JPH06104547A - Flexible board - Google Patents

Abstract

PURPOSE:To prevent short circuit between contact patterns due to leakage of solder to the outside of a predetermined region and to enhance solder bonding strength of contact pattern when a contact pattern on a flexible board is connected electrically, through soldering, with a contact pattern on a printed board. CONSTITUTION:The flexible board 1 to be connected electrically, through soldering, with a printed board 2 is provided with contact patterns 5a, b of similar profile as the contact patterns 5c, d on the printed board 2 at the end parts of a plurality or layers opposing to the printed board. In such structure, a dummy pattern 8 is provided at a position opposing to the contact pattern on the printed board between the inner layer contact patterns of the flexible board.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flexible substrate, and more particularly to a flexible substrate which is preferably electrically connected to a printed circuit board and electronic components are properly mounted.

[0002]

2. Description of the Related Art Generally, a flexible board and a printed board are used by electrically connecting a contact part such as a contact pattern on the flexible board and a corresponding contact part on the printed board by soldering.

As a concrete structure for this electrical connection, conventionally, for example, the coverlay film is removed at the substrate end of a flexible substrate to expose copper foil patterns arranged in parallel at a constant pitch. To form a contact pattern. A method is often used in which the contact patterns formed on the printed circuit board side are superposed on each other, and the solder previously attached to the surface of each contact pattern is melted to provide electrical connection.

The above-described connection structure is directly applied to the case where the contact patterns of a plurality of layers are connected to the printed board at the board end of the multilayer flexible board.
The connection structure of this conventional example will be described with reference to FIG.

In FIG. 5, reference numeral 1 denotes a multilayer flexible substrate, in which case a copper foil pattern on one side of the base film 3 of the 4-layer flexible substrate, that is, a copper foil pattern on the surface layer and a copper foil pattern on the inner layer are connected. The part pulled out as a part is shown. The copper foil pattern is covered with the coating layer 4. The coating layer 4 is generally called a cover lay film, and is formed of a material having high heat resistance and chemical resistance, and strong against bending, for example, a film of polyimide or the like. By partially removing the coating layer 4 at the substrate end of such a multilayer flexible substrate 1, the copper foil patterns arranged in parallel at a constant pitch are exposed to form the surface layer contact pattern 5a and the inner layer contact pattern 5b. is doing. At this time, the surface of each of the contact patterns 5a and 5b is usually subjected to solder plating. Further, positioning holes 6 are provided on both sides of the contact patterns 5a and 5b.

A printed circuit board 2 has contact patterns 5c, 5d and a positioning hole 6 of the same shape formed on the printed circuit board at positions corresponding to the surface layer contact pattern 5a, the inner layer contact pattern 5b and the positioning hole 6 of the multilayer flexible board 1. Has been done. In this case, the surface of the contact patterns 5c and 5d is usually subjected to solder leveler processing.

In the above structure, the multilayer flexible board 1 and the printed board 2 are aligned by the positioning holes 6 and the contact patterns 5, 5a, 5b are in close contact with each other. The heating means melts and fixes the solder on the contact pattern.

Further, conventionally, when electronic parts such as switches and connectors are soldered to a flexible substrate, positioning is performed by the structure shown in FIGS. 7 and 8. Where 2
1 is an electronic component, 22 is a positioning dowel, 23 is a lining, 2
4 is an engagement hole, 25 is an adhesive, 26 is a flexible substrate,
27 is an escape hole.

Further, in FIG. 7, an engaging hole 24 with which a positioning dowel 22 provided in the electronic component 21 is engaged.
Backing made of glass epoxy resin, metal, etc. 2
3 and is bonded to the flexible substrate 26 by using a thermosetting adhesive or the like. When soldering an electronic component, the positioning dowel 22 and the engagement hole 24 are engaged with each other, and the lead terminal (not shown) of the electronic component and the flexible substrate are soldered in a positioned state.

Further, in FIG. 8, an escape hole 27 having a diameter larger than that of the engaging hole 24 is provided in the flexible substrate 26, and bonding is performed so that the centers of the holes are aligned with each other. The same as in the case of 7.

[0011]

However, as shown in FIG.
In the conventional flexible board that electrically connects the contact patterns described with reference to 6, when the number of electrical connections increases, or the flexible board 1
When the width of the contact pattern is narrowed and the width of the contact pattern is limited, it is necessary to narrow the contact pattern width, and as shown in FIG. The solder 7 flowing out from the surface layer contact pattern 5a causes a solder bridge between the adjacent inner layer contact pattern 5b, which causes difficulty in manufacturing. Further, when a strong force is applied to the multilayer flexible substrate 1 in the peeling direction, the smaller the area of the contact pattern, the easier the peeling occurs.

A first object of the present invention is to solve the above problems, and to provide a flexible substrate having a structure in which connection with a printed circuit board is firmly performed at a narrow pitch. It is intended.

Further, in the conventional example shown in FIGS. 7 and 8, in the case of FIG.
Since pressure is applied from both sides, the adhesive 25 protrudes from the side surface of the engagement hole. Therefore, when the positioning dowel is engaged, the adhesive protruding from the dowel comes into contact with the dowel, and the electronic component is positioned in a state of being lifted or inclined from the backing surface, and soldering is performed. In the case of FIG.
The adhesive 25 that protrudes toward the engagement hole 24 flows out toward the side surface of the escape hole 27 of the flexible substrate, and therefore does not solidify on the side surface of the engagement hole. However, since holes are formed in the flexible substrate, it is necessary to escape the copper foil pattern on the flexible substrate, which makes high-density wiring difficult. Further, it is difficult to provide the component insertion hole for the electronic component in the area close to the engagement hole.

A second object of the present invention is to solve the above-mentioned problems, and the flexible board is so arranged that the dowel of the electronic component can be properly positioned without tilting to the engaging hole of the backing. To provide.

[0015]

In order to achieve the above-mentioned first object, the solution means of the present invention provides a contact pattern having substantially the same shape as the contact pattern of the printed circuit board on the surface facing the printed circuit board. In a flexible board which has an end portion of a plurality of layers and is electrically connected to the printed board by soldering, a dummy pattern is provided between the inner layer contact patterns of the flexible board and at a position facing the contact pattern of the board print. It was

According to this means, the dummy patterns provided on the multilayer flexible substrate and the contact patterns provided on the printed circuit board are welded to each other by soldering, so that the two boards are connected at a narrow pitch. It will be done firmly with being told.

In order to achieve the second object,
The solution means of the present invention is to bond the backing and the flexible board, which have the engagement holes for engaging the positioning dowels of the electronic parts such as the switch and the connector, on the surface side to be bonded to the flexible board, and the counterbore. It is a thing.

According to the means, the electronic component is positioned at a normal position without rising from the backing surface and is properly mounted on the flexible substrate.

[0019]

1 is a perspective view showing an embodiment of the present invention, and FIG. 2 is a plan view showing a joint surface of a multilayer flexible substrate 1. In FIGS. 1 and 2, reference numerals 1 to 6 denote the same members as those in FIGS. 5 and 6. 8 is a dummy pattern made of a copper foil pattern provided between the inner layer contact patterns at the substrate end of the multilayer flexible substrate 1,
Also on the printed circuit board 2, contact patterns are provided at opposing positions.

Next, in the above structure, solder plating is applied to the surfaces of the surface layer contact pattern 5a, the inner layer contact pattern 5b and the dummy pattern 8 on the multilayer flexible substrate 1.
The surface of the contact pattern 5 on the printed board 2 is subjected to a solder leveler process. Then, positioning is performed using the positioning holes 6 provided on both sides of each contact pattern 5, and the surface layer contact pattern 5a and the inner layer contact pattern 5b are aligned.
While the contact pattern 5 and the contact pattern 5 are in close contact with each other, the solder on the contact pattern is melted and fixed by a soldering iron or a heating means such as a laser. Further, at this time, the excess solder 7 flowing out from the surface layer contact pattern 5a becomes integrated with the solder on the dummy pattern 8 and the solder on the contact pattern 5 at the time of melting, as shown in FIG. It will flow from the surface to the outside area.

In such a structure, solder bridging between contact patterns arranged in parallel on the multilayer flexible substrate 1 and the printed substrate 2 is prevented, and the multilayer flexible substrate 1 is peeled from the printed substrate 2. Even for force, it is an effective reinforcement because the joint area increases.

FIG. 4 shows another embodiment of the present invention. Here, 21 is an electronic component, 22 is a positioning dowel provided on the electronic component 21, 23 is a lining, 24 is an engagement hole, 25 is an adhesive, 26 is a flexible substrate, and 28 is a counterbore.

Next, in the above structure, the backing 23 is provided with an engagement hole 24 with which the positioning dowel 22 provided in the electronic component 21 is engaged. At this time, a counterbore 28 is formed on the surface side of the engaging hole 24 that contacts the flexible substrate 26. Thereafter, the flexible substrate 26 and the backing 23 are bonded together by using a thermosetting adhesive or the like. At this time, pressure is applied from both the flexible substrate side and the backing side, and the engaging hole 24
The adhesive 5 that protrudes in the direction hardens while remaining around the spot facing 28. When the electronic component 21 is soldered to the flexible substrate 26 to which the backing 23 is adhered as described above, the positioning dowel 22 is engaged with the backing 23 without coming into contact with the protruding adhesive, so that the electronic component 21 has a backing surface. Positioning is performed in a contact state without floating from above, and soldering is performed at a normal position.

[0024]

As described above, according to the present invention,
In the flexible board connected to the contact pattern of the printed board, the dummy pattern is provided between the inner layer contact patterns of the flexible board and the contact pattern of substantially the same shape is also provided on the opposing printed board for solder welding. This prevents a solder bridge between the contact patterns when the contact pattern pitch is narrowed, and is an effective reinforcing means against the force in the peeling direction.

Further, by gluing the backing and the flexible board, which have a counterbore shape on the surface side where the engaging holes for engaging the positioning dowels of electronic parts such as switches and connectors are adhered to the flexible board, (1 ) The electronic component is positioned at a normal position without floating from the backing surface. (2) It is not necessary to provide an escape hole for the engagement hole on the flexible substrate, and high-density wiring is possible. (3) There is an effect that it becomes possible to provide a component insertion hole for an electronic component in a region close to the engagement hole.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of a flexible substrate of the present invention.

FIG. 2 is a plan view showing an example of a joint surface of a flexible substrate of the present invention.

FIG. 3 is a cross-sectional view showing an example of joining the flexible substrates of the present invention.

FIG. 4 is a sectional view showing another embodiment of the flexible substrate of the present invention.

FIG. 5 is a perspective view showing an example of a conventional flexible substrate.

FIG. 6 is a view showing a joint surface of a conventional flexible substrate.

FIG. 7 is a cross-sectional view showing an example of a conventional flexible substrate on which electronic components are mounted.

FIG. 8 is a cross-sectional view showing another example of a conventional flexible board on which electronic components are mounted.

[Explanation of symbols]

1 ... Flexible substrate 2 ... Printed circuit board 3 ... Base film 4 ... Covering layer 5 ... Contact pattern 5a ... Surface layer contact pattern 5b ... Inner layer contact pattern 6 ... Positioning hole 7 ... Solder 8 ... Dummy pattern 21 ... Electronic component 22 ... Positioning dowel 23 ... Lining 24 ... Engagement hole 25 ... Adhesive 26 ... Flexible substrate 27 ... Escape hole 28 ... Counterbore

Claims (2)

[Claims] 1. A flexible board having contact patterns of substantially the same shape as the contact pattern of the printed board at the ends of a plurality of layers on the surface facing the printed board, and electrically connected to the printed board by soldering. In the flexible board, a dummy pattern is provided between the inner layer contact patterns of the flexible board and at a position facing the contact pattern of the printed board. 2. A flexible board, wherein a backing having a counterbore shape is adhered to an engaging hole for engaging a positioning dowel of an electronic component such as a switch or a connector on a surface side to be adhered to the flexible board. .