JP2631441B2 - Method for producing polyimide film / metal foil composite film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
The present invention relates to a method for producing a metal foil composite film.

[0002]

2. Description of the Related Art Among heat-resistant polymers, aromatic polymers represented by polyimide are considered to be the best as super engineering plastics. Aromatic polymer has heat resistance, flame retardancy, mechanical strength, dimensional stability,
It has excellent thermal, physical, chemical, and electrical properties such as chemical resistance and electrical properties, and is also highly reliable. Therefore, it is used for space and aircraft, automobiles, electronics, gas separation membranes, etc. Demand is high in various advanced industries. However, aromatic polymers are highly crystalline and
Therefore, it has the property that the surface is inert,
Therefore, when compounding with other materials, the adhesive strength is weak,
The composite material does not necessarily utilize the above advantages of the aromatic polymer. Furthermore, as for the heat resistance, the heat resistance temperature range is currently narrowed. For example, regarding a flexible printed wiring board (FPC) based on a polyimide film, most of currently used FPCs are used to cover the weak adhesive force on the surface of the polyimide film by using an adhesive. Is polyimide film / adhesive /
It has a three-layer structure of copper foil. The three-layer FPC has, for example, the following problems in terms of adhesion, heat resistance, contamination, and reliability. 1) Since the heat resistance of the adhesive used is lower than that of the polyimide film, the production efficiency is not improved. In other words, when speeding up the production line to increase production efficiency, the set temperature of the soldering process may be increased, but since the heat resistance temperature of the adhesive is low, the soldering process temperature can only be set lower, Therefore, the production efficiency does not improve. 2) With the progress of higher density, higher speed, lighter, thinner and smaller electronic devices,
Packaging technology using FPC and the like is also progressing to high-density packaging. As a result, there arises a problem of migration of the copper foil into the adhesive, which could not occur conventionally. 3) If an FPC is used to further increase the number of layers, the use of an adhesive not only complicates the process but also causes a problem of reliability of through-hole plating in which electrical bonding between the layers occurs.

[0003]

In the future, in order to make electronic equipment smaller, thinner and more compact, F
As for PC, it is necessary to reduce the width and thickness of the conductor. By the way, copper also has an electric resistance, and heat is naturally generated by flowing a current through it. The amount of generated heat reaches a certain temperature when heat radiation and heat generation are well balanced. For example, copper foil 35 μm, width 0.15 mm, 400 m
When the current of A is passed, the temperature rises by about 75 ° C. In electronic equipment, since copper exists as a fine circuit, the temperature is expected to rise to a considerably high temperature, and it is increasingly required that the heat resistance of the FPC be excellent.
The present invention has been made in view of the above-described circumstances in the related art, and has as its object to improve the adhesive strength between a polyimide film and a metal foil, and to form a two-layer structure without using an adhesive. It is an object of the present invention to provide a method capable of producing a polyimide / metal foil composite film. Another object of the present invention is to provide not only FPC but also TAB (Tape Automated Bonding), a conductive composite film, a film for a heating element, and a polyimide film / metal that can be applied to various industrial fields. An object of the present invention is to provide a method for producing a foil composite film.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to improve the adhesive strength between a polyimide film and a metal foil and to omit an adhesive layer between the polyimide film and the metal foil. . As a result of the study, the present inventors have generated radicals by plasma treatment on the polyimide film surface before forming the metal foil film, and then graft-polymerized a monomer having an imidazole ring having a strong adhesive force with the metal foil. Then, it was found that the above object was achieved by forming a metal complex at the interface between the polyimide film and the metal foil, and the present invention was completed. That is, in the method for producing a polyimide film / metal foil composite film of the present invention, a step of plasma-treating the surface of the polyimide film to generate radicals, and graft-polymerizing vinylimidazole to radical species generated on the surface of the plasma-treated polyimide film And a step of fixing a metal foil film to the surface of the polyimide film subjected to the graft polymerization by sputtering or vapor deposition.

Hereinafter, the present invention will be described in detail. The plasma treatment for the surface modification of the polyimide film, which is the first step of the present invention, can be performed using, for example, a batch-type parallel plate electrode type plasma apparatus shown in FIG.
That is, in the parallel plate electrode type plasma apparatus shown in FIG. 1, two electrode plates 2, 2 arranged in parallel with each other are provided in a bell jar 1, and the above-mentioned polyimide film 3 is placed on its lower electrode. . The inside of the bell jar 1 is a closed space, and is decompressed and maintained at a constant pressure during plasma processing. High frequency power supply 4 between two electrodes
To generate a plasma atmosphere, and a plasma processing gas is supplied from the gas supply path 5 under the plasma atmosphere to plasma-treat the surface of the polyimide film. Reference numeral 6 denotes an electrode support for supporting the upper electrode plate, and reference numeral 7 denotes an exhaust port for discarding gas in the bell jar.

[0006] The plasma processing gas that can be used in the present invention includes oxygen gas, nitrogen gas, hydrogen gas, dry air, argon gas, helium gas, ammonia gas, nitrogen monoxide gas, nitrogen dioxide gas, carbon monoxide gas, and carbon dioxide. It is at least one selected from gas.

In the present invention, high frequency (13.56 MH)
z) The output of the power supply is set in the range of 3W to 200W, preferably in the range of 5 to 50W. When the output is more than 200 W, the polyimide film is deteriorated by the plasma treatment, while when the output is less than 3 W, no plasma is generated. The plasma processing pressure is 1.33 Pa to 1
Within the range of 330 Pa, preferably 6.7 Pa to 266 P
It is set in the range of a. When the pressure is less than 1.33 Pa, the effect of the plasma treatment is small.
If it is higher than a, no plasma is generated. The plasma processing time is set in the range of 0.2 seconds to 120 seconds, preferably in the range of 2 seconds to 60 seconds. If the processing time is less than 0.2 seconds, the processing effect is small, while
If it is longer than 120 seconds, the polyimide film deteriorates.

In the present invention, not only the batch type parallel plate electrode type plasma apparatus, but also a plasma continuous processing apparatus in which film unwinding and winding is installed inside a vacuum chamber, or film unwinding and winding up It is also possible to apply a plasma processing apparatus such as an air-to-air system having a mechanism outside the vacuum chamber, and the type of the plasma apparatus is not particularly limited. By the above plasma treatment, carbon radicals or oxygen radicals are generated on the surface of the polyimide film, and the graft ratio in the subsequent step of graft polymerization of vinylimidazole can be increased.

Next, the graft polymerization step will be described. The graft polymerization treatment may be performed by immersing the plasma-treated polyimide film in a solution obtained by dissolving vinylimidazole in an organic solvent, and heating the film to an appropriate temperature. Organic solvents include benzene, toluene,
Xylene or the like can be used. The concentration of vinylimidazole is preferably in the range of 10 to 30% by volume. Further, the treatment temperature is preferably in the range of a temperature equal to or lower than the boiling point of the organic solvent.
It is desirable that the homopolymer contained in the polyimide film subjected to the graft polymerization treatment is removed by extraction. The extraction may be performed, for example, using a Soxhlet extractor and using a suitable solvent that dissolves the homopolymer, for example, methanol, ethanol, or the like.

[0010] Next, a metal foil film is fixed on the surface of the polyimide film subjected to the plasma treatment and the graft polymerization treatment as described above by sputtering or vapor deposition of a metal. Sputtering or vapor deposition can be performed by a known method using a known sputtering device or vapor deposition device. As a metal for forming a metal foil film,
Examples include copper, chromium, nickel, and palladium.
By forming the metal foil film as described above, a metal complex of polyvinylimidazole is formed on the polyimide surface, and the adhesion between the polyimide film and the metal foil becomes excellent. At the same time, improvement in heat resistance and moisture resistance is promoted. Thereafter, when the thickness of the metal foil is further required, electroless plating or electrolytic plating is performed to obtain a desired polyimide / metal foil composite film.

[0011]

The present invention will be described below by way of examples. Example 1 Using a parallel plate electrode type plasma apparatus shown in FIG. 1, a polyimide film (Kapton 200H, manufactured by DuPont, USA, thickness: 50 μm) was subjected to argon gas plasma treatment. The plasma processing conditions were 13.56 MHz high frequency output 25 W,
The test was performed at a pressure of 13.3 Pa and an irradiation time of 20 seconds. After the plasma-treated film was once put into the air, the plasma-treated polyimide film was immersed in a degassed vinylimidazole / benzene solution, and graft polymerization was performed at 70 ° C. Then, the polyimide film on which vinylimidazole was graft-polymerized was treated with methanol as an extract using a Soxhlet extractor to extract and remove the homopolymer. Thereafter, the obtained polyimide film was dried. Next, a 2000 Å thick copper foil layer was formed on the surface of the polyimide film treated as described above by vapor deposition. The vapor deposition was performed using a vapor deposition device (VPC-250FA, manufactured by Vacuum Riko).

Example 2 A plasma treatment was performed using the same apparatus as in Example 1 and using the same polyimide film. Plasma processing is
Using a high frequency of 13.56 MHz, output 10 W, pressure 1
The test was performed under the conditions of 3.3 Pa and an irradiation time of 10 seconds. Thereafter, a graft polymerization treatment of vinylimidazole was performed in the same manner as in Example 1, and a copper foil layer was formed in the same manner.

Comparative Example 1 The same apparatus as in Example 1 was used, and the same polyimide film was used for surface modification by plasma treatment. The plasma treatment was performed using a high frequency of 13.56 MHz, under the conditions of an output of 25 W, a pressure of 13.3 Pa, and an irradiation time of 20 seconds. In addition, except not performing the graft polymerization treatment,
A comparative sample was obtained in the same manner as in Example 1. Comparative Example 2 Without performing the plasma treatment and the graft polymerization treatment,
The polyimide film of Example 1 was used as it was, and a copper foil film was formed thereon in the same manner as in Example 1 to obtain a comparative sample.

As shown in FIG. 2, an aluminum plate was adhered to the copper-deposited surface of the samples of the above Examples and Comparative Examples via an adhesive, and the 180 ° C. peel strength of the polyimide film of the sample 150 mm × 10 mm was measured.
Examples 1 and 2 and Comparative Examples 1 and 2 were compared. The adhesive used here was an epoxy adhesive (Ablebond 868).
-7UNF, manufactured by Nippon Able Stick Co., Ltd.), which was cured for 24 hours at a pressure of 1 kg / cm ² and a temperature of 25 ° C. Table 1 shows the results of the peeling test. In FIG. 2, reference numeral 11 denotes a polyimide film, and a vapor-deposited copper foil 13 is formed on the surface-modified portion 12. In addition, 1
Reference numeral 4 denotes an adhesive for bonding the aluminum plate 15.

[0015]

[Table 1] As is clear from Table 1, in the case of Examples 1 and 2 which were subjected to the grafting treatment, the peel strength was higher than in the cases of Comparative Examples 1 and 2, and therefore, the adhesive strength was more excellent. In addition, when the peeled surfaces of the polyimide film side and the aluminum plate side were observed by an electron micrograph, in the case of Comparative Example 2, no copper foil remained on the polyimide film side, and all of them were transferred to the aluminum plate side. In other samples, the copper foil remains on both sides of the polyimide film side and the aluminum side, and the size of the trace of delamination of the copper foil decreases in the order of Comparative Example 1, Example 2, and Example 1. It turned out that it occurred uniformly. This result indicates that the present invention has an excellent effect.

[0016]

According to the present invention, since a polyimide film, which is a heat-resistant polymer material, is surface-modified in advance by a plasma graft technique and a metal foil is formed thereon, a metal foil, particularly a copper foil, is used. In the case of a printed circuit board, there are advantages such as 1) use at a higher temperature, 2) less short-circuit trouble, 3) easy formation of through holes, and 4) downsizing of a circuit. Also,
According to the present invention, economical effects such as cost reduction of products due to miniaturization of circuits, saving of material costs by not using adhesives, and eliminating the need for an environmental pollution prevention device because no solvents are used are extremely significant. large. The composite film of the present invention,
It can be widely applied not only in the space and aircraft industries but also in the field of consumer equipment. As conductive composite films, especially in the fields of electronics and information industries such as transparent electrode films and heating element films, heat ray shielding films, heat insulation films, etc. Can also be used in the construction industry.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an example of a parallel plate type plasma apparatus.

FIG. 2 is a diagram illustrating a state of bonding samples at the time of a peel test.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Bell jar 2 ... Electrode plate 3 ... Polyimide film 4 ... High frequency power supply 5 ... Gas supply path 6 ... Electrode support 7 ... Exhaust port 11 ... Polyimide film 12 ... Surface modification part 13 ... Evaporated copper foil 14 ... Adhesive 15 ... Aluminum Board

Claims (3)

(57) [Claims] A step of generating radicals by plasma-treating the surface of the polyimide film; a step of graft-polymerizing vinylimidazole to radical species generated on the surface of the polyimide-treated plasma film; Fixing the metal foil film to the surface of the polyimide film by sputtering or vapor deposition. 2. The plasma processing is performed at a frequency of 13.56 MH.
Using high frequency of z, output 5W-50W, pressure 6.7Pa
The method for producing a polyimide film / metal foil composite film according to claim 1, wherein the method is performed under the conditions of -266 Pa and irradiation time of 2 seconds-60 seconds. 3. The polyimide film according to claim 1, wherein the plasma-treated polyimide film is immersed in a solution obtained by dissolving vinyl imidazole in an organic solvent to graft-polymerize vinyl imidazole to the polyimide. A method for producing a metal foil composite film.