JPH09307208A - Connecting end part structure of flexible printed board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly reliable connecting end part structure hardly subjected to any disconnection. SOLUTION: An FPC 14 having signal patterns 12 formed on one side of an insulation film 11 and a conductive film 13 formed on the other side of the film 11 so as to be made into a microstrip line structure, wherein an end edge 13a of the conductive film 13 is set back by a predetermined distance from a connecting end edge 14a of the FPC 14 to form on the other side of the connecting end part of the FPC 14 where no conductive film 13 is formed, connecting pads 21 connected with the signal patterns 12 through via holes 22.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a connecting end portion of a flexible printed circuit board (hereinafter referred to as FPC) having a microstrip line structure.

[0002]

2. Description of the Related Art When an FPC of this type is connected to, for example, a circuit board, the connection end of the FPC has conventionally been constructed as shown in FIG. 3A. That is, the insulating film 11
In the FPC 14 having a microstrip line structure in which a plurality of signal patterns 12 are formed in an array on one surface and a planar conductive film 13 is formed on the other surface, the edge 13a of the conductive film 13 is the FPC 14 at the connection end. Connection edge 14a
Further, the signal pattern 12 is retracted by a predetermined amount, a through hole 15 is formed in the insulating film 11 in the portion where the conductive film 13 is not present, and the signal pattern 12 is exposed. The exposed portion serves as a connection portion of the signal pattern 12.

FIG. 3B shows a structure of a circuit board 16 connected to the FPC 14, and the board surface thereof has an FP.
A signal pad 17 corresponding to each signal pattern 12 of C14
Are arranged in an array, and a ground pad 18 is formed so as to face the end of the conductive film 13 of the FPC 14.
In the figure, 19 is a signal pattern reaching each signal pad 17.

The FPC 14 and the circuit board 16 are connected by the corresponding signal pattern 12, signal pad 17, and conductive film 1.
3 and the ground pad 18 are soldered to each other. FIG. 3C shows this connected state.

[0005]

DISCLOSURE OF THE INVENTION The conventional FPC described above
In the connection end structure of 14, since each signal pattern 12 is exposed, disconnection is likely to occur at this portion,
That is, there is a problem in reliability, and connection work is difficult to perform. SUMMARY OF THE INVENTION It is an object of the present invention to provide a connection end structure of an FPC that eliminates the conventional drawbacks, can perform a connection work easily without causing a disconnection, and is excellent in reliability.

[0006]

According to the present invention, a signal pattern is formed on one surface of an insulating film, and a conductive film is formed on the other surface of the insulating film. The end edge is set at a position retracted from the connection end edge of the FPC by a predetermined amount, and a connection pad connected to the signal pattern via a via hole is formed on the other surface of the connection end portion without the conductive film.

[0007]

Embodiments of the present invention will be described with reference to the accompanying drawings. Parts corresponding to those in FIG. 3 are denoted by the same reference numerals, and description thereof is omitted. FIG. 1 shows an embodiment of the present invention. In this example, the edge 13a of the conductive film 13 is located at a position retracted by a predetermined amount from the connection edge 14a of the FPC 14 as in the conventional connection end structure shown in FIG. A plurality of connection pads 21 are formed on the top. These connection pads 21 are arranged along the connection edge 14a of the FPC 14 so as to face the signal patterns 12 located on the back surface side. The opposing connection pads 21 and the signal patterns 12 are connected to each other via the via holes 22, that is, these connection pads 21 serve as the connection portions of the signal patterns 12. In addition, each signal pattern 12
In the portion where the via hole 22 is formed, is slightly wider as shown in the figure.

FIG. 2A shows a connection state between the FPC 14 having the above-mentioned connection end structure and the circuit board 16, and FIG. 2B shows an enlarged cross section thereof. Each connection pad 21 of the FPC 14 is connected to the corresponding signal pad 17 of the circuit board 16 by the solder 23, and the end portion of the conductive film 13 and the ground pad 18 are connected by the solder 23. As shown in FIG. 2B, the ground pad 18 on the circuit board 16 is a via hole 24.
Are connected to the ground layer 25 via the ground layer 25 and the signal pattern 19 so that the circuit board 16 also has a microstrip line structure.

The connection pad 21 and the signal pad 17, and the conductive film 13 and the ground pad 18 may be connected to each other by means other than solder, for example, a conductive adhesive may be used.

[0010]

As described above, according to the present invention, the connection pad 21 connected to the signal pattern 12 through the via hole 22 is provided on the same surface as the conductive film 13 to serve as the connection portion of the signal pattern 12. Therefore, the connection can be satisfactorily performed without causing a break in the signal pattern 12, and thus a highly reliable connection end structure can be obtained.

[Brief description of drawings]

FIG. 1 is a view showing an embodiment of the present invention, A is a plan view, B is a front view, and C is a bottom view.

2 is a perspective view showing a state in which the FPC shown in FIG. 1 is connected to a circuit board, and B is an enlarged sectional view thereof.

FIG. 3A is a perspective view showing a connection end structure of a conventional FPC, B is a perspective view of a circuit board, and C is a perspective view showing a state in which they are connected.

Claims (1)

[Claims] 1. A structure of a connection end portion of a flexible printed circuit board having a microstrip line structure in which a signal pattern is formed on one surface of an insulating film and a conductive film is formed on the other surface, and the edge of the conductive film is formed. Is a position retracted from the connection end edge of the flexible printed circuit board by a predetermined amount, and a connection pad connected to the signal pattern via a via hole is formed on the other surface of the connection end without the conductive film. Characteristic flexible printed circuit board connection end structure.