JP2007161880A - Polyamic acid varnish composition and metal polyimide composite material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a metal polyimide composite material which has excellent adhesiveness to metals without intervening an adhesive layer and has the same polyimide linear thermal expansion coefficient as that of a metal, and to provide a polyamic acid varnish composition giving the same. <P>SOLUTION: This polyamic acid varnish composition is obtained by adding a vinyltriazine compound to a polyamic acid varnish comprising a solvent and a polyamic acid obtained by the addition polymerization of an aromatic tetracarboxylic acid dianhydride to an aromatic diamine. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a highly adhesive metal polyimide composite for flexible printed circuit boards, a polyimide resin used therefor, and a polyamic acid varnish composition for producing this polyimide resin.

  In recent years, with the miniaturization and portability of electronic devices, the use of flexible printed boards capable of high-density mounting of components and elements as circuit board materials is increasing. From the viewpoint of reliability such as miniaturization of wiring corresponding to further higher density and folding resistance, matching of linear thermal expansion coefficient of metal and insulating resin, improvement of adhesion, and polyimide layer forming insulating resin layer It is necessary to reduce the film thickness.

As a method for producing a metal polyimide composite material for a flexible substrate, a casting method in which a polyamic acid solution is directly applied to a metal foil to form a film is known. However, it has good linear thermal expansion coefficient matching with metal and high adhesion. It is difficult to apply at the same time, and in order to ensure adhesion, a thermoplastic polyimide, a soluble polyimide with a low glass transition temperature, or an adhesive layer with a polyamic acid solution with a low glass transition temperature after imidation is required, In order to realize this, a manufacturing method using multi-layer coating has been adopted (see Patent Document 1). Therefore, an increase in manufacturing cost, an increase in substrate cost due to a thick film, a decrease in folding resistance, and a decrease in reliability such as a wiring failure due to deformation of the adhesive layer during high-temperature bonding during mounting have been brought about. Although studies have been made to improve adhesion by using an additive such as an imidazole compound in the varnish without separately providing an adhesive layer (see Patent Document 2), the imidazole compound works as a plasticizer in the film. Therefore, there is a problem that the heat resistance such as the glass transition temperature and the linear thermal expansion coefficient is reduced.
Japanese Patent No. 2746555 Japanese Unexamined Patent Publication No. 4-85363

  The present invention has been made in view of the above situation, and the polyimide insulating layer on the metal has excellent adhesion to the metal without using an adhesive layer, and the linear thermal expansion coefficient of the metal is linear thermal expansion. It aims at providing the polyamic-acid varnish composition which can form the insulating layer used as an equivalent rate, and the metal polyimide composite for flexible printed circuit boards using the same.

As a result of intensive studies to solve the above problems, the present inventor has developed a polyamic acid varnish comprising a polyamic acid obtained by addition polymerization of an aromatic tetracarboxylic dianhydride and an aromatic diamine, and a solvent. In addition, the present inventors have found that the above-mentioned object can be achieved by applying and drying a polyamic acid varnish composition obtained by adding a vinyltriazine compound onto a metal foil and imidizing it.
That is, the present invention is as follows.
(1) A polyamic acid varnish comprising a polyamic acid obtained by addition polymerization of an aromatic tetracarboxylic dianhydride and an aromatic diamine, and a solvent, the polyamic acid varnish composition comprising a vinyltriazine compound object.
(2) The polyamic acid varnish composition wherein the vinyl triazine compound of (1) is 0.01 to 10 parts by weight with respect to 100 parts by weight of the polyamic acid.
(3) The polyimide resin whose linear thermal expansion coefficient in 50-200 degreeC after making it imidate from the polyamic-acid varnish composition of (1) is 8-25 ppm / degrees C.
(4) A metal polyimide composite comprising a polyimide layer obtained by imidizing the polyamic acid varnish composition described in (1) above on a metal.
(5) A polyimide copper composite in which the metal according to (4) is copper.

  The polyamic acid varnish composition of the present invention can be prepared, for example, by applying the polyamic acid varnish composition onto a metal, drying, and heating and imidizing. The metal polyimide composite thus obtained has excellent adhesion to the metal, and the linear thermal expansion coefficient of the polyimide resin is equivalent to the linear thermal expansion coefficient of the metal foil. It is suitable for wiring substrates such as required flexible printed boards and IC package boards.

Hereinafter, the present invention will be specifically described.
The vinyl triazine compound is a compound having a triazine skeleton and a functional group having a double bond derived from a vinyl group bonded to the triazine skeleton. Specifically, as shown in (Formula 1) to (Formula 4), 2,4-diamino-6-vinyl-s-triazine (Formula 1), 2,4-diamino-6-methacryloyloxyethyl-s -Triazine (formula 2) and 2,4-diamino-6-vinyl-s-triazine with an acid added thereto, isocyanuric acid adduct (formula 3), 2,4-diamino-6-methacryloyloxyethyl-s-triazine Isocyanuric acid adduct (formula 4) and the like. In view of heat resistance and price, 2,4-diamino-6s-triazine and 2,4-diamino-6-methacryloyloxyethyl-s-triazine are preferably used.

  The blending amount of the vinyl triazine compound in the polyamic acid varnish composition is preferably 0.01 to 10 parts by weight, more preferably 100 parts by weight of the polyamic acid which is a solid component, from the viewpoint of adhesion and heat resistance. 0.1 to 5 parts by weight. This is because if the amount is less than 0.01 part by weight, the adhesive strength and the heat resistance tend to be inferior, and if it exceeds 10 parts by weight, the heat resistance tends to decrease.

  A conventionally well-known thing can be used as aromatic tetracarboxylic dianhydride in the polyamic-acid varnish of this invention. For example, 3,4,3 ′, 4′-biphenyltetracarboxylic acid, 1,3-dihydro-1,3-dioxo-5-isobenzofurancarboxylic acid-1,4-phenylene ester, 2,3,3 ′, And dianhydrides such as 4′-biphenyltetracarboxylic acid, pyromellitic acid, benzophenonetetracarboxylic acid, oxydiphthalic acid, diphenylsulfonetetracarboxylic acid, and 2,3,6,7-naphthalenetetracarboxylic acid. From the viewpoint of improving heat resistance such as linear thermal expansion coefficient and glass transition temperature, 3,4,3 ′, 4′-biphenyltetracarboxylic dianhydride, 1,3-dihydro-1,3-dioxo-5- Use of isobenzofurancarboxylic acid-1,4-phenylene ester dianhydride, pyromellitic dianhydride, benzophenone tetracarboxylic dianhydride, 2,3,6,7-naphthalene tetracarboxylic dianhydride preferable.

  Moreover, each aromatic tetracarboxylic dianhydride may be used alone or in combination. Moreover, you may use dianhydrides, such as a non-aromatic tetracarboxylic dianhydride, cyclobutane tetracarboxylic acid, and cyclohexane tetracarboxylic acid, in the range which does not impair the effect of this invention.

  A conventionally well-known thing can be used also in the aromatic diamine in the polyamic-acid varnish of this invention. For example, paraphenylenediamine, metaphenylenediamine, 4,4′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, 4,4′-diaminobenzanilide, 2,2-dimethyl-4,4-diaminobiphenyl, 1, 3-bis (4-aminophenoxy) benzene, 1,3-bis (3-aminophenoxy) benzene, 2,2-bis (4-aminophenoxyphenyl) propane, 4,4′-bis (4-aminophenoxy) Biphenyl, 4,4′-bis (3-aminophenoxy) biphenyl, bis (4- (4-aminophenoxy) phenyl) sulfone, and bis (4- (3-aminophenoxy) phenyl) sulfone are exemplified. From the viewpoint of improving heat resistance such as linear thermal expansion coefficient performance and glass transition temperature, paraphenylenediamine, metaphenylenediamine, 4,4′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, 4,4′-bis ( 4-aminophenoxy) biphenyl is preferably used.

  The polyamic acid in this invention is obtained by making the said tetracarboxylic dianhydride component and diamine component react. The regularity of the repeating unit constituting the polyamic acid may include a block structure or a random structure.

  The polyimide resin of the present invention can be obtained by imidizing the polyamic acid varnish composition of the present invention. Usually, the molecular weight and terminal structure of the polyimide resin to be produced can be adjusted by adjusting the charging ratio of the tetracarboxylic dianhydride and the diamine compound used in the production. The molar ratio of total tetracarboxylic dianhydride to total diamine for obtaining a preferred molecular weight is 0.90 to 1.10.

  The terminal structure of the resulting polyimide becomes an amine or acid anhydride structure depending on the molar charge ratio of all tetracarboxylic dianhydrides and all diamines at the time of production. When the terminal structure is an amine, it may be end-capped with a carboxylic acid anhydride. Examples of these include phthalic anhydride, 4-phenylphthalic anhydride, 4-phenoxyphthalic anhydride, 4-phenylcarbonylphthalic anhydride, 4-phenylsulfonylphthalic anhydride, and the like. It is not limited to. You may use these carboxylic anhydrides individually or in mixture of 2 or more types.

  In addition, when the terminal structure is an acid anhydride, the terminal structure may be capped with a monoamine. Specific examples include aniline, toluidine, aminophenol, aminobiphenyl, aminobenzophenone, naphthylamine and the like. You may use these monoamines individually or in mixture of 2 or more types.

  From the viewpoint of consistency with the linear thermal expansion coefficient of the metal foil, the polyimide resin of the present invention is preferably a polyimide having a linear thermal expansion coefficient at 50 to 200 ° C. of 8 to 25 ppm / ° C. Adjustment of such a linear thermal expansion coefficient can be performed by adjustment of selection of aromatic tetracarboxylic dianhydride and aromatic diamine.

  As a solvent in the polyamic acid varnish composition of the present invention, any solvent can be used as long as it is mixed with the above polyamic acid. Examples thereof include γ-butyrolactone, γ-valerolactone, N-methyl-2-pyrrolidone, N, N- Examples include dimethylformamide, N, N-dimethylacetamide, dimethyl sulfoxide, 1,3-dioxane, 1,4-dioxane, cyclopentanone, cyclohexanone, diethylene glycol dimethyl ether, and tetramethylurea. Preferred solvents for use in the present invention are γ-butyrolactone, N, N-dimethylacetamide and N-methyl-2-pyrrolidone. These can be used alone or in admixture of two or more.

  There is no restriction | limiting in particular in the usage-amount of these solvents, According to the viscosity etc. of a polyamic-acid varnish composition, it can utilize.

  In addition, as long as physical properties are not impaired, additives such as dehydrating agents, fillers such as silica, surface modifiers such as silane coupling agents and titanate coupling agents, and pyridine, imidazole, and triazole that promote curing of polyimide An imidizing agent, etc. may be added.

  In the polyamic acid varnish composition of the present invention, a vinyl triazine compound is added to a polyamic acid varnish obtained by addition polymerization of an aromatic tetracarboxylic dianhydride and an aromatic diamine in a solvent, and mixed and dissolved. Can be obtained.

  There is no restriction | limiting in particular in solid content concentration in a solvent. The solid content concentration is a percentage of the weight of the wholly aromatic tetracarboxylic dianhydride and the aromatic diamine to the total weight of the wholly aromatic tetracarboxylic dianhydride and the aromatic diamine including the solvent. A preferable solid content concentration is 5 to 35%. More preferably, it is 10 to 25%.

About addition polymerization conditions, it can carry out according to the addition polymerization conditions of the polyamic acid currently performed conventionally. Specifically, first, an aromatic diamine is dissolved in a solvent at 0 ° C. to 80 ° C. in an inert atmosphere such as nitrogen, helium, or argon at atmospheric pressure, and the tetracarboxylic acid nitric acid is dissolved at 40 ° C. to 100 ° C. The addition polymerization is carried out for 4 to 8 hours while the anhydride is quickly added. Thereby, a polyamic acid varnish composition is obtained. About the viscosity of the polyamic acid varnish obtained, it is preferable to adjust the solid content concentration so as to be from 1 poise to 250 poise.

  The polyimide resin of the present invention can be obtained by subjecting the polyamic acid varnish composition of the present invention to solvent removal and thermal imidization (dehydration) under heating. There are no particular restrictions on the conditions for solvent removal and thermal imidization, but it can be carried out at 200 to 400 ° C., which is the temperature at which the imidization reaction proceeds, preferably in an inert atmosphere such as nitrogen, helium, or argon. . Although there is no restriction | limiting in particular also about reaction time, When progress of imidation and productivity are considered, Preferably it is 10 minutes-6 hours. From the viewpoint of reliability when a composite is formed with a metal, the linear thermal expansion coefficient of the polyimide resin at 50 to 200 ° C. is preferably 8 to 25 ppm / ° C.

  The metal polyimide composite of the present invention is one in which a polyimide resin insulating layer is provided on a metal. Although the thickness of a polyimide layer is not specifically limited, Preferably it is 50 micrometers or less, More preferably, it is 3-25 micrometers.

  Various metals can be used, but metal foils such as aluminum foil, copper foil, and stainless steel foil, stainless steel plate, and aluminum plate are suitably used for flexible printed circuit boards. These metal foils may be subjected to surface treatment such as mat treatment, plating treatment, chromate treatment, aluminum alcoholate treatment, aluminum chelate treatment, silane coupling agent treatment, and the like.

  Although the thickness of a metal is not specifically limited, Preferably it is 35 micrometers or less, More preferably, it is 18 micrometers or less.

  The metal polyimide composite can be produced as follows. First, the polyamic acid composition of the present invention is coated on a metal using a blade coater, a lip coater, a gravure coater or the like, and then dried to form a polyamic acid layer as a polyimide precursor layer. The coating thickness is affected by the solid content concentration of the polyamic acid varnish composition. A polyimide resin insulating layer can be formed by thermally imidizing the polyamic acid layer at 200 to 400 ° C. in an inert atmosphere such as nitrogen, helium, and argon.

  The metal polyimide composite obtained in this way has good adhesion between metal, particularly copper and the polyimide resin layer.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

In the following examples, the properties of the polyamic acid varnish composition and the physical properties of the polyimide resin after imidization and the copper polyimide composite were measured as follows.
(1) E-type viscosity Using an E-type viscometer (manufactured by Toki Sangyo Co., Ltd.), the viscosity of the polyamic acid varnish was measured at 23 ° C. at a rotational speed of 1 rpm to 5 rpm.
(2) Glass transition temperature (Tg) and coefficient of linear thermal expansion (CTE)
The obtained copper polyimide composite was cut into a length of 50 mm, a width of 3 mm, and a thickness of 25 μm, immersed in a ferric chloride aqueous solution (manufactured by Tsurumi Soda), and the copper layer was etched and washed with water. After drying the obtained polyimide film at 105 ° C. with a hot air dryer, using a thermal analyzer (TMA-50, manufactured by Shimadzu Corporation), a tensile mode, a 5 g load, a sample length of 15 mm, and a heating rate. Measurement was performed at 10 ° C./min in an N ₂ atmosphere, Tg was determined from the intersection of tangents, and the linear thermal expansion coefficient from 50 ° C. to 200 ° C. was calculated.
(3) Adhesive strength In the same manner as described above, a copper polyimide composite was cut into a length of 150 mm, a width of 10 mm, and a thickness of 25 μm, and a width of 3 mm at the center of the width of 10 mm was masked with a vinyl tape. The copper layer was etched and washed with water. Thereafter, the vinyl tape was removed, and the obtained flexible substrate was dried with a hot air dryer at 105 ° C., and then a copper foil having a width of 3 mm was peeled from the polyimide layer, and the stress was measured. The peeling angle was 180 degrees and the peeling speed was 50 mm / min.
(4) Solder heat resistance Cut out 3cm x 6cm copper polyimide composite, mask 2.5cm x 2.5cm at the center with vinyl tape, and immerse in ferric chloride aqueous solution (Tsurumi Soda). The copper foil layer was etched and washed with water. Thereafter, the vinyl tape was removed, and the obtained copper polyimide composite was dried with a hot air dryer at 105 ° C., and then the sample was placed in a solder bath set at 300 ° C. with the copper foil glossy side as a solder bath. Evaluation was performed based on changes in appearance when left to stand for 1 min.
(5) Boiling solder heat resistance In the same manner as described above, a copper polyimide composite having a length of 3 cm and a width of 6 cm was cut out, and a central portion of 2.5 cm × 2.5 cm was masked with vinyl tape, and a ferric chloride aqueous solution (Tsurumi The copper foil layer was etched and washed with water. Thereafter, the vinyl tape was removed, and the obtained sample was immersed in boiling water for 2 hours, then immersed in water at room temperature, taken out, wiped off water adhering to the surface, and immediately left at 280 ° C. for 1 min. Evaluation was made based on the appearance change.
(6) Water Absorption Rate The obtained copper polyimide composite was cut into a length of 10 cm × width of 10 cm × thickness of 25 μm and immersed in a ferric chloride aqueous solution (manufactured by Tsurumi Soda), and the copper foil layer was etched and washed with water. . The obtained polyimide film was heated and dried at 105 ° C. for 60 minutes, and then the mass was measured. Thereafter, the polyimide film was immersed in water at room temperature for 24 hours, and then water droplets on the film surface were wiped off and the mass was measured. The water absorption was calculated by the following formula.
Water absorption (%) = (mass after immersion−mass before immersion) / mass before immersion × 100

[Example 1]
To a 1000 ml glass separable three-necked flask equipped with a stainless steel vertical stirrer, 23.7 g (hereinafter abbreviated as PPD) of paraphenylenediamine (Seiko Chemical Co., Ltd.), 4,4′-diamino Dimethyl ether (manufactured by Wakoyama Seika Kogyo Co., Ltd.) (hereinafter abbreviated as ODA) 11 g of dimethylacetamide (dehydrated) (manufactured by Wako Pure Chemical Industries, Ltd.) (hereinafter DMAc) so that the solid content concentration is 15 wt% in a nitrogen gas atmosphere. It was dissolved in 694 ml at 50-80 ° C. and kept at 80 ° C. Thereafter, 80.8 g of 3,4,3 ′, 4′-biphenyltetracarboxylic dianhydride (manufactured by Ube Industries) (hereinafter abbreviated as BPDA) was gradually added to the flask and kept at 80 to 100 ° C. for 4 hours. Stir.

  The solid content concentration of the polyamic acid resin solution after completion of the reaction was 15 wt%, and the E-type viscosity was 65 poise. To 50 g of this polyamic acid, 0.45 g of 2,4-diamino-6-vinyl-s-triazine (product name VT manufactured by Shikoku Kasei Co., Ltd.) (corresponding to 6 parts by weight with respect to the solid content) was added and stirred. A uniform polyamic acid varnish was obtained. The E type viscosity was 75 poise.

  This polyamic acid varnish was coated on copper foil F3-WS (thickness 18 μm, electrolytic foil: Furukawa Circuit Foil Co., Ltd.) kept at 80 ° C. and allowed to stand for 30 minutes, and then 100 ° C. for 30 minutes in an air circulating drying oven. It dried and formed the 45-micrometer-thick polyamic acid layer. Heat treatment (imidization) at 150 ° C. for 30 minutes, 200 ° C. for 60 minutes, and 400 ° C. for 60 minutes (temperature increase rate: 5 ° C./min) in a nitrogen circulating oven in an air circulation type drying furnace, and a polyimide of 25 to 26 μm A copper polyimide composite having an insulating layer was obtained.

[Example 2]
To 50 g of the polyamic acid synthesized in Example 1, 0.27 g of 2,4-diamino-6-vinyl-s-triazine (product name VT manufactured by Shikoku Kasei Co., Ltd.) (corresponding to 3.6 parts by weight relative to the solid content) ), 2-ethyl-2-ethyl-4-methyl-imidazole (product name 2E4MZ, manufactured by Shikoku Kasei Co., Ltd.) 0.18 g (equivalent to 2.4 parts by weight with respect to the solid content) was added and stirred to obtain a uniform polyamide. An acid varnish was obtained. The E type viscosity was 75 poise.

  This polyamic acid varnish was coated on copper foil F3-WS (thickness 18 μm, electrolytic foil: Furukawa Circuit Foil Co., Ltd.) kept at 80 ° C. and allowed to stand for 30 minutes, and then 100 ° C. for 30 minutes in an air circulating drying oven. It dried and formed the 45-micrometer-thick polyamic acid layer. Heat treatment (imidization) at 150 ° C. for 30 minutes, 200 ° C. for 60 minutes, and 400 ° C. for 60 minutes (temperature increase rate: 5 ° C./min) in a nitrogen circulating oven in an air circulation type drying furnace, and a polyimide of 25 to 26 μm A copper polyimide composite having an insulating layer was obtained.

[Comparative Example 1]
In a 1000 ml glass separable three-necked flask equipped with a stainless steel vertical stirrer, 23.7 g of PPD (manufactured by Seiko Chemical Co., Ltd.) and 11 g of ODA (manufactured by Wakayama Seika Kogyo Co., Ltd.) are added with nitrogen gas. It melt | dissolved in 694 ml of DMAc (dehydration) (made by Wako Pure Chemical Industries Ltd.) at 50-80 degreeC so that it might become 15 wt% of solid content concentration under an atmosphere, and hold | maintained at 80 degreeC. Thereafter, 80.8 g of BPDA (manufactured by Ube Industries) was gradually added to the flask and stirred for 4 hours while maintaining at 80 to 100 ° C.

  The solid content concentration of the polyamic acid resin solution after completion of the reaction was 15 wt%, and the E-type viscosity was 65 poise. To 50 g of polyamic acid, 0.45 g of 2-ethyl-4-methyl-imidazole (product name 2E4MZ, manufactured by Shikoku Kasei Co., Ltd.) (equivalent to 6 parts by weight with respect to the solid content) was added and stirred to obtain a uniform polyamic acid varnish. Got. The E type viscosity was 75 poise.

  This polyamic acid varnish was coated on copper foil F3-WS (thickness 18 μm, electrolytic foil: Furukawa Circuit Foil Co., Ltd.) kept at 80 ° C. and allowed to stand for 30 minutes, and then 100 ° C. for 30 minutes in an air circulating drying oven. It dried and formed the 45-micrometer-thick polyamic acid layer. Heat treatment (imidization) at 150 ° C. for 30 minutes, 200 ° C. for 60 minutes, and 400 ° C. for 60 minutes (temperature increase rate: 5 ° C./min) in a nitrogen circulating oven in an air circulation type drying furnace, and a polyimide of 25 to 26 μm A copper polyimide composite having an insulating layer was obtained.

[Comparative Example 2]
In a 1000 ml glass separable three-necked flask equipped with a stainless steel vertical stirrer, 23.7 g of PPD (manufactured by Seiko Chemical Co., Ltd.) and 11 g of ODA (manufactured by Wakayama Seika Kogyo Co., Ltd.) are added with nitrogen gas. It melt | dissolved in 694 ml of DMAc (dehydration) (made by Wako Pure Chemical Industries Ltd.) at 50-80 degreeC so that it might become 15 wt% of solid content concentration under an atmosphere, and hold | maintained at 80 degreeC. Thereafter, 80.8 g of BPDA (manufactured by Ube Industries) was gradually added to the flask and stirred for 4 hours while maintaining at 80 to 100 ° C.

  The solid content concentration of the polyamic acid resin solution after completion of the reaction was 15 wt%, and the E-type viscosity was 65 poise. 0.45 g of benzoguanamine (manufactured by Wako Pure Chemical Industries, Ltd.) (equivalent to 6 parts by weight with respect to the solid content) was added to 50 g of polyamic acid and stirred to obtain a uniform polyamic acid varnish. The E type viscosity was 90 poise.

  This polyamic acid varnish was coated on copper foil F3-WS (thickness 18 μm, electrolytic foil: Furukawa Circuit Foil Co., Ltd.) kept at 80 ° C. and allowed to stand for 30 minutes, and then 100 ° C. for 30 minutes in an air circulating drying oven. It dried and formed the 45-micrometer-thick polyamic acid layer. Heat treatment (imidization) at 150 ° C. for 30 minutes, 200 ° C. for 60 minutes, and 400 ° C. for 60 minutes (temperature increase rate: 5 ° C./min) in a nitrogen circulating oven in an air circulation type drying furnace, and a polyimide of 25 to 26 μm A copper polyimide composite having an insulating layer was obtained.

  In the polyamic acid varnish composition of the present invention, the polyimide insulating layer has excellent adhesion to metal without using an adhesive, and the linear thermal expansion coefficient of polyimide is equivalent to the linear thermal expansion coefficient of metal. Can be formed. It is suitable for wiring base materials such as high-density wiring and highly reliable flexible printed circuit boards and IC package boards.

Claims (5)

  A polyamic acid varnish comprising a polyamic acid obtained by addition polymerization of an aromatic tetracarboxylic dianhydride and an aromatic diamine, and a solvent, comprising a vinyltriazine compound.   A polyamic acid varnish composition, wherein the vinyl triazine compound according to claim 1 is 0.01 to 10 parts by weight with respect to 100 parts by weight of polyamic acid.   The polyimide resin whose linear thermal expansion coefficient in 50-200 degreeC after imidating the polyamic-acid varnish composition of Claim 1 is 8-25 ppm / degrees C.   A metal-polyimide composite comprising a polyimide layer obtained by imidizing the polyamic acid varnish composition according to claim 1 on a metal.   The metal-polyimide composite according to claim 4, wherein the metal is copper.