JPH11121900A - Production of circuit board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure highly accurate machining while shortening the machining time by employing a both-sided FPC plate and drilling an insulation layer using a bored copper foil on one side as a mask. SOLUTION: A copper foil layer is formed on the opposite sides of a polyimide film to produce a both-sided board. An opening 4 is then made in the lower copper foil 1" of the both-sided FPC board at a part of a PI film 2 corresponding to a through hole. The PI film 2 is then subjected to laser machining using the copper foil on one side having the bored copper face as a mask thus forming a bored PI film. When the machined board is immersed into an electrodeposition resist tank, electrodeposition resist adheres only to the upper front copper foil 1'. The rear part 1" of copper foil can also be coated and upper and lower resist coated parts 5, 5' are formed. The copper foil mask layer on one side is removed while leaving the upper copper foil 1' and a conductor circuit is formed simultaneously on the upper copper foil 1'.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a method for forming small holes for electrical connection on a single-sided printed circuit board, particularly a single-sided FPC board. More specifically, the present invention relates to an improvement in a method for forming small holes for electrical connection in a single-sided FPC circuit board in which a hole is formed in an insulating layer using a double-sided FPC board and a perforated single-sided copper foil as a mask. .

[0002]

2. Description of the Related Art Conventionally, miniaturization of small holes (through holes) for electrical connection of a multilayer printed circuit board is essential for realizing high-density wiring. However, for that,
At present, holes are formed one by one by laser processing from the insulating substrate side of a single-sided FPC circuit board. FIGS. 2A and 2B are schematic diagrams illustrating a method of forming through holes by laser drilling on a single-sided FPC board according to a conventional method. FIG. 2A is a schematic diagram illustrating a circuit forming process thereof, and FIG. It is a circuit side plan view, (c)
FIG. 4 is a plan view of a PI film side. In FIG. 2, 1 is a copper foil, 2 is an insulating film, especially a PI (polyimide) film, 3 is a copper foil circuit, and 4 is an opening (hole).

[0003] That is, as shown in FIG.
A single-sided FPC board having a copper foil 1 provided on one side of a film 2 is prepared. Then, one to four holes are laser-processed one by one from the PI film side by a carbon dioxide gas galvano laser machine, and finally the copper foil side. Is usually formed by removing a portion of the copper foil other than a predetermined portion by etching or the like to form a copper circuit composed of a conductor pattern. However, according to this method, it is necessary to drill holes one by one with a laser machine, which requires extra time, increases the cost of laser processing, and makes it necessary to drill holes individually. There was a problem that it was difficult to form a hole.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to improve a method for manufacturing a single-sided FPC board with small holes for electrical connection in a short time and with high precision by using a double-sided FPC board as a starting board and making a hole. About.

[0005]

As a result of various studies on the above-mentioned problems, the present inventor has found that when manufacturing a single-sided FPC board with small holes for electrical connection by drilling, a double-sided FPC board is used to form a perforated single-sided copper foil. It has been found that by performing perforation processing on an insulating layer as a mask, processing time can be reduced and high-precision processing can be performed, and the present invention has been completed.

That is, the present invention provides a method of manufacturing a circuit board having a conductor pattern on one side, an insulating layer on one side, and a hole for electrical connection in the insulating layer of the conductor pattern portion. At the time of drilling, a metal mask layer having the same hole as the hole of the insulating layer is formed in advance on the drilling surface of the insulating layer on the opposite side of the conductor pattern, and etching is performed after drilling the insulating layer. The present invention provides a method for manufacturing a circuit board, which removes a metal mask layer by using the method described above. Another feature is that removing the metal mask layer includes a step of protecting both the circuit surface and the circuit back surface exposed by the holes in the insulating layer on the opposite surface of the circuit with a resist. Another feature is that the resist is an electrodeposition resist. Another feature is that the circuit board is a flexible printed circuit board.

Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic diagram illustrating a method for forming small holes (through holes) for electrical connection by perforation processing using a double-sided FPC board according to the present invention. In FIG. 1, 1 is a copper foil, 1 ′ is an upper copper foil, 1 ″ is a lower copper foil, 2 is a PI film, 3 is a copper foil circuit, 4 is an opening, 5 is an upper resist coating, and 5 ′ is This is the lower resist coating section.

In FIG. 1, (a) In a double-sided FPC board, a perforated portion 4 corresponding to a portion to be a perforated portion of the PI film 2 corresponding to a predetermined small hole for electrical connection is formed on the lower side by etching or the like. A perforated copper surface is formed on the copper foil 1 ". (B) Using the one-sided copper foil as a mask, a perforation process is performed on the PI film 2 by laser processing or the like to form a PI perforated film. (C) Next, the processed substrate is immersed in an electrodeposition resist bath, and power is supplied only to the upper copper foil 1 ′, and is not supplied to the copper foil back surface 1 ″. When the resist is applied to the entire surface, the electrodeposited resist is applied only to the entire surface of the upper copper foil 1 ′, and can also be applied to the copper foil back surface portion 1 ″ exposed by the hole of the insulating layer on the opposite surface. Form resist application section 5, lower resist application section 5 ' . Leaving the (d) the upper copper foil 1 to be formed a conductor pattern '
The single-sided copper foil mask layer is removed by etching or the like. Thereafter, a conductor circuit is formed on the upper copper foil 1 '(not shown) by appropriate means such as etching to form a single-sided FP.
A C substrate was produced. Also, the steps (c) and (d) and the formation of the conductor circuit can be performed simultaneously.

The printed circuit board used in the present invention is typically a polyimide board, but is not limited thereto. For example, a usual epoxy resin or polyamide-impregnated glass fiber board can be used. In addition, the method of the present invention is particularly suitable for F
It is preferably applied to a PC board. The use of a carbon dioxide laser is important for the processing speed,
It is desirable from the viewpoint of the finished hole formation, but is not limited thereto, and a YAG laser, an excimer laser, a gas phase etching, a chemical etching, or the like can be used. The resist is not limited to the electrodeposition resist, and application of a photosensitive resin (film), application of a liquid resist, or spraying can also be used. The insulating film is not particularly limited. For example, a polyimide film is typical, and other polyester films and the like can also be used.

[0010]

EXAMPLES The present invention will be specifically described with reference to examples, but these do not limit the scope of the present invention. Example 1 An 18 μm copper foil layer is formed on both sides of a 50 μm thick polyimide film by a casting method, and a double-sided board is manufactured in advance. According to FIG. 1- (a), an opening (hole) (300 μm diameter) 4 corresponding to a portion to be a perforated portion of the PI film 2 corresponding to a predetermined through hole is etched by etching the lower copper on the double-sided FPC board. Foil 1 "is formed to form a perforated copper surface. According to Fig. 1- (b), using a single-sided copper foil having a perforated copper surface as a mask, scanning is performed on PI film 2 using a laser processing machine manufactured by Sumitomo Heavy Industries. Method (while continuously irradiating the laser beam to the substrate processing surface,
Laser processing is performed with an energy equivalent to 5 shots by a method of scanning a processing area) to form a PI perforated film. In that case, it took only 15 minutes to process 30,000 holes. In this case, laser processing could be performed with a high precision of a hole size of 300 μm, a positional accuracy of ± 20 μm, and a size accuracy of ± 20 μm.

According to FIG. 1- (c), the processed substrate is immersed in an electrodeposition resist bath, and
When the resist is deposited by electrodeposition for 5 seconds, power is supplied to the upper copper foil 1 'and not to the rear surface of the copper foil, so that the electrodeposition resist is applied only to the entire surface of the upper copper foil 1', and the insulating layer on the opposite surface is applied. Can be applied also to the copper foil back surface portion 1 "exposed by the holes, thereby forming an upper resist coating portion 5 and a lower resist coating portion 5 ', respectively. A conductor pattern is to be formed according to FIG. The one-sided copper foil mask layer was removed by etching or the like while leaving the upper-side copper foil 1 ', and at the same time, a predetermined conductor circuit was formed on the upper-side copper foil 1' by etching to produce a one-sided FPC board.

Comparative Example 1 According to the method shown in FIG.
5 shots with a galvanic carbon dioxide laser processing machine
Laser drilling was performed under the hole conditions to produce a single-sided FPC board. In that case, it took 30 minutes to process 30,000 holes.

[0013]

As described above, according to the present invention, when manufacturing a single-sided FPC board having small holes (through holes) for electrical connection,
Using a double-sided FPC board as a starting material and drilling holes in the insulating layer using a single-sided copper foil that has the same holes as the holes in the insulating layer in advance as a mask, processing time can be reduced and high-precision processing is possible. The following effect can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic view illustrating a method for forming small holes (through holes) for electrical connection by perforating using a double-sided FPC board using a laser or the like according to the present invention.

FIG. 2 is a schematic view for explaining a method for forming a small hole (through hole) for electrical connection on a single-sided FPC board by laser drilling according to a conventional method, and FIG. It is a schematic diagram, (b) is the circuit side plan view, (c) is the PI film side plan view.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Copper foil 1 'Upper copper foil 1 "Lower copper foil 3 Copper foil circuit 4 Opening (hole) 5 Upper resist application part 5' Lower resist application part

Claims (4)

[Claims] 1. A method of manufacturing a circuit board having a conductor pattern on one side and an insulating layer on one side and a hole for electrical connection in the insulating layer of the conductor pattern portion, A metal mask layer having the same hole as the hole of the insulating layer is formed in advance on the hole-formed surface of the insulating layer on the opposite side of the conductor pattern, and a metal mask is formed by etching or the like after the hole is formed in the insulating layer. A method for manufacturing a circuit board, comprising removing a layer. 2. The method according to claim 1, wherein removing the metal mask layer includes a step of protecting both the circuit surface and the circuit back surface exposed by the holes in the insulating layer on the opposite surface of the circuit with a resist. Item 2. The method for manufacturing a circuit board according to Item 1. 3. The method according to claim 2, wherein the resist is an electrodeposition resist. 4. The method for manufacturing a circuit board according to claim 1, wherein the circuit board is a flexible printed circuit board.