JPS60149195A - Method of producing printed circuit board - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a printed wiring board in which a conductor is selectively formed on the outer side wall surface of the printed wiring board.

Conventionally, as a printed wiring board in which a conductor is formed on the side wall surface of the printed wiring board, a through hole is formed as shown in the perspective view of Fig. 1, and then the through hole is cut vertically to form an open conductor (2). A printed wiring board is disclosed, for example, in Japanese Utility Model Application Publication No. 50-92356. The manufacturing method for such a board is to drill holes on the outline of the printed circuit board, apply through-hole plating, and then punch out holes in the thickness direction of the board, that is, in a direction substantially perpendicular to the horizontal direction of the board, by punching a mold. A method has been adopted in which a portion of the through hole is separated by cutting, and the remaining portion of the hole is used to form the conductor of the printed circuit board.

Another method is to make a cut (3) in a part of the conductor formed on the side wall surface, as shown in the perspective view of FIG. 2, to form an insulated and independent pattern on the side wall surface of the printed circuit board. There is a way.

However, all of the conventional examples described above have the disadvantage that when cutting the through-hole or cutting a portion of the conductor on the side wall surface, a portion of the through-hole or the conductor peels off, resulting in so-called burrs. These drawbacks include the fact that as the thickness of the substrate increases, the through-holes are cut more frequently, causing noticeable peeling and burring of the plating, which has a significant negative impact on the yield of the product.

As an example of resolving these shortcomings,
According to Publication No. 648, "Tlt?iU of circuit board for watch"
According to the invention, a pair of small holes are formed at a certain interval on a watch circuit board, and a diameter is formed to cover at least a part of each of the small holes. The corner where the through hole to be cut and the punching line of the mold intersect, that is, the intersection It shows how to set the angles to appropriate values. As a result, the intersecting angle of the small holes provided on the left and right sides of the large hole is adjusted, which prevents the pattern, that is, the plating layer, from peeling off when punching the through hole (large hole). However, as printed wiring boards are becoming increasingly finer due to the recent demand for high-density packaging, the pattern spacing tends to become narrower. 3
Providing two holes is not suitable for miniaturization and high density, and is an undesirable method. In addition, uncut portions of the glass cloth and copper foil in the base material of the printed wiring board protrude from the overlapping portion of the large hole and the small hole in the shape of whiskers, and through-hole plating is also formed on these protruding whiskers, so through-hole plating is performed. There is a drawback that it requires an extra step of 4♀ to remove the beard that protrudes from the front.

The object of the present invention is to manufacture a printed wiring board having a conductive circuit formed on its outer peripheral side wall, and to solve the drawbacks of the prior art and provide an inexpensive and high-yield method.

The method for manufacturing a printed wiring board of the present invention will be explained in detail below based on the drawings. Fig. 3 is a perspective view showing a state in which a hole is made in the printed wiring board, and the hole (5) is a hole in the product. This hole is drilled so as to cover a part of the hole on the outer circumference, that is, on the solid line, and will become a conductor on the side wall surface of the board in the final product. In Fig. 3, (4) is a substrate for printed wiring, and examples of this substrate include glass epoxy resin substrates, paper phenol resin substrates, paper epoxy resin substrates, polyimide resin substrates, and triazine resin substrates. A conductive film such as copper foil may be laminated and adhered to one or both surfaces of the base material in advance.

Next, a catalyst for electroless plating is applied to the entire surface of the substrate having holes as described above, including at least the wall surfaces of the holes, by a generally known method.

Next, the substrate including a portion of the hole extending over the product outer peripheral portion of the substrate coated with a catalyst for electroless plating is cut and removed to expose the hole wall surface on the side wall surface of the outer shape of the substrate.

Figure 4 is a perspective view of the board with parts other than the product part removed along the outline. In this figure, (6) is a hole in which a catalyst for electroless plating is applied to the wall, and This shows a state in which the wall surface of the hole is exposed on the side wall surface. Fifth
The figure is a perspective view showing a state in which a part of the board has been removed in the form of a groove along the outline of the board. In this figure, the intended product part (9) is supported by the printed wiring board (7) at the outer periphery by the bridge part (10)K. As shown in Fig. 5, the planned product part (9) is supported by the printed wiring board (7) on the outer periphery by the bridge part (10), so that in the subsequent process, a large printed wiring board can be used. Since the substrate can be handled in this state, the workability is significantly simplified. Methods for removing the substrate around the hole include punching with a mold, cutting with a router/end mill, etc., and laser processing, but are not particularly limited. FIG. 6 is an enlarged perspective view of the vicinity of the hole in FIGS. 4 and 5, and the hole (6) is provided with a catalyst for electroless plating. However, since the catalyst is not applied to the side wall surface (11) of the outer shape between the holes, a metal layer is not deposited on the side wall surface (11) of the outer shape in the subsequent electroless plating process. First, the space between the holes remains electrically insulated. In the step of removing the substrate around the hole, the catalyst for electroless plating does not fall off the wall of the hole.Next, the substrate from which the area around the hole has been removed is immersed in an electroless plating solution. Metal is deposited on the substrate surface including the hole wall surface by electroless plating. The electroless plating is not particularly limited, but copper plating, nickel plating, etc. are preferable. Moreover, in order to further improve the reliability of the through holes, electroplating may be further applied.

Next, a photosensitive resin film is applied to the surface of the substrate after through-hole plating, and a negative pattern is formed by known means such as exposure and exposure. FIG. 7 is a perspective view showing a state in which a negative pattern has been formed. is the circuit pattern on the top surface (7) of the board. Furthermore, gold-14 plating different from the through-hole plating layer, such as solder and tin.

A metal layer is applied to the hole (13) and the circuit (14) in FIG. 7 by plating with gold or the like, and after forming a circuit including the hole, the photosensitive resin film is removed and the foreign metal is used as an etching resist. Etching is performed to form the desired conductive circuit.

Another method of forming a conductor on the side wall surface of the external shape is to drill holes in the printed wiring board, apply a catalyst for electroless plating, and apply a photosensitive resin film to the surface of the board to form a positive pattern. Form. In this case, the holes corresponding to the side conductor portions are completely covered with a photosensitive resin coating. FIG. 8 shows the cause of the cross section of the substrate in this state. In this figure (15
) is a photosensitive resin film, and (16) is a conductive film such as copper foil.

Next, a circuit pattern is formed by etching.

At this time, since the electroless plating catalyst on the wall surface of the hole is completely covered by the photosensitive resin film, the etching solution does not penetrate, and therefore, no etching occurs.

Next, a part of the substrate around the hole is removed to expose the hole wall surface ff to which the catalyst has been applied to the outer side wall surface, and then the substrate is immersed in an electroless plating solution, and the substrate including at least the hole wall surface is exposed. Metal is deposited on the surface by electroless plating to form a desired circuit pattern including conductor portions on the side surfaces of the substrate. As a method of further electroplating the board, as shown in FIG.
This lead wire is a circuit pattern (18) as a lead wire for shorting with the pattern of the product part.
By connecting with the lead lead wire (17)
Electroplating of the conductor parts on the side walls of all patterns and holes is possible through 'e. After electroplating, the shorting lead wire (18) is separated by etching, counterboring, etc., and the circuit patterns of the product are insulated.

FIG. 10 is an example of a perspective view of a printed wiring board in which a conductor is formed on the outer side wall surface by the manufacturing method of the present invention. In this figure, (20) is a conductor portion on the side surface.

As described above, according to the manufacturing method of the present invention, after applying a catalyst for electroless plating to the holes of a printed wiring board, a part of the holes is cut and removed, and then through-hole plating is performed, so that the side wall surface of the external shape is improved. This method eliminates the disadvantage of peeling and burring of the through-hole plating layer when cutting through-holes in conventional methods, and significantly improves the yield of printed wiring boards. I can do it.

[Brief explanation of drawings]

1 and 2 are perspective views of a conventional printed wiring board, FIGS. 3 to 7, and 10 are perspective views of a printed wiring board according to the present invention, and FIG. 8 is a longitudinal section of the same board. figure,
FIG. 9 is a plan view of the same substrate. (1)・・・・・・・・・ Printed wiring board (2)
......Side conductor part (3)...
...Notch (4) ...... Printed wiring board (5)
・・・・・・・・・・・・ Hole (6)・・・・・・・・・ Hole with electroless plating catalyst applied to the wall (7)・・・・・・・・・・・・Printed wiring board (8)...Groove section (9)...Product section (10)...
...Bridging part (11) ...... Side wall surface of external shape (insulating layer) (1
2)...Photosensitive resin coating (13)...
......Side conductor part (14)...Circuit pattern (15)...Photosensitive resin film (16)
)......Conductive film (19)......Circuit pattern on the board (
20) - ・・・・・・・・・・・・・・・・・・・・・・Patent applicant Jun Taga, representative of IBIDEN Co., Ltd.

Claims (1)

[Claims] 1o Drill a hole in a desired position of the printed wiring board, including a hole that partially covers the outer periphery of the product, and then apply electroless plating to at least the wall of the hole and the surface of the printed wiring board. After applying the catalyst, a part of the product outer periphery of the printed wiring board including the hole is removed to expose a part of the wall surface of the hole on the side wall surface of the outer shape of the printed wiring board, and then at least A printed wiring board characterized in that a conductor is selectively formed on the wall surface of a hole extending around the outer periphery of a printed wiring board by depositing electroless plating on the wall surface of the hole provided with a catalyst and on the surface of the printed wiring board. Production method.