JPH04137591A - Multilayer circuit board - Google Patents

Abstract

PURPOSE:To prevent the occurrence of cracks and disconnections in a conductive pattern by forming a bent section to a multilayer circuit board and, at the same time, making the film thickness of the conductive pattern formed in the bent section thinner than that of the conductive pattern formed in the other section. CONSTITUTION:A conductive pattern 21 is formed in the flat plate section 20 of a film substrate by printing conductive paste. The thickness of the conductive pattern 23 of the conductive paste formed at the bent section 22 of the film substrate is made thinner than that of the conductive pattern 21 formed in the flat plate section 20 which is different from the bent section 22 and set at, for example, about 10mum. Since the thickness of the pattern 23 formed at the bent section 22 of the multilayer circuit substrate M is thinner than that of the pattern 23 formed in the section 20 and, even when the film substrate formed by thermocompression bonding is deformed, the pattern 23 follows the deformation, the pattern 23 becomes free from cracks, disconnections, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a multilayer circuit board, and particularly to a multilayer circuit board having a bent portion.

(Prior Art) Recently, as electronic devices have become smaller, lighter, and thinner, control circuit devices and the like used in these electronic devices have been required to be smaller, lighter, and thinner. This control circuit device is one in which electronic components such as semiconductors are mounted on a substrate having a conductive pattern, and in order to achieve miniaturization, weight, and thickness, it is necessary to downsize the control components such as semiconductors and the substrate.

Boards used for this type of control circuit device, etc. include printed circuit boards such as ordinary Gala Evo boards, polyester,
Flexible printed (FPC) boards are often used, in which a conductive layer made of a conductive paste or a conductive layer made of a copper foil pattern is formed on a resin such as polyimide.

However, the glass epoxy board requires a complicated plating process, and since the conventional FPC board is a single layer, there are problems such as difficulty in high-density wiring.

In order to solve these problems, progress has been made in the development of high-density mounting multilayer circuit boards in which conductive patterns are formed on film-like resin substrates and a plurality of these substrates are stacked.

This multilayer circuit board is generally shown in FIG. 4, and is manufactured, for example, by the following method.

First, a heat deformable film substrate 10 made of a thermoplastic resin such as polycarbonate, polysulfone, or polyarylate is provided, and through holes 11 are formed in appropriate places in the film substrate 10, and for example, 20 holes are formed on the surface of the film substrate 10.
A conductive pattern is formed by printing a conductive paste to a thickness of approximately μm.

A plurality of second film substrates 10 are stacked to form through-holes 11.
, conductive pattern] 2, insert it between the fixed plates 13.13 of the heat press, and thermocompress these film substrates 10 together with the conductive pattern 12 etc. by the fixed plate 13.13. As a result, a multilayer circuit board A as shown in FIG. 5 is manufactured.

This multilayer circuit board A is integrally bonded to the conductive pattern or film substrate, eliminating the conventional plating process, etc., and multiple conductive patterns are mounted three-dimensionally, achieving high density. can.

Note that 14 and 4 are electrodes formed on the front and back surfaces of the substrate.

(Invention or problem to be solved) 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), it may be necessary to use it as a multilayer circuit board B bent at a right angle, as shown in FIG.

Since this rectangular multilayer circuit board B is manufactured by bending the flat multilayer circuit board A, not only the heat deformable resin film board but also the conductive pattern can be deformed. In particular, a large bending stress is applied to the conductive pattern perpendicular to the bent part, causing cracks in the conductive pattern, or in the worst case, breaking the conductive pattern, resulting in a lack of reliability as a product. etc.

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

[Structure of the invention]

(Means for Solving the Problems) The present invention involves laminating a film substrate on which a conductive pattern is formed using a conductive paste using a thermoplastic resin as a binder on a resin film made of a thermoformable resin, and bonding the film by thermocompression. A multilayer circuit board integrated by a multilayer circuit board, wherein the multilayer circuit board is formed with a bent part, and the film thickness of the conductive pattern formed in the bent part is different from that formed in the part other than the bent part. The thickness of the conductive pattern is smaller than that of the conductive pattern.

Further, the multilayer circuit board has a bent portion formed therein, and the thickness of the film substrate at the bent portion is thinner than the thickness of the film substrate other than the bent portion.

(Function) When a multilayer circuit board is bent, the thin conductive pattern at the bent portion follows the bending and bends well, so that the conductive pattern does not crack or break.

In addition, since the bending part of the multilayer circuit board is made thinner, the deformation of this multilayer circuit board when folding is reduced.
The stress applied to the conductive pattern is reduced, preventing it from cracking or breaking.

(Embodiment) An embodiment of the multilayer circuit board of the present invention will be described below with reference to the drawings.

The method for manufacturing the multilayer circuit board M of the present invention shown in FIG.
Since this method is similar to the conventional multilayer circuit board manufacturing method shown in FIGS. 4 and 4, detailed explanation will be omitted.

This multilayer circuit board M also has through holes formed at appropriate locations on a film substrate made of a heat deformable resin, and a conductive paste with a thickness of about 20 μm is printed on the flat plate portion 20 of the film substrate, and a conductive batten 21 is printed on the flat plate portion 20 of the film substrate. It is formed.

The conductive pattern 23 of the conductive paste formed on the bent portion 22 of this film substrate is thinner than the conductive pattern 21 of the flat plate portion 20 at a location other than the bent portion, for example, by 10 mm.
It is formed to a thickness of about μm.

After a plurality of these film substrates are stacked and their positions adjusted, they are inserted between fixed plates of a heat press, and are integrally pressure-molded, and then bent into a square shape by a bending machine to form a multilayer circuit board M. Ru.

In this way, since the conductive pattern 23 located at the folded portion 22 of the multilayer circuit board M is thinner than the conductive pattern 21 on the flat plate portion 20, even if the thermocompression-bonded film board is deformed, the conductive pattern 23 is It follows the deformation and does not cause cracks or disconnections in the conductive pattern 23. Therefore, highly reliable multilayer circuit board M
Can you get it?

FIG. 2 shows another multilayer circuit board N of the present invention.

This multilayer circuit board N is basically shown in FIG.
It is manufactured in the same manner as the manufacturing method shown in FIGS.

Through holes are formed at appropriate locations on a film substrate made of a heat deformable resin of this multilayer circuit board N, and a conductive pattern 30 of about 20 μm is formed on the surface of the film substrate by screen printing.

A plurality of these film substrates are laminated and bonded together by thermocompression. This pressure-molded substrate is bent by a bending machine (not shown).

The molding die of this bending machine has, for example, a convex portion extending along the bending line, so that the thickness of the bending portion 31 of the film substrate is thinner than that of other portions.

In this way, when the multilayer circuit board N is bent,
The stress in the bent portion 31 is reduced and the conductive pattern 30
The distortion added to the is reduced. Therefore, there is little deformation of the conductive pattern 30 located at the bent portion, and the occurrence of cracks, disconnections, etc. in the conductive pattern 30 is less likely.

〔Effect of the invention〕

The multilayer circuit board of the present invention is a multilayer circuit 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 a resin film made of a thermodeformable resin and integrated by thermocompression bonding. In the substrate, the multilayer circuit board has a bent portion formed therein, and the thickness of the conductive pattern formed on the bent portion is equal to or greater than that of the conductive pattern formed outside the bent portion. Because it is smaller than the film thickness, when the film substrate is bent, even if the film substrate deforms, the conductive pattern will follow this deformation well, causing cracks and disconnection accidents in the film-shaped conductive pattern. Never.

Further, since the multilayer circuit board is formed with a bent portion and the thickness of the film substrate at the bent portion is thinner than the thickness of the film substrate other than the bent portion, when the multilayer circuit board is bent, The stress on the substrate is reduced, the strain applied to the conductive pattern is reduced, and cracks and disconnections in the conductive pattern can be prevented.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the main parts of a multilayer circuit board according to the present invention, FIG. 2 is a sectional view showing the main parts of another multilayer circuit board according to the invention, and FIG. 3 is a sectional view showing the main parts of a conventional multilayer circuit board. FIG. 4 is a sectional view of a heat press section schematically showing the manufacturing process of a general multilayer circuit board, and FIG. 5 is a side view of the multilayer circuit board. ]O...Film substrate, 11...Through hole, 1
2.21.30 Conductive pattern, 13 Heat press plate, 14 Electrode, 22 Corner, 23 Thin conductive pattern, 31 Thin substrate. Applicant's agent: Sato

Claims (2)

[Claims] 1. 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 a resin film made of a thermodeformable resin and integrated by thermocompression bonding. A bent portion is formed on the circuit board, and the film thickness of the conductive pattern formed at the bent portion is smaller than the film thickness of the conductive pattern formed outside the bent portion. Features a multilayer circuit board. 2. 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 a resin film substrate made of a thermodeformable resin and integrated by thermocompression bonding. A multilayer circuit board, characterized in that the multilayer circuit board is formed with a bent portion, and the thickness of the film substrate at the bent portion is thinner than the thickness of the film substrate other than the bent portion.