JP2006130710A - Metal composite film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a metal composite film for a flexible printed wiring board excellent in heat resistance and adhesion and enabling the formation of fine wiring. <P>SOLUTION: The metal composite film is constituted by forming a thermoplastic polyimide layer at least on one side of an insulating film and applying electroless plating and electrolytic plating to the surface of the thermoplastic polyimide layer successively to form a metal layer. Since this metal composite film is excellent in heat resistance and adhesion and also excellent in adhesion even after the fine wiring is formed. It is suitably used as a high density flexible wiring board having a micro-circuit and the industrial practicality of a metal composite substrate to which this invention is adapted is extremely high. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a metal composite film that can be used as a flexible printed wiring board and has excellent adhesion between a metal and an insulating layer and adhesion in fine wiring.

  Conventionally, a flexible printed wiring board having a three-layer structure of insulating substrate / adhesive / metal foil using epoxy, acrylic, polyamide, phenol, etc. as an adhesive is well known. In addition, the adhesion of the metal layer was determined by the properties of the adhesive, and there were many problems in terms of heat resistance. In addition, a flexible printed wiring board (for example, Patent Documents 1 and 2) in which a thermoplastic polyimide precursor is used as an adhesive for improving heat resistance and a metal foil is thermocompression bonded at a high temperature is known. Since it has to be thermocompression bonded at a high temperature, there is a problem of residual distortion after processing, and since the thickness of the metal foil used for pressure bonding is usually 10 μm or more, patterning with a narrow pitch is difficult.

  Also known is a flexible printed wiring board having a two-layer structure in which a metal layer is formed by electrolytic plating after sputtering or electroless plating of a metal directly on an insulating film such as a non-thermoplastic polyimide film or an aramid film. In addition, there is a drawback in that the adhesion is low and the deterioration of the adhesion after heat load is particularly large.

  A flexible printed wiring board is also known in which a thermoplastic polyimide layer is provided on a non-thermoplastic polyimide, copper is sputtered on the surface, and then a metal layer is formed by electrolytic plating (for example, Patent Document 3). There was a problem that the adhesion in the wiring was lowered.

JP-A-4-146690 JP 2000-167980 A JP 2003-251773 A International Publication WO99 / 19771

  The objective of this invention is providing the metal composite film for flexible printed wiring boards excellent in heat resistance and adhesiveness in which fine wiring formation is possible.

  As a result of diligent research, the inventors of the present application have provided a thermoplastic polyimide layer on at least one surface of an insulating film, and formed a metal layer on the thermoplastic polyimide layer by electroless plating, and then by electrolytic plating. And it discovered that the metal composite film for flexible printed wiring boards excellent in adhesiveness and fine wiring formation was obtained, and reached | attained this invention.

  That is, the present invention provides a metal composite film having a metal layer formed by forming a thermoplastic polyimide layer on at least one surface of an insulating film, and further performing electroless plating on the surface of the thermoplastic polyimide layer, followed by electrolytic plating. provide.

  Since the metal composite film obtained in the present invention is excellent in heat resistance and adhesion and excellent in adhesion even after the formation of fine wiring, it is preferably used as a high-density flexible printed wiring board having fine circuits. The industrial utility of the metal composite substrate of the invention is extremely high.

  The insulating film used in the present invention is not particularly limited as long as it is an insulating film. Preferred examples include polyethylene terephthalate, polynaphthalene terephthalate, polyphenylene sulfide, and polyphenylene ether that have been used in flexible printed wiring boards. Resins, polyamide resins, aromatic polyamide resins such as Aramika (manufactured by Teijin Advanced Film Co., Ltd.), non-thermoplastic polyimide series and products under the trade name "Kapton" (manufactured by Toray DuPont, DuPont) Non-thermoplastic polyimide series with the name “UPILEX” (manufactured by Ube Industries), polyimide resin such as the non-thermoplastic polyimide series with the product name “APICAL” (manufactured by Kaneka Chemical Co., Ltd.), tetrafluoroethylene resin, fluoride Ethylene pro It can be mentioned alkylene copolymer resin, fluorine resin such as perfluoroalkoxy resin, trade name "VECSTAR" (manufactured by Kuraray Co., Ltd.) such as liquid crystal polymer or the like.

  Although the thickness of an insulating film is not specifically limited, 5-500 micrometers is preferable, More preferably, it is 5-125 micrometers.

  As the thermoplastic polyimide used in the present invention, a solvent-soluble polyimide resin is preferably used. Here, “solvent soluble” means dissolution in N-methyl-2-pyrrolidone (NMP) at a concentration of 5 wt% or more, preferably 10 wt% or more. When the insulating film has high heat resistance like a polyimide resin, it is possible to provide a thermoplastic polyimide layer by applying a polyamic acid solution, which is a precursor of the thermoplastic polyimide, followed by a heat dehydration cyclization reaction However, in consideration of application to a substrate having low heat resistance, a method of applying and drying a polyimide solution can be applied to a wider range of insulating films.

  A solvent-soluble polyimide can be produced by a direct imidation reaction between a diamine component and tetracarboxylic dianhydride (Patent Document 4). Preferred examples of the tetracarboxylic dianhydride constituting the polyimide (described in the form of a monomer) include 3,4,3 ′, 4′-biphenyltetracarboxylic dianhydride, 3,4,2 ′, 3 ′. -Biphenyltetracarboxylic dianhydride, 3,4,3 ', 4'-diphenyl ether tetracarboxylic dianhydride, 3,4,3', 4'-diphenylsulfone tetracarboxylic dianhydride, benzophenone tetracarboxylic acid Dianhydride, bis (dicarboxyphenyl) propane anhydride, pyromellitic acid, 4,4 ′-(2,2-isopropylidene) diphthalic dianhydride, bicyclo [2,2,2] oct-7-ene- 2,3,5,6-tetracarboxylic dianhydride and the like.

  Preferred examples of the diamine component constituting the polyimide (described in the form of monomer) include 3,3′-dicarboxyl-4,4′-diaminodiphenylmethane, 3,5-diaminobenzoic acid, and 2,4-diamino. Phenylacetic acid, 2,5-diaminoterephthalic acid, 1,4-diamino-2-naphthalenecarboxylic acid, 2,5-diamino-n-valeric acid, 1,4-diaminobenzene, 1,3-diaminobenzene, 2, 4-diaminotoluene, 4,4′-diaminodiphenylmethane, 3,4′-diaminodiphenyl ether, 4,4′-diaminodiphenyl ether, 3,3′-dimethyl-4,4′-diaminobiphenyl, 2,2′-dimethyl -4,4'-diaminobiphenyl, 4,4'-diaminobenzophenone, 3,3'-diaminobenzophenone, 4, 4′-bis (4-aminophenyl) sulfide, 4,4′-diaminodiphenylsulfone, 4,4′-diaminobenzanilide, 9,9-bis (4-aminophenyl) fluorene, 1,4-bis (4 -Aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 4,4'-bis (4-aminophenoxy) biphenyl, 4,4'-bis (3-aminophenoxy) biphenyl, 2,2 -Bis (4-aminophenoxyphenyl) propane, bis [4- (4-aminophenoxy) phenyl] sulfone, 2,2, -bis [4- (4-aminophenoxy) phenyl] hexafluoropropane, 3,3 ' -Dicarboxy-4,4'-diaminodiphenylmethane, 3,3 ', 5,5'-tetramethyl-4,4'-diaminodiphenylmeta 3,3 ′, 5,5′-tetraethyl-4,4′-diaminodiphenylmethane, 3,3′-diethyl-5,5′-dimethyl-4,4′-diaminodiphenylmethane, 3,3′-dihydroxy- 4,4′-diaminobiphenyl, hexamethylenediamine, isophoronediamine, 1,3-bis (3-aminopropyl) -1,1,3,3-tetramethyldisiloxane, α, ω-bis (3-aminopropyl) ) Polydimethylsiloxane and the like.

  It is preferable that the polyimide to be used contains a carboxyl group because it is particularly excellent in heat resistance and adhesion. The polyimide containing a carboxyl group can be preferably produced by using a diamine component having a carboxyl group. Examples of such diamine components include 3,3′-dicarboxyl-4,4′-diaminodiphenylmethane, 3,5-diaminobenzoic acid, 2,4-diaminophenylacetic acid, 2,5-diaminoterephthalic acid, 1 , 4-diamino-2-naphthalenecarboxylic acid, 2,5-diamino-n-valeric acid, and the like.

  Further, when bicyclo [2,2,2] oct-7-ene-2,3,5,6-tetracarboxylic dianhydride is contained as a tetracarboxylic dianhydride component, heat resistance and adhesion It is preferable because it is particularly excellent.

The direct imidation reaction between the diamine component and the tetracarboxylic dianhydride component can be carried out using a catalyst system utilizing the following equilibrium reaction of lactone, base and water.
{Lactone} + {base} + {water} = {acid group} ⁺ {base} ^―

Using this {acid group} ⁺ {base} ⁻ system as a catalyst, a polyimide solution can be obtained by heating to 120 to 200 ° C. Water generated by the imidization reaction is azeotroped with toluene and removed from the reaction system. When the imidization of the reaction system is completed, {acid group} ⁺ {base} ⁻ becomes a lactone and a base and loses the catalytic action, and at the same time is removed from the reaction system together with toluene. The polyimide solution obtained by this method can be used as it is as a high-purity polyimide solution because the catalyst substance is not contained in the polyimide solution after the reaction. It is also possible to use an acid catalyst such as p-toluenesulfonic acid.

  As a reaction solvent used for the imidization reaction, a polar organic solvent is used in addition to the above-described toluene. Examples of these organic solvents include polar solvents that dissolve polyimide, such as N-methyl-2-pyrrolidone, dimethylformamide, dimethylacetamide, dimethyl sulfoxide, sulfolane, and tetramethylurea γ-butyrolactone. It is also possible to use a mixture of ester, ketone or ether solvents, such as methyl benzoate as the ester solvent, methyl ethyl ketone, methyl propyl ketone, methyl isopropyl ketone as the ketone solvent. , Methyl butyl ketone, methyl isobutyl ketone, methyl-n-hexyl ketone, diethyl ketone, diisopropyl ketone, diisobutyl ketone, cyclopentanone, cyclohexanone, methylcyclohexanone, acetylacetone, diacetone alcohol, cyclohexene-n-one, etc. Solvents include dipropyl ether, diisopropyl ether, dibutyl ether, tetrahydrofuran, tetrahydropyran, ethyl isoamyl alcohol, ethyl tert-butyl ether, ethyl benzyl Ether, diethylene glycol dimethyl ether, Que Jill methyl ether, anisole, phenetole and the like can be used.

  In addition, γ-valerolactone is preferable as the lactone, and pyridine and / or methylmorpholine is preferable as the base.

  The mixing ratio (acid / diamine) of tetracarboxylic dianhydride and diamine used for the imidization reaction is preferably about 1.05 to 0.95 in terms of molar ratio. The concentration of the acid dianhydride in the entire reaction mixture at the start of the reaction is preferably about 4 to 16% by weight, the concentration of the lactone is preferably about 0.2 to 0.6% by weight, and the concentration of the base is 0.00. About 3 to 0.9% by weight is preferable, and the concentration of toluene is preferably about 6 to 15% by weight. Moreover, reaction time is not specifically limited, Although it changes with the molecular weight etc. of the polyimide which is going to manufacture, it is about 2 to 10 hours normally. The reaction is preferably performed with stirring.

  In addition, the manufacturing method of the polyimide itself using the two-component catalyst consisting of a lactone and a base is known, and is described in Patent Document 4, for example.

  A block copolymerized polyimide can be produced by sequentially performing the above-described imidization reaction in two steps using different acid dianhydrides and / or different diamines. According to the conventional method for producing polyimide via a polyamic acid, only a random copolymer can be produced. A block copolymerized polyimide can be produced by selecting any acid and / or diamine component, so that any desired property or function such as adhesion, dimensional stability, or low dielectric constant can be imparted to the polyimide. can do. In the present invention, such a copolymerized polyimide can be preferably employed.

  As a preferred method for producing a block copolymerized polyimide, a polyimide oligomer is obtained by using an acid catalyst produced from the above lactone and a base and increasing the amount of either an aromatic diamine or tetracarboxylic dianhydride component. Then, aromatic diamine and / or tetracarboxylic dianhydride is added (molar ratio of total aromatic diamine to total tetracarboxylic dianhydride is 1.05-0.95), and two-stage polycondensation is performed. A method can be mentioned.

  The thermoplastic polyimide used in the present invention desirably has a weight average molecular weight of 50,000 or more from the viewpoint of film properties, and preferably has a weight average molecular weight of 300,000 or less from the viewpoint of paint viscosity. Moreover, the ratio of the tetracarboxylic dianhydride and diamine used for the molecular weight control does not necessarily need to be equimolar. Further, the resin terminal may be sealed with an acid anhydride such as maleic anhydride or phthalic anhydride, or a monoamine such as aniline.

  The thermoplastic polyimide layer of the present invention can be easily formed by coating and drying the polyimide solution obtained by the above-described method on the surface of an insulating film. As the coating method, various methods such as reverse roll, rod (bar), blade, knife, comma, die, lip, gravure, and rotary screen are possible. The drying is not particularly limited as long as it can apply a temperature sufficient to remove the solvent to be used, such as a hot air dryer or an infrared dryer. 1-20 micrometers is preferable and, as for the thickness (after drying) of the thermoplastic polyimide layer of this invention, it is more preferable that it is 2-10 micrometers. If it is 1 micrometer or less, the effect of a resin layer will not fully be acquired but adhesiveness will fall. On the other hand, when it becomes thicker than 20 μm, there is a problem that the rate of dimensional change and solder heat resistance during moisture absorption are lowered.

  In the present invention, the metal used for the metal layer is not particularly limited as long as it is a practical metal for wiring, and copper is preferably used. Various methods can be used to form the metal layer. In the present invention, the metal layer is formed by electroless plating and then electrolytic plating on the thermoplastic polyimide layer.

  Since the electroless plating method itself is well known and various electroless plating solutions are commercially available, these commercially available solutions can be preferably used in the present invention. For example, after processing with Desmear liquid DS-250 and Neutralized reducing liquid DS-350 manufactured by EBARA Eugilite Co., Ltd., treatment with pre-dip liquid PI-3000, catalyst liquid PI-3500, and accelerator liquid PI-4000 It can be performed. Then, an electroless copper plating film can be deposited by immersing in electroless copper plating solution PI-5000.

  The electroless plating method itself is well known, and various apparatuses and solutions therefor are commercially available. In the present invention, these commercially available apparatuses and solutions can be preferably used. For example, after treatment with acidic degreasing solution PB-242D manufactured by EBARA Eugelite Co., Ltd., acid activation is performed, and electrolytic copper plating can be performed using Cu-Brite TH-RII (trade name). An arbitrary copper foil thickness can be obtained by changing the current density and the plating time.

  From the viewpoint that the thickness of the metal layer formed by the electroless plating and electrolytic plating (total thickness of both platings) has appropriate conductivity as the wiring, and has appropriate flexibility. 1-40 micrometers is preferable.

  Hereinafter, the present invention will be described more specifically based on examples. However, the present invention is not limited to the following examples.

Synthesis example 1
(A 2-liter capacity three-necked separable flask was equipped with a stainless steel squid type stirrer, a nitrogen gas inlet tube, and a reflux condenser with a condenser tube with a ball on a trap with a stopcock. Reacts in a stream of air: 44.9 g (200 mmol) of bicyclo [2,2,2] oct-7-ene-2,3,5,6-tetracarboxylic dianhydride, 3,5-diaminobenzoic acid 15 0.22 g (100 mmol), 3.0 g (30 mmol) of γ-valerolactone, 3.6 g (40 mmol) of pyridine, 300 g of N-methylpyrrolidone and 60 g of toluene were added to this at 180 ° C. while passing nitrogen gas. Toluene and water azeotrope was removed, and 29.4 g (100 milliliters) of 3,4,3 ′, 4′-biphenyltetracarboxylic dianhydride was added to the reaction mixture. Mol), 58.46 g (200 mmol) of 1,3-bis- (3-aminophenoxy) benzene, 268 g of N-methylpyrrolidone and 40 g of toluene were added, and the mixture was reacted for 1 hour at room temperature while passing nitrogen gas. The reaction was conducted for 3 hours while removing the azeotrope of toluene and water, and the polymerized polyimide had a polystyrene equivalent molecular weight of 58,900 in terms of number average molecular weight and 95,000 in terms of weight average molecular weight. Was 213-226 ° C., and the thermal decomposition start temperature was 422 ° C. The polyimide concentration in the obtained polyimide solution was 19.5% by weight.

Example 1
The thermoplastic polyimide solution obtained in Synthesis Example 1 is applied to a Kapton 100EN (trade name, manufactured by Toray DuPont Co., Ltd.) using a reverse roll coating machine, and then dried to a thickness of 5 μm. A polyimide layer was provided. Using a commercially available kit for electroless plating (manufactured by Sugawara Eugleite), electroless copper plating treatment was carried out in the steps shown in Table 1, and then, using a commercially available apparatus and kit (made by Sugawara Eugleite), Table 2 In this process, electrolytic copper plating was performed. A metal composite substrate of the present invention having a metal layer thickness of 12 μm was obtained. The evaluation results are shown in Table 3. In addition, the name of the various solutions described in Table 1 and Table 2 is a brand name of Ebara Eugelite.

Example 2
A metal composite substrate of the present invention was obtained in the same manner as in Example 1 except that Apical 25 NPI (trade name, manufactured by Kaneka Chemical Co., Ltd.) was used instead of Kapton 100EN (trade name).

Example 3
A metal composite substrate of the present invention was obtained in the same manner as in Example 1 except that Upilex 25SGA (trade name, manufactured by Ube Industries, Ltd.) was used instead of Kapton 100EN (trade name).

Comparative Example 1
A metal composite substrate similar to that of Example 1 was obtained except that the thermoplastic polyimide layer was not provided on Kapton 100EN. Table 3 shows the evaluation results of the obtained metal composite substrate.

Comparative Example 2
A 10 nm thick Ni thin film was formed on Kapton 100EN by sputtering, and then a 200 nm thick copper thin film was formed on the Ni film by sputtering. Thereafter, a copper plating layer having a thickness of 12 μm was provided by electroplating. The evaluation results are shown in Table 3.

Comparative Example 3
A metal composite substrate having a metal layer of 12 μm was obtained by the method described in Patent Document 3. The evaluation results are shown in Table 3.

線間絶縁抵抗：Ｌ／Ｓ＝５０μｍ、×：パターン形成不可能につき測定不能
吸湿ハンダ耐熱：Ｄ−２／１００＋６０ｓ／２８０℃

Insulation resistance between lines: L / S = 50 μm, X: Unmeasureable due to inability to form a pattern Heat-absorbing solder heat resistance: D-2 / 100 + 60 s / 280 ° C.

Claims (8)

  A metal composite film in which a thermoplastic polyimide layer is formed on at least one surface of an insulating film, and a metal layer is formed by electroless plating and then electrolytic plating on the surface of the thermoplastic polyimide layer.   The insulating film is made of any one of polyethylene terephthalate, polynaphthalene terephthalate, polyphenylene sulfide, polyphenylene ether resin, polyamide resin, aromatic polyamide resin, polyimide resin, fluorine resin, and liquid crystal polymer. Item 2. A metal composite film according to Item 1.   The metal composite film according to claim 1, wherein the insulating film has a thickness of 5 to 500 μm.   The metal composite film according to claim 1, wherein the thermoplastic polyimide is a polyimide resin having a carboxyl group.   The thermoplastic polyimide has a tetracarboxylic dianhydride component containing at least bicyclo [2,2,2] oct-7-ene-2,3,5,6-tetracarboxylic dianhydride and a carboxyl group. The metal composite film according to claim 4, which is a polyimide obtained by polycondensation with a diamine component containing at least a diamine.   The metal composite film according to any one of claims 1 to 5, wherein the thermoplastic polyimide is a block copolymerized polyimide.   The metal composite film according to any one of claims 1 to 6, wherein a thickness of the thermoplastic polyimide layer is 1 to 20 µm. The metal composite film according to claim 1, wherein the metal layer has a thickness of 1 to 40 μm.