JP2005067145A - Metalized polyimide film and its production method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a metalized polyimide film which does not deteriorate the etching characteristic and plating life of a wiring circuit pattern and has a strong adhesive strength, excellent durability and good migration resistance, and also to provide its production method. <P>SOLUTION: This metalized polyimide film has a nickel-chrome alloy-sputtered layer as a base layer and a thickened metal layer, and has an oxygen permeability of ≤20 ml/m<SP>2</SP>/day/atm and a thermal linear expansion coefficient of ≤12 ppm/°C. The production method for the film comprises plasma-treating the surface of the film, sticking nickel-chrome alloy thereon by sputtering to obtain a thickness of 20-2,000 Å, sticking a thickened metal, electroplating the thickened metal, and then performing heat treatment at 200-350°C. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a metallized polyimide film for use in a flexible printed wiring board that reduces the size and weight of electronic devices and components. More specifically, the present invention relates to the metallized polyimide film for flexible printed wiring boards used in TAB, COF, PGA, etc. in semiconductor packaging. In more detail, by using a polyimide film having a specific composition as a base film and providing a sputter layer (seed layer) of a nickel-chromium alloy with a certain thickness between the base film and the copper layer, adhesion, reliability, etc. The present invention relates to a metallized polyimide film improved in the thickness and a method for producing the same.

  Conventionally, a metallized polyimide film used for a so-called three-layer flexible printed wiring board in which a metal foil such as a copper foil or an aluminum foil is bonded to a polyimide film with an adhesive is known. This has the following problems considered to be caused by the adhesive used. First of all, there are drawbacks in that the dimensional accuracy is deteriorated due to thermal inferior performance than the film, and the electrical characteristics are deteriorated due to impurity ion contamination. In addition, there is a drawback that the workability such as the thickness of the adhesive layer and the drilling of a double-sided hole is lowered. Therefore, it can be said that there are many inconvenient points for reducing the size and weight.

On the other hand, a metal layer is formed on a polyimide film by a method such as vacuum deposition, sputtering, ion plating, or copper plating without using an adhesive. For a two-layer flexible printed wiring board without a so-called thin film type adhesive layer Metallized polyimide films have been proposed.
For example, a flexible electric circuit carrier in which a chromium-based ceramic vapor deposition layer, a copper or copper alloy vapor deposition layer, and a copper plating layer are sequentially provided on an insulating film has been proposed (see Patent Document 1).
JP-A-4-329690

In addition, a method for producing a metal-film laminate, in which a metal oxide by plasma is randomly arranged on a polymer film and then includes a metal vapor deposition layer and a metal plating layer has been proposed (see Patent Document 2).
Further, a chromium / chromium oxide sputtering layer having a thickness of 25 to 150 Å is provided on the electrically insulating support film, and a copper sputtering layer having a thickness of less than 1 micron is applied, and a photoresist composition is applied to the copper layer. A method for manufacturing a circuit material has been proposed (see Patent Document 3).
JP-A-4-290742 Japanese Patent Application Laid-Open No. Sho 62-293689

In addition, a part or all of the deposited metal is mixed in the film in the thickness direction facing inward from the surface of the film on one or both sides of the polyimide film containing 0.02 to 1% by weight of tin in the film. A flexible print comprising a first vapor-deposited metal layer having a thickness in a range of 10 to 300 angstroms including the mixed layer, and then a second vapor-deposited layer made of copper on the vapor-deposited layer. It is a wiring board, and the first metal layer is preferably at least one selected from the group of chromium, a chromium alloy and a chromium compound, and the metal constituting the first vapor-deposited metal layer is less than 20% chromium. A flexible printed wiring board made of nichrome has been disclosed (see Patent Document 4).
JP-A-8-330728

As can be seen from these examples, the conventional thin film type metallized polyimide film is produced by first forming some base layer on the polyimide film and then forming copper as a good conductive material thereon. . There is no chemical bonding force between the metal layer, which is the conductive layer, and the polyimide film, which is the base material, and a micro base layer is microscopically applied to the surface of the base material, while copper is a metal / metal bond. Thus, the adhesive force is expressed through the underlayer.
When a non-metal or metal oxide is used for the underlayer, it is difficult to remove the underlayer by etching, and the metal oxide left between the lines due to the reducing action in the electroless plating process, etc. May be reduced and become a conductive metal foreign matter, resulting in poor insulation between wires. Further, chromium oxide often used as an underlayer is considered to be an unfavorable compound for environmental hygiene.

  When a metal other than copper is used for the underlayer, it becomes a problem whether the underlayer can be removed with a copper etching solution. If a metal having better corrosion resistance than copper is used, the removal of the underlying metal becomes insufficient, and the insulation between the lines may be lowered. In the case of a metal that is easier to etch than copper, the underlying portion is easily over-etched, and the effective adhesive strength of the conductor is likely to be reduced. Furthermore, even if the lowering of the insulation property due to the base metal itself is not a problem, the metal remaining during the electroless plating in the subsequent process shows catalytic activity, and the plated metal may be deposited between the lines to cause a short circuit. is there. Furthermore, there is a concern that the base material remaining between the wirings may deteriorate the migration resistance between the wirings.

A base metal thin film and a copper thin film were formed on one surface of the polyimide film, and the other surface was constituted by a thin film with low oxygen permeability, and a circuit copper layer was provided on one or both surfaces of the polyimide film. Materials for flexible printed circuit boards have been proposed (see Patent Document 5).
The proposal was made from the viewpoint that the decrease in adhesive force is due to the oxidation of the interface between the metal and the polyimide film. However, all the materials with low oxygen permeability exemplified are brittle and have high flexibility. It is unsuitable for the required flexible printed wiring board.
JP-A-6-29634

From this point of view, in recent years, metalized polyimide films using nickel-chromium-based alloys as a base have attracted attention, and nickel-chromium-based alloy layers are used as base layers for general polyimide films, and further thickened with copper. There is an example of a metallized film (see, for example, Patent Document 6).
Nickel-chromium alloys are materials that have a relatively high resistance to oxidative embrittlement and can be expected to have an appropriate anchor effect. In the case of a nickel-chromium alloy, if the chromium content is relatively low, it can be easily removed with a copper etchant, resulting in an abnormal deposition of electroless plating and a decrease in insulation between wires due to migration. Hateful. However, if the chromium content is low, the hardness of the alloy is low, so that the anchoring effect is low, and furthermore, the oxidation resistance is lowered, so that it is difficult to obtain sufficient adhesion. Conversely, if the chromium content is large, the adhesive strength is improved, but the corrosion resistance of the alloy film is increased and the removal by etching becomes difficult, so that the insulation reliability between the wirings is lowered.
JP 2002-252257 A

  In recent years, the demand for high-density wiring in the semiconductor industry has been advanced, and in the above-described advanced semiconductor package for high-density wiring, the above-described conventional technology has reliability such as durability against changes in temperature and humidity in the usage environment. Sex cannot meet market demands.

  In view of such a situation, the present inventors have excellent adhesion between a copper foil and a substrate, are excellent in insulation reliability and migration resistance, and are practically used as a highly reliable substrate such as COF, TAB, and FPC. As a result of continuing research aimed at realizing sufficient metallized polyimide film, the specific characteristics of metallized polyimide film with a sputter layer of nickel-chromium alloy having a certain thickness as the underlayer for metallization It has been found that the above-mentioned object can be achieved by using a polyimide film having the above as a base material.

That is, according to the present invention, a metallized polyimide film having a sputter layer of nickel-chromium alloy as the underlayer and further having a thickened metal layer, the oxygen permeability of the polyimide film is 20 ml / m ² · day · It is a metallized polyimide film characterized by having a thermal linear expansion coefficient of 12 ppm / ° C. or less, and atm or less. Preferably, the polyimide is a metallized polyimide film comprising a polyimide obtained by reacting an aromatic diamine having a benzoxazole structure and an aromatic tetracarboxylic acid anhydride. Further, after the surface of the polyimide film is plasma-treated, a nickel-chromium alloy is deposited by sputtering so as to have a thickness of 20 to 2000 mm, and then a thick metal is deposited by sputtering and / or vapor deposition, Furthermore, it is a manufacturing method of the metallized polyimide film characterized by carrying out the electrolytic plating of the thick metal, and also performing the heat processing of 200-350 degreeC.

  The metallized polyimide film of the present invention uses a polyimide film having a specific structure having a low oxygen permeability and a low coefficient of thermal expansion as a base material, and further has a base film by heat treatment in the manufacturing process. Since the strain and strain generated in the process of metallized polyimide film are alleviated, the deterioration of interfacial adhesion due to oxidative degradation of the underlayer is suppressed, and its durability is improved, and the substrate due to changes in heat and humidity Since there are few changes in the shape of the film, it has excellent electrical characteristics, without reducing the etching properties and plating resistance of the wiring circuit pattern, and without lowering the adhesive strength even when exposed to prolonged heating or wet heat, Furthermore, it has excellent migration resistance. Therefore, even in a thin semiconductor package with high-density wiring, durability against changes in temperature and humidity in the usage environment of the semiconductor package is improved, and the reliability of the semiconductor is increased. In the production method of the present invention, the metallized polyimide film having the above-described characteristics can be produced stably and economically.

Hereinafter, embodiments of the metallized polyimide film of the present invention and the manufacturing method thereof will be described in detail.
A schematic cross-sectional view of the metallized polyimide film of the present invention is shown in FIG. As shown in FIG. 1, the metallized polyimide film of the present invention has a base film 1 and a thick metal layer (3. conductive layer (sputter) and 4. thick layer (electroplating)), A sputter layer 2 of nickel-chromium alloy is provided.

In the present invention, it is essential to use a polyimide film having an oxygen permeability of 20 ml / m ² · day · atm or less and a thermal linear expansion coefficient of 12 ppm / ° C. or less. Oxygen permeability is preferably from ^{14ml / m 2 · day · atm} , more preferably not more than ^{9ml / m 2 · day · atm} , and particularly preferably ^{7ml / m 2 · day · atm} .
In the metallized polyimide film, the adhesion between the metal foil and the film is governed by the anchor effect. In order for the anchor effect to be exhibited effectively, the interface needs to be robust. The greatest cause of the deterioration of the interface robustness is the oxidative deterioration of the metal surface. By using a material having a low oxygen permeability, the deterioration of the interface robustness can be minimized.

In the present invention, the thermal expansion coefficient of the polyimide film is preferably in the range of 0 to 11 ppm / ° C, more preferably in the range of 2 to 10 ppm / ° C, and still more preferably in the range of 3 to 9 ppm / ° C. By using a polyimide film having such characteristics, the above-described metallized polyimide film having excellent durability can be obtained.
If the coefficient of thermal linear expansion greatly exceeds this range, the dissociation from the coefficient of thermal linear expansion of the metal increases, and stress may be generated between the film and the metal surface when heated to cause a decrease in adhesive strength. In addition, since the region of about 12 to 18 is close to the thermal linear expansion coefficient of copper, which is a metal layer that is preferably used, it does not affect the film / metal adhesion. The dissociation from the thermal linear expansion coefficient of the element, particularly silicon or gallium athenite single crystal, is increased, and breakage of the junction is likely to occur during soldering or during a long-term temperature cycle. Furthermore, when the linear expansion coefficient is smaller than a predetermined range, the difference between both the metal and the semiconductor becomes large, so that the reliability is greatly lowered.

Water vapor permeability of the polyimide film in the present invention is preferably at least ^{3ml / m 2 · day · atm} , more preferably not less than ^{6ml / m 2 · day · atm} , more 12ml / m ² · day · atm is more preferred 20 ml / m ² · day · atm or more is particularly preferable.
Polyimide is a material that easily absorbs moisture due to its imide structure. Moisture absorption of the base film is a troublesome problem that may cause various problems in the process of releasing absorbed moisture when heated. Such moisture that has been absorbed becomes particularly problematic at the bonding interface between the film and the metal. A high water vapor transmission rate means that moisture absorbed near the interface can be effectively released. Such an effect becomes more prominent as the water vapor transmission rate is higher, and is further promoted as the water vapor transmission rate is higher than the oxygen transmission rate.

  Control of the oxygen permeability and water vapor permeability of such a polyimide film can be realized, for example, by compounding a polyimide film with a material that can control gas permeability. As such a gas permeability control material, polyvinylidene chloride, polyvinyl alcohol, ethylene-polyvinyl alcohol copolymer and the like are used for polymer materials, and alumina-silica ceramic thin film, zinc sulfide thin film, SiO 2 for inorganic materials. -X thin film etc. can be illustrated. Examples of the composite form include multilayering, blending, dispersion, solid solution, blending, alloying, and the like.

Since the polyimide film in the present invention needs to have a low thermal linear expansion coefficient as well as control of oxygen transmission rate and water vapor transmission rate, it is a preferred embodiment to use a polyimide having a specific composition described below. This method is recommended because it has a merit that durability can be improved as compared with the method in which the oxygen permeability is lowered by the above method.
In the case of polyimide, when an ether bond is introduced into the main chain, the flexibility of the molecule is increased and the free volume is increased, so that both oxygen permeability and water vapor permeability are increased. On the other hand, if the main chain has no bent structure such as an ether bond, and a component in which the planar structure of the aromatic ring is coplanar is introduced, a structure in which the aromatic ring is laminated by orientation is developed, rigidity is increased, oxygen Both the transmittance and water vapor permeability are low.
Even in such a rigid structure, the inventors have a polar structure (for example, benzoxazole structure) in the main chain, the nonpolar gas permeability is maintained in a low state, but a polar gas, for example, water vapor As a result, the inventors have found that the permeability increases, and a polyimide film having a low water vapor transmission rate and a high water vapor transmission rate has been obtained.
That is, the polyimide preferably used in the present invention specifically includes a polyimide obtained by condensation of a diamine having a benzoxazole structure and an aromatic tetracarboxylic acid anhydride. In general, polyimide is a green film obtained by applying a polyamic acid solution obtained by reacting diamines and tetracarboxylic anhydride in a solvent to a support and drying to form a green film. Further, on the support or from the support. The green film can be obtained by subjecting the green film to a high temperature heat treatment in a peeled state to carry out a dehydration ring closure reaction.

Specific examples of the aromatic diamine having a benzoxazole structure in the present invention include the following.

Can be illustrated. Even if this diamine is individual, it is also possible to use 2 or more types.

  In the present invention, one or two or more diamines having no benzoxazole structure exemplified below may be used as long as they are 30 mol% or less of the total diamine. For example, 4,4′-bis (3-aminophenoxy) biphenyl, bis [4- (3-aminophenoxy) phenyl] ketone, bis [4- (3-aminophenoxy) phenyl] sulfide, bis [4- (3 -Aminophenoxy) phenyl] sulfone, 2,2-bis [4- (3-aminophenoxy) phenyl] propane, 2,2-bis [4- (3-aminophenoxy) phenyl] -1,1,1,3 , 3,3-hexafluoropropane, m-phenylenediamine, o-phenylenediamine, p-phenylenediamine, m-aminobenzylamine, p-aminobenzylamine, 3,3′-diaminodiphenyl ether, 3,4′-diamino Diphenyl ether, 4,4′-diaminodiphenyl ether, 3,3′-diaminodiphenyl sulfide, 3, '-Diaminodiphenyl sulfoxide, 3,4'-diaminodiphenyl sulfoxide, 4,4'-diaminodiphenyl sulfoxide, 3,3'-diaminodiphenyl sulfone, 3,4'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl sulfone 3,3′-diaminobenzophenone, 3,4′-diaminobenzophenone 4,4′-diaminobenzophenone, 3,3′-diaminodiphenylmethane, 3,4′-diaminodiphenylmethane, 4,4′-diaminodiphenylmethane, bis [ 4- (4-aminophenoxy) phenyl] methane, 1,1-bis [4- (4-aminophenoxy) phenyl] ethane, 1,2-bis [4- (4-aminophenoxy) phenyl] ethane, 1, 1-bis [4- (4-aminophenoxy) phenyl Propane, 1,2-bis [4- (4-aminophenoxy) phenyl] propane, 1,3-bis [4- (4-aminophenoxy) phenyl] propane, 2,2-bis [4- (4-amino) Phenoxy) phenyl] propane, 1,1-bis [4- (4-aminophenoxy) phenyl] butane, 1,3-bis [4- (4-aminophenoxy) phenyl] butane, 1,4-bis [4- (4-aminophenoxy) phenyl] butane, 2,2-bis [4- (4-aminophenoxy) phenyl] butane, 2,3-bis [4- (4-aminophenoxy) phenyl] butane, 2- [4 -(4-aminophenoxy) phenyl] -2- [4- (4-aminophenoxy) -3-methylphenyl] propane, 2,2-bis [4- (4-aminophenoxy) -3-methylphen Nyl] propane, 2- [4- (4-aminophenoxy) phenyl] -2- [4- (4-aminophenoxy) -3,5-dimethylphenyl] propane, 2,2-bis [4- (4- Aminophenoxy) -3,5-dimethylphenyl] propane, 2,2-bis [4- (4-aminophenoxy) phenyl] -1,1,1,3,3,3-hexafluoropropane, 1,4- Bis (3-aminophenoxy) benzene, 1,3-bis (3-aminophenoxy) benzene 1,4-bis (4-aminophenoxy) benzene, 4,4′-bis (4-aminophenoxy) biphenyl, bis [ 4- (4-aminophenoxy) phenyl] ketone, bis [4- (4-aminophenoxy) phenyl] sulfide, bis [4- (4-aminophenoxy) phenyl] sulfoxide Bis [4- (4-aminophenoxy) phenyl] sulfone, bis [4- (3-aminophenoxy) phenyl] ether, bis [4- (4-aminophenoxy) phenyl] ether, 1,3-bis [4- (4-aminophenoxy) benzoyl] benzene, 1,3-bis [4- (3-aminophenoxy) benzoyl] benzene, 1,4-bis [4- (3-aminophenoxy) benzoyl] benzene, 4,4 ′ -Bis (3-aminophenoxy) benzoyl] benzene, 1,1-bis [4- (3-aminophenoxy) phenyl] propane, 1,3-bis [4- (3-aminophenoxy) phenyl] propane, 3, 4'-diaminodiphenyl sulfide, 2,2-bis [3- (3-aminophenoxy) phenyl] -1,1,1,3,3,3-hexaph Oropropane, bis [4- (3-aminophenoxy) phenyl] methane, 1,1-bis [4- (3-aminophenoxy) phenyl] ethane, 1,2-bis [4- (3-aminophenoxy) phenyl] Ethane, 2,2-bis [4- (3-aminophenoxy) phenyl] sulfoxide, 4,4′-bis [3- (4-aminophenoxy) benzoyl] diphenyl ether, 4,4′-bis [3- (3 -Aminophenoxy) benzoyl] diphenyl ether, 4,4'-bis [4- (4-amino-α, α-dimethylbenzyl) phenoxy] benzophenone, 4,4'-bis [4- (4-amino-α, α -Dimethylbenzyl) phenoxy] diphenylsulfone, bis [4- {4- (4-aminophenoxy) phenoxy} phenyl] sulfone, 1,4-bis 4- (4-aminophenoxy) phenoxy-α, α-dimethylbenzyl] benzene, 1,3-bis [4- (4-aminophenoxy) phenoxy-α, α-dimethylbenzyl] benzene, 1,3-bis [ 4- (4-Amino-6-trifluoromethylphenoxy) -α, α-dimethylbenzyl] benzene, 1,3-bis [4- (4-amino-6-fluorophenoxy) -α, α-dimethylbenzyl] Benzene, 1,3-bis [4- (4-amino-6-methylphenoxy) -α, α-dimethylbenzyl] benzene, 1,3-bis [4- (4-amino-6-cyanophenoxy) -α , Α-dimethylbenzyl] benzene, 3,3′-diamino-4,4′-diphenoxybenzophenone, 4,4′-diamino-5,5′-diphenoxybenzophenone, 3,4 ′ Diamino-4,5′-diphenoxybenzophenone, 3,3′-diamino-4-phenoxybenzophenone, 4,4′-diamino-5-phenoxybenzophenone, 3,4′-diamino-4-phenoxybenzophenone, 3,4 '-Diamino-5'-phenoxybenzophenone, 3,3'-diamino-4,4'-dibiphenoxybenzophenone, 4,4'-diamino-5,5'-dibiphenoxybenzophenone, 3,4'-diamino-4 , 5′-dibiphenoxybenzophenone, 3,3′-diamino-4-biphenoxybenzophenone, 4,4′-diamino-5-biphenoxybenzophenone, 3,4′-diamino-4-biphenoxybenzophenone, 3,4 '-Diamino-5'-biphenoxybenzophenone, 1,3-bis (3-amino- 4-phenoxybenzoyl) benzene, 1,4-bis (3-amino-4-phenoxybenzoyl) benzene, 1,3-bis (4-amino-5-phenoxybenzoyl) benzene, 1,4-bis (4-amino) -5-phenoxybenzoyl) benzene, 1,3-bis (3-amino-4-biphenoxybenzoyl) benzene, 1,4-bis (3-amino-4-biphenoxybenzoyl) benzene, 1,3-bis ( 4-amino-5-biphenoxybenzoyl) benzene, 1,4-bis (4-amino-5-biphenoxybenzoyl) benzene, 2,6-bis [4- (4-amino-α, α-dimethylbenzyl) Phenoxy] benzonitrile and some or all of the hydrogen atoms on the aromatic ring of the above aromatic diamine are halogen atoms or alkyl groups having 1 to 3 carbon atoms. Or an alkoxy group, a cyano group, or an alkyl group or an aromatic diamine substituted with an alkyl group or a halogenated alkyl group having 1 to 3 carbon atoms substituted with a halogen atom or an alkoxy group Is mentioned.

The tetracarboxylic acid anhydrides used in the present invention are aromatic tetracarboxylic acid anhydrides. Specific examples of the aromatic tetracarboxylic acid anhydrides include the following.

Is preferred. These tetracarboxylic dianhydrides can be used alone or in combination of two or more.

  In the present invention, one or two or more non-aromatic tetracarboxylic dianhydrides exemplified below may be used in combination as long as they are 30 mol% or less of the total tetracarboxylic dianhydrides. Examples of the tetracarboxylic anhydride used include butane-1,2,3,4-tetracarboxylic dianhydride, pentane-1,2,4,5-tetracarboxylic dianhydride, and cyclobutanetetracarboxylic acid. Dianhydride, cyclopentane-1,2,3,4-tetracarboxylic dianhydride, cyclohexane-1,2,4,5-tetracarboxylic dianhydride, cyclohex-1-ene-2,3,5 , 6-tetracarboxylic dianhydride, 3-ethylcyclohex-1-ene-3- (1,2), 5,6-tetracarboxylic dianhydride, 1-methyl-3-ethylcyclohexane-3- (1,2), 5,6-tetracarboxylic dianhydride, 1-methyl-3-ethylcyclohex-1-ene-3- (1,2), 5,6-tetracarboxylic dianhydride, 1-ethylcyclohexane -(1,2), 3,4-tetracarboxylic dianhydride, 1-propylcyclohexane-1- (2,3), 3,4-tetracarboxylic dianhydride, 1,3-dipropylcyclohexane- 1- (2,3), 3- (2,3) -tetracarboxylic dianhydride, dicyclohexyl-3,4,3 ′, 4′-tetracarboxylic dianhydride, bicyclo [2.2.1] Heptane-2,3,5,6 lacarboxylic dianhydride, 1-propylcyclohexane-1- (2,3), 3,4-tetracarboxylic dianhydride, 1,3-dipropylcyclohexane-1- ( 2,3), 3- (2,3) -tetracarboxylic dianhydride, dicyclohexyl-3,4,3 ′, 4′-tetracarboxylic dianhydride, bicyclo [2.2.1] heptane-2 , 3,5,6-tetracarboxylic dianhydride, Biciku [2.2.2] Octane-2,3,5,6-tetracarboxylic dianhydride, bicyclo [2.2.2] oct-7-ene-2,3,5,6-tetracarboxylic dianhydride Such as anhydrides. These tetracarboxylic dianhydrides can be used alone or in combination of two or more.

In addition, maleic anhydride or the like can be used to seal the molecular ends of the linear polyimide or linear polyamic acid of the present invention with terminal groups having a carbon-carbon double bond. The amount of maleic anhydride used is 0.001 to 1.0 molar ratio per mole of aromatic diamine component.
The polar organic solvent used in the synthesis of the polyamic acid of the present invention is not particularly limited as long as it dissolves both the raw material monomer and the produced polyamic acid. For example, N-methyl-2-pyrrolidone, N- Acetyl-2-pyrrolidone, N, N-dimethylformamide, N, N-diethylformamide, N, N-dimethylacetamide, dimethyl sulfoxide, hexamethylphosphoric amide, ethyl cellosolve acetate, diethylene glycol dimethyl ether, sulfolane, halogenated phenols, etc. These solvents can be used alone or in combination. The amount of the polar organic solvent used may be an amount sufficient to dissolve the charged monomer, usually 5 to 50% by weight, preferably 10 to 20% by weight. .

  The organic solvent solution of the polyamic acid used in the present invention preferably contains 5 to 40% by weight, more preferably 10 to 30% by weight of the solid content, and the viscosity is measured by a Brookfield viscometer. Those having a viscosity of 10 to 2000 Pa · s, preferably 100 to 1000 Pa · s are preferred because stable liquid feeding is possible. The polymerization reaction is continuously carried out in the temperature range of 0 to 80 ° C. for 10 minutes to 30 hours while stirring and / or mixing in an organic solvent. The polymerization reaction can be divided or the temperature can be increased or decreased as necessary. It doesn't matter. In this case, the order of addition of both reactants is not particularly limited, but it is preferable to add aromatic tetracarboxylic anhydrides to the solution of aromatic diamines.

In the present invention, a ring-closing catalyst may be used. Specific examples of the ring-closing catalyst used in the present invention include aliphatic tertiary amines such as trimethylamine and triethylamine, and heterocyclic tertiary amines such as isoquinoline, pyridine and betapicoline. It is preferable to use at least one amine selected from tertiary amines.
Specific examples of the ring-closing catalyst used in the present invention include aliphatic tertiary amines such as trimethylamine and triethylamine, and heterocyclic tertiary amines such as isoquinoline, pyridine and betapicoline. It is preferable to use at least one amine selected from tertiary amines.

  Vacuum defoaming during the polymerization reaction is an effective method for producing a high-quality polyamic acid organic solvent solution. Moreover, you may perform polymerization by adding a small amount of terminal blockers to aromatic diamines before a polymerization reaction.

  Specific examples of the dehydrating agent used in the present invention include aliphatic carboxylic acid anhydrides such as acetic anhydride, propionic anhydride, and butyric anhydride, and aromatic carboxylic acid anhydrides such as benzoic anhydride, Acetic anhydride and / or benzoic anhydride are preferred. The content of the ring-closing catalyst with respect to the polyamic acid is preferably in a range where the content (mol) of the ring-closing catalyst / the content (mol) of the polyamic acid is 0.5 to 8. In addition, the content of the dehydrating agent relative to the polyamic acid is preferably in a range where the content of dehydrating agent (mole) / polyamic acid content (mole) is 0.1 to 4. In this case, a gelation retarder such as acetylacetone may be used in combination.

  The polyimide film of the present invention is obtained by continuously extruding or applying a polyamic acid solution to a support in the form of a film, followed by drying, peeling the green film from the support, stretching, drying, and heat treatment. As a typical method for producing a polyimide film from an organic solvent of polyamic acid, an organic solvent solution of polyimide acid that does not contain a ring-closing catalyst and a dehydrating agent is cast on a support from a nozzle with a slit. The film is then formed into a film and heated to dry on the support to form a green film having self-supporting properties. Then, the film is peeled off from the support and further heat-dried at a high temperature for imidization, Then, an organic solvent of polydoic acid containing a ring-closing catalyst and a dehydrating agent is cast from a slit base onto a support. Examples include a chemical ring closure method in which a film is formed into a film and partially imidized on a support to form a film having self-supporting properties, then the film is peeled off from the support, dried / imidized by heating, and heat-treated. It is done.

  The support in the present invention is a drum or belt-like rotating body used when forming a polyamic acid solution into a film. The polyamic acid solution is applied on a support and is self-supporting by heat drying. The surface of the support may be metal, plastic, glass, porcelain, etc., preferably metal, and more preferably SUS material that does not rust and has excellent corrosion resistance. Further, metal plating such as Cr, Ni, Sn may be performed. The surface of the support in the present invention can be mirror-finished or processed into a satin finish if necessary.

The nickel-chromium alloy sputter layer 2 provided on the surface of the base film has a thickness of 20 to 2000 mm, preferably 40 to 1000 mm, and more preferably 80 to 500 mm. If the thickness of the sputter layer 2 of nickel-chromium alloy is less than 20 mm, the adhesion is not sufficient, and if it exceeds 2000 mm, abnormal deposition of electroless tin plating applied to the circuit board becomes remarkable.
Further, the chromium content in the nickel-chromium alloy is desirably 1 to 10% by weight, more preferably 2 to 8%, and still more preferably 3 to 6%. When the chromium content is less than 1% by weight, there is no effect of improving the migration resistance, and even if it exceeds 10% by weight, the effect of improving the migration resistance is almost the same. There is a problem that the footsteps of copper increase.
The thickness of the copper layer provided on the nickel-chromium alloy sputter layer is preferably 1 to 12 μm, more preferably 1 to 9 μm, and even more preferably about 2 to 5 μm.

  The manufacturing method of the metallized polyimide film of this invention is demonstrated. In the present invention, as described in claim 7, after the surface of the polyimide film is subjected to plasma treatment, a nickel-chromium alloy is deposited to a thickness of 20 to 2000 mm by sputtering, and then the conductive layer is sputtered. It is a preferred embodiment to deposit by a vapor deposition method and / or an electroless plating method, and then further electrolytically plate a thick metal and then perform a heat treatment at 200 to 350 ° C.

  First, the surface of the polyimide film is subjected to surface treatment by plasma treatment. Such plasma is inert gas plasma, and nitrogen gas, Ne, Ar, Kr, and Xe are used as the inert gas. There is no particular limitation on the method for generating plasma, and an inert gas may be introduced into the plasma generator to generate plasma. There is no particular limitation on the plasma treatment method, and a plasma treatment apparatus used for forming a metal layer on the base film may be used. The time required for the plasma treatment is not particularly limited, and is usually 1 second to 30 minutes, preferably 10 seconds to 10 minutes. There are no particular restrictions on the frequency and output of the plasma during the plasma processing, the gas pressure for generating the plasma, and the processing temperature as long as they can be handled by the plasma processing apparatus. The frequency is usually 13.56 MHz, the output is usually 50 W to 1000 W, the gas pressure is usually 0.01 Pa to 10 Pa, and the temperature is usually 20 ° C. to 250 ° C., preferably 20 ° C. to 180 ° C. If the output is too high, the substrate film surface may crack. Further, if the gas pressure is too high, the smoothness of the surface of the electrical insulating layer may be reduced. There is no particular limitation on the sputtering method, and direct current bipolar sputtering, high frequency sputtering, magnetron sputtering, counter target sputtering, ECR sputtering, bias sputtering, plasma controlled sputtering, multi-target sputtering, and the like can be used. Among these, direct current bipolar sputtering or high frequency sputtering is preferable. There are no particular restrictions on the output during sputtering processing, the gas pressure for generating plasma, and the processing temperature, so long as they can be handled by the sputtering apparatus. The output is usually 10 W to 1000 W, the gas pressure is usually 0.01 Pa to 10 Pa, and the temperature is usually 20 ° C. to 250 ° C., preferably 20 ° C. to 180 ° C. The film forming rate is 0.1 Å / second to 1000 Å / second, preferably 1 Å / second to 100 Å / second. If the film formation rate is too high, the formed metal film may be cracked. Moreover, when gas pressure is too high, there exists a possibility that adhesiveness may fall.

  Next, a nickel-chromium alloy is deposited on the surface-treated surface by sputtering to form a sputter layer of nickel-chromium alloy having a thickness of 20 to 2000 mm. The sputtering conditions are arbitrary. The sputtering layer of nickel-chromium alloy may be a method using a nickel-chromium alloy target, a method of performing dual simultaneous sputtering, or a method of sputtering nickel and chromium independently and diffusing both in a later step. Can do.

  Next, a thick metal layer is formed. The thick metal layer is composed of a conductive layer and a thick layer, and the conductive layer may be formed by any one of a sputtering method, a vapor deposition method, and a wet electroless plating method, and preferably two or more. It is formed by combining methods. In the present invention, after a nickel-chromium alloy sputtering layer, a copper layer of about 0.1 to 3 μm is first formed as a conductive layer by sputtering, vapor deposition or electroless plating, and then thickened. As the layer, a method of further increasing the thickness of the copper layer by electroplating can be preferably used. As the metal of the thick metal layer, silver, copper, gold, platinum, rhodium, nickel, aluminum, iron, zinc, tin, brass, white copper, bronze, monel, tin-lead solder, tin-copper solder, tin silver A system solder or the like is used, but copper is a preferred embodiment in terms of a balance between performance and economy.

  Further, in the present invention, a method of forming a metal copper layer of about 0.1 to 3 μm by a vapor deposition method as a conductive layer after a sputter layer of nickel-chromium alloy can be particularly preferably used. Of course, the thickness of the metal copper layer can be increased by an electroplating method or the like thereafter. The film during vapor deposition is maintained at 100 ° C to 400 ° C, preferably 150 ° C to 300 ° C. By this method, the adhesion between the base layer and the copper layer becomes more robust. In such a process, it is presumed that a part of the base alloy and the metal copper to be deposited are diffused to each other, and a region having a composition gradient is formed at the interface. It is a preferable embodiment that copper is used for the metal as described above.

  Electroplating can be used for forming the copper layer that is preferably used as the thickening layer of the thickening metal layer of the present invention. As the electroplating method, copper pyrophosphate plating or copper sulfate plating can be preferably used.

  In the present invention, it is a great feature that the composite of the polyimide film and metal obtained by the above method is further heat-treated at 200 to 350 ° C. 220-330 degreeC is preferable and 240-310 degreeC is more preferable. The heat treatment reduces the strain of the base film and the strain generated in the manufacturing process of the metallized polyimide film, and can more effectively express the effects of the present invention. Reliability can be improved. If it is less than 200 ° C., the effect of alleviating the strain becomes small. Conversely, if it exceeds 350 ° C., the polyimide film of the base material is deteriorated, which is not preferable.

  The metallized polyimide film of the present invention thus obtained is coated with a photoresist on the copper layer side by an ordinary method, dried, and then exposed, developed, etched, and stripped of the photoresist by a step of removing the photoresist. Then, if necessary, solder resist coating, curing and electroless tin plating are performed to obtain a circuit board.

Hereinafter, the effectiveness of the present invention will be described with reference to examples, but the present invention is not limited thereto. In addition, the evaluation method of the physical property in the following examples is as follows.
1. Reduced viscosity of polyamic acid (ηsp / C)
A solution dissolved in N-methyl-2-pyrrolidone so that the polymer concentration was 0.2 g / dl was measured at 30 ° C. using an Ubbelohde type viscosity tube.

2. Film thickness of polyimide film The thickness of the film was measured using a micrometer (manufactured by Fine Reef, Millitron 1245D).

3. Tensile modulus, tensile breaking strength and breaking elongation of polyimide film Test piece by cutting the dried film into a strip of 100 mm length and 10 mm width in the longitudinal direction (MD direction) and the width direction (TD direction), respectively. And using a tensile tester (manufactured by Shimadzu Autograph (R) model name AG-5000A) at a tensile speed of 50 mm / min and a distance between chucks of 40 mm to determine tensile modulus, tensile strength and elongation at break. .

5). Linear expansion coefficient (CTE) of polyimide film
The expansion / contraction rate was measured under the following conditions, and the range from 30 to 300 ° C. was divided at 15 ° C. intervals and obtained from the average value of the expansion / contraction rate / temperature of each divided range.
Device name: TMA4000S manufactured by MAC Science
Sample length; 20mm
Sample width: 2 mm
Temperature rise start temperature: 25 ° C
Temperature rising end temperature: 400 ° C
Temperature increase rate: 5 ° C / min
Atmosphere: Argon

6). Melting point of polyimide film, glass transition temperature A sample was subjected to DSC measurement under the following conditions, and a melting point (melting peak temperature Tpm) and a glass transition point (Tmg) were determined under the following measurement conditions in accordance with JIS K7121.
Device name: DSC3100S manufactured by MAC Science
Pan ： Aluminum pan (non-airtight)
Sample weight; 4mg
Temperature rising start temperature: 30 ° C
Temperature increase rate: 20 ° C / min
Atmosphere: Argon

7). Thermal decomposition temperature of polyimide film The thermal decomposition temperature was defined by 5% weight loss by TGA measurement (thermobalance measurement) of a sufficiently dried sample under the following conditions.
Device name: TG-DTA2000S manufactured by MAC Science
Pan ： Aluminum pan (non-airtight)
Sample weight: 10mg
Temperature rising start temperature: 30 ° C
Temperature increase rate: 20 ° C / min
Atmosphere: Argon

8). Oxygen permeability of polyimide film MOCON oxygen permeability measuring device OX-TRAN ten. Using fifty, measurement was performed at 23 ° C. and 65% RH by a method in accordance with JIS K7126 B method.
9. Water vapor transmission rate of polyimide film Using a water vapor transmission rate measuring device PERMATRAN-W 3/31 manufactured by MOCON, measurement was performed at 40 ° C. and 90% RH by a method in accordance with JIS K7129.

10. Initial conductor adhesion of metallized polyimide film A 90-degree peel test was performed by a method according to JIS C5016.
11. Conductor adhesion after heating test of metallized polyimide film After leaving in a dry oven at 150 ° C. for 100 hours, a 90 ° peel test was performed by a method in accordance with JIS C5016.
12 Conductor adhesion after pressurization and humidification test of metalized polyimide film A PCT tester manufactured by Hirayama Seisakusho was treated under conditions of 121 ° C and 2 atm (saturation) for 100 hours, and then a 90 ° peel test was performed in accordance with JIS5016 I went there.
In addition, in copper foil 5 μm, copper foil was frequently cut and satisfactory evaluation could not be performed. Therefore, only for the items (7) to (9), the copper foil thickness was further increased to 35 μm by electroplating. went.

13. Volume resistivity of metallized polyimide film It was performed by a method according to JIS C6481.
14 Surface resistance of metallized polyimide film It was performed by a method according to JIS C6481.
15. Migration resistance of metalized polyimide film A voltage (DC60V) is applied to a comb-shaped electrode with a pitch of 40μm, and it is placed in a constant temperature and humidity chamber (FX412P type, manufactured by ETAC) at 85 ° C and 85% RH. The insulation resistance value was measured and recorded every 5 minutes as it was, and the time for the resistance value between the lines to reach 100 M ohms or less was measured for migration evaluation.

(Example 1)
<Polymerization and Film Production Example 1>
After the inside of a reaction vessel equipped with a nitrogen introduction tube, a thermometer, and a stirring rod was purged with nitrogen, 500 parts by weight of 5-amino-2- (p-aminophenyl) benzoxazole was charged. Next, 5000 parts by weight of N-methyl-2-pyrrolidone was added and completely dissolved, and then 485 parts by weight of pyromellitic dianhydride was added and stirred at a reaction temperature of 25 ° C. for 15 hours. A polyamic acid solution was obtained. Ηsp / C of this product was 2.0.
Subsequently, this polyamic acid solution was coated on a stainless steel belt so as to have a wet film thickness of 180 microns and dried at 80 ° C. for 60 minutes. The polyamic acid film that became self-supporting after drying was peeled from the stainless steel belt to obtain a green film. The obtained green film was passed through a continuous drying furnace, heated from 200 ° C. to 400 ° C. almost linearly in 20 minutes, cooled in 10 minutes, and a brown polyimide film (film 1) having a thickness of 25 μm was obtained. Obtained. Table 1 shows the characteristic values of the obtained polyimide film. In Table 1, Kapton (R) H is a polyimide film manufactured by Toray DuPont. Upilex S is a polyimide film manufactured by Ube Industries.

<Production method of metallized film>
The film 1 was cut into a square of 25 cm × 25 cm and fixed by being sandwiched between stainless steel frames having a direct 24 cm opening. Next, plasma treatment of the film surface was performed. The plasma treatment conditions were a xenon gas, a frequency of 13.56 MHz, an output of 100 W, a gas pressure of 0.8 Pa, a treatment temperature of 25 ° C., and a treatment time of 5 minutes. Next, using a nickel-chromium (3%) alloy target under conditions of a frequency of 13.56 MHz, an output of 400 W, a gas pressure of 0.8 Pa, and a thickness of 50 mm at a rate of 10 mm / second by RF sputtering in a xenon atmosphere. The nickel-chromium alloy film (underlayer) was formed. Next, the temperature of the substrate was raised to 250 ° C., and copper was deposited at a rate of 100 Å / sec to form a copper thin film (conductive layer) having a thickness of 0.5 μm.
The obtained metallized film is re-fixed to a plastic frame, and a thick copper plating layer (thickening layer) having a thickness of 5 μm is formed using a copper sulfate plating bath, followed by heat treatment at 300 ° C. for 10 minutes. The intended metallized polyimide film was obtained.
Using the obtained metallized polyimide film, photoresist: FR-200, manufactured by Shipley Co., Ltd. was applied and dried, then contacted and exposed with a glass photomask, and further developed with a 1.2% KOH aqueous solution. Next, etching is performed with a cupric chloride etching line containing HCl and hydrogen peroxide at 40 ° C. and a spray pressure of ² kgf / cm ² to form a test pattern necessary for an evaluation test described later, and then a thickness of 0.5 μm. Electroless tin plating was performed. Thereafter, annealing was performed at 125 ° C. for 1 hour.
Test evaluation was performed using the obtained test pattern. The results are shown in Table 2.

(Examples 2 to 4)
The same operation as in Example 1 was performed except that the thickness of the nickel-chromium alloy layer was changed, and evaluation was performed. The results are shown in Table 2.
(Examples 5 to 8)
<Polymerization and film production example 2>
A polyamic acid solution was obtained in the same manner as in Example 1 (Film 1) except that 653 parts by weight of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride was used as the tetracarboxylic dianhydride. Ηsp / C of this was 1.5, and a brown polyimide film (film 2) having a thickness of 25 μm was obtained in the same manner as in Example 1 (film 1). Table 1 shows the characteristic values of the obtained polyimide film.
<Production method of metallized film>
Except having changed the base film into the said film 2, it operated similarly to Examples 1-4 and evaluated. The results are shown in Table 3.
(Examples 9 and 10)
Using the polyimide film 1, the chromium content of the nickel-chromium alloy was changed, and the other operations were performed and evaluated in the same manner as in Example 1. The results are shown in Table 4.
(Examples 11 and 12)
Using the film 2, the chromium content of the nickel-chromium alloy was changed, and other operations were performed and evaluated in the same manner as in Example 5. The results are shown in Table 4.

(Comparative Examples 1-4)
Operations were evaluated in the same manner as in Examples 1 to 4 except that the base film was changed to Kapton (R) H manufactured by Toray DuPont. The results are shown in Table 5.
(Comparative Examples 5-8)
The same operation as in Examples 1 to 4 was performed, except that the base film was changed to Upilex (R) S manufactured by Ube Industries, Ltd., and evaluated. The results are shown in Table 6.
(Comparative Examples 9-12)
The film 1 was used as the base film, and the film thickness of the nickel-chrome layer and the chromium content were changed, and the evaluation was performed in the same manner. The results are shown in Table 7.

  The metallized polyimide films obtained in Examples 1 to 12 are excellent in adhesive strength between the conductor and the base film, particularly after heat treatment and after the humidification heating test, and there is no abnormal deposition of electroless tin plating. In addition, there is no problem in migration resistance, and the insulation reliability is excellent and the quality is high. On the other hand, the metallized polyimide films obtained in Comparative Examples 1 to 8 have poor adhesion strength between the conductor and the base film after the humidification heating test, and the metallized polyimide films obtained in Comparative Examples 9 to 12 are electroless tin. Abnormal deposition of plating is likely to occur, migration resistance is poor, and insulation reliability is poor.

  As described above, the metallized polyimide film of the present invention uses a polyimide film having a specific structure having a low oxygen permeability and a low coefficient of thermal expansion as a base material, and further, the metallized polyimide film is subjected to heat treatment in the manufacturing process. Since the strain that the material film has and the strain that occurs during the manufacturing process of the metallized polyimide film are relaxed, the decrease in interfacial adhesion due to oxidative degradation of the underlayer is suppressed, and its durability is improved, and Since the shape of the substrate film changes little due to changes in heat and humidity, it excels in electrical characteristics, and does not degrade the etchability and plating resistance of the wiring circuit pattern, and can be bonded even when exposed to long-term heating or wet heat. Since it is excellent in migration resistance without lowering its strength, it is useful as a flexible electronic circuit board material. Therefore, even in a thin semiconductor package with high-density wiring, durability against changes in temperature and humidity in the usage environment of the semiconductor package is improved, and the reliability of the semiconductor is increased. Moreover, in the manufacturing method of this invention, since the metallized polyimide film of the above-mentioned characteristic can be manufactured stably and economically, it greatly contributes to the industry.

FIG. 1 is a schematic cross-sectional view of a metallized polyimide film of the present invention.

Explanation of symbols

1. Polyimide film Sputtered nickel-chromium layer (underlayer)
3. Thick metal layer (conductive layer)
4). Thickened metal layer (thickened layer)

Claims (7)

In a metallized polyimide film having a nickel-chromium alloy sputter layer as an underlayer and further having a thickened metal layer, the oxygen permeability of the polyimide film is 20 ml / m ² · day · atm or less, and the thermal linear expansion coefficient Is 12 ppm / ° C. or less, a metallized polyimide film. ^2. The metallized polyimide film according to claim 1, wherein the water vapor permeability ratio of the polyimide film is 3 ml / m ² · day · atm or more.   3. The metallized polyimide according to claim 1, wherein the polyimide comprises a polyimide obtained by reacting an aromatic diamine having a benzoxazole structure and an aromatic tetracarboxylic acid anhydride. 4. the film.   The metallized polyimide film according to any one of claims 1 to 3, wherein the sputter layer of the nickel-chromium alloy has a thickness of 20 to 2000 mm.   The metallized polyimide film according to any one of claims 1 to 4, wherein the sputter layer of the nickel-chromium alloy has a chromium content of 1 to 10% by weight.   The metallized polyimide film according to any one of claims 1 to 5, wherein the thickness of the thickened metal layer is 1 to 12 µm.   After the polyimide film surface is plasma treated, a nickel-chromium alloy is deposited by sputtering to a thickness of 20 to 2000 mm, and then a conductive layer is deposited by sputtering and / or vapor deposition and / or electroless plating. The method of manufacturing a metallized polyimide film according to any one of claims 1 to 6, further comprising electrolytically plating a thickened metal and further performing a heat treatment at 200 to 350 ° C.