Method for Forming Perforations on a Printed Circuit Board

The present invention relates to a method for forming perforations on a printed circuit board consisting of a mother portion and supplementary portions to be separated from the mother portion.

When manufacturing printed circuit boards, perforations are formed on the board to make possible the separation of the supplementary portions from the mother portion.

In this case, the usual perforation process is to simultaneously punch a plurality of through holes along a line. This process often causes a serious strain along the line, the magnitude and orientation of which depends on the arrangement of the holes. This strain leads to the formation of cracks which renders the product defective and unacceptable.

There is a known method for manufacturing printed circuit boards that prevents such defects. Such a conventional method is disclosed, for example, in Japanese Patent No. H1-49031. The method employs a technique in which a metal mold punch is used to form waste holes in a neighboring supplementary portion at the same time that perforations are formed, thus preventing the neighboring supplementary portion from moving outwards, which in turn prevents the formation of cracks along the perforations or a premature separation of the supplementary portion.

However, the above conventional method requires that the structure of the conventional metal mold for press-working a printed circuit board be modified significantly in order to introduce such extra punches onto the structure. In addition, this increases the stress on the entire mold, thereby shortening the life of the mold.

The object of the present invention is to eliminate the above disadvantage associated with the conventional method for manufacturing a printed circuit board and to provide a method for forming perforations on a printed circuit board without modifying the conventional press-working procedure or causing any of the above problems.

The present invention provides a method for forming perforations on a printed circuit board by means of press-working, in which the perforations (used to facilitate the separation of the mother portion from the supplementary portions of the printed circuit board) are formed on the copper-film coated area of the printed circuit board by means of press-working in such a way that the copper film will prevent the formation of cracks around the perforations.

According to the above method for forming perforations on a printed circuit board by means of press-working, the copper film effectively absorbs the stress exerted when perforations are formed, protects the area around the perforations, prevents the formation of cracks around the perforations or premature separation between the supplementary and mother portions of the printed circuit board along the perforations, and improves the manufacturing yield on printed circuit boards.

These and other objectives, features, aspects, and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawing.

The accompanying drawing is an enlarged view of a printed circuit board with perforations, and is an embodiment of the present invention.

The accompanying drawing is an enlarged view of a printed circuit board with perforations and is an embodiment of the present invention.

Referring to the figure, reference numeral 1 indicates a printed circuit board having opposed major surfaces. Reference numeral 2 indicates the mother portion of the printed circuit board, which has printed circuits formed on one or both major surfaces thereof.

Reference numeral 3 represents a supplementary portion to be separated from the mother portion (2) through the a line of perforations (4).

In the preferred embodiment, before forming perforations (4) by press-working, the area surrounding that were the perforations are to be formed is coated with a strain absorbing copper film (5) in a way such that the perforations will be formed on the copper film (5). Accordingly, when forming the perforations (4) by using a press mold (not shown) the copper film (5) can absorb both the strain produced by the punches and the tensile force exerted on the supplementary portion (3) in the direction of separation of the supplementary portion (3) from the mother portion (2). Accordingly, the copper film (5) effectively absorbs the strain produced during press-working and thereby serves to prevent both the formation of cracks around the perforations (4) and premature separation, of the supplementary portion (3) from the mother portion (2) which is possibly caused by external forces during or after the formation of perforations (4).

Although the copper film (5) covers half of each of the perforations (4) in the embodiment described above, it is equally possible to apply the copper film to completely coat the area surrounding the perforations to be formed. It is also possible to apply the copper film to coat the opposite side of the printed circuit board in a position corresponding to the copper film (5) on the first side.

The copper film (5) may be the remaining portion of the copper film formed and processed in the course of forming printed circuits on the mother portion (2). In this case, no extra copper coat is required.