JPH11340623A - Manufacture of flexible printed board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a flexible printed board by which a plating film does not overlap a metal film on the surface of a laminated board, front-rear conducting holes can be plated selectively, and plating liquid does not infiltrate into between the surface of the laminated board and a mask, by masking the surface of the laminated board having front-rear conducting holes with a film except on the front-rear conducting holes. SOLUTION: On a laminated board 3, having metal layers 1 on the both front and rear planes of an insulating layer, a front-rear conducting hole 4 that penetrates the metal layer 1 is formed, and a plating film is formed on the inner plane of the front-rear conducting hole 4 in a method for manufacturing a flexible printed board. The method includes a process of adhering a film on the surface of the laminated board 3 except on the front-rear conducting hole 4, a process of forming a plating film 6 by plating the front-rear conducting hole 4 of the laminated board 3, and a process of peeling the film from the surface of the laminated board 3 after plating and polishing the surface of the laminated board 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a flexible printed wiring board (hereinafter abbreviated as FPC) used for electric and electronic equipment, and more particularly to a method of manufacturing an FPC having plated front and back conduction holes. .

[0002]

2. Description of the Related Art FPCs are widely used in electronic devices such as portable terminals, cellular phones, small video devices, and small electronic cameras, as well as hard disks and CD-ROMs as storage media for computers. In order to reduce the size and weight of these electronic devices and to improve the functionality and reliability of storage media, higher performance FPCs are required.

An FPC having a hole for conduction from the front surface to the back surface is used. Conventional FPC
Will be described with reference to FIGS. 4A to 4D. That is, the laminated plate 3 having the metal layer 1 on both front and back surfaces of the insulating layer 2
Then, a front and back conduction hole 4 is opened, and plating for front and back conduction is performed on the laminate 3 to form plating films 6 and 11, thereby obtaining a laminated plate 3 having plated front and back conduction holes. Next, a circuit 8 is formed on the front and back surfaces of the obtained laminated board 3 by an etching method or the like to obtain an FPC 9.

The conventional method has the following problems.

[0005] (1) The metal layer formed on the surface of the obtained laminated plate 3 is formed by laminating the metal layer 1 of the laminated plate 3 of the starting material and the plating film 11, and each processing tolerance is added. Since the surface roughness is increased, the adhesiveness of the circuit forming resist film adhered to the surface of the obtained laminate 3 is deteriorated, and the circuit forming yield is reduced.

(2) Since the metal layer formed on the surface of the obtained laminate 3 is formed by superposing the metal layer 1 of the laminate 3 of the starting material and the plating film 11, the metal layer becomes thicker. Since the variation in thickness increases due to the processing tolerance, it is difficult to form a high-definition circuit.

(3) Since the metal layer formed on the surface of the obtained laminate 3 is formed by superposing the metal layer 1 of the laminate 3 of the starting material and the plating film 11, the thickness is increased. FPC9 has poor bending performance.

[0008] Another conventional method for manufacturing an FPC will be described with reference to FIGS. 5A to 5D. That is, a film 5 is partially adhered and masked on the surface of the laminate 3 of the above-described conventional manufacturing method in which the front and back conduction holes 4 are opened, and then the laminate 3 is plated for front and back conduction. The plating films 6 and 11 are formed, and then the mask film is peeled off. Next, the step 12 on the surface of the laminate 3 where the plating film is formed and the portion where the plating film is not formed is polished to obtain a laminate 3 having plated front and back conduction holes. Next, a circuit 8 is formed on the front and back surfaces of the obtained laminated board 3 by an etching method or the like to obtain an FPC 9.

According to this method, although the obtained laminate 3 has a thin portion in which the surface metal layer is composed of only the metal layer 1 of the laminate 3 of the starting material, the laminate 3 of the laminate having the surface metal of the starting material has a thin portion. It also has a thick portion where the metal layer 1 and the plating film 11 are layered, and since the thickness is partially different, the adhesion of the circuit-forming resist film adhered to the surface of the obtained laminate 3 is obtained. However, there is a problem that the circuit formation yield is deteriorated.

[0010] In the case of a general printed wiring board, as a method of manufacturing a printed wiring board having front and back conduction holes, when plating the front and back conduction holes, a plating film is also formed on the surface of the laminate of the starting material, In order to solve the problem that the metal layer on the surface of the laminate is a layer of the metal layer of the starting laminate and the plating film, use a scissors jig when plating the front and back conduction holes. A method has been proposed in which a surface other than the front and back conduction holes is masked and the front and back conduction holes are plated (JP-A-9-214134).

However, when the method disclosed in this publication is applied to a method of manufacturing an FPC, the adhesion between the scissors jig and the laminate of the starting material for the FPC is low, and therefore, when plating is performed on the laminate. Then, the plating solution is soaked between the scissors jig and the surface of the laminate to form a thin plating layer. For this reason, it becomes difficult to remove the scissors jig from the laminate after plating, and at the time of removal, the plating layer between the scissors jig and the laminate is peeled off, and burrs (convex portions) or burrs (concave portions) are generated. There is a disadvantage that the surface of the plate becomes rough.

[0012]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a method of manufacturing an FPC having front and back conduction holes. By attaching a film to the surface of the laminated board other than the front and back conduction holes and masking it, it is possible to selectively plating the front and back conduction holes without overlaying the plating film on the metal layer on the surface of the laminate. It is another object of the present invention to provide a method of manufacturing an FPC that can prevent a plating solution from permeating between a surface of a laminate and a mask.

[0013]

According to a first aspect of the present invention, there is provided a method of manufacturing an FPC, comprising forming a front and back conduction hole penetrating a metal layer in a laminate having a metal layer on both sides of an insulating layer. In the method of manufacturing a flexible printed wiring board in which a plating film is formed on the inner surface of the front and back conduction holes, a step of attaching a film to the surface of the laminate other than the front and back conduction holes, plating the front and back conduction holes of the laminate to form a plating film. Forming,
Further, after the plating, the method includes a step of peeling the film from the surface of the laminate and polishing the surface of the laminate, thereby achieving the above object.

One embodiment includes the step of applying electroless plating to the laminate before attaching the film to the laminate.

In one embodiment, the surface of the laminate is smooth to ensure that the circuit-forming resist film adheres tightly.

In one embodiment, no plating film adheres to the surface of the laminate.

The operation of the present invention is as follows.

According to the present invention, plating is performed in a state where a film is stuck and masked on the surface other than the front and back conduction holes of the laminated plate having the front and back conduction holes. The film and the surface of the laminate have good adhesion, and there is no gap between the film and the surface of the laminate, so that the plating solution does not soak. Further, a plating film can be selectively formed in the front and back conduction holes of the laminate, and the plating film does not overlap the metal layer on the surface of the laminate.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for manufacturing an FPC according to the present invention will be described with reference to the drawings.

FIGS. 1, 2 and 3 show an FP according to the present invention.
It is sectional drawing which shows the process of 1st and 2nd embodiment of the manufacturing method of C.

The first embodiment of the method of manufacturing an FPC according to the present invention is manufactured by steps shown in FIGS. 1A to 1D and FIGS. 2E to 2G.

As shown in FIG. 1A, a laminate 3 having a metal layer 1 on both sides of an insulating layer 2 is used. Examples of the metal layer 1 include copper, aluminum, brass, and nickel. Examples of the insulating layer 2 include a polyimide film and a polyester film. An adhesive may be used to bond the metal layer 1 and the insulating layer 2 together.

Next, as shown in FIG. 1B, front and back conduction holes 4 penetrating through the laminate 3 are formed. The front and back conduction holes 4 are usually formed by a drill or the like.

Next, as shown in FIG. 1C, a film 5 is stuck on the surface of the laminate 3 other than the front and back conduction holes, and masked. Examples of the film 5 for a mask include a dry film.

Next, as shown in FIG. 1D, plating for front-to-back conduction is performed to form a plating film 6. Examples of the plating method include electroless plating and electrolytic plating. Next, as shown in FIG. 2E, the film 5 for a mask is peeled off.

Since the adhesion between the mask film 5 and the surface of the laminate 3 is good, the plating solution does not seep between the mask film 5 and the laminate 3 to form a thin plating layer. Therefore, it is easy to peel off the mask film 5 from the surface of the laminate 3 after plating, and the surface of the laminate 3 does not become rough.

Next, as shown in FIG. 2F, a portion 13 protruding from the surface of the metal layer 1 of the laminate 3 is polished to obtain a laminate 3 having plated front and back conduction holes 3. The metal layer 1 of the laminated plate 3 should be 1 to 2 μ
It is more preferable to perform extra polishing.

Next, as shown in FIG. 2g, a circuit 8 is formed on the front and back surfaces of the laminate 3 to obtain an FPC 9. As a method of forming the circuit 8, for example, the following etching method can be mentioned, and a resist film is attached to the surface of the laminate 3;
A mask film is attached and exposed, developed, patterned on a resist film, and then etched to form a circuit.

Since the plating film is not formed on the surface of the laminate 3, no plating film is further formed on the metal layer 1 of the laminate 3, and the resulting metal layer on the surface of the laminate 3 is It consists only of the metal layer 1 of the laminate 3 of the material. For this reason, the surface of the obtained laminate 3 is flat, and the resist film for circuit formation adhered to the surface of the obtained laminate 3 surely adheres, and therefore, the circuit formation yield is excellent.
In addition, the metal layer on the surface of the obtained laminate 3 is thin and has a small variation in thickness, so that it is easy to form a high-definition circuit. Further, since the metal layer on the surface of the obtained laminate 3 is thin, the obtained FPC 9 has excellent bending performance.

The second embodiment of the method of manufacturing an FPC according to the present invention includes the steps of FIG.
h.

In the first embodiment described above, electroless plating is performed on the laminated plate 3 in which the front and back conduction holes 4 are opened, as shown in FIG. Then, as shown in FIGS. 1c, 1d, 2e-2g,
The process is performed in the same manner as the process of the first embodiment. By applying the electroless plating, the adhesion of the entire plating film including the subsequently applied plating to the laminate 3 can be increased.

[0032]

The present invention will be described in more detail with reference to the following examples.

(Embodiment 1) FIGS. 1a to 1d and 2e
2g.

Using a laminate 3 having a copper metal layer 1 (18 μm) on both front and back sides of an insulating layer 2 of a polyimide film,
The front and back conduction holes 4 penetrating the laminated plate 3 were formed by drilling. Next, the film 5 was stuck on the surface of the laminated plate 3 other than the front and back conduction holes to mask, and then electrolytic plating of copper for front and back conduction was performed to form a plating film 6. Next, the mask film 5 was peeled off. Peeling of the mask film 5 was easy. Further, plating was provided only on the front and back conduction holes and the periphery thereof, and no plating was provided on the surface 7 of the masked laminate 3. Then
A portion 13 of the laminated plate 3 protruding from the surface of the copper metal layer 1 is polished, and the laminated plate 3 having plated front and back conduction holes is provided.
I got The thickness of the copper metal layer portion of the obtained laminate 3 was 18 μm, which was the same as that of the laminate 3 of the starting material.

With respect to the obtained laminated board 3, a circuit 8 was formed on the front and back surfaces thereof by an etching method to obtain an FPC 9. The circuit interval of the obtained FPC 9 could be 50 μm. When the bending performance was evaluated by the IPC method (bending radius: 5 mm, stroke: 40 mm), no increase in resistance was observed even after 20 million times.

(Comparative Example 1) A description will be given with reference to FIGS. 4A to 4D.

In the first embodiment, the laminated plate 3 having the front and back conductive holes 4 formed therein is not provided with a mask for attaching a film.
Electroplating of copper was performed for front-to-back conduction, plating films 6 and 11 were formed, and a laminated board 3 having plated front-back conduction holes was obtained. The thickness of the copper metal layer of the obtained laminate 3 was 33 μm (18 μm of copper metal layer of the laminate 3 as a starting material + 15 μm of copper plating film). Next, a circuit 8 is formed on both the front and back surfaces of the obtained laminate 3 by an etching method,
PC9 was obtained. The circuit interval of the obtained FPC 9 was 100 μm. When the bending performance was evaluated in the same manner as in Example 1, an increase in resistance was observed at 1.5 million times.

(Comparative Example 2) This will be described with reference to FIGS. 5A to 5D.

In the first embodiment, a polyimide film 5 is partially adhered to the surface of the laminated plate 3 in which the front and back conduction holes 4 are opened and masked, and then, electrolytic plating of copper is performed for front and back conduction. Plating films 6 and 11 were formed.
Next, the mask film was peeled off. Next, the step 12 between the plated portion and the non-plated portion on the surface of the laminate was smoothed by polishing to obtain a laminate 3 having plated front and back conduction holes. About the obtained laminate,
A circuit 8 is formed on the front and back surfaces by an etching method to form an FPC 9
I got Although the obtained laminate 3 has a portion where the thickness of the copper metal layer is thin, the thickness is partially different, so that the adhesion of the circuit-forming resist film adhered to the surface of the obtained laminate 3 is obtained. Poor performance and inferior circuit formation yield.

[0040]

According to the method of manufacturing an FPC of the present invention, when plating the front and back conduction holes of the laminate of the starting material, a film is attached to the surface of the laminate other than the front and back conduction holes and masked. The film and the surface of the laminate have good adhesion, and there is no gap between the film and the surface of the laminate, so that the plating solution does not soak. Further, since the plating film is not overlaid on the metal layer on the surface of the laminate, the resulting laminate has a smooth surface, a thin metal layer on the surface, and little variation in thickness. For this reason, this laminated board has high adhesion of the circuit-forming resist film adhered to the surface of the laminated board, improves the yield of circuit formation, and facilitates the formation of a high-definition circuit. The resulting FPC has excellent bending performance.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing steps of a method for manufacturing an FPC of the present invention.

FIG. 2 is a cross-sectional view showing steps of a method for manufacturing an FPC of the present invention.

FIG. 3 is a cross-sectional view showing steps of a method for manufacturing an FPC of the present invention.

FIG. 4 is a cross-sectional view showing steps of a conventional method for manufacturing an FPC.

FIG. 5 is a cross-sectional view showing steps of a conventional method for manufacturing an FPC.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Metal layer 2 Insulating layer 3 Laminate board 4 Front and back conduction hole 5 Film for mask 6 Plating film 7 Surface 8 Circuit 9 FPC 10 Electroless plating film 11 Plating film 12 Step 13 Projection

Claims (4)

[Claims] 1. A method of manufacturing a flexible printed wiring board, comprising: forming a front and back conduction hole penetrating a metal layer in a laminate having a metal layer on both front and back surfaces of an insulating layer; and forming a plating film on the inner surface of the front and back conduction hole. In, the step of attaching a film to the surface of the laminate other than the front and back conduction holes, the step of plating the front and back conduction holes of the laminate to form a plating film, and
A method of manufacturing a flexible printed wiring board, comprising a step of peeling a film from a surface of a laminate after the plating and polishing the surface of the laminate. 2. The method for manufacturing a flexible printed wiring board according to claim 1, further comprising a step of subjecting the laminate to electroless plating before attaching the film to the laminate. 3. The method for manufacturing a flexible printed circuit board according to claim 1, wherein the surface of the laminate is smooth so that the circuit-forming resist film is securely adhered. 4. The method for manufacturing a flexible printed wiring board according to claim 1, wherein said plating film is not adhered to the surface of said laminated board.