JPH0423494A - Flexible printed wiring board - Google Patents

Abstract

PURPOSE:To enable easy soldering of a lead-out wire by forming a multilayer connection end part by bending and laminating a wide connection end part so that its width is approximately the same as that of a fine pattern formation part. CONSTITUTION:A connection end part 2 of FPC is divided into three connection end parts of 12a to 12c, and the width of each connection end part is formed a little larger than the width of a fine pattern formation part 11, respectively. An external connecting end part 3b is exposed to a front side and external connecting end parts 3a, 3c are exposed to a rear side. Furthermore, the end part 12a is bent above the end part 12b along line C-C, the end part 12c is bent below the end part 12b along line D-D; a lamination part thereof is jointed through adhesive 4. Thereby, it is possible to enlarge a wire cable to a circuit pitch which can be connected by soldering and to simplify soldering operation.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a flexible printed wiring board, and particularly to a refined flexible printed wiring board.

[Prior art and problems to be solved by the invention] Flexible printed circuit boards (hereinafter abbreviated as FPC) are
Because of its thin and flexible characteristics, it is widely used as a wiring material for highly integrated electronic devices and highly integrated electronic devices that are becoming increasingly smaller and lighter. At the same time, with the increase in wiring density, both circuit width and circuit gaps are becoming finer (hereinafter abbreviated as "fineness").

-i, the wire cable is connected to the FPC via a connector, but in order to do so, the circuit pattern pitch at the end of the FPC circuit pattern must be expanded to the wiring pitch at the connector connection part, and in addition, Considering the wiring route to the connector connection land, an FPC configuration with a large connector connection land as shown in FIG. 6 is inevitable.

In FIG. 6, reference numeral 11 indicates a fine pattern forming portion of the FPC, and the circuit pattern made of the conductive metal foil 2 in this portion is formed with fine circuit width and circuit pitch. Reference numeral 12 denotes a connection end of the FPC, and a connection land 8 is provided at the connection end in correspondence with the above-mentioned circuit pattern, and a circuit pattern in the fine pattern forming section 11 is formed on each connection land 8. A metal foil 2 is extended and connected. This connection portion is omitted in the figure and simply indicated by a broken line.

For this reason, even though the fine pattern forming portion 11 is reduced in size, the connection end portion 12 is not reduced in size.
The actual external size of the FPC must be made larger than the required external size for the wiring capacity of the FPC, which becomes an obstacle to downsizing the system.

Therefore, efforts have been made to connect the wire cable and the FPC directly by soldering without using a connector to solve the problem of expanding the external shape of the FPC due to the connector.

However, for example, 0.2 mm (circuit width 0.1 mm)
, for a refined circuit pattern with a circuit gap of 0.1 mm or less, directly and individually connect the lead wire of a wire cable with an outer diameter of at least around 0.4 mm for stranded wires and 0.2 mm @ 7i for solid wires. It is practically difficult to solder the terminals of the circuit pattern to a wiring pitch that allows soldering. Therefore, in this case as well, the enlargement of the outer shape of the FPC cannot be canceled.

Therefore, in order to make the FPC outer shape the same size as the fine pattern forming part, it is conceivable to multilayer the wiring of the circuit pattern according to the enlargement magnification. However, in this case, it is necessary to provide a large number of through holes depending on the circuit pattern.
This results in an outer shape that is not much different from the FPC outer shape shown in the figure, and moreover, the FPC cost increases significantly.

[Means to solve the problem]

The present invention has been made to solve the above-mentioned problems, and provides an FPC in which the FPC and a wire cable are directly connected by soldering, and which can achieve fineness with the following configuration. .

In a flexible printed wiring board consisting of a conductive metal foil on which a circuit pattern is formed and an insulating film made of plastic laminated on both sides, the circuit patterns are arranged at a narrow pitch in the fine pattern forming area and the pitch increases toward the edge. is enlarged and extended to a wide connecting end connected to the fine pattern forming section, and the wide connecting end is bent and overlapped so that the width is approximately equal to the width of the fine pattern forming section, and the wide connecting end is overlapped. The mating portions are bonded via an adhesive to form a multilayer connection end, and the ends of the circuit patterns distributed and arranged with the above-mentioned pitch expanded in each layer of the connection end are provided with steps. The flexible printed wiring board is characterized in that the flexible printed wiring board is exposed to form an end part for external connection.

[Effect]

As described above, by bending the connecting ends of the FPC to form a multilayer structure, the outer shape of the FPC can be reduced, and the external connecting ends formed at the terminals of the circuit pattern can be connected to wire cables. The circuit pitch has been expanded to the extent that the lead wires can be soldered, and
Since the end portion for external connection is formed by providing a step for each layer and exposing it, the lead wire can be easily soldered.

〔Example〕

FIG. 1 is a plan view of an embodiment of the FPC according to the present invention, FIG. 2 is a longitudinal sectional view taken along line A-A in FIG. 1, and FIG. 3 is a line 13-B in FIG. 1. 4 is a developed view of the FPC shown in FIG. 1.

In these figures, a conductive metal foil 2 with a circuit pattern formed thereon is laminated between two insulating films IA and IB made of polyimide films via an adhesive (the adhesive is not shown in the figures). A fine pattern forming section 11 is formed on the FPC, and the circuit pattern in this fine pattern forming section 11 is formed by conductive metal foil 2 to have a small circuit width, a small circuit gap, or a small circuit pitch.

12 is the connection end of the FPC, 12a, 12b,
Divided into three connection ends 12c, each of these connection ends 12a, 12b, 12c is formed to have a width slightly thicker than the width of the fine pattern forming portion 11, and its length is 12a, 12b. , 12c. 3a, 3b, and 3c are external connection end portions formed by extending the metal foil 2 forming the circuit pattern in the fine pattern forming portion 11 and expanding the pitch by approximately three times, as shown in FIG. In FIG. 4, the external connection end 3b is exposed on the front side, and the external connection end 3a and 30 are exposed.
is exposed on the back side. These external connection ends 3
a, 3b, and 3c are connected by circuit patterns corresponding to the circuit patterns in the fine pattern forming section 11, but the portion 12a in FIG.
- Fold over part 12b along line C, and fold part 12G under part 12b along line D-D to overlap, and these overlapping parts are joined via adhesive 4. ing. By overlapping the connection ends in this way, the FPC shown in FIGS. 1 to 3 is obtained.

Furthermore, an embodiment of a two-legged FPC will be explained using the manufacturing process shown in FIG.

First, Figure 5 (1-a) is an assembled perspective view, Figure 5 (1b)
As shown in the cross-sectional view taken along the E-E line in FIG. Opening 1 as shown in side insulation film 1^
After opening 3a and 13c, the conductive metal foil 2 made of a rolled copper foil having a thickness of 35 am and the above insulating film LA are laminated via an adhesive 5, and the adhesive 5 is cured to completely adhere.

Next, as shown in the cross-sectional view in FIG. 5 (2-a), the metal foil 2
After coating the upper side with an etching resist 6 for pattern formation and an etching resister so as to completely cover the exposed surfaces of the metal foil 2 in the openings 13a and 13c of the insulating film 1^, the etching resist 6 is coated with an etching resist 6, and then etched with a chlorine-based etching method. A predetermined circuit pattern is formed by etching. After etching, the pattern-forming etching resist 6 and the etching resist 7 are simultaneously removed, and the metal foil 2 is formed into a circuit pattern as shown in FIG. 5 (lb) and its perspective view (2-c). The circuit 2 that appears floating in the air in (2-b) shows a circuit pattern exposed on the front and back (top and bottom in the figure) formed by bridging the openings 13a and 13c. Incidentally, the main body part of the FPC, the circuit pattern in the fine pattern forming part 11, and the external connection end part 3a
, 3b, 3C1 and the circuit pattern portion 2a to which these are connected are formed at the same time.

Next, as shown in the assembled perspective view in FIG. 5(3), as in the case of FIG. 25μ
A coverlay insulating film IB made of a polyimide film with a thickness of
The opening 13b and the fine pattern forming part 1 are arranged so that the external connection end 3b is exposed on the surface when the external connection end 3b is overlapped on top of the opening 13b and the fine pattern forming part 1.
An opening 13d exposing the metal foil 1 to the upper surface is provided, and the adhesive 5 is laminated in contact with the metal foil 2 side, and the adhesive 5 is cured to completely adhere. After that, the outer shape is punched out along the outer shape line F, and the perspective view is shown in Fig. 5 (4-a), and C-C is shown in Fig. 5 (4-b).
A wiring board shown in an enlarged cross-sectional view along the line is obtained.

Next, the connecting ends 12a and 12c are bent above and below the connecting end 12b along the lines C-C and DD in FIG. 5(4-a) as shown in FIG. 5(5), and the overlapping portions are Although not shown in Figure 5 (5), Figures 2 and 3
As shown in the figure, they are overlapped with an adhesive 4 interposed therebetween. The adhesive used at this time is to be used by applying an adhesive resin onto a release sheet to semi-cure, then removing the release sheet, and after the above-mentioned overlapping, complete adhesion is achieved by heating press. In this way, an FPC not shown in FIG. 1 is obtained.

In the above, the circuit pitch of the circuit pattern in the fine pattern forming section 11 is expanded three times, and the external connection end 3a,
3b and 3c are formed, and therefore the connecting end 12 is expanded to approximately three times the width of the fine pattern forming part 11, and this is folded to form a three-layer structure, but it is also possible to form more layers if necessary. It is.

Further, in the above embodiment, the connection end 1 at the connection end 12
2a and 12c were extended and extended on both sides of 12b, and the connection ends 12a and 12c on both sides were bent in an S shape above and below 12b, but 12a and 12c were placed on one side of 12b, and both were placed above 12b. Alternatively, they may be bent downward, or they may be folded into a 0-shape so as to hug each other instead of an S-shape.

Furthermore, when the number of stages to be expanded and deployed increases, an external connection end formed in a step-like manner to one side (in the above example, 3
Needless to say, it can be formed not only on a, 3b, and 3c) but also on both sides, that is, on the front side and the back side.

〔Effect of the invention〕

Since the FPC of the present invention has a connection end portion bent into multiple layers, it has the following effects and can be made finer.

■While maintaining the width of the fine pattern forming part of the FPC main body, it is possible to expand the circuit pitch to a point where wire cables can be connected to the ends by soldering.

■Wiring can be distributed between upper and lower wiring layers in a multilayer structure without the need for through holes.

■It is possible to connect the FPC and wire cable directly by soldering without using a connector, and the space of the entire system can be saved.

■The magnification of narrow pitch wiring can be easily changed by setting the number of bends at the design stage.

■Although the connecting end has a multilayer structure, the manufacturing process and cost can be made comparable to a single layer structure.

■The connection end with the wire cable is multi-layered, which increases strength and reduces deformation, making handling such as soldering work easier and preventing damage from tearing of the FPC due to movement of the wire cable. can do.

[Brief explanation of the drawing]

FIG. 1 is a plan view of an embodiment of a flexible printed wiring board according to the present invention, FIG. 2 is a longitudinal sectional view taken along line A-A in FIG. 1, and FIG. 3 is a B in FIG. 1. −
A lateral sectional view taken along line B, FIG. 4 is a developed view of the FPC shown in FIG. 1, and FIG. 5 is an FPC according to the present invention.
FIG. 6 is a schematic diagram of the main parts of a conventional flexible printed wiring board. 1A, IB: insulating film, 2: conductive metal foil, 3a,
3b, 3c: External connection end, 4: Adhesive, 5: Adhesive, 6: Etching resist for pattern formation, 7: Etching resist, 8: Connection land, 11: Fine pattern forming part, 12: Connection end , 12a, 12b, 12c:
Connecting ends 13a and 13b are subdivided connecting ends 12. 13c, 13d: Openings provided in the insulating film.

Claims (1)

[Claims] 1. In a flexible printed wiring board consisting of a conductive metal foil on which a circuit pattern is formed and an insulating film made of plastic laminated on both sides, the circuit patterns are arranged at a narrow pitch in the fine pattern forming area and the pitch increases toward the edge. is enlarged and extended to a wide connecting end connected to the fine pattern forming section, the wide connecting end is bent and overlapped, and the overlapping parts are joined with an adhesive to form a multilayer. In addition, the ends of the circuit patterns in which the pitch is expanded and distributed in each layer of the connection end are exposed with a step to form an external connection end. A flexible printed wiring board characterized by: