JPH07142827A - Manufacture of flexible printed circuit board - Google Patents

Abstract

PURPOSE:To improve the heat-resistance and the adhesion by a method wherein specific mixed solvent is employed as the solvent of polyimide precursor resin solution to be applied. CONSTITUTION:A metal foil is coated with polyimide precursor resin solution dissolved in solvent by causing the solution to flow directly on the surface of the metal foil. After the metal foil is heated and dried, the metal foil is subjected to roll-to-roll heating to cure the polyimide precursor resin. The mixed solvent of high boiling point polar solvent and low boiling point solvent is employed as the solvent of the precursor resin solution. The polyimide precursor resin is dissolved in the mixed solvent to obtain the polyimide precursor resin solution. Precursor resin synthesized from the monomer of diamine and tetra carbonic acid or the copolymer of them, the mixture of several types of precursor resins, etc., can be used as the precursor resin.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a polyimide-based flexible printed circuit board which is excellent in heat resistance and adhesiveness and has high productivity with no adhesion between a metal surface and a polyimide precursor resin dry surface during production. .

[0002]

2. Description of the Related Art A conventional polyimide-based flexible printed circuit board is prepared by bonding a polyimide film and a metal foil with an adhesive, or by directly casting a polyimide precursor resin solution on the metal foil and heat-curing it. Are manufactured.

However, the former polyimide film and metal foil bonded with an adhesive has a drawback that the heat resistance of the adhesive is low and the heat resistance, which is the greatest advantage of the polyimide film, cannot be fully utilized. On the other hand, the latter metal foil, which is directly cast and coated with a polyimide precursor resin solution and heat-cured, needs to be cured at a high temperature for a long time in order to obtain a reliable polyimide film, and the production equipment is expensive. There is a disadvantage that it becomes a thing.
Therefore, a method has been proposed in which a polyimide precursor resin solution is directly cast onto a metal foil, heated and dried, and then the metal foil is wound and cured by heating. However, in this method, on the metal foil, the polyimide precursor resin solution is directly cast and applied, and after heating and drying, since the metal foil is wound up, the coated surface and the uncoated metal foil surface come into contact with each other, and There is a drawback that the resin does not adhere and the film itself is not formed.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned drawbacks and is excellent in heat resistance and adhesion, and does not require expensive manufacturing equipment at the time of manufacturing the same. An object of the present invention is to provide a highly reliable method for producing a flexible printed circuit board, which is free from adhesion of a metal foil surface to a resin and has good film formability.

[0005]

Means for Solving the Problems As a result of earnest studies to achieve the above object, the present inventor has found that the use of a specific mixed solvent as a solvent for a polyimide precursor resin solution to be coated results in The inventors have found that the object can be achieved and completed the present invention.

That is, according to the present invention, a flexible polyimide precursor resin solution dissolved in a solvent is directly cast on a metal foil, heated and dried, and then the metal foil is wound and heated to cure the polyimide precursor resin. In printed circuit boards,
In the method for manufacturing a flexible printed circuit board, the solvent of the precursor resin solution is a mixed solvent of a polar solvent having a high boiling point and a solvent having a low boiling point.

The present invention will be described in detail below.

The metal foil used in the present invention is used as a conductor of a flexible printed circuit board, and examples thereof include copper foil, nickel foil, and aluminum foil. It is desirable that these metal foils have a thickness of 5 to 200 μm.

The polyimide precursor resin solution used in the present invention is a solution of polyimide precursor resin dissolved in a mixed solvent. As the polyimide precursor resin, a precursor resin synthesized by homopolymerization or copolymerization of diamine and tetracarboxylic acid, a mixture of several kinds of precursor resins, and the like can be used. Examples of the diamine used here include m-phenylenediamine, p-phenylenediamine, 1,3-bis (4-aminophenyl) propane, 2,2-bis (4-aminophenyl) propane, 1,2-bis ( 4-aminophenyl) ethane, 1,1-bis (4-aminophenyl) ethane, 4,4′-diaminodiphenylmethane, 2,2′-diaminodiethyl sulfide, 2,4′-diaminodiphenyl sulfide, bis (4- Aminophenyl) sulfide, bis (3-aminophenyl) sulfone, bis (4-aminophenyl) sulfone, 4,4'-diaminodibenzyl sulfoxide, bis (3-aminophenyl) ether, bis (4-aminophenyl) ) Ether, bis (4-aminophenyl) diethylsilane, bis (4-aminophenyl) diphenylsilane, bis (4-aminophenyl) ethylphosphine oxide, bis (4 -Aminophenyl) phenylphosphine oxide, bis (4-aminophenyl) -N-phenylamine, bis (4-aminophenyl) -N-methylamine, 1,
2-diaminonaphthalene, 1,4-diaminonaphthalene, 1,5-
Diaminonaphthalene, 1,6-diaminonaphthalene, 1,7-diaminonaphthalene, 1,8-diaminonaphthalene, 2.3-diaminonaphthalene, 2,6-diaminonaphthalene, 1,4-diamino-2-methylnaphthalene, 1,5 -Diamino-2-methylnaphthalene, 1,3-diamino-2-phenylnaphthalene, 4,
4'-diaminobiphenyl, 3,3'-diaminobiphenyl, 3,3'-dichloro-4,4'-diaminobiphenyl,
3,3'-Dimethyl-4,4'-diaminobiphenyl, 3,4 '
-Dimethyl-4,4'-diaminobiphenyl, 3,3'-dimethoxy-4,4'-diaminobiphenyl, 4,4'-bis (4-
Aminophenoxy) biphenyl, 2,4-diaminotoluene, 2,5-diaminotoluene, 2,6-diaminotoluene, 1,
3-diamino-2,5-dichlorobenzene, 1,4-diamino-2,
5-dichlorobenzene, 1-methoxy-2,4-diaminobenzene, 1,4-diamino-2-methoxy-5-methylbenzene, 1,
4-diamino-2,3,5,6-tetramethylbenzene, 1,4-bis (2-methoxy-4-aminopentyl) benzene, 1,4-bis (1,1-dimethyl-5-aminopentyl) Benzene, 1,4-bis (4-aminophenoxy) benzene, o-xylenediamine, m-xylenediamine, p-xylenediamine, 3,3 '
-Diaminobenzophenone, 4,4'-diaminobenzophenone, 2,6-diaminopyridine, 3,5-diaminopyridine, 1,3-diaminoadamantane, 3,3'-diamino-1,
1,1'-diadamantane, N- (3-aminophenyl) -4
-Aminobenzamide, 4-aminophenyl-3-aminobenzoate, 2,2-bis (4-aminophenyl) hexafluoropropane, 2,2-bis (3-aminophenyl) hexafluoropropane, 2- (3- Aminophenyl) -2- (4-aminophenyl) hexafluoropropane, 2,2-bis [4-
(4-Aminophenoxy) hexafluoropropane, 2,2-
Bis [4- (2-chloro-4-aminophenoxy) phenyl]
Hexafluoropropane, 1,1-bis (4-aminophenyl) -1-phenyl-2,2,2-trifluoroethane, 1,1-bis [4- (4-aminophenoxy) phenyl] -1-phenyl
-2,2,2-trifluoroethane, 1,4-bis (3-aminophenyl) but-1-ene-3-yne, 1,3-bis (3-aminophenyl) hexafluoropropane, 1,3 -Bis (3-aminophenyl) decafluoropropane and the like can be mentioned, and these can be used alone or in combination of two or more kinds. Further, as the tetracarboxylic acid, for example, pyromellitic acid, 1,2,3,4-benzenetetracarboxylic acid, 3,3 ′, 4,4 ′
-Biphenyl tetracarboxylic acid, 2,3,3 ', 4'-biphenyl tetracarboxylic acid, 3,3', 4,4'-biphenyl ether-
Tertetracarboxylic acid, 2,3,3 ', 4'-biphenyl ether
Tertetracarboxylic acid, 2,2-bis (3,4-dicarboxyphenyl) propane, 2,2-bis (2,3-dicarboxyphenyl) propane, bis (3,4-dicarboxyphenyl) methane, bis (2,3-dicarboxyphenyl) methane, 1,1-bis (2,3-dicarboxyphenyl) ethane, 2,2-bis (3,
4-dicarboxyphenyl) hexafluoropropane,
3,3 ′, 4,4′-diphenylsulfone tetracarboxylic acid,
2,3,3 ', 4'-diphenylsulfone tetracarboxylic acid,
2,3,6,7-naphthalene tetracarboxylic acid, 1,4,5,8-naphthalene tetracarboxylic acid, 1,2,5,6-naphthalene tetracarboxylic acid, 3,4,9,10-tetracarboxyperylene , 2-bis [4- (3,4-dicarboxyphenoxy) phenyl] propane, 2,2-bis [4- (3,4-dicarboxyphenoxy) phenyl] hexafluoropan, etc. Lower alkyl esters and the like can be mentioned, and these can be used alone or in combination.

The reaction between diamine and tetracarboxylic acid is
It is preferable to carry out in equimolar amount as much as possible, and the degree of polymerization also becomes large. If either one of the components exceeds 5%, the degree of polymerization is remarkably lowered, and the film forming property is poor, which is not preferable. Also,
The reaction is preferably carried out in an inert gas atmosphere in order to prevent the oxidation of diamines, and dry nitrogen gas is generally used.

The mixed solvent used in the present invention is a mixture of a high boiling point polar solvent and a low boiling point solvent. As the high boiling point polar solvent, N-methyl-2-pyrrolidone,
Examples thereof include N, N-dimethylformamide, N, N-dimethylacetamide, dimethylsulfoxide, phenol and halogenated phenol, and these can be used alone or in combination. Further, examples of the low boiling point solvent include tetrahydrofuran and the like, and these can be used alone or in combination. The proportion of the low boiling point solvent in the mixed solvent is preferably 5 to 50%.
If it is less than 5%, the volatilizing effect of the solvent during drying is not sufficient, and if it exceeds 50%, the polyamic acid as the polyimide precursor is not dissolved, which is not preferable. As a method of adding a mixed solvent to the polyimide precursor, a mixed solvent prepared by mixing a high-boiling point polar solvent and a low-boiling point solvent is added, but after dissolving the polyimide precursor in the high-boiling point polar solvent in advance, at a predetermined ratio. As such, a low boiling point solvent can be added. In this way, the polyimide precursor can be dissolved in the mixed solvent to form a polyimide precursor resin solution.

The polyimide precursor resin solution thus obtained is applied to a metal foil. As a coating method, a known coating means such as a bar coater, a roll coater, a knife coater, a doctor blade, a flow coater, etc., is used for 30 to 1000.
Cast coating to a uniform thickness of μm. Next, the polyimide precursor resin solution is made into a film state by heating and drying.
At this time, the heating is performed at a temperature of 80 to 200 ° C so that the temperature gradually rises from a low temperature. After drying, it is wound on a metal tube or the like and finally post-cured at 200 to 350 ° C. for imidization. As a method of winding the metal cylinder or the like, the metal foil surface or the polyimide film surface may be faced up. Therefore, it is not necessary to wind the metal foil or the heat resistant film. The heat-curing atmosphere may be in air, but it is preferably performed under reduced pressure or under a non-oxidized state while flowing an inert gas. In this way, a flexible printed circuit board can be obtained.

[0013]

In the method for manufacturing a flexible printed circuit board of the present invention, since a specific mixed solvent is used as a solvent for the polyimide precursor resin, there is no adhesion between the metal surface and the resin dry surface during manufacturing, and the film forming ability is improved. It is possible to obtain a highly reliable product having excellent heat resistance and adhesiveness.

[0014]

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

Example 1 A flask equipped with a stirrer, a condenser and a nitrogen inlet tube was equipped with 5.4 g (0.05 mol) of paraphenylenediamine and N-methyl-.
2-Pyrrolidone (80.4 g) was added and dissolved. 14.7 g (0.05 mol) of 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride was added to this solution at room temperature in a dry nitrogen atmosphere while paying attention to the temperature rise of the solution, and the reaction was stirred for 12 hours. A polyamic acid resin solution (A) was obtained.

In a flask prepared in the same manner as above, 5.0 g (0.05 mol) of diaminodiphenyl ether and N-methyl-
2-Pyrrolidone (63.6 g) was added and dissolved. 10.9 g of pyromellitic dianhydride was added to this solution at room temperature under a dry nitrogen atmosphere.
(0.05 mol) was added while paying attention to the temperature rise of the solution, and the mixture was stirred and reacted for 12 hours to obtain a polyamic acid resin solution (B).

50 g of the polyamic acid resin solution (B) was added to 50 g of the polyamic acid resin solution (A) and stirred to obtain a polyamic acid resin mixed solution. 25 g of tetrahydrofuran was added to 100 g of this mixed solution of polyamic acid resin and stirred to obtain a polyimide precursor resin solution.

Comparative Example 1 25.0 g of N-methyl-2-pyrrolidone was added to 100 g of a mixed solution of a polyamic acid resin synthesized by the same method as in Example 1 and stirred to obtain a polyimide precursor resin solution.

Comparative Example 2 25.0 g of N, N-dimethylacetamide was added to 100 g of a polyamic acid resin mixed solution prepared in the same manner as in Comparative Example 1.
The mixture was added and stirred to obtain a polyimide precursor resin solution.

The polyamic acid resin solution (polyimide precursor resin solution) obtained in Examples and Comparative Examples 1 and 2 was applied to a copper foil having a thickness of 35 μm with a bar coater, and the temperature was from 80 ° C to 120 ° C.
It was gradually heated to dryness. After drying, the metal foil was wound up as it was and gradually heated and cured to 300 ° C. to manufacture a flexible printed circuit board. The obtained flexible printed circuit board was tested for adhesion between the coated surface and the metal foil surface and peel strength. The results are shown in Table 1.
It was shown to. The present invention is excellent in all characteristics, and the effects of the present invention could be confirmed.

[0021]

[Table 1] * 1: ○: No adhesion and no curl, ×: Adhesion

[0022]

As is clear from the above description and Table 1, the method for manufacturing a flexible printed circuit board of the present invention is excellent in heat resistance and adhesiveness, does not adhere to the metal foil surface and the resin surface, and is a film. It has forming ability, high productivity and high reliability.

Claims (1)

[Claims] 1. A substrate for a flexible printed circuit in which a polyimide precursor resin solution dissolved in a solvent is directly cast onto a metal foil, heat-dried, and then the metal foil is wound and heated to cure the polyimide precursor resin. The method for producing a flexible printed circuit board according to claim 1, wherein the solvent of the precursor resin solution is a mixed solvent of a polar solvent having a high boiling point and a solvent having a low boiling point.