiring board 1 is manufactured. Adhesive 1
2 and 13 are preferably epoxy-based materials of the same quality as the insulating substrates of the outer layer plates 2 and 3 and the inner layer plate 4, and are used in such amounts that they do not flow into the groove 11.

In the printed wiring board 1 described above, since the groove 11 is formed in the inner layer board 4, it is
Residual stress due to the difference in expansion coefficient based on the difference in copper residual ratio between the outer layer plates 2 and 3 and the inner layer plate 4 is absorbed by the groove 11 and the occurrence of warpage is reduced.

In the above embodiment, the groove 11 is formed in the inner layer plate 4
Although it may be formed on the outer layer plates 2 and 3, it may be formed on a plurality of inner layer plates 4 when there are a plurality of inner layer plates 4. Although the groove 11 is formed in the width direction, it may be formed in the longitudinal direction. Further, although the case where the outer layer plates 2 and 3 are formed in advance has been described, the prepreg may be laminated in the state where the groove 11 is filled with the filler as in the conventional case, and may be integrally formed by the heat press.

[0013]

According to the present invention, since the groove is formed in the inner layer plate or the outer layer plate, the residual stress generated due to the difference in expansion coefficient based on the difference in the copper residual rate is absorbed in the groove even when hot pressing is performed. This is effective in reducing the occurrence of sleds.

[Brief description of drawings]

1 is a cross-sectional view taken along the line AA of FIG. 2 showing a printed wiring board according to an embodiment.

FIG. 2 is a plan view of FIG.

FIG. 3 is a cross-sectional view of a conventional printed wiring board.

[Explanation of symbols]

 1 Printed wiring board 2, 3 Outer layer board 4 Inner layer board 5, 6, 7 Circuit pattern 11 Groove 12, 13 Adhesive

Claims (1)

Claim: What is claimed is: 1. A printed wiring board in which an inner layer board and an outer layer board each having a circuit pattern are laminated, wherein a groove is formed in the inner layer board or the outer layer board to laminate the printed wiring board. .