JPH11193461A - Production of base material having copper layer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a base material having a two layer type copper layer capable of stably obtaining the adhesive strength between a polyimide film and a copper layer in an ordinary condition by subjecting the polyimide film to heat treatment. SOLUTION: A polyimide film previously subjected to primary heat treatment is coated with a polyimide silicone varnish and is thereafter subjected to secondary heat treatment, and the surface of the polyimide silicone varnish is deposited with copper grains by their thermal decomposition of copper formate, electroless plating, vapor deposition, sputtering, ion plating, CVD or the like.

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 producing a substrate having an adhesive-less (no adhesive) copper layer, which is generally called a plating method, specifically, a copper-clad polyimide film. More specifically, the copper layer is more firmly adhered to the polyimide film, and is preferably used particularly in the field of electric and electronic materials.

[0002]

2. Description of the Related Art As a method for producing a polyimide film having a copper layer, a casting obtained by applying a polyamic acid, which is a precursor of a polyimide, on a copper foil and then thermally curing the same is generally used. Metallization obtained by directly forming a copper thin layer, generally a copper layer, on a substrate and a polyimide film as a conductive layer by sputtering, vapor deposition, electroless plating, etc., and then thickening the copper layer by electroplating. There is a substrate (JP-A-6-158337, electronic material, October 1996, pages P13 to P16).

The former has the advantage that the adhesion strength of the metal layer is high and stable.

On the other hand, the latter has an advantage that the thickness of the copper layer can be arbitrarily adjusted, but has a disadvantage that the adhesion strength of the copper layer is not so high.

Therefore, in the latter case, the surface of the polyimide film is subjected to, for example, an alkali treatment, a plasma treatment, a corona treatment, or a silicone coupling agent treatment to improve the adhesion strength to the copper layer. Not enough. In particular, the adhesion after leaving for a long time in a high-temperature atmosphere is insufficient.

The present invention is to stabilize the adhesion strength between a polyimide film and a copper layer in a normal state by heat-treating the polyimide film without physically or chemically treating the highly hygroscopic polyimide film. Obtained 2
It is intended to provide a method for producing a substrate having a layer type copper layer.

[0007]

The gist of the present invention will be described.

[0008] After a polyimide silicone varnish is coated on the polyimide film which has been subjected to the first heat treatment in advance, a second heat treatment is applied. Then, thermal decomposition of copper formate, electroless plating, vapor deposition, sputtering, The present invention relates to a method for manufacturing a substrate having a copper layer, characterized by depositing copper particles by ion plating, CVD, or the like.

Further, in the method for producing a substrate having a copper layer according to the first aspect, the polyimide film is subjected to a first heat treatment at 300 to 350 ° C. in a state where tension is not applied, and the water content is 0.6 to 500 ° C. The present invention relates to a method for producing a substrate having a copper layer, which is set at 0.9%.

In the method for producing a substrate having a copper layer according to any one of claims 1 and 2, a polyimide film is coated with a polyimide silicone varnish, and then the polyimide film is dried. The present invention relates to a method for manufacturing a substrate having a copper layer.

In the method for producing a substrate having a copper layer according to any one of claims 1 and 2, the polyimide film is coated with a polyimide silicone varnish, and then the polyimide film is dried. And subjecting the polyimide film to a second heat treatment at 300 to 350 ° C., which is related to a method for producing a substrate having a copper layer.

[0012]

The present invention has been confirmed by various experiments, and the claims summarize the results of the experiments.

However, although it is not clear, the mechanism of the remarkable improvement effect of the adhesion in the present invention is that the adhesion cannot be obtained only by providing an intervening layer between the polyimide film and the copper layer. For the first time, excellent adhesion and heat resistance can be obtained. According to SEM observation (Figs. 1 and 2 are copies of SEM photographs), fine protrusions that are not seen before heat treatment are newly found in the intervening layer after heat treatment. This is considered to be based on the fact that the intervening layer and the copper layer and the surface of the polyimide film mutually diffused to generate a specifically strong anchoring effect.

Further, the present inventors have previously disclosed in Japanese Patent Application Nos.
No. 3775 proposes a method for producing a polyimide film having a copper layer.

[0015] This manufacturing method can be used to produce a polyimide film having a two-layer type copper layer which excels in the adhesion strength of the copper layer without performing an alkali treatment or the like on the polyimide film and also in the adhesion strength after thermal aging. It can be provided at the localization level.

However, this manufacturing method has a disadvantage that, on an industrial scale, the adhesion strength to a copper layer is reduced due to the influence of room temperature during handling. Therefore, production on an industrial scale or actual production Reliability in use has been an issue.

Further, the polyimide film inherently very easily absorbs moisture, and there is a disadvantage that the adhesive strength with the copper layer is greatly reduced in a water-absorbed state (for example, Japanese Patent Application Laid-Open No. 5-2396).
issue).

Accordingly, there is an increasing demand for a polyimide resin having a lower water absorption while maintaining the high heat resistance and the high mechanical strength of the polyimide resin, and various studies have been made. , Water absorption is 1.0 ~
The actual situation is around 2.0%.

Therefore, heat treatment (first heat treatment of claim 1)
By removing the water contained in the polyimide film by, for example, vapor deposition or expansion of the water does not occur when the copper layer is deposited, and the adhesion strength of the interface of the polyimide film with the copper layer on the deposition surface Can be eliminated.

After the polyimide film is coated with polyimide silicone varnish and dried,
By performing the second heat treatment at 00 to 350 ° C., the crosslink density of the polyimide silicone varnish is increased, and the effect of evaporating the high boiling point solvent also contributes to the improvement of the adhesion of the copper layer. it is conceivable that.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A specific embodiment of the present invention will be described.

In this embodiment, a polyimide film subjected to a first heat treatment is coated with a polyimide silicone varnish and then subjected to a second heat treatment. Subsequently, thermal decomposition of copper formate and electroless plating are performed on the polyimide silicone varnish. , Evaporation, sputtering, ion plating, C
The present invention relates to a method for producing a substrate having a copper layer on which copper particles are deposited by VD or the like.

As the polyimide film, a film obtained by condensing pyromellitic acid or a pyromellitic acid derivative and / or a biphenylcarboxylic acid or a biphenylcarboxylic acid derivative with an aromatic diamine is used. It is made of a polyimide resin which is commercially available under the trade names such as DuPont, Upilex (Ube Industries, Ltd.) and Apical (Kanebuchi Chemical Industry Co., Ltd.).

The first heat treatment and the second heat treatment are performed for a predetermined treatment time by a device appropriately selected from a hot air circulation type oven, an electric furnace, infrared rays, far infrared rays and the like. Selection of equipment and selection of processing time, when heating the polyimide film coated with a polyimide film and polyimide silicone varnish, remove moisture and distortion of the polyimide film, complete curing of the polyimide silicone to complete curing, the degree of crosslinking Perform so that it can be raised.

The first heat treatment of this polyimide film is as follows:
The polyimide film is applied without tension in the width direction and the length direction without tension. This first heat treatment, for example, the polyimide film is 300 to 350
C., 23.degree. C..times.50% RH for 1 hour, until the moisture content of the polyimide film becomes 0.6 to 0.9%.

On a surface of the polyimide film having a water content of 0.6 to 0.9%, a solution of a polyimide silicone varnish containing at least a carboxylic acid, an amine and a silicone compound of the following structural formulas as essential constitutional units is thinly and uniformly applied. At a temperature of about 150 to 250 ° C. for 1 to 100
After drying for about a minute, a second heat treatment is further performed at 300 to 350 ° C. to deposit about 0.1 to 2.0 g / m ² as the resin content of the polyimide silicone solid.

Embedded image If the amount of the solid content resin of the polyimide silicone is less than 0.1 g / m ² , no effect is obtained, so that it is not preferable. Also,
If it is more than 2.0 g / m ^2, it becomes difficult to adhere the solid resin of polyimide silicone, which is not preferable.

The solution of the polyimide silicone varnish is selected from solvents such as ketones and lactams, and has a concentration of 1.0.
６6.0 wt%.

The method for uniformly adhering the polyimide silicone varnish can be appropriately selected from known methods such as dipping, spray coating, reverse coating, kiss coating, and gravure coating.

When a copper layer is formed by depositing copper particles on the polyimide silicone varnish coating surface by thermal decomposition of copper formate, the polyimide film and copper formate are allowed to coexist and the copper formate is heated to a temperature of 200 to 400 ° C. And pyrolyze it with
Copper is deposited on the surface of the polyimide film. As this method, for example, a method disclosed in Japanese Patent Application Laid-Open No. 2-305965 can be mentioned.

The copper formate is usually a cupric formate compound, and examples thereof include anhydrous copper formate, copper formate tetrahydrate, and a mixture thereof. Particularly preferred is anhydrous copper formate.

The copper layer can be formed by a method of depositing copper particles by non-decomposition plating, vapor deposition, sputtering, ion plating, CVD or the like, in addition to thermal decomposition of copper formate.

The polyimide film on which the copper layer is formed by such various means has excellent adhesion strength in a normal state as compared with the conventional one, has less variation in adhesion strength between lots of the polyimide film, and has high reliability. Will be high.

When the copper layer is thin, the copper layer can be thickened by electrolytic copper plating.

In general, electrolytic copper plating is used.
Electroless or electrolytic plating of nickel, gold, and other metals is also possible.

Further, the polyimide film has a high adhesion strength without an alkali etching treatment or the like, and the reliability after the heat aging is substantially negligible or small and the reliability is high.

Hereinafter, the present invention will be described in more detail with reference to specific examples and comparative examples.

Example 1 A polyimide film having a thickness of 25 μm (trade name: Kapton 100V, manufactured by Toray Dupont Co., Ltd.) was heated for 1 hour (first heat treatment) at 320 ° C. in a hot-air circulation system, and was heated to 23 ° C. × 50% RH (relative humidity 50
%), And a polyimide silicone varnish (trade name: KJR-66) is applied to one side of the polyimide film.
3, a 3.0% N-methylpyrrolidone / cyclohexanone (45/55 wt% ratio) solution of Shin-Etsu Chemical Co., Ltd. was applied.
Heating was performed at 80-190 ° C for about 2-3 minutes.

The polyimide silicone adhered 0.60 g / m ² as a solid resin amount.

On the other hand, 25 g of copper formate anhydride was pulverized in a mortar, 80 g of butanol was added thereto, and a slurry obtained by ultrasonic stirring was uniformly applied to the bottom of a 300 mm square aluminum dish and dried. did.

Subsequently, the polyimide film subjected to the above treatment was fixed to an aluminum plate, the aluminum plate was covered with the polyimide film side as an inner surface, the aluminum plate was wrapped with aluminum foil, and placed in a vacuum container. I put it.

Subsequently, the pressure inside the vacuum vessel was reduced to 0.2 to 0.6 Torr, and the vessel was heated at 300 to 350 ° C. for 15 minutes (second heat treatment).

Subsequently, after cooling the aluminum dish to room temperature, the polyimide film was taken out of the aluminum dish.

A glossy copper layer having a thickness of 0.29 μm was formed on the surface of the polyimide film. A known electrolytic copper plating was applied to the polyimide film having the copper layer formed thereon, so that the thickness of the copper layer was 18 μm.

The 90 ° peeling strength (corresponding to the adhesion strength) of the polyimide film on which the copper layer was formed was 0.95 kg · f / cm under normal conditions.

The water content of the polyimide film before the first heat treatment was 1.005%, and the polyimide film was heated at 320 ° C. for 1 hour (first heat treatment), at 23 ° C. × 50.
The moisture content after standing at% RH was 0.782%.

The moisture content was measured using a trace moisture analyzer (manufactured by Hiranuma Sangyo Co., Ltd.).

Example 2 In Example 1, after the polyimide film was subjected to a first heat treatment at 320 ° C., a polyimide silicone varnish solution was applied to one surface of the polyimide film, and air-dried. Heating was performed for about 2 to 3 minutes, followed by reheating (second heat treatment) at 320 ° C. for about 60 minutes. Other conditions were the same as in Example 1.

The 90 ° peel strength of the polyimide film on which the copper layer was formed was 1.10 kg · f / cm under normal conditions.

Example 3 In Example 1, a polyimide silicone varnish solution was applied to one surface of the polyimide film without performing the first heat treatment on the polyimide film.
After air-drying, heating was performed at 180 to 190 ° C. for about 2 to 3 minutes, followed by reheating at 320 ° C. for about 60 minutes (second heat treatment). Other conditions were the same as in Example 1. Incidentally, 0.880 g / m ^{2 of} the polyimide silicone adhered as a solid resin amount.

The 90 ° peel strength of the polyimide film on which the copper layer was formed was 1.00 kg · f / cm under normal conditions.

Comparative Example 1 Comparative Example 1 corresponds to an example of Japanese Patent Application No. 9-123775, which is a prior application of the present inventors.

In Example 1, the polyimide film was not subjected to the first heat treatment, and a polyimide silicone varnish solution was applied to one surface of the polyimide film and air-dried. In addition, reheating (second heat treatment) after air drying was not performed, and the other conditions were the same as in Example 1. Incidentally, 0.88 g / m ^{2 of} the polyimide silicone varnish adhered as a solid resin amount.

The 90 ° peel strength of the polyimide film on which the copper layer was formed was 0.68 kg / cm under normal conditions.

The above results are shown in Table 1 below.

[Table 1] According to Embodiments 1, 2, and 3 as described above, the polyimide film is subjected to the first heat treatment in advance, or the polyimide silicone varnish is applied and dried, and then the second heat treatment is performed, or the first heat treatment and the first heat treatment are performed. By performing both of the two heat treatments, a polyimide film having a copper layer in which the adhesion strength of the copper layer is further improved can be manufactured.

Therefore, it is possible to provide a polyimide film having a two-layer type copper layer, etc., at a practically practical level.

[Brief description of the drawings]

FIG. 1 is a copy of an SEM photograph of a copper-side interface of an intervening layer before heat treatment.

FIG. 2 is a copy of an SEM photograph of a copper-side interface of an intermediate layer after heat treatment.

FIG. 3 is an explanatory diagram of FIG. 1;

FIG. 4 is an explanatory diagram of FIG. 2;

Claims (4)

[Claims] 1. A polyimide film which has been subjected to a first heat treatment in advance and coated with a polyimide silicone varnish, followed by a second heat treatment, followed by thermal decomposition of copper formate on the polyimide silicone varnish, electroless plating, vapor deposition, A method for producing a substrate having a copper layer, wherein copper particles are deposited by sputtering, ion plating, CVD, or the like. 2. The method for producing a substrate having a copper layer according to claim 1, wherein the polyimide film is subjected to a first heat treatment at 300 to 350 ° C. without tension.
A method for producing a substrate having a copper layer, wherein the water content is set to 0.6 to 0.9%. 3. The method for producing a substrate having a copper layer according to claim 1, wherein the polyimide film is dried after coating the polyimide film with a polyimide silicone varnish. A method for producing a substrate having a copper layer. 4. The method for producing a substrate having a copper layer according to claim 1, wherein the polyimide film is coated with a polyimide silicone varnish, and then the polyimide film is dried. A method of producing a substrate having a copper layer, wherein the polyimide film is subjected to a second heat treatment at 300 to 350 ° C.