JPH05299819A - Flexible circuit board - Google Patents

Abstract

PURPOSE: To provide a flexible circuit board having a metallic thin-film layer on one or each side of a polyimide film with adhesion between this film and metallic thin-film layer. CONSTITUTION: This flexible circuit board comprises a polyimide film, a first metallic thin film on one or each side of the polyimide film, and a second metallic thin film formed on this first metallic thin film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flexible circuit board having a metal thin film layer on one or both sides of a polyimide film, and more particularly to a flexible circuit board having good adhesion between the metal thin film layer and the polyimide film. Regarding

[0002]

2. Description of the Related Art As a flexible circuit board in which a metal layer is formed on an insulating polymer film, there is conventionally a flexible circuit board in which a metal thin film and a polymer film are bonded with an adhesive. However, in these flexible circuit boards, the thermal performance of the adhesive is inferior to that of the polymer film, and it is difficult to perform fine processing with a width of several 10 μm because the thickness of the metal thin film is as thick as 10 μm or more. Therefore, there are problems such as not being able to cope with high-density wiring in the semiconductor industry, poor dimensional stability, and rising of products.

In order to solve the above problems, techniques for forming a metal thin film on a polymer film without using an adhesive have been studied. Examples thereof include thin film forming methods such as vacuum deposition and sputtering. Since the metal thin film obtained here has a thin film thickness of 1 μm or less, it is easy to form a circuit pattern by fine processing with a width of several 10 μm. A finely processed conductive layer can be formed by further depositing and growing a metal on the formed circuit pattern by electrolytic plating or the like.

However, in the flexible circuit board obtained by such a technique, a metal is laminated on the circuit pattern forming step using the lithography technique and on the formed circuit pattern for the purpose of lowering conduction resistance and improving mechanical strength. In the electroplating process, etc., there is a problem that the metal layer peels off from the polymer film, and there is a problem that the adhesive force between the metal layer and the polymer film is lowered.

Various prior art techniques are known which aim to improve the adhesion between the metal layer and the polymer film. That is, in JP-A-02-98994, a chromium layer of 0.01 to 5 μm is formed by sputtering, and in JP-A-62-181488, 50-1.
0000 angstrom nickel or nickel-
Forming a chromium layer by vapor deposition, JP-A-62-6255
No. 1 discloses that a chromium layer is formed by vapor deposition.
2-47908 discloses forming a nickel layer by vapor deposition, JP-A-61-128593 discloses forming a metal layer by vapor deposition, and JP-B-57-18357 discloses nickel, cobalt, zirconium or Forming a palladium layer by an ion plating method, Japanese Patent Publication Sho 57
JP-A-18356 has already disclosed that nickel and nickel alloy layers are formed by an ion plating method.

However, it has been difficult to provide a material sufficiently satisfactory for enabling high-density wiring in the semiconductor industry by using any of these known techniques.

[0007]

SUMMARY OF THE INVENTION The present invention is to solve the above-mentioned conventional problems, and the object thereof is to:
It is to provide a flexible circuit board in which a metal layer is formed on a polyimide film without an adhesive in order to enable high-density wiring in the semiconductor industry, and particularly in a post-process such as circuit pattern formation and electrolytic plating. It is an object of the present invention to provide a flexible circuit board which overcomes the problem of layers peeling from a polyimide film.

[0008]

Means for Solving the Problems In the production of a flexible circuit board composed of a copper layer / polyimide film, the inventors have formed a nickel-copper alloy ultra-thin film on the polyimide film and then formed the ultra-thin film on the ultra-thin film. The present invention was found to be extremely effective in preventing peeling of the copper layer from the polyimide film in a subsequent step such as circuit pattern formation and electrolytic plating by forming a copper thin film having good electrical conductivity, and the present invention Has been completed.

That is, one embodiment of the present invention is a flexible circuit board composed of a copper layer / polyimide film formed by laminating a first metal thin film and a second metal thin film in this order on one surface of a polyimide film. Another aspect of the present invention is a flexible circuit board comprising a copper layer / polyimide film / copper layer formed by laminating a first metal thin film and a second metal thin film on both sides of a polyimide film in this order. is there. Here, the copper layer is a generic term for a metal thin film layer formed by laminating a first metal thin film and a second metal thin film in this order.

The first metal thin film is a copper-nickel alloy, preferably 40 to 80% by weight of nickel and 20 to 6 of copper.
It is formed by sputtering with a copper-nickel alloy containing 0% by weight as a target so as to have a film thickness of 50 to 500 angstrom. A copper-nickel alloy called monel metal is particularly effective as the target.

The second metal thin film has a film thickness of 100 by sputtering targeting highly electrically conductive copper.
It is formed to have a thickness of 0 to 42,000 angstroms.

The sputtering method is not particularly limited. Thin film forming techniques such as DC magnetron sputtering, high frequency magnetron sputtering, and ion beam sputtering are effectively used by using targets corresponding to the first metal thin film and the second metal thin film, respectively.

The thickness of the polyimide film is typically 10 to 500 μm, particularly preferably 25 to 125 μm, and commercially available polyimide films such as Kapton, Upilex and Apical are effectively used.

[0014]

Example 1 A Kapton-V film (manufactured by DuPont) having a film thickness of 50.8 μm was used as a polyimide film, and an average film thickness of about 70 angstrom was obtained by sputtering using Monel metal as a target material on one surface of the film. After forming the first metal thin film, the second metal having an average film thickness of about 2,500 Å is continuously sputtered on the first metal thin film without breaking the vacuum state. The thin films were laminated. This flexible circuit board having the above-mentioned metal layer on one surface of the polyimide film is one embodiment of the present invention.

A circuit pattern having a pitch of 80 μm and a width of 60 μm is formed on the metal layer by photolithography, and a thickness of 25 μ is formed on the circuit pattern by electrolytic plating.
m copper was deposited. In the above-mentioned circuit pattern formation and electroplating process, the flexible circuit board did not suffer from problems such as peeling and side etching, which have occurred in conventional techniques.

Example 2 A Kapton-E (manufactured by DuPont) having a film thickness of 25.4 μm was used as a polyimide film, and one surface of the polyimide film having an average film thickness of about 50 Å was sputtered by using a target material of monel metal. After the first metal thin film is formed, the second metal thin film having an average film thickness of about 6000 angstroms is continuously sputtered on the first metal thin film without breaking the vacuum state. Were laminated. This flexible circuit board having the above-mentioned metal layer on one surface of the polyimide film is one embodiment of the present invention.

A circuit pattern having a pitch of 100 μm and a width of 80 μm is formed on the metal layer by photolithography, and a thickness of 25 μ is formed on the circuit pattern by electrolytic plating.
m copper was deposited. In this case as well, problems such as peeling and side etching, which have occurred in the conventional technique, did not occur.

Example 3 Kapton-E (manufactured by DuPont) having a film thickness of 76.2 μm was used as a polyimide film, and one side of the polyimide film having an average film thickness of about 500 Å was sputtered by using a target material of monel metal. After forming one metal thin film, continuously without breaking the vacuum state,
A second metal thin film having an average film thickness of about 2500 angstrom was laminated on the first metal thin film by sputtering using copper as a target material. Under the same conditions, a first metal thin film having an average film thickness of about 500 Å and a second metal thin film having an average film thickness of about 2500 Å were laminated on the other surface of the polyimide film. This flexible circuit board having a metal layer as described above on both sides of a polyimide film is one embodiment of the present invention.

A 60 μm pitch and 60 μm were formed on the metal layers on both sides of the polyimide film by photolithography.
Each circuit pattern having a width was formed, and copper having a thickness of 25 μm was deposited on the circuit patterns on both sides by electrolytic plating. In this case as well, problems such as peeling and side etching, which have occurred in the conventional technique, did not occur.

Comparative Example 1 A Kapton-V film (manufactured by DuPont) having a film thickness of 50.8 μm was used as a polyimide film, and nickel having an average film thickness of about 70 angstrom was sputtered on one surface of the film by using nickel as a target material. After the layer is formed, the average film thickness is about 250 by sputtering on the nickel thin film continuously without breaking the vacuum state.
A 0 angstrom copper thin film was laminated. This flexible circuit board having the above-mentioned metal layer on one surface of the polyimide film is one comparative example of the present invention.

A circuit pattern having a pitch of 80 μm and a width of 60 μm is formed on the metal layer by photolithography,
Copper having a thickness of 25 μm was deposited on the circuit pattern by electrolytic plating. In the circuit pattern formation and the electroplating process described above, problems such as peeling and side etching, which have occurred in the related art, occur, and it is impossible to form a fine circuit on the flexible circuit board.

Comparative Example 2 As a polyimide film, Kapton-E (manufactured by DuPont) having a film thickness of 25.4 μm was used, and a copper thin film having an average film thickness of about 6000 angstrom was laminated on one surface thereof by sputtering. This flexible circuit board having a copper thin film on one surface of a polyimide film is one comparative example of the present invention.

A circuit pattern having a pitch of 100 μm and a width of 80 μm is formed on the metal layer by photolithography, and a thickness of 25 μ is formed on the circuit pattern by electrolytic plating.
m copper was deposited. In the circuit pattern formation and the electroplating process described above, problems such as peeling and side etching, which have occurred in the related art, occur, and it is impossible to form a fine circuit on the flexible circuit board.

Comparative Example 3 A Kapton-E film (manufactured by DuPont) having a film thickness of 76.2 μm was used as a polyimide film, and nickel having an average film thickness of about 500 Å was sputtered on one surface of the film by sputtering using nickel as a target material. After the layer is formed, the average film thickness is about 25 by sputtering on the nickel thin film continuously without breaking the vacuum state.
A copper thin film of 00 angstrom was laminated. Under the same conditions, a nickel layer having an average film thickness of about 500 Å and a copper thin film having an average film thickness of about 2500 Å were laminated on the other surface of the polyimide film. This flexible circuit board having the above-mentioned metal layers on both sides of the polyimide film is one comparative example of the present invention.

60 μm pitch, 60 μm by photolithography on the metal layers on both sides of the polyimide film
Each circuit pattern having a width was formed, and copper having a thickness of 25 μm was deposited on the circuit patterns on both sides by electrolytic plating. In the circuit pattern formation and electroplating process described above, problems such as peeling and side etching, which have occurred in the related art, still occur, and it is not possible to form a fine circuit.

[0026]

As is apparent from the above examples and comparative examples, the present invention can provide a flexible circuit board which enables miniaturization of a circuit required for high-density wiring in the semiconductor industry. It is an extremely useful invention for industry.

Claims (19)

[Claims] 1. A flexible circuit board having a polyimide film, a first metal thin film formed on one surface of the polyimide film, and a second metal thin film formed on the first metal thin film. 2. The flexible circuit board according to claim 1, wherein the first metal thin film is a copper-nickel alloy. 3. The flexible circuit according to claim 2, wherein the first metal thin film is a thin film formed by sputtering a copper-nickel alloy containing at least 40 to 80% by weight of nickel and 20 to 60% by weight of copper as a target. substrate. 4. The flexible circuit board according to claim 2, wherein the copper-nickel alloy is Monel metal. 5. The second metal thin film is copper.
Flexible circuit board according to. 6. The film thickness of the first metal thin film is 50 to 50.
The flexible circuit board according to claim 1, which has a thickness of 0 angstrom. 7. The film thickness of the second metal thin film is from 1000 to 1000.
The flexible circuit board according to claim 1, which has a thickness of 42000 angstroms. 8. The thickness of the polyimide film is 25 to
The flexible circuit board according to claim 1, which has a thickness of 125 μm. 9. A flexible circuit board having a polyimide film, a first metal thin film formed on both surfaces of the polyimide film, and a second metal thin film formed on both surfaces of the first metal thin film. 10. The flexible circuit board according to claim 9, wherein the first metal thin film is a copper-nickel alloy. 11. The flexible circuit according to claim 10, wherein the first metal thin film is a thin film formed by sputtering a copper-nickel alloy containing at least 40 to 80% by weight of nickel and 20 to 60% by weight of copper as a target. substrate. 12. The flexible circuit board according to claim 10, wherein the copper-nickel alloy is Monel metal. 13. The flexible circuit board according to claim 9, wherein the second metal thin film is copper. 14. The film thickness of the first metal thin film is 50-5.
The flexible circuit board according to claim 9, which has a thickness of 00 Å. 15. The film thickness of the second metal thin film is 1000.
The flexible circuit board according to claim 9, wherein the flexible circuit board has a thickness of about 42,000 angstroms. 16. The film thickness of the polyimide film is 25.
The flexible circuit board according to claim 9, which has a thickness of ˜125 μm. 17. The flexible circuit board according to claim 1, wherein the polyimide film is Kapton (registered trademark), Upilex (registered trademark) or Apical (registered trademark). 18. A first metal thin film having a thickness of 50 to 500 angstroms is formed by sputtering by contacting one side of a polyimide film having a thickness of 25 to 125 μm with a target of Monel metal, and sputtering the first metal. A flexible circuit board in which a second metal thin film having a film thickness of 1000 to 42000 angstroms is formed by sputtering in contact with the thin film and using copper as a target. 19. A first metal thin film having a thickness of 50 to 500 angstroms is formed by sputtering by contacting both sides of a polyimide film having a thickness of 25 to 125 μm with a target of Monel metal, and sputtering. A flexible circuit board in which a second metal thin film having a film thickness of 1000 to 42000 angstroms is formed by sputtering by contacting both surfaces of the thin film and using copper as a target.