JPH04137590A - Multilayer circuit board - Google Patents

Abstract

PURPOSE:To prevent the occurrence of cracks and disconnections in a conductive pattern by forming a bent section which obliquely CONSTITUTION:Through holes are provided at suitable locations of a film substrate made of a resin having heat deformation property and a conductive pattern 21 is formed on the surface of flat plate sections 20a and 20b other than a bent section by, for example, screen-printing conductive paste to a thickness of about 20mum The conductive pattern 23 is formed so that the pattern 23 can obliquely intersect the bending line of the bent section 22. When the intersecting angle is set at 30 deg. against the bending line, the width (w) of the pattern 21 intersecting the bending line is increased by about 15% and the bent cross section of the section 22 increases. Therefore, the conductive pattern is hardly disconnected at the bent section of the film substrate.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention relates to a multilayer circuit board, The present invention relates to a multilayer circuit board having a multilayer circuit board.

In particular, bending parts (prior art) Recently, as electronic devices have become smaller, lighter, and thinner, control circuit devices used in these electronic devices are also required to be smaller, lighter, and thinner. ing. Since this control circuit device has electronic components such as semiconductors mounted on a substrate having a conductive pattern, it is necessary to downsize the control components such as semiconductors and the substrate in order to make the device smaller, lighter, and thinner. be.

Substrates used in this type of control circuit devices include glass-epoxy substrates made of glass mixed with epoxy resin and plated with conductive patterns on the surface, and conductive substrates made of polyester, polyimide, and other resins with conductive paste. Flexible printing (FPC) with attached layers or copper foil
) boards are often used.

However, the Gala Evo board requires a complicated plating process, and since the conventional FPC board is a single layer, there are problems such as high-density wiring is difficult.

In order to solve these problems, high-density mounting multilayer circuit boards have been developed in which conductive patterns are formed on film-like resin substrates and a plurality of these substrates are stacked on top of each other.

This multilayer circuit board is generally shown in FIG. 3 and is manufactured, for example, by the following method.

First, a heat deformable film substrate 1 made of thermoplastic resin such as polycarbonate, polysulfone, polyarylate, etc.
This film substrate 10 is provided with through holes] 1 at appropriate locations, and a conductive pattern 12 made of a conductive base with a thickness of about 20 μm, for example, is formed on the surface of the film substrate 10.
form.

After stacking a plurality of film substrates 10 and adjusting the positions of the through holes 11 and conductive patterns 12, the film substrates 10 are inserted between the fixed plates 13.13 of a heat press. Conductive pattern 12 by 13
By thermocompression bonding together with the above components, a multilayer circuit board A as shown in FIG. 4 is formed.

Since this multilayer circuit board A is integrally bonded to the conductive pattern or the film substrate, the conventional plating process etc. is eliminated, and multiple conductive patterns are mounted three-dimensionally.
High-density substrates will be realized.

Note that 14 and 14 are electrodes formed on the front and back surfaces of the substrate.

(Problem to be solved by the invention) By the way, is it possible for this multilayer circuit board A to be used as a flat board?
Depending on the structure of electronic equipment (not shown), etc., it may be necessary to use the multilayer circuit board B bent at right angles as shown in FIG.

Since this rectangular multilayer circuit board B is formed by bending the flat multilayer circuit board A, not only the heat-deformable film substrate 10 but also the conductive pattern 12 can be bent and deformed. This deformation applies a large bending stress to the film substrate 10 and the conductive pattern 12, which may cause cracks in the conductive pattern 12 at the bent portion or, in the worst case, break the wire.

An object of the present invention is to obtain a multilayer circuit board having the above-mentioned bent portions in which cracks, wire breaks, etc. do not occur.

[Structure of the invention]

(Means for Solving the Problems) The present invention consists of laminating a film substrate on which a conductive pattern is formed using a conductive base using a thermoplastic resin as a binder on an insulating film made of a thermoplastic resin, and integrally bonding the film with a conductive pattern by thermocompression bonding. The multilayer circuit board is provided with a bent portion that obliquely intersects with the conductive pattern.

(Function) The folded cross section of the conductive pattern located at the folded curved portion is increased, and the conductive pattern at the folded portion of the film substrate is less likely to be disconnected.

(Example) An example of the circuit board of the present invention will be described below with reference to FIG.

The manufacturing method of the multilayer circuit board opening E of the present invention shown in FIG. 1 is almost the same as that of the conventional multilayer circuit board opening B shown in FIGS. 2 and 3, so a detailed explanation will be omitted.

This multilayer circuit board opening E is provided with a through hole at an appropriate location on a film board made of a thermodeformable resin, and flat plate portions 20a and 20b are provided at locations other than the bent portions of the film board.
A conductive pattern 21 is formed on the surface of the substrate by screen printing a conductive base to a thickness of, for example, about 20 μm. Further, this conductive pattern 23
It is formed to intersect diagonally with the bending line.

If we make the slope of the lever 30 degrees to the bending line,
As shown in FIG. 1(b), the width W of the conductive pattern 21 that intersects with this bending line increases by about 15%, and therefore the bending cross section thereof increases.

A plurality of film substrates printed with such patterns are stacked one on top of the other, and after adjusting the positions of through holes, conductive patterns, etc., they are inserted between the fixed plates of a heat press and bonded by thermocompression. This crimped board is bent using, for example, a bending machine to form a multilayer circuit board opening E.

In a substrate having a conductive pattern inclined in this manner, the bending cross section of the conductive pattern passing through the inclined portion can be increased, so that the problem of wire breakage due to cracks can be reduced by the increased amount.

〔Effect of the invention〕

The multilayer circuit board of the present invention is a multilayer circuit board in which a film board on which a conductive pattern is formed using a conductive paste using a thermoplastic resin as a binder is laminated on an insulating film made of a thermoplastic resin and integrated by thermocompression bonding. Since the multilayer circuit board is formed with a bent portion diagonally intersecting the conductive pattern, the bent cross section of the conductive pattern passing through the inclined portion can be enlarged, and therefore the bent portion of the bent portion can be enlarged. The trouble of wire breakage caused by cracks can be significantly reduced.

[Brief explanation of drawings]

FIG. 1(a) is a perspective view of the circuit board of the present invention, FIG. 1(b)
1(a) is an enlarged perspective view showing the inclined conductive pattern in FIG. 1(a), FIG. 2 is a perspective view of a conventional circuit board, FIG. FIG. 4 is a side view of the circuit board. 10...Film substrate, 1]...Through hole,]
2.21... Conductive pattern, 13 Heat press fixed plate, 14... Electrode, 20a, 20b... Flat plate part, 22
. . . bent portion, 23 . . . inclined conductive pattern.

Claims (1)

[Claims] A multilayer circuit board in which a film substrate on which a conductive pattern is formed using a conductive paste using a thermoplastic resin as a binder is laminated on an insulating film made of a thermoplastic resin and integrated by thermocompression bonding, the multilayer circuit board A multilayer circuit board characterized in that a bent portion is formed to obliquely intersect with the conductive pattern.