JPH08125296A - Double-sided flexible printed wiring board and formation of connection part thereof - Google Patents

Abstract

PURPOSE: To prevent generation of a solder bridge, by forming a double-sided flexible printed wiring board which has at least two opposite semicircular through-holes per unit terminal in a connection terminal conductor and covering a part of the front or back side of a bottom section of the connection terminal conductor with a cover lay film layer alone. CONSTITUTION: Opposite through-holes are formed by boring a through-hole section 4. The through-hole section 4 is then treated by copper through-hole plating. Pattern forming is carried out in a non-terminal conductor 8 except for terminal forming sections 2, 3. Then, cover lay films 5, 6 are laminated in such a manner that a section 7 is opened or exposed. Subsequently, a connection terminal is formed by stamping out portions along bold lines 9 by a metal mold. Thus, a connection part with high solder strength in which solder bridges are unlikely to be generated is formed easily and efficiently.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a double-sided flexible printed wiring board, and more particularly to a double-sided flexible printed wiring board having a connection portion and a method for forming the same, which has high strength with a hard printed wiring board or a flexible printed wiring board. The present invention relates to a double-sided flexible printed wiring board that enables connection and a method for forming a connection portion thereof.

[0002]

2. Description of the Related Art Conventionally, as an example of connecting a flexible printed wiring board to another hard printed wiring board, a flexible printed wiring board or the like, after forming a pattern of a terminal portion conductor 2 as shown in FIG. A method is used in which a through hole is formed at the tip of the partial conductor 2, the through hole is plated on this portion, and then the outer shape is punched by a die or the like.

Further, Japanese Patent Publication No. 6-52824 shown in FIG.
As can be seen in the publication, a terminal portion conductor pattern is formed by leaving a conductor layer at the end of the base film, and then the conductor layer is subjected to through hole processing and through hole plating,
After that, a method of punching the outer shape of the through hole so that the center of the through hole becomes the tip of the terminal is performed.

[0004]

However, in any of these conventional methods, since the through hole and the through hole plating are applied only to the tip end portion of the terminal portion conductor, the solder fillet portion (solder puddle) generated in the subsequent connection step is formed. As a result, the conductor tip is relatively thin and has a long shape, so that the conductor is often cut.

Further, conventionally, in the through hole processing step, there is only one through hole formed in the conductor layer by one through hole, and there is a problem in working efficiency.

Further, for example, as shown in FIGS. 3 and 4, in the terminal connecting portion, the portion covered with the coverlay film layer 5 is always in a retreat position relative to the base film 1, and the coverlay film is formed. The layer does not completely cover the base film. For this reason, there is a problem that a solder bridge is apt to be formed between the roots of the terminal portion conductors to cause a lot of conduction.

[0007]

The present inventors have arrived at the present invention as a result of intensive studies to solve the above-mentioned conventional problems. That is, the present invention is a double-sided flexible printed wiring board characterized by having at least two opposing semicircular through holes in a connection terminal portion conductor per unit terminal, and as a preferred embodiment thereof, a connection terminal. The flexible printed wiring board is characterized in that at least a part of the front surface and / or the back surface of the root portion of the partial conductor is covered with the coverlay film layer alone. Furthermore, according to the present invention, after the conductor is subjected to through-hole processing and through-hole plating, pattern formation is performed while leaving the terminal portion conductor at the end of the base film, and then the circumference of the through-hole portion is centered. The present invention also relates to a method for forming a connecting portion of the double-sided flexible printed wiring board, which is characterized in that punching processing is performed so that both sides remain opposite to the terminal portion conductor.

According to the present invention: 1) By providing one through hole on the conductor of the terminal portion, at least two through holes can be obtained per unit terminal as shown in FIGS. 1 and 2. As a result, High soldering strength is obtained,

2) Since at least a part of the front surface and the back surface of the root portion of the connecting terminal portion conductor are covered with the coverlay film layer alone, the base portion of the terminal portion is sufficiently covered with the coverlay film. Therefore, solder bridges between the terminal conductors are unlikely to occur, and even if solder bridges occur, they can be easily removed and corrected. 3) At the same time, it is possible to provide various advantages such that the coverlay film layer is covered, which contributes to maintaining or improving the strength of the terminal conductor itself.

In the present invention, as shown in FIGS. 1 and 2, there are at least two opposed through holes formed in the terminal conductor, and the strength of the terminal conductor is remarkable. As long as it does not decrease, more through holes can be formed to improve the reliability of soldering.

The shape of the through hole formed in the present invention is not particularly limited, and it depends on the site where the through hole is formed, or the desired area of the desired through hole plated portion,
Alternatively, it may be arbitrarily selected from the viewpoints of shape and design such as width and length of the terminal portion conductor, and may be one that forms a part of the arc of the circumference.

Further, the cover lay film shown in FIGS. 1 and 2 can be coated up to the vicinity of the through-hole portion of the terminal conductor if necessary, and the width of the coating is not limited at all, and can be arbitrarily designed and set. I do not care. Although it may be coated only on the front surface or only on the back surface, coating on both surfaces is preferable from the viewpoint of preventing solder bridges and maintaining the strength of the terminal conductor itself.

[0013]

EXAMPLES The outline of the method for forming the connecting portion of the double-sided flexible printed wiring board of the present invention is shown below. 1) The through holes shown in FIGS. 1 and 2 are perforated to form opposed through holes, and then the through holes are plated with copper through holes by a conventionally known method. 2) Patterning is performed on the non-terminal portion conductor portion (portion in the direction of the arrow 8) other than the terminal portion forming portion. 3) Next, a coverlay film is laminated so that the portion 7 is opened (exposed). 4) A connecting terminal is formed by punching with a die along the thick line portion 9 shown in FIG.

[0014]

According to the present invention, soldering strength is strong, solder bridges and the like are less likely to occur, and the strength of terminal conductors is particularly maintained. Particularly excellent double-sided flexible printed wiring board connection portions can be formed easily and efficiently. To be done.

[Brief description of drawings]

FIG. 1 shows a perspective view of a specific example of a terminal conductor portion of a flexible printed wiring board according to the present invention.

FIG. 2 is a plan view of a specific example of a terminal conductor portion of a flexible printed wiring board according to the present invention.

FIG. 3 shows a perspective view of an example of a terminal conductor portion of a conventional flexible printed wiring board.

FIG. 4 shows a perspective view of an example of a terminal conductor portion of a conventional flexible printed wiring board.

FIG. 5 shows a plan view of an example of a terminal conductor portion of a conventional flexible printed wiring board.

[Explanation of symbols]

 1: Base film 2, 3: Terminal part conductor part 4: Through hole part 5, 6: Coverlay film 7: Coverlay film opening (exposed part) 8: Non-terminal part conductor part 9: Die punching part (thick) solid line)

Claims (3)

[Claims] 1. A double-sided flexible printed wiring board, characterized in that the connecting terminal conductor has at least two opposing semicircular through holes per unit terminal. 2. The double-sided flexible printed wiring board according to claim 1, wherein at least a part of the front surface and / or the back surface of the root portion of the connecting terminal portion conductor is covered with the coverlay film layer alone. 3. After conducting through-hole processing and through-hole plating on the conductor, pattern formation is performed by leaving the terminal portion conductor at the end of the base film, and thereafter both sides of the circumference centered on the through-hole portion are formed. The method for forming a connecting portion of a double-sided flexible printed wiring board according to claim 1 or 2, wherein a punching process is performed so as to face the terminal conductor.