JPH1117331A - Manufacture of flexible circuit board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form bumps to be connected to circuit parts with high accuracy without using any plated lead, etc., by forming the bumps before forming a circuit pattern. SOLUTION: After a material having a flexible insulating base material 2 is prepared on one surface of conductive foil 1, openings 3 are formed through the base material 2 and a mask layer 4 is formed on the external surface of the foil 1. Then bumps 5 are formed in the openings 3 and metallic layers having high corrosion resistances are formed on the surfaces of the bumps 5. After the formation of the metallic layers, the mask layer 4 is removed and resist layers 4A and 4B which are used for the formation of circuit patterns 1A and 1B are formed. When the resist layers 4A and 4B are removed thereafter, the circuit patterns 1A and 1B can be formed in connection with the bumps 5. Then surface protective layers 6 can be formed by laminating cover films, etc., upon the outsides of the patterns 1A and 1B. When the cover films, etc., are laminated, pads 7 can also be formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a flexible circuit board, and more particularly to a method for forming a bump for connecting to a circuit component such as an IC chip without using a plating lead or the like. The present invention relates to a method for manufacturing a flexible circuit board.

[0002]

2. Description of the Related Art In order to manufacture a flexible circuit board with bumps of this type, conventionally, a desired circuit wiring pattern is first formed, and then surface protection for protecting the circuit wiring pattern is performed. The layers are laminated, and then, for example, an opening for forming a bump is formed on the surface protective layer side, and another opening for a connection land is formed on the other side of the insulating base material side. The method may be adopted.

In such a method, in order to form a bump by electrolytic plating, a mask is applied to a side other than the surface on which the bump is to be formed, then a bump is formed in the opening by plating means, and the mask is removed. Then, in a state where a mask is provided on the bump side, required plating is applied to the land portion exposed to the opening, and finally, the mask on the bump side is removed to obtain a product.

[0004]

In the above-mentioned method, it is necessary to repeatedly attach and remove a mask for electrolytic plating, which complicates the process and increases the manufacturing cost. Also, when the number of bumps increases and the pitch of the bumps becomes narrower, it is difficult to draw out plating leads, which limits the circuit design, or the plating leads cannot be drawn out, making production impossible. There was also.

[0005] When the number of bumps increases and the pitch of the bumps becomes narrow, the conductor width and the number of plating leads are limited, and a distribution of plating current is generated, resulting in a uniform distribution of bumps. There is a problem that the growth of the plating is hindered.

Accordingly, the present invention provides a method of manufacturing a flexible circuit board capable of forming bumps for connecting to circuit components such as IC chips with high precision without using plating leads or the like. .

[0007]

Therefore, in the method of manufacturing a flexible circuit board according to the present invention, a bump is formed on a predetermined portion of a flexible insulating base material provided on one surface of a conductive foil. After forming an appropriate number of openings, forming a mask layer on the other surface of the conductive foil, and then forming a bump in the opening by electrolytic plating means, forming a highly corrosion-resistant metal layer on the surface of the bump. Thereafter, a required circuit wiring pattern is formed on the conductive foil in relation to the bump.

Here, the metal layer having high corrosion resistance can be formed by electrolytic plating means or electroless plating means, and a required surface is provided on the surface of the circuit wiring pattern opposite to the side where the bumps are formed. Necessary connection lands or pads can be formed while forming the surface protective layer.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be further described below with reference to the drawings. 1 (1) to 1 (7) are manufacturing process diagrams of a flexible circuit board according to the present invention. First, as shown in FIG. 1 (1), for example, using a flexible single-sided copper-clad board or the like. A material having a flexible insulating base material 2 on one side of a conductive foil 1 such as a copper foil is prepared.

Therefore, as shown in FIG. 1B, an opening 3 for forming a bump at a predetermined diameter and a predetermined pitch is formed at a predetermined position of the flexible insulating base material 2 by means of a laser or the like. Several pieces are formed, and a mask layer 4 is uniformly formed on the outer surface of the conductive foil 1.

Next, as shown in FIG. 1C, the bumps 5 are formed by plating the openings 3 by electrolytic plating means. By such means, the diameter of the bumps 5 can be formed to 100 μm or less, and their pitch can be formed to 150 μm or less.

Next, on the surface of such a bump 5,
Using electrolytic plating means or electroless plating means, gold,
A highly corrosion-resistant metal layer such as platinum, tungsten, titanium, solder or rhodium is formed.

Therefore, as shown in FIG. 4 (4), the mask layer 4 is removed, and then a dry film material is subjected to exposure and development processing to form a resist for forming a desired circuit wiring pattern. The layers 4A and 4B are formed.

Next, by performing an etching process and removing unnecessary resist layers 4A and 4B, desired circuit wiring patterns 1A and 1A in relation to each bump 5 as shown in FIG. 1B can be formed.

Then, as shown in FIG. 6 (6), a surface protective layer 6 is formed by laminating a cover film or the like in a desired shape at a predetermined location on the outer surfaces of the circuit wiring patterns 1A and 1B. In this case, connection lands or pads 7 obtained by exposing predetermined portions of the circuit wiring patterns 1A and 1B can be formed.

As shown in FIG. 7 (7), electroless plating layers 8 and 9 for terminal surface treatment using a material such as gold are formed on the portions of the bumps 5 and the connection lands or pads 7 as shown in FIG. Of course, it is also possible.

[0017]

According to the method of manufacturing a flexible circuit board according to the present invention, before forming circuit wiring patterns, bumps can be formed by electrolytic plating means, so that plating leads are unnecessary as in the prior art. In addition, it is possible to solve the problem of lead out of the plating lead and the problem of the distribution of the plating current, etc., and to provide a highly accurate, fine and high-density flexible circuit board with bumps.

In addition, the degree of freedom in designing circuit wiring patterns is increased, the uniformity of plating for forming bumps can be improved, and the conventional mask bonding and removal processes can be performed. By reducing the number of man-hours due to the drastic reduction, the occurrence of defects can be reduced and the manufacturing cost can be reduced.

[Brief description of the drawings]

FIGS. 1 (1) to 1 (7) are manufacturing process diagrams of a flexible circuit board according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Conductive foil 1A, 1B Circuit wiring pattern 2 Flexible insulating base material 3 Opening 4 Mask layer 4A, 4B Resist layer 5 Bump 6 Surface protection layer 7 Land or pad for connection

Claims (4)

[Claims] An appropriate number of openings for forming bumps are formed in predetermined places of a flexible insulating base material provided on one surface of a conductive foil, and a mask layer is formed on the other surface of the conductive foil. Forming
Then, after forming a bump in the opening by electrolytic plating means, to form a highly corrosion-resistant metal layer on the surface of the bump,
Thereafter, a required circuit wiring pattern is formed on the conductive foil in relation to the bumps. 2. The method for manufacturing a flexible circuit board according to claim 1, wherein said metal layer having high corrosion resistance is formed by electrolytic plating means. 3. The method for manufacturing a flexible circuit board according to claim 1, wherein said metal layer having high corrosion resistance is formed by electroless plating means. 4. A flexible connection land or pad according to claim 1, wherein a required connection land or pad is formed while a required surface protection layer is formed on the surface of said circuit wiring pattern opposite to the side where said bump is formed. Manufacturing method of circuit board.