JPH1186985A - Connection structure for flexible printed board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the mechanical strength of a connection structure for a flexible printed board (FPC). SOLUTION: A FPC 2 is placed on the set-up surface of the base 10 of a terminal 1 and a conductor film 22 is thrusted by the outer periphery of a cylindrical contact barrel 12 and the protrusion 113 of a contact spring 11 to provide good electrical and mechanical connection between the FPC 2 and the terminal 1. An insulation film 23 is thrusted by the end 141 of an insulation barrel 14 to provide mechanical connection between the FPC 2 and the terminal 1. A portion thrusted by the insulation barrel 14 is the thick portion of the FPC 2 on which the insulation film 23 is formed, and so the mechanical strength to bending and tension can be increased.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a connection structure for a flexible printed circuit board, and more particularly to a connection structure having enhanced mechanical strength such as tensile strength and flexural strength.

[0002]

2. Description of the Related Art Conventionally, a flexible printed board (hereinafter, referred to as a flexible printed board) has been used.
An FPC is used, for example, as a membrane switch for detecting the presence or absence of an occupant on a seat and a lead for leading an electric signal from the switch to the outside. For example, a connection structure shown in FIG. 5 is known as an electrical and mechanical connection structure between an end of the lead and an external line. In this connection structure, the circuit film 4
1. An FPC 4 composed of a conductor 42 and an insulation film 43 is disposed on a terminal 3 and an arc-shaped contact barrel 32 provided on both sides of the terminal 3
And the contact spring 31 arranged opposite to the conductor 42 of the FPC 4 against the conductor 42 by pressing
Get electrical and mechanical connections.

[0003]

However, in the above prior art, since the terminal 3 has a structure in which the FPC 4 is connected to a thin portion where the insulation film 43 is not formed, the FPC 4 is connected to the end of the insulation film 43. Part 431 and end 3 of terminal 3
There is a problem that it is easy to bend and the strength against pulling is low.

Accordingly, an object of the present invention is to provide a connection structure having high mechanical strength by mechanically connecting a terminal with a thick portion on which an insulation film of an FPC is formed, in view of the above problems. is there.

[0005]

According to a first aspect of the present invention, there is provided an FPC board comprising: a resin film; a conductive film formed on the resin film; And an insulating film formed by coating except for a connection portion of the conductor film. The terminal is electrically connected to the connection portion of the conductor film by the electric connection means, and is mechanically connected to the insulating film by mechanical connection means formed integrally with the electric connection means. Thus, the thick portion of the FPC on which the insulating film is formed is mechanically connected to the terminal, so that the strength against tension and bending can be increased.

According to the second aspect of the present invention, the mechanical connection means presses the insulating film in a planar manner,
Since stress concentration on the FPC by the mechanical connection means is reduced, damage to the FPC can be prevented.

According to the third aspect of the present invention, the terminal has a base having an installation surface on which the FPC is installed, and a terminal provided at one longitudinal end of the base. . The mechanical connection means extends from both sides substantially orthogonal to the longitudinal direction of the base, and is formed to be bent inward facing the installation surface, and the FPC is fixedly pressed by the mechanical connection means and the installation surface. Thus, the means described in claim 1 can be more specifically realized.

According to the fourth aspect of the present invention, the mechanical connection means is formed to be bent in a cylindrical shape inwardly facing the installation surface of the terminal, and the FPC is formed on the outer peripheral surface of the mechanical connection means. And the installation surface. This alleviates the stress concentration on the FPC by the mechanical connection means, thereby preventing the FPC from being damaged. Also, due to aging, F
Even if the wall thickness is reduced due to stress relaxation of the PC, an elastic force can be applied to the FPC from the bent beam, so that the FPC can be stably connected with time. Since this bent beam has a small spring constant, a decrease in elastic pressing force due to a decrease in the thickness of the FPC can be reduced.

According to the fifth aspect of the present invention, when the mechanical connection means penetrates through the FPC and the tensile force acts, the terminal and the FPC are locked at the penetrating portion. The tensile strength can be further increased.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described based on specific embodiments. FIG. 1 is a schematic diagram showing a connection state between a terminal 1 and an FPC 2 according to a specific embodiment of the present invention. The FPC 2 includes a circuit film (resin film) 21 made of PET (polyethylene terephthalate), PI (polyimide) or the like, and a conductor film 22 formed thereon. The FPC 2 is formed by forming a metal foil such as copper on the film 21 and etching the metal foil into a predetermined shape to form the conductor film 22.
And a method of printing the conductive ink on the film 21 to form the conductive film 22.
An insulation film (insulating film) 23 is formed on the conductor film 22 except for a connection portion. This FPC 2 is used, for example, when activating an airbag device.
It is used to derive a detection signal of a membrane switch for detecting whether or not an occupant is on the seat to the outside.

The terminal 1 is obtained by bending a single metal plate. Terminal 1 has FP on the installation surface
It has a long plate-shaped base 10 on which C2 is placed, and x of the base 10
At one end in the direction (longitudinal direction), a claw 17 for locking the outer skin 52 of the lead wire 5 and a claw (terminal) 16 for locking the conductive wire 51 are provided.
Are provided. The lead wire 5 is used for electrical connection with the outside. At the other end of the base 10 in the x direction, a plurality of (one on each side) contact barrels (electric connection means)
12 and insulation barrel (mechanical connection means) 1
4 are provided. The barrels 12 and 14 both extend from both sides of the base 10 in the y direction substantially orthogonal to the x direction. The barrel 12 is formed into a cylindrical shape inside and presses the conductor film 22 on the outer peripheral surface. Also, barrel 1
4 is bent inward and presses the film 23 at its end 141.

A contact spring 11 and a cover 15 are provided between the barrel 12 and the claw 16. The spring 11 has a plate shape, extends from one side of the base 10 in the y direction, is formed by bending, and has a fixed end 111 at one end.
And a free end 112 at the other end. The spring 11 is disposed so as to face the base 10, and has a bent portion 113 having a “<”-shaped protruding portion 113 on the base 10 side. When the protrusion 113 presses the FPC 2, the FPC 2 and the terminal 1 are electrically connected.
The cover 15 is bent and formed to extend from a side different from the side where the spring 11 in the y direction of the base 10 extends, and to support the spring 11 from a side different from the installation surface side.

Next, a method of connecting the FPC 2 to the terminal 1 will be described. Before the connection of the FPC 2, the FPC is placed between the barrels 12 and 14 of the terminal 1 and the installation surface.
A sufficient space for mounting the PC 2 is provided.
Further, the cover 15 does not support the spring 11, and no pressing force acts on the base 10 side of the spring 11. In this state, the barrel 12 is placed on the installation surface of the base 10 with the conductor film 22 of the FPC 2 facing upward, and the barrel 12 is caulked in a cylindrical shape so that the outer peripheral surface of the barrel 12 presses the conductor film 22. The barrel 14 is caulked so that the end 141 presses the film 23. Thereby, barrel 1
2 and the conductive film 22 are in contact with each other, so that the FPC 2 and the terminal 1 are electrically connected. Further, the FPC 2 is pressed by the barrel 12 and the barrel 14 and the base 10, so that the FPC 2 and the terminal 1 are also mechanically connected. Next, the conductive film 22 is formed by the convex portion 113 of the spring 11.
Is pressed, and in this state, the cover 15 is bent from above the spring 11 so as to support the fixed end 111 and the free end 112. Thereby, the conductor film 22 and the spring 11
Are completely electrically connected. In this way, FPC
2 and the terminal 1 are electrically and mechanically connected with high performance.

As shown above, pressing the film 23 with the end 141 of the barrel 14 causes the FPC 2
Since the thick portion on which the film 23 is formed and the terminal 1 are mechanically connected, mechanical strength such as tensile strength and bending strength of the mechanical connection portion can be increased. or,
By bringing the barrel 12 and the spring 11 into contact with the conductive film 22, a good electrical connection between the terminal 1 and the FPC 2 can be obtained. In particular, by bringing the terminal 1 and the FPC 2 into surface contact, the density of the current flowing into the contact surface during energization can be reduced, so that a relatively high current of the order of several hundred mA can flow. In addition, since the spring 11 can be effectively elastically pressed against the FPC 2, the mechanical connection strength can be improved, and the electrical contact characteristics can be improved even with a carbon electrode having a lower conductivity than a metal electrode. Can be obtained stably.

In the above embodiment, the barrel 14 is swaged from both sides of the FPC 2 so that the FPC 2 is connected to the terminal 1.
The barrel 14 is connected to the FP.
It may penetrate C2. FIG. 2 schematically shows the connection structure in this case. In FIG. 2, a plurality (two in the figure) of FPCs
2 are integrally formed, and each FPC 2 is connected to the terminal 1. In each terminal 1, an inner barrel 14 passes through the FPC 2. Thus, barrel 1
By penetrating through 4, the barrel 14 and the FPC 2 are locked at the penetrating portion, so that the tensile strength can be further increased.

In the configuration shown in FIG. 1, the portion of the mounting surface of the base 10 which is pressed against the barrel 12 may be shaped so as to have a curvature substantially equal to the curvature of the outer peripheral surface of the barrel 12.
Thereby, a sufficient contact area between the barrel 12 and the conductive film 22 can be obtained, and stress concentration can be further reduced. or,
The serration may be provided corresponding to the barrel 12 in the y direction of the installation surface. Thereby, when tensile stress acts on the FPC 2, the barrel 12 is locked by the serrations, so that the FPC 2 can be prevented from coming off. Base 1
0, a configuration in which a hole, a concave portion, or the like is provided at a position corresponding to the convex portion 113 may be adopted. Thereby, better electrical connection between the spring 11 and the conductor film 22 can be achieved.

In the connection structure shown in FIG. 1, the barrel 12 and the spring 11 of the terminal 1 are brought into contact with the conductor film 22 of the FPC 2 so that the FPC 2 and the terminal 1 are connected.
Although the electrical connection with this is obtained, the electrical connection by the spring 11 can be sufficiently obtained, so that the barrel 12 may not be provided as shown in FIG. Also, barrel 1
Since good electrical and mechanical connection can be obtained even if only 2 is used, a configuration without the spring 11 may be adopted. or,
As shown in FIG. 3, the barrel 14 may be formed by bending the inside into a cylindrical shape and bending into a beam, and pressing the film 23 on the outer peripheral surface thereof. Thereby, FPC2 and barrel 1
Since the surface of the FPC 2 is in surface contact with the FPC 2, stress is not concentrated on the FPC 2 and damage due to the concentration of stress on the FPC 2 is prevented. Further, by pressing the FPC 2 on the outer peripheral surface of the barrel 14, the pressing force of the barrel 14 acts in a direction substantially orthogonal to the surface of the FPC 2, so that the thickness of the FPC 2 is reduced due to a decrease in stress over time and the like. Also F from barrel 14
The elastic force can be satisfactorily applied to PC2. Barrel 14
Has a low spring constant because it has a bent beam structure.
Since the degree of decrease in elastic force due to the decrease in wall thickness is small, F
The elastic pressing on the PC 2 can be stabilized with time. The surface contact structure between the FPC 2 and the barrel 14 may be other than the cylindrical beam structure shown in FIG. For example, FIG.
As shown in (1), a configuration may be used in which the corrugated barrel 14 is used to make surface contact with the FPC 2.

In the above-described embodiment, the FPC 2 is placed on the installation surface with the conductive film 22 facing upward, but the electrical connection between the FPC 2 and the terminal 1 can be established even with the conductive film 22 facing downward. It is possible. In the above embodiment, the turner mill 1 is connected to the FPC 2 derived from the membrane switch provided on the seat. However, the application of the present invention is not limited to this. Can be used for terminals.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a connection structure between an FPC and a turner mill according to a specific embodiment of the present invention.

FIG. 2 is a schematic diagram showing a state in which an insulation barrel penetrates the FPC in a connection structure between the FPC and the turner mill according to a specific embodiment of the present invention.

FIG. 3 is a schematic diagram showing a configuration in which a contact barrel is not provided in a connection structure between an FPC and a terminal according to a specific embodiment of the present invention.

FIG. 4 is a schematic diagram showing a state in which an insulation barrel is in surface contact with an FPC in a connection structure between an FPC and a terminal according to a specific embodiment of the present invention.

FIG. 5 is a schematic diagram showing a conventional connection structure between an FPC and a terminal.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Terminal 2 FPC 10 Base 11 Contact spring 12 Contact barrel 14 Insulation barrel 21 Circuit film 22 Conductive film 23 Insulation film

Claims (5)

[Claims] 1. A flexible printed board comprising a resin film, a conductor film formed on the resin film, and an insulating film formed by coating except for a connection portion of the conductor film, and a connection portion of the conductor film. Connecting the flexible printed circuit board with an electrical connection means electrically connected to the insulating film, and a terminal integrally formed with a mechanical connection means mechanically connected to the insulating film. Construction. 2. The flexible printed circuit board connection structure according to claim 1, wherein the mechanical connection means presses the insulating film in a planar manner. 3. The terminal has a base having an installation surface on which the flexible printed board is installed, and a terminal provided at one end in a longitudinal direction of the base, and the mechanical connection means includes: Extending from both sides substantially perpendicular to the longitudinal direction of the base, and being bent inward facing the installation surface, the flexible printed circuit board is fixedly pressed by the mechanical connection means and the installation surface. The connection structure for a flexible printed circuit board according to claim 1, wherein the connection is made. 4. The mechanical connection means has a curved beam shape formed by inwardly bending a cylindrical shape in opposition to the installation surface, and the flexible printed board is provided with an outer peripheral surface of the mechanical connection means. The connection structure for a flexible printed board according to claim 3, wherein the connection structure is pressed and fixed to the installation surface. 5. The flexible printed circuit board connection structure according to claim 1, wherein said mechanical connecting means penetrates said flexible printed circuit board.