JPH08107274A - Four layer type printed-wiring board - Google Patents

Abstract

PURPOSE: To provide a printed-wiring board extremely suppressing the manufacturing cost in a simple alignment in the manufacturing step by a method wherein respective specific base film, coverlays, prepregs or bonding sheet and conductor circuits are provided. CONSTITUTION: The four layer type printed-wiring board is provided with a base film 10 with conductor circuits 12, 13 formed on both surfaces, coverlays 21, 22 formed by entirely covering both surfaces of the base film 10 for curing a bonding sheet in semicured state comprising polyimide base resin, furthermore, a pair of prepregs 14, 15 or bonding sheet having openings 16, 17 respectively laminated on the coverlays 21, 22 as well as the conductor circuits 12, 13 formed by etching the copper foils 31, 32 entirely covering them. Besides, respective prepregs 14, 15 or bonding sheet are arranged so that the positions of the openings 16, 17 may correspond to each other.

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 having conductor circuits formed in four layers.

[0002]

2. Description of the Related Art Conventionally, as a four-layer type printed wiring board, there is known a four-layer printed wiring board which is formed by bonding two base films made of a polyimide resin with an adhesive layer made of a polyimide resin. That is, on both sides of each base film,
Conductor circuits are formed respectively, and these base films are bonded by a bonding sheet made of a polyimide resin.

[0003]

In such a conventional four-layer type printed wiring board, the base film and the bonding sheet are all made of polyimide resin, and they have great flexibility. In addition, there is a problem that the positioning work is difficult, the relative positions of the rounds of the conductor circuits are easily displaced, and the yield is not good. Further, since this printed wiring board is basically made of polyimide resin, there is a problem that the cost is too high.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a four-layer type printed wiring board in which the positioning in the manufacturing process is simple and the manufacturing cost is suppressed as much as possible.

[0005]

A printed wiring board according to the present invention has a base film having conductor circuits formed on both surfaces, and a semi-cured state made of a polyimide-based resin that entirely covers both surfaces of the base film. A cover lay formed by curing the bonding sheet of, a pair of prepregs or bonding sheets each having an opening and laminated on these cover lays, and a copper foil that entirely covers these prepregs or bonding sheets. And a conductor circuit formed by etching.

[0006]

The present invention will be described below with reference to illustrated embodiments. 1 and 2 show a state in the middle of a process of manufacturing a printed wiring board which is an embodiment of the present invention, and FIG. 3 shows a layered structure of this printed wiring board.

During the process of manufacturing this printed wiring board, as shown in FIGS. 1 and 2, the base film 10 is a sheet material 1 molded from a polyimide resin.
It is obtained by laminating copper foils 12 and 13 on both sides of 1, and by etching the copper foils 12 and 13, a predetermined conductor circuit is formed. The copper foils 12 and 13 are covered with coverlays 21 and 22 made of a polyimide resin. The coverlay 21 has substantially the same outer shape as the base film 10. The coverlay 21 is formed by disposing a semi-cured single-layer bonding sheet made of a polyimide resin on the copper foil 12 and thermocompression-bonding the copper foil 12 at a predetermined pressure and temperature. Coverlay 22 is also Coverlay 2
It is thermocompression bonded in the same manner as 1 and laminated on the copper foil 13.
The base film 10 and the coverlays 21 and 22 form a first laminate.

A prepreg 14 formed by impregnating a glass fiber sheet with an epoxy resin is formed on the surface of the coverlay 21 opposite to the base film 10. An opening 16 is provided in the prepreg 14. Similarly, the prepreg 15 is also arranged on the surface of the cover lay 22 opposite to the base film 10.
An opening 17 is provided in the. These openings 16,
17 are formed at positions corresponding to each other. Copper foils 31 and 32 are provided on the prepregs 14 and 15, respectively. Unlike the prepregs 14 and 15, the copper foils 31 and 32 do not have openings, that is, the openings 14 and 15
Is placed on the prepregs 14 and 15 so as to cover the prepregs. Base film 10, prepregs 14 and 15,
The outer shapes of the copper foils 31 and 32 are substantially the same.

Base film 10 and coverlay 2
1st laminated body consisting of 1, 22 and prepreg 14, 1
5. The copper foils 31 and 32 are thermocompression bonded under a predetermined condition, whereby a second laminated body is obtained. Then, a hole is formed in a predetermined portion to form a hole. In this state, that is, in a state where the openings 16 and 17 are covered with the copper foils 31 and 32, copper plating is applied to the through holes 42 and 43.
(See FIG. 3) is formed. Then, the copper foils 31 and 32 are etched to form a conductor circuit, and predetermined portions are covered with a solder resist (insulating layer).

After this, the openings 1 of the prepregs 14 and 15 are formed.
Edges 6 and 17 (see FIG. 1) of the base film 10 are removed, as shown in FIG.
A bendable flex portion F is formed by covering Nos. 1 and 22. On both sides of the flex portion F, the base film 10, the coverlays 21 and 22, the prepreg 1 are provided.
Rigid portions R composed of 4, 15 and copper foils 31, 32 are formed. That is, in this printed wiring board, the rigid portion R has copper foils 31 and 32 bonded to both sides of the same laminated body as the flex portion F via the prepregs 14 and 15, and has holes at the portions to be through holes 42 and 43. It is constructed by drilling, plating and etching.

As described above, the flex portion F in this embodiment has the prepreg 1 provided with the openings 16 and 17 in advance.
It is formed by using Nos. 4 and 15. The openings 16 and 17 are made of copper foil 31 and 3 in the plating process.
2 is closed. Therefore, the ions contained in the plating solution do not adhere to the end faces of the prepregs 14 and 15 exposed at the peripheral portions of the openings 16 and 17, and the characteristics of the electric circuit of this printed wiring board are not impaired.

Further, in this embodiment, the first laminate and the copper foil 3 are
Numerals 1 and 32 are adhered by prepregs 14 and 15, and these prepregs 14 and 15 are very inexpensive. Therefore, according to this embodiment, the manufacturing cost of the printed wiring board can be reduced.

The prepregs 14 and 15 may be glass fiber sheets impregnated with a polyimide resin.

Instead of the prepregs 14 and 15, it is possible to use a bonding sheet made of a polyimide resin.

[0015]

As described above, according to the present invention, it is possible to significantly reduce the manufacturing cost of a four-layer rigid / flex printed wiring board.

[Brief description of drawings]

FIG. 1 is a perspective view showing each sheet material in an exploded manner during a process of manufacturing a printed wiring board that is an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a layer structure of each sheet material of the printed wiring board of FIG.

3 is a cross-sectional view showing a laminated structure of a finished product of the printed wiring board of FIG.

[Explanation of symbols]

 10 Base Film 14, 15 Prepreg 16, 17 Opening 21, 22 Coverlay 31, 32 Copper Foil 42, 43 Through Hole

Claims (4)

[Claims] 1. A base film having conductor circuits formed on both sides, and both sides of the base film are entirely covered,
A cover lay formed by curing a semi-cured bonding sheet made of a polyimide resin, a pair of prepregs or bonding sheets each having an opening and laminated on these cover lays, and these prepregs or bonding sheets. A four-layer type printed wiring board, comprising: a conductor circuit formed by etching a copper foil covering the entire surface. 2. The four-layer printed wiring board according to claim 1, wherein the prepregs or the bonding sheets are arranged so that the positions of the openings provided therein correspond to each other. 3. The four-layer type prepreg wiring board according to claim 1, wherein the copper foil is arranged so as to close all openings provided in the prepreg or the bonding sheet. 4. The four-layer printed wiring board according to claim 1, wherein the prepreg is formed by impregnating a glass fiber sheet with an epoxy resin or a polyimide resin.