JPH11302809A - Manufacture of copper thin film substrate and printed circuit board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a printed circuit board in which a desired circuit element can be firmly adhered to a desired position easily and surely without using any special adhesive or mechanical means, the printed circuit board itself can be adhered to a desired member and further, a fine circuit can be easily formed and to provide a copper thin film substrate to be utilized in manufacturing the printed circuit board. SOLUTION: The copper thin film substrate 10 is prepared by forming a molten adhesive layer 14 consisting of a thermoplastic polyimide resin on one of the main surface of a main body layer consisting of a heat resistant insulation base material 11, forming a copper thin film layer 12 by a sputtering method as a first layer on the other main surface and forming a copper thick layer 13 by an electric plating method as a second layer on the copper thin film layer 12. The printed circuit board manufactured by using the copper thin film substrate 10 is also prepared.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0101]

TECHNICAL FIELD The present invention relates to a fine circuit (usually,
The present invention relates to a printed wiring board having a conductor width of 50 μm or less and a conductor width of 50 μm or less) or a copper thin film substrate used for manufacturing electronic component devices and sensors used in the semiconductor field.

[0092]

2. Description of the Related Art A conventional flexible circuit board is manufactured by bonding a polyimide film and a metal foil using an adhesive such as an epoxy resin. However, the properties of the adhesive used are dominant, and the excellent properties of polyimide are not sufficiently utilized, and the heat resistance is not sufficient. For the copper foil, 18, 35 and μm are used. It is not enough to cope with the fine circuit formation accompanying the recent high density and high performance. Therefore, copper foil thinning has been attempted by forming a copper thin film layer on a heat-resistant insulating base material by a vacuum evaporation method, a sputtering method, an ion plating method, an electroless plating method, or the like. There are various problems, and none is suitable for manufacturing a printed wiring board having a fine circuit. There is a demand for a copper thin-film substrate having no organic adhesive layer and having a copper layer as thin as possible.

[0093]

SUMMARY OF THE INVENTION The present invention aims to solve the above-mentioned problems. Specifically, an object of the present invention is to provide a simple and reliable method without the need for preparing a special adhesive. A printed circuit board capable of strongly adhering a desired circuit element to a desired position, adhering itself to a desired member, and easily forming a fine circuit, and copper that can be used for manufacturing a printed circuit board It is to provide a thin film substrate.

[0093]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for forming a heat-resistant insulating base material on one main surface of a main adhesive layer comprising a thermoplastic polyimide resin and a second main surface. This is achieved by a copper thin film substrate comprising a copper thin film layer formed by a sputtering method as a first layer and a copper thick layer formed by an electroplating method as a second layer on the copper thin film layer.

That is, the present invention provides (1) a fusion bonding layer made of a thermoplastic polyimide resin formed on both sides or one side of a main layer made of a heat-resistant insulating base material, and a first layer formed on one main surface. As a copper thin film layer formed by a sputtering method, and a copper thin film substrate comprising a copper thick layer formed by an electroplating method as a second layer on the copper thin film layer,
(2) The first copper thin film layer formed by the sputtering method has a copper thickness of at most 1 μm (1).
(3) The copper thin film substrate according to (1) or (2), wherein the copper thickness of the copper thick layer formed by the second layer electroplating method is 1 μm or more and 18 μm or less. (4) The copper thin film substrate according to any one of (1) to (3), wherein the heat-resistant insulating substrate is a non-thermoplastic polyimide film, and (5) (1) ) ~
A printed wiring board having a fine circuit, wherein the circuit is formed by using the copper thin film substrate according to any one of the above (4).

[0086]

DESCRIPTION OF THE PREFERRED EMBODIMENTS There are various methods for forming a copper thin film layer by a sputtering method, but there is no particular limitation. It is understood by those skilled in the art that a target is appropriately selected and used in accordance with a thin film to be formed. The sputtering method is not limited, and a method such as DC magnetron sputtering, high-frequency magnetron sputtering, or ion beam sputtering is advantageously used.

In the present invention, it is preferable from the viewpoint of adhesion that a base metal layer is formed between the heat-resistant insulating base material and the first copper thin film layer by a sputtering method. The base metal layer is made of cobalt nickel, chromium, nichrome, titanium,
Molybdenum, tungsten, zinc, tin, indium, indium tin, silicon, monel metal, etc., and oxides, carbides, nitrides, etc. thereof are useful. It is sufficient that the thickness of the underlayer metal layer is 0.03 to 0.1 μm. 0.03
If it is less than μm, the effect of adhesion is not sufficient. If it exceeds 0.1 μm, problems such as a decrease in conductivity, a decrease in circuit workability due to etching, and an increase in cost become apparent.

The method for continuously forming the second thick copper layer of the copper thin film substrate according to the present invention is based on an electroplating method.
m or more and 18 μm or less. The setting of the copper thickness is selected depending on the type of the target fine circuit formation.
Copper thickness below μm is a general trend. According to this method, a copper thin film substrate having no pinholes, which is economically practical, can be obtained. The electroplating method for continuously forming an arbitrary thick copper layer as the second layer of the copper thin film substrate of the present invention is based on a known method.

The heat-resistant insulating base material used for the copper thin film substrate of the present invention is various polyimide films. For example, Kapton film (manufactured by Du Pont-Toray Co., Ltd.) and Apical Film (manufactured by Kanegafuchi Chemical Industry Co., Ltd.) Manufactured by Ube Industries, Ltd.), and the thickness is 25, 50 μm.
m is practical.

[0010] The thermoplastic polyimide used for the copper thin film substrate of the present invention is a polymer having an imide structure in the main chain and has a glass transition temperature preferably in the range of 150 ° C to 350 ° C. In the above-mentioned temperature range, the elastic modulus sharply decreases.

Hereinafter, the production of the copper thin film substrate of the present invention will be described. A thermoplastic polyimide is laminated on a long polyimide film suitable for the purpose of use. This thermoplastic polyimide is applied on a polyimide film in a state where the polyimide or the precursor of the polyimide is dissolved in a solvent,
This is preferably heated to a tack-free state. There is no particular limitation on the method of coating, and a known coating device such as a comma coater, a knife coater, a roll coater, a reverse coater, a die coater, a gravure coater, or a wire bar can be used. As a heating method, a known method such as hot air, hot nitrogen, far infrared rays, and high frequency can be used.

After the desired polyimide layer is formed, it is necessary to sufficiently heat it to remove volatile components in the layer and complete the condensation reaction when a polyimide precursor is applied. . In this case, as the heating method, various known methods according to the above can be used. The heating temperature is preferably a temperature equal to or higher than the glass transition temperature of the polyimide to be laminated.

After the formation of the molten adhesive layer, the other surface is placed on the pay-out portion of the sputtering apparatus so that the other surface is located on the copper target side. A copper thin film layer is continuously formed under a predetermined optimum condition so that a prescribed sputtering copper thickness is formed, and is wound around a tube made of resin or the like, and the copper thin film layer is formed by sputtering the first layer. Complete. Next, the long polyimide film on which the copper thin film layer is formed by the sputtering of the first layer is placed in the feeding portion of the electroplating apparatus in order to form the copper thick layer by the electroplating of the second layer. Form a long continuous copper thick layer under the optimal conditions predetermined so that the specified copper thickness is formed, wind it up on a tube made of resin, etc., and form the copper thick layer by electroplating the second layer Complete. In this production, the long polyimide film on which the copper thin film layer formed by the sputtering of the first layer is formed is supplied to the electroplating process without being once wound, and the formation of the copper thick layer of the second layer is performed in a continuous process. Is also possible. It is preferable that the production of the copper thin film substrate of the present invention be carried out in an environment as clean as possible and that the control of the electroplating solution be strictly performed.

The measurement of the adhesive strength and the pinhole between the polyimide film and the copper thin film layer of the copper thin film substrate of the present invention will be described below. The adhesion strength was measured using IPC-TM-65 on a sample taken from both ends of a long copper thin film substrate.
Perform according to 0-2.4.9. On the other hand, in the measurement of the pinhole, the passage of light from below is confirmed on a light table for a sample sampled in the same manner as the adhesive strength.

Next, the manufacture of a printed wiring board having a fine circuit by the subtractive method using the copper thin film substrate of the present invention will be described below. First, if necessary, apply a liquid photo-etching resist ink on the entire surface of the copper surface of the copper thin film substrate whose copper surface has been pre-treated, or attach a dry film on the entire surface, and apply a photomask having a desired circuit pattern to an ultraviolet ray or the like. The resist material is exposed to light by passing through the active light, and is developed to form a desired circuit pattern. Thereafter, the copper surface other than the circuit pattern is dissolved and removed with an etching solution such as ferric chloride, cupric chloride, persulfates, and alkaline etchants, thereby obtaining a printed wiring board having a desired fine circuit.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described below. Example 1 A polyamic acid solution (Mitsui Chemicals, Inc.), a precursor of a thermoplastic polyimide, was applied to a commercially available long polyimide film (Apical NPI, manufactured by Kaneka Chemical Co., Ltd., thickness: 25 μm).
Co., Ltd., PI-A) was applied to one side of a polyimide film by a coating machine and dried to obtain a molten adhesive layer (thickness: 10 μm). Further, a copper thin film layer of 0.25 μm was formed on the other surface by continuous sputtering to obtain a desired copper thin film substrate. The adhesive strength of this copper thin film substrate was 14.7 N / cm, and there was no pinhole.

Next, the above-mentioned film was used as a double-sided printed wiring board made of a glass polyimide resin substrate (manufactured by Matsushita Electric Works, Ltd.).
R4775 0.5mm thick)
C., 3.9 MPa) for 30 minutes to form a single-sided copper-clad laminate. Further, a dry film type photosensitive resist (Asahi Kasei AQ2536) was applied to the surface. Exposure to resist (6
0mj) A development step was performed to form a hole pattern for forming a via hole, and a hole pattern was formed in the copper foil by wet etching (ferric chloride). After removing the resist, a CO ₂ laser (Mitsubishi Electric ML505) is used with this copper foil as a mask.
GT) to process via holes. Electroless copper plating (8 μm) was performed starting from the copper at the bottom of the via hole, and the via hole was filled with copper. The conductor layers were a copper thin film layer and a plated copper thick layer. For the signal lines, a liquid photo-etching resist ink was applied on the entire surface of the conductor layer by a roll coater and dried to form a film of the liquid photo-etching resist ink. Next, the circuit pattern portion was exposed through a photomask having a desired fine circuit, a circuit film was formed, and developed to obtain a desired circuit pattern. After a while
The printed wiring board having a desired fine circuit was obtained by etching with ferric chloride, dissolving and removing the copper surface other than the circuit pattern, and removing the liquid photo-etching resist ink film on the circuit pattern.

The adhesion strength between the glass polyimide resin substrate and the polyimide film of the obtained printed wiring board was measured by I
As a result of performing according to PC-TM-650-2.4.9,
A value of 9.8 N / cm was obtained. Further, as a result of observing the cross section of the obtained printed wiring board with an optical microscope and a scanning electron microscope, a portion having no adhesive layer and a portion having been peeled were not observed. The conductor width (L) and the distance between conductors (S) of the obtained printed wiring board are L / S = 15/15
It was a fine circuit of μm.

Example 2 A printed wiring board was manufactured in the same manner as in Example 1 except that a commercially available flexible printed wiring board was used instead of using the glass polyimide resin substrate.

Comparative Example 1 A printed wiring board was manufactured in the same manner as in Example 1 except that the thickness of the fusion bonding layer formed on one side of the polyimide film was 5 μm. The adhesion strength between the glass polyimide resin substrate and the polyimide film of the obtained printed wiring board was measured by IPC-TM-650-2.
As a result of performing the measurement according to 4.9, a value of 1.96 N / cm was not obtained, and did not satisfy the value required for the printed wiring board. Further, as a result of observing the cross section of the obtained printed wiring board with a metallographic microscope and a scanning electron microscope, a portion having no adhesive layer was observed, and a peeled portion was also observed.

Comparative Example 2 A printed wiring board was manufactured in the same procedure as in Example 1 except that the electroless thickness was 20 μm. As a result of observing the obtained fine circuit portion (L / S = 15/15 μm) with an optical microscope (× 40), many short-circuit portions were observed, and it was impossible to form a fine circuit.

[0022]

In producing a printed wiring board using the copper thin film substrate of the present invention, there is no need to use a special adhesive, and finer circuit formation can be easily and easily performed by the ordinary subtractive method. Became accurate.

[Brief description of the drawings]

FIG. 1 is an example of a layer configuration of a copper thin film substrate of the present invention.

FIG. 2 is an example of a layer configuration of a copper thin film substrate of the present invention.

[Explanation of symbols]

 10, 20, copper thin film substrate 11, 21, heat-resistant insulating base material 12, 22, sputtered copper thin film layer 13, plated copper thick layer 14, 24, fusion bonding layer

Claims (5)

[Claims] 1. A fusion bonding layer made of a thermoplastic polyimide resin formed on both surfaces or one surface of a main layer made of a heat-resistant insulating base material, and a first layer formed on one main surface by a sputtering method. A copper thin film substrate comprising: a copper thin film layer; and a copper thick layer formed by electroplating as a second layer on the copper thin film layer. 2. The copper thin film substrate according to claim 1, wherein the copper thin film layer of the first layer formed by sputtering has a thickness of at most 1 μm. 3. The copper thin film substrate according to claim 1, wherein the copper thickness of the copper thick layer formed by the electroplating method of the second layer is 1 μm or more and 18 μm or less. 4. The copper thin film substrate according to claim 1, wherein the heat-resistant insulating substrate is a non-thermoplastic polyimide film. 5. A printed wiring board having a fine circuit, which is manufactured by forming a circuit using the copper thin film substrate according to claim 1.