JPH04262590A - Flexible circuit board - Google Patents

Abstract

PURPOSE:To easily bend a flexible circuit board, to reduce a height required for bending, to reduce in size a device smaller, to alleviate a stress generated at a connector for bending, and to increase reliability of the connector. CONSTITUTION:In a flexible printed circuit board 4 in which a metal wiring material 2 is provided on a board material 1, a cutout 3 is provided partly at the material 1, and the rigidity of the cutout 3 is reduced as compared with that of other part.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flexible wiring board, and more particularly to a flexible wiring board that relieves stress at bent portions and enables further miniaturization of devices.

0002

[Prior Art] As electronic devices and module products become smaller and thinner, flexible printed circuits (Fl.
Exible Print Circuit：FP
Mounting components on FPCs (abbreviated as C) is an effective technique, but due to its flexibility, FPCs are often incorporated into equipment in a bent state.

0003

In this case, as shown in FIG. 5, there is a limit to reducing the height (H) after assembly due to the thickness of the FPC at the folded portion. In addition, in the case of the example in Fig. 5, due to the rigidity of the FPC base material, the board connection part (anisotropic conductive material, solder, Au-S
n-eutectic, etc.), leading to a decrease in the reliability of the connection.Furthermore, in order to alleviate the stress on the connection, design measures such as increasing the distance between the connection and the bent portion may be taken. There was a problem in that restrictions occurred.

The present invention aims to solve the above-mentioned problems, and its purpose is to make it easier to bend the FPC, reduce the height required for bending, and make the device more compact. Furthermore, it is possible to alleviate the stress generated in the connecting portion due to bending, and it is possible to bend the connecting portion in the vicinity without reducing the reliability of the connecting portion.

[0005]

[Means for Solving the Problems] The present invention provides a flexible wiring board in which a metal wiring material is applied on a base material, in which a part of the base material is cut, and the rigidity of the cut part is lowered than that of other parts. It is characterized by the fact that

[0006]

EXAMPLES Next, the present invention will be explained with reference to examples shown in the drawings. FIG. 1 is a plan view showing a flexible wiring board of the present invention, and FIG. 2 is a sectional view taken along line II.

In FIGS. 1 and 2, reference numeral 1 denotes a base material, which is made of a heat-resistant synthetic resin such as polyimide, glass epoxy, PET (polyethylene terephthalate), etc., is flexible, and has a thickness of several tens of μm. ~ several hundred μm. 2 is a metal wiring material such as copper foil, usually 15~
The thickness is about 40 μm. 3 is a notch portion. Since the flexible wiring board 4 is provided with the notches 3, the rigidity of the notches (slits) is lower than other parts, and as shown in FIG.
The parts can be easily bent. In FIG. 4, 6 is a rigid substrate of a wiring board made of ceramic glass epoxy or the like. Further, no stress is applied to the board connection part 5 in the bent state, and the connection part becomes highly reliable. Furthermore, the distance between the connecting portion and the bending portion can be reduced, which reduces design restrictions and allows the device to be made smaller.

[0008] Furthermore, depending on the curvature at the time of bending and the area of the copper foil pattern that straddles the bend, the pattern of the metal wiring material in the cut may be made thinner at the center of the cut than at other parts (FIGS. 1 and 3). Make multiple cuts (
(Fig. 3), the degree of freedom in design can be further increased.

When a pattern of metal wiring material is cut and made thinner in the center than in other parts, and bending with a smaller curvature is required, the edge of a cut (slit) made in the base material as shown in FIG. This prevents stress concentration from occurring in the copper foil at the center of the slit and lowers the rigidity at the center of the slit, thereby making stress uniform.

Manufacturing Example A flexible wiring board was prepared according to the following procedure, and a mounting casing was mounted. (a) First, a copper foil pattern was formed on a polyimide base material in which notches were formed in advance. (b) An insulating resin (solder resist, etc.) was applied except for the connection parts. (c) Solder leveling was performed on the board connection area. (d) Chip components, surface mount ICs, etc. were mounted on the FPC. (e) The solder land of the ceramic substrate on which components had been mounted in advance and the connecting portion of the FPC were soldered using a heating tool. (f) The FPC notch was bent to form a mounting casing.

It goes without saying that the present invention can be applied to a so-called TAB type mounting board that includes a bare IC connected to the FPC of the above embodiment by a gold or solder pamphlet.

0012

According to the invention as set forth in claim 1, since the base material has a notch, the thickness of the bent portion of the flexible wiring board can be suppressed, and the influence of stress on the neighboring parts during bending can be reduced. Can be reduced.

According to the invention described in claim 2, when bending with a smaller curvature is required, stress is prevented from concentrating on the copper foil at the edge of the cut provided in the base material, and the stress at the center of the slit is prevented. Stress can be equalized by reducing rigidity.

According to the third aspect of the invention, when the copper foil pattern area is large or the thickness is large and the rigidity of the bent portion is greater, the plurality of cut portions are provided. Furthermore, stress leveling can be promoted and bending of the flexible wiring board can be facilitated.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing a flexible wiring board of the present invention.

FIG. 2 is a sectional view taken along line II in FIG. 1;

FIG. 3 is a plan view showing a flexible wiring board in which notches are provided at a plurality of adjacent locations.

FIG. 4 is an explanatory diagram showing a state in which the flexible wiring board of the present invention is bent and connected to a substrate that does not dry naturally.

FIG. 5 is an explanatory diagram showing a state in which a conventional flexible wiring board is bent and connected to an inflexible board.

[Figure 6] When bending with a small curvature,
FIG. 2 is a schematic perspective view for explaining stress concentration when only a notch is provided in a base material.

[Explanation of sign]

1 Base material 2 Metal wiring materials 3 Notch part 4 Flexible wiring board 5　Board connection part 6 Rigid board 7 Stress concentration area

Claims (3)

[Claims] 1. A flexible wiring board in which a metal wiring material is applied on a base material, characterized in that a notch is provided in a part of the base material, and the rigidity of the notch is lower than that of other parts. Flexible wiring board. 2. A flexible wiring board characterized in that the pattern of the metal wiring material in the notch has a width narrower at the center of the notch than at other parts. 3. The flexible wiring board according to claim 1, wherein the notches are provided at a plurality of adjacent locations.