JP2010144179A - Surface treating method and polyimide film having thin metal film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface treating method for a polyimide film causing little decrease of peeling strength even after leaving a thin metal film-laminated polyimide film made by forming a thin metal film on the biphenyltetracarboxylic acid-based polyimide film surface under heated or humid conditions, and to provide the polyimide film having the thin metal film. <P>SOLUTION: The surface treating method comprises treating the surface of the polyimide film having the biphenyltetracarboxylic acid component with a solution containing potassium permanganate and/or sodium permanganate and potassium hydroxide and/or sodium hydroxide, and then treating the resulting material with an acid. By this the adhesion strength between the film and the metal is improved. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to an improved polyimide film surface treatment method and a polyimide film having a metal thin film. More specifically, the present invention improves the peel strength of a metal thin film laminated polyimide film having a metal thin film formed on the polyimide film surface and heating conditions. The present invention relates to a polyimide film surface treatment method and a polyimide film having a metal thin film that maintain a relatively large peel strength even after being placed under or under humidified conditions.

Aromatic polyimide films are widely used as applications for electronic devices such as cameras, personal computers, and liquid crystal displays. In order to use an aromatic polyimide film as a substrate material such as a flexible printed board (FPC) or tape-automated bonding (TAB), a copper foil is bonded using an adhesive such as an epoxy resin. The method is adopted.

An aromatic polyimide film is excellent in high heat resistance, mechanical strength, electrical characteristics, and the like, but it has been pointed out that since the high heat resistance of the adhesive is inferior, the characteristics of the original polyimide are impaired. In order to solve such problems, without using an adhesive, metal such as nickel or chromium is deposited on a polyimide film to electroplate copper, or a polyamic acid solution is applied to a copper foil, and then dried and imidized. Or, an all-polyimide substrate that has been thermocompression bonded with thermoplastic polyimide has been developed. However, it has been pointed out that these all-polyimide copper-clad plates have a low adhesive strength or have impaired electrical properties.

For example, Patent Document 1 discloses a polyimide laminate in which a polyimide adhesive is sandwiched between a polyimide film and a copper layer. However, this polyimide laminate has a problem that the adhesive strength is low for a low thermal linear expansion biphenyltetracarboxylic acid-based polyimide film.

For this reason, there has been proposed a method using a roll laminating method obtained by using a specific aromatic diamine as a heat-fusible polyimide. However, even with polyimide copper-clad plates obtained by these methods, the peel strength after being placed under humid conditions may be small, or it may be impossible to reduce the thickness of the metal layer. It was difficult to change.

Patent Document 2 is known as an improvement of the plating method. According to the publication, the surface of the polyimide film is treated with an aqueous solution of a permanganate such as sodium permanganate or potassium permanganate or a hypochlorite such as sodium hypochlorite or potassium hypochlorite. The surface treatment method of the polyimide film to be hydrophilized, and the treated surface is electrolessly plated to form a nickel or cobalt thin metal layer, and in some cases further electrolessly plated to form a copper layer and then electroplated. The copper polyimide substrate on which the copper layer is formed is considered to have a negligible decrease in adhesion strength when left for a long time in a high temperature environment.

However, the polyimide film described in the above publication is pyromellitic acid-based Kapton (Toray DuPont), and the inventors applied the surface treatment method to a biphenyltetracarboxylic acid-based polyimide film. However, it became clear that there was no effect.

Patent Document 1 US Pat. No. 4,543,295 Patent Document 1 JP-A-6-21157

The object of the present invention is to treat the surface of a polyimide film with little decrease in peel strength even after a metal thin film laminated polyimide film having a metal thin film formed on the surface of a biphenyltetracarboxylic acid-based polyimide film is placed under heating or humidification conditions. A method and a polyimide film having a metal thin film.

That is, according to the present invention, after the surface of a polyimide film having a biphenyltetracarboxylic acid component is immersed in a solution containing potassium permanganate and / or sodium permanganate and potassium hydroxide and / or sodium hydroxide, It is related with the surface treatment method characterized by improving the adhesive force with a metal by processing.

The present invention also relates to a polyimide film having a metal thin film formed by forming a metal film by a vapor deposition method or a combination of a vapor deposition method and a plating method on a polyimide film having improved adhesion to a metal by the surface treatment method described above. .

In this invention, the surface of a polyimide film having a biphenyltetracarboxylic acid component is treated by leaching, spraying, or the like with a solution containing potassium permanganate and / or sodium permanganate and potassium hydroxide and / or sodium hydroxide. After that, it is important to combine the acid treatment, so that even a polyimide film having a biphenyltetracarboxylic acid component, a metal thin film laminated polyimide film having a metal thin film formed on the film surface is heated or humidified. It is possible to reduce the decrease in peel strength after being placed under conditions.

According to the present invention, it is possible to obtain a polyimide film that maintains a relatively large peel strength even after a polyimide film having a metal thin film having a metal thin film formed on the polyimide film surface is placed under heating or humidification conditions. Moreover, according to this invention, the polyimide film which has a metal thin film which maintains comparatively big peel strength even after putting on heating conditions or humidification conditions is obtained.

The preferred embodiments of the present invention are listed below.
1) The alkaline permanganate treatment comprises potassium permanganate and / or sodium permanganate at a concentration of 10 to 100 g / L and potassium hydroxide and / or sodium hydroxide at a concentration of 10 to 100 g / L. The said surface treatment method performed by immersing for about 10 to 600 second in 85 degreeC aqueous solution.
2) The surface treatment method described above, wherein the surface is further subjected to plasma treatment.

3) The surface treatment method described above, wherein the polyimide film is a multilayer polyimide film in which a biphenyltetracarboxylic acid-based thermoplastic polyimide layer is laminated on both surfaces of a biphenyltetracarboxylic acid-based high heat-resistant polyimide layer.
4) The first vapor deposition layer metal provided by the vapor deposition method is nickel, chromium, cobalt, palladium, molybdenum, tungsten, titanium, or zirconium, and the thickness is 1 to 30 nm, and the second metal layer is the vapor deposition method or vapor deposition. The metal provided by the plating method and the plating method is nickel, cobalt, or an alloy thereof, or Cu, and the thickness is 0.1 to 2.0 μm, and the outermost layer by the plating method is copper having a thickness of 0 to 30 μm. A polyimide film having the metal thin film as a layer.

In the present invention, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride (hereinafter sometimes simply referred to as s-BPDA) and 4,4′-diaminodiphenyl are preferably used as the polyimide film. Ether (hereinafter sometimes abbreviated simply as DADE), optionally further para-phenylenediamine (hereinafter sometimes simply abbreviated as PPD), and optionally further pyromellitic dianhydride (hereinafter simply referred to as PMDA). ) And 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride (BTDA) and a s-BPDA-DADE system (s-BPDA) having a thickness of 5 to 120 μm. And DADE.) Polyimide film.

Other types of aromatic tetracarboxylic dianhydrides and aromatic diamines such as 4,4'-diaminodiphenylmethane may be used as long as the physical properties of the polyimide film are not impaired. In addition, a substituent such as a hydroxyl group, a methyl group, or a methoxy group may be introduced into the aromatic ring of the aromatic tetracarboxylic dianhydride or aromatic diamine.

In particular, as the biphenyltetracarboxylic acid-based polyimide film in the present invention, a multilayer polyimide film in which a biphenyltetracarboxylic acid-based thermoplastic polyimide layer having a Tg (glass transition temperature) of 200 to 300 ° C. is laminated on both surfaces of a high heat-resistant polyimide layer. Is preferred. The biphenyltetracarboxylic acid-based polyimide film has a biphenyltetracarboxylic acid-based thermoplastic polyimide layer thickness of 1 to 10 μm, a high heat-resistant polyimide layer thickness of 5 to 120 μm, and an overall thickness of about 7 to 125 μm. A biphenyltetracarboxylic acid-based multilayer polyimide film having a high level of dimensional accuracy and rigidity is preferable.

As the above-mentioned high heat-resistant polyimide, in the case of a single-layer polyimide film, those which cannot be confirmed at a glass transition temperature of less than about 350 ° C. are preferable, and in particular, the linear expansion coefficient (50 to 200 ° C.) (MD , TD, and average of these) are preferably 5 × 10 ^{−6 to} 25 × 10 ⁻⁶ cm / cm / ° C. This highly heat-resistant polyimide is a random polymerization so that an arbitrary tetracarboxylic acid component and an aromatic diamine are approximately 1: 1 if the linear expansion coefficient and glass transition temperature of the finally obtained polyimide film are within the above ranges. It can be obtained by block polymerization, blending, or any method in which two or more kinds of polyamic acid solutions are synthesized in advance and the respective polyamic acid solutions are mixed to obtain a copolymer by recombination of the polyamic acids.

Among them, in particular, as a high heat-resistant polyimide, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride and para-phenylenediamine and optionally 4,4′-diaminodiphenyl ether Further, s-BPDA- obtained from pyromellitic dianhydride (hereinafter sometimes simply referred to as PMDA) and / or 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride (BTDA) PPD-based (meaning containing s-BPDA and PPD) polyimide film is preferred.

Examples of the aromatic tetracarboxylic acid component that gives the thermoplastic polyimide include 2,3,3 ′, 4′-biphenyltetracarboxylic dianhydride (hereinafter sometimes abbreviated as a-BPDA) and 3,3. ', 4,4'-biphenyltetracarboxylic dianhydride is mentioned, and a part of it is replaced with pyromellitic dianhydride, 3,3', 4,4'-benzophenonetetracarboxylic dianhydride, etc. Also good.

Examples of aromatic diamines that give thermoplastic polyimide include 4,4'-diaminodiphenyl ether, 4,4'-diaminobenzophenone, 4,4'-diaminodiphenylmethane, and 2,2-bis (4-aminophenyl). ) Propane, 1,3-bis (4-aminophenoxybenzene), 1,4-bis (4-aminophenoxy) benzene, 4,4′-bis (4-aminophenyl) diphenyl ether, 4,4 ′ -Bis (4-aminophenyl) diphenylmethane, 4,4'-bis (4-aminophenoxy) diphenyl ether, 4,4'-bis (4-aminophenoxy) diphenylmethane, 2,2-bis [4- ( Mention may be made of flexible aromatic diamines having a plurality of benzene rings such as aminophenoxy) phenyl] propane.

A part of the aromatic diamine is mixed with aliphatic diamine such as 1,4-diaminobutane, 1,6-diaminohexane, 1,8-diaminooctane, 1,10-diaminodecane, 1,12-diaminododecane, bis It may be replaced by diaminodisiloxane such as (3-aminopropyl) tetramethyldisiloxane. In addition, dicarboxylic acids such as phthalic anhydride and substituted products thereof, hexahydrophthalic anhydride and substituted products thereof, succinic anhydride and substituted products and derivatives thereof, etc. are used to seal the amine terminal of the thermoplastic polyimide. In particular, phthalic anhydride may be used.

Each of the polyimides described above is prepared by reacting the above components with other tetracarboxylic dianhydrides and other diamines in an organic solvent at a temperature of about 100 ° C. or less, particularly 20 to 60 ° C. An acid solution can be used as the dope solution. In order to obtain the polyimide film in the present invention, in the above organic solvent, the total amount of acids (as the total moles of tetraacid dianhydride and dicarboxylic acid) used as a ratio to the diamine (as moles) A ratio of 0.92 to 1.1, particularly 0.98 to 1.1, and particularly 0.99 to 1.1 is particularly preferable.

Further, for the purpose of limiting the gelation of polyamic acid, phosphorus stabilizers such as triphenyl phosphite and triphenyl phosphate are 0.01 to 1% based on the solid content (polymer) concentration during polyamic acid polymerization. It can be added in the range of. For the purpose of promoting imidization, a basic organic compound-based catalyst can be added to the dope solution. For example, imidazole, 2-imidazole, 1,2-dimethylimidazole, 2-phenylimidazole and the like are 0.01 to 20% by weight, particularly 0.5% with respect to the polyamic acid (solid content). It can be used at a ratio of -10% by weight. Since these form a polyimide film at a relatively low temperature, they are used to avoid imidation becoming insufficient.

Further, an organoaluminum compound, an inorganic aluminum compound or an organotin compound may be added to the thermoplastic polyimide raw material dope. For example, aluminum hydroxide, aluminum triacetylacetonate, or the like can be added in an amount of 1 ppm or more, particularly 1 to 1000 ppm as an aluminum metal with respect to polyamic acid (solid content).

The organic solvent used to obtain the polyamic acid is N-methyl-2-pyrrolidone, N, N-dimethylformamide, N, N-dimethylacetamide for both high heat-resistant polyimide and thermoplastic polyimide. N, N-diethylacetamide, dimethyl sulfoxide, hexamethylphosphoramide, N-methylcaprolactam, cresols and the like. These organic solvents may be used alone or in combination of two or more.

In the production of the multilayer polyimide film, a coextrusion-casting method, for example, a thermoplastic polyimide or a precursor solution thereof is coextruded on one or both sides of the polyamic acid solution of the high heat resistance polyimide described above. Then, a method of casting this on a support surface such as a stainless steel mirror surface or a belt surface, and making it a semi-cured state or a dried state before it at 100 to 200 ° C. is suitable. This semi-cured state or an earlier state means that it is in a self-supporting state by heating and / or chemical imidization.

The coextrusion of the polyamic acid solution that gives the high heat-resistant polyimide and the polyamic acid solution that gives the thermoplastic polyimide is, for example, a coextrusion method described in JP-A-3-180343 (Japanese Patent Publication No. 7-102661). Can be supplied to a three-layer extrusion die and cast on a support.

A multilayer film is formed by laminating a polyamic acid solution that gives thermoplastic polyimide on one or both sides of the extrudate layer that gives the high heat-resistant polyimide, and then deteriorates above the glass transition temperature of the thermoplastic polyimide. Is heated to a temperature below the temperature at which the water is generated, preferably 300 to 500 ° C. (surface temperature measured with a surface thermometer) (preferably heated at this temperature for 1 to 60 minutes) and dried and imidized. A multilayer polyimide film having thermoplastic polyimide on one or both sides, preferably both sides, of the high heat-resistant polyimide layer (base layer) can be produced.

The high heat-resistant polyimide layer has a thickness of 5 to 120 μm, particularly 5 to 70 μm, and preferably 5 to 40 μm. If the thickness is less than 5 μm, problems arise in the mechanical strength and dimensional stability of the produced multilayer polyimide film. On the other hand, when the thickness is more than 120 μm, there are difficulties in removing the solvent and imidization. The thermoplastic polyimide layer preferably has a thickness of 1 to 10 μm, particularly about 2 to 5 μm. If it is less than 1 μm, the adhesive performance is lowered, and even if it exceeds 10 μm, it can be used, but it is not particularly effective, but rather the heat resistance of the polyimide film is lowered.

The multilayer polyimide film has a thickness of 7 to 125 μm, and preferably 7 to 50 μm. When the thickness is less than 7 μm, it is difficult to handle the prepared film. When the thickness is greater than 125 μm, there are difficulties in removing the solvent and imidization. According to the co-extrusion-casting film forming method, a high heat-resistant polyimide layer and a single-sided or double-sided thermoplastic polyimide can be firmly laminated, and a multilayer polyimide film having good electrical and mechanical properties Can be obtained.

In the present invention, the surface of the polyimide film having the biphenyltetracarboxylic acid component is treated by leaching into a solution containing potassium permanganate and / or sodium permanganate and potassium hydroxide and / or sodium hydroxide. Then, a surface treatment is performed by acid treatment.

In the above leaching treatment, potassium permanganate and / or sodium permanganate at a concentration of 10 to 100 g / L and potassium hydroxide and / or sodium hydroxide at a concentration of 10 to 100 g / L are contained at 20 to 85 ° C. Preferably, the polyimide film is immersed in an aqueous solution of about 10 to 600 seconds. Before the leaching treatment, the surface is swollen with a mixed aqueous solution of diethylene glycol monobutyl ether (25%), ethylene glycol (10%) and sodium hydroxide (1 to 10 g / L). It doesn't matter. Moreover, although the said leaching process can also be performed by a batch method, it is preferable to perform continuously.

A leaching treatment is performed by the above-described method, and then an acid treatment is performed to neutralize the polyimide film surface. The conditions for the acid treatment are not particularly limited, but the treatment is completed with an inorganic acid such as sulfuric acid, hydrochloric acid or nitric acid, or an organic acid such as acetic acid or formic acid, preferably sulfuric acid, and preferably washed with water. To do. Following the surface treatment, it is preferable that the surface of the film is further subjected to plasma treatment immediately before forming the first layer metal thin film to clean the film surface and further improve the adhesion to the metal.

In the present invention, a metal film is formed on the surface-treated surface of the polyimide film whose adhesion to metal has been improved by the surface treatment method described above by a vapor deposition method or a combination of a vapor deposition method and an electroless plating and / or electroplating method. The polyimide film which has a metal thin film can be obtained.

In this invention, the metal vapor deposition onto the surface-treated surface of the polyimide film may be formed from two layers of a first vapor deposition metal layer and a second metal layer composed of a metal film sequentially laminated. As the metal constituting the first vapor-deposited metal layer deposited on the surface-treated surface of the polyimide film, there is no diffusion due to heat, one that strengthens the adhesion between the polyimide and the second vapor-deposited layer sequentially laminated, It is important to be strong and have good chemical properties and heat resistance. For this reason, it is preferable to use at least one selected from the group consisting of nickel, chromium, cobalt, palladium, molybdenum, tungsten, titanium, and zirconium.

In the above case, the deposition film thickness of the first deposited metal layer is preferably in the range of 1 to 30 nm. In these ranges, it is necessary to increase the adhesive strength and maintain the durability after heat load. If the vapor deposition film thickness is less than 1 nm, the adhesion to the polyimide film is insufficient, and the chemical resistance and heat resistance are insufficient, which is not preferable. On the other hand, if the deposited film thickness exceeds 30 nm, cohesive failure occurs inside the first deposited metal layer, causing a decrease in adhesive strength. Further, it is not preferable in terms of etching efficiency.

According to the surface treatment method of the present invention, a large number of irregularities are formed on the film surface as shown in the SEM observation diagram of FIG. For this reason, the first vapor-deposited metal layer is formed on the polyimide film surface-treated surface (one side or both sides) so that the vapor-deposited metal is mixed in the film in the thickness direction from the surface of the film. It is necessary to maintain durability after strengthening and heat loading. From the surface of the polyimide film, it is preferably formed so that the deposited metal is mixed in the film from a deep part of 1 nm or more, more preferably 2 nm or more. It is considered that the deposited layer to be formed becomes strong due to the anchoring effect by forming the deposited metal from the polyimide film.

The first vapor-deposited metal layer is preferably formed by vapor deposition on the surface-treated surface (one side or both sides) of the polyimide film by a heating vapor deposition method, a sputtering method, an ion plating method, or an ion assist method. As a vapor deposition condition for the first vapor deposition layer metal, it is preferable that the degree of vacuum when forming the vapor deposition film is a high vacuum of 5 × 10 ⁻⁴ Pa or less in advance. For sputtering, the gas pressure is preferably from the viewpoint of densification processing stability and film to not more than 5 Pa, it is preferable to hold the following further 5 × 10 -1 ^Pa. As the gas species to be used, nitrogen and hydrogen can be adopted in addition to rare gases such as argon, neon, krypton, and helium, but argon and nitrogen are more preferable because they are inexpensive.

It is preferable to warm the film temperature in the range of 30 to 280 ° C. in advance immediately before the vapor deposition in order to prevent the metal film from being oxidized by moisture adsorbed on the film and to increase the density and uniformity of the film. Furthermore, it is more preferable to set it as 30-120 degreeC. If it exceeds 280 ° C., it is not preferable because of blocking from uncooled after processing and generation of wrinkles during processing. For this heating, a heating roll or a heating heater just before vapor deposition may be used. Further, it is preferable that the surface of the film is further subjected to plasma treatment immediately before the first-layer metal thin film is formed after heating to further improve the adhesion with the metal by cleaning the film surface.

In the case of forming a second deposited layer of copper on the first deposited metal layer, the second deposited layer of copper is formed by depositing copper by a sputtering method, an ion plating method, an electron beam deposition method or the like. The thickness of the second deposited layer of copper is preferably in the range of 10 nm to 5 μm, and more preferably in the range of 100 to 500 nm. If the deposited film thickness is less than 10 nm, it is not preferable because it cannot be sufficiently fulfilled as a metal underlayer for plating. On the other hand, if the thickness exceeds 5 μm, the cost increases.

The vapor deposition processing of the first vapor-deposited metal layer and the second vapor-deposited layer may be carried out sequentially or discontinuously during film running. For example, the vapor deposition polyimide film once provided with the first vapor deposition metal layer may be conveyed in the reverse direction to vapor deposit the next second vapor deposition layer. However, releasing the vacuum system once after the first metal layer is deposited is not preferable from the viewpoint of adhesive strength because the first metal layer is oxidized.

The degree of vacuum when forming the second vapor deposition layer is preferably a high vacuum of 5 × 10 ⁻⁵ Pa or less in advance. In the case of sputtering, the gas pressure is preferably 5 Pa or less from the viewpoint of processing stability and film densification. Furthermore, it is preferable to hold | maintain to 5 * 10 < ^-1 > Pa or less. As the gas species used for vapor deposition, nitrogen and hydrogen can be adopted in addition to rare gases such as argon, neon, krypton, and helium, but argon and nitrogen are preferred because they are inexpensive.

On the second vapor deposition layer, a copper plating layer may be formed by a plating method including electroless plating and / or electroplating to thicken the conductor layer. The plating film thickness of the copper plating layer is preferably in the range of 0 to 20 μm. If it exceeds 20 μm, the accuracy of the line width in the high-density wiring is lowered, and it is disadvantageous in terms of light weight and downsizing in component mounting. Further, the cost increases, which is not preferable.

The polyimide film having a metal thin film according to the present invention is subjected to various treatments such as roll winding, etching, and, in some cases, curling back, and then cut into a predetermined size if necessary. Can be used as a substrate. For example, it can be suitably used as a substrate of FPC, TAB, multilayer FPC, or flex-rigid substrate.

Hereinafter, the present invention will be described in more detail with reference to examples. In each of the following examples, the peel strength of the polyimide film having a metal thin film is as follows: untreated after copper plating, 24 hours, 150 ° C. for 24 hours, 200 ° C. for 24 hours, and 121 ° C. for 2 atmospheres of humidity. The 90 ° peel strength (peel at a rate of 50 mm / min) of a sample cut into a width of 10 mm was measured for each of the samples that were left in a 100% atmosphere for 24 hours (PCT24H). The mechanical properties of the polyimide film were measured by ASTM D882.

Reference example 1
Preparation of multilayer polyimide film A highly heat-resistant polyimide dope having a monomer concentration of 18% by weight obtained by polymerizing PPD and s-BPDA in a molar ratio of 1: 1 in N-methyl-2-pyrrolidone; Three-layer extrusion molding of a dope for producing thermoplastic polyimide having a monomer concentration of 18% by weight obtained by polymerizing DADE and s-BPDA in a 1: 1 molar ratio in N-methyl-2-pyrrolidone A film forming apparatus provided with a die for use (multi-manifold type die) was cast on a metal support and continuously dried with hot air at 150 ° C. to form a solidified film. After peeling the solidified film from the support, the temperature is gradually raised from 200 ° C. to 525 ° C. in a heating furnace to remove the solvent and imidize, and the three-layer extruded polyimide film is taken up on a take-up roll. Thus, a three-layer extruded polyimide film was obtained.

The obtained three-layer extruded polyimide film exhibited the following physical properties.
Thickness configuration: 3 μm / 44 μm / 3 μm (total 50 μm)
The thermoplastic polyimide had a Tg of 275 ° C.
Volume resistance> 1 × 10 ¹⁵ Ω · cm
This multilayer polyimide film had a thermal linear expansion coefficient (50 to 200 ° C .: both MD and TD) in the range of 10 × 10 ^{−6 to} 20 × 10 ⁻⁶ × cm / cm / ° C.

Example 1
The multilayer polyimide film was surface-treated sequentially by the following steps.
1. Process 1
After immersing in an aqueous solution of potassium permanganate: 60 g / L and sodium hydroxide: 45 g / L for 1 minute, washed with water, neutralized with sulfuric acid: 50 mL / L, washed again with water, and the immersion treatment was completed.
2. Process 2
After the film treated in the treatment 1 is placed in the substrate folder in the sputtering apparatus, after evacuation to a vacuum of 2 × 10 ⁻⁴ Pa or less, argon is introduced to 0.67 Pa, and then the high frequency power of 13.56 MHz is applied to the electrode The surface was cleaned by plasma treatment at 500 w for 1 minute.

The obtained surface-treated film was formed into a metal film by the following process.
3. Metal film formation In succession to the above process, a 10 nm chromium thin film was formed in an argon 0.67 Pa atmosphere, and then a 0.4 μm copper thin film was formed and taken out into the atmosphere. Furthermore, using an electrolytic plating solution of an acidic copper sulfate aqueous solution, copper plating was performed so that the metal film had a thickness of 20 μm to obtain a polyimide film having a metal thin film. The evaluation results are summarized in Table 1.

Examples 2 and 3
Example 1 except that the time of immersion in an aqueous solution of potassium permanganate: 60 g / L and sodium hydroxide: 45 g / L was changed to 3 minutes (Example 2) or 5 minutes (Example 3) in Treatment 1. In the same manner as in No. 1, the polyimide film was surface-treated to obtain a polyimide film having a metal thin film. The results are summarized in Table 1.

Comparative Example 1
A polyimide film having a metal thin film was obtained in the same manner as in Example 1 except that the treatment 1 was not performed. Although the initial peel strength was 0.86 kg / cm, the peel strength of each sample after retreating at 150 ° C. and 200 ° C. and at 121 ° C. in an atmosphere of 2 atm humidity and 100% humidity for 24 hours significantly decreased. . The results are shown in Table 1 (processing time 0 min).

Comparative Example 2
The polyimide film was surface-treated in the same manner as in Example 1 except that Kapton H (Toray DuPont) was used as the polyimide film. After performing the treatment 1, the film surface was remarkably dissolved and could not proceed to the next step.

1 is an SEM observation view of the polyimide film surface-treated by treatment 1 in Example 1. FIG. FIG. 2 is an SEM observation view of an untreated polyimide film of Comparative Example 1.

Claims (6)

The surface of the polyimide film having a biphenyltetracarboxylic acid component is immersed in a solution containing potassium permanganate and / or sodium permanganate and potassium hydroxide and / or sodium hydroxide, and then treated with an acid to treat the metal. The surface treatment method characterized by improving the adhesive force of. The dipping treatment comprises potassium permanganate and / or sodium permanganate at a concentration of 10 to 100 g / L and potassium hydroxide and / or sodium hydroxide at a concentration of 10 to 100 g / L and 20 to 85 ° C. The surface treatment method according to claim 1, wherein the surface treatment is performed by immersing in an aqueous solution for about 10 to 600 seconds. The surface treatment method according to claim 1, further comprising plasma-treating the surface after the acid treatment. The surface according to any one of claims 1 to 3, wherein the polyimide film is a multilayer polyimide film in which a biphenyltetracarboxylic acid-based thermoplastic polyimide layer is laminated on one side or both sides of a biphenyltetracarboxylic acid-based high heat-resistant polyimide layer. Processing method. 5. A polyimide film having improved adhesion to metal by the surface treatment method according to claim 1, and having a metal thin film formed by forming a metal film by a vapor deposition method or a combination of a vapor deposition method and a plating method. Polyimide film. The first vapor deposition layer metal provided by the vapor deposition method is any one of nickel, chromium, cobalt, palladium, molybdenum, tungsten, titanium, zirconium, and has a thickness of 1 to 30 nm, and the second metal layer is a vapor deposition method or a vapor deposition method. The metal provided by the plating method is nickel, cobalt, or an alloy thereof, or copper, the thickness is 0.1 to 2.0 μm, and the outermost layer by the plating method is a copper layer having a thickness of 0 to 30 μm. A polyimide film having the metal thin film according to claim 4.

Images