JPH0760935B2 - Flexible printed circuit board manufacturing method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for manufacturing a flexible printed circuit board,
More specifically, the present invention relates to a method for manufacturing a flexible printed circuit board by directly coating a polyimide resin on a conductor.

[Prior Art] Conventionally, a flexible printed circuit board is manufactured by bonding a polyimide film onto a conductor using an adhesive such as an epoxy resin or a urethane resin.

Although the polyimide film itself has excellent heat resistance, there is a problem that the heat resistance of the adhesive is inferior and blistering or peeling occurs when heated to high temperature with solder, or the flame retardancy of the circuit is reduced. It was

In addition, there are problems that the dimensions change when heated to a high temperature and that the adhesive agent is put down by various chemicals used when processing into a circuit to lower the adhesive force.

On the other hand, as a method of manufacturing a flexible printed circuit board by directly coating a polyimide-based precursor resin solution on a conductor, a method of correcting curl caused by a difference in thermal expansion coefficient between the conductor and the resin after coating and curing ( JP-A-56-23,7
No. 91, etc.) and a method for preventing curling by applying a low thermal expansion resin (Japanese Patent Application Laid-Open No. 60-243,120, etc.) have been proposed, but none of them has been sufficient.

[Problems to be Solved by the Invention] Therefore, the present inventor has conducted diligent research in order to solve such problems, and by drying a certain amount or more of a solvent at a certain temperature range before proceeding with a curing reaction, Finds that it is possible to produce a curled-free flexible printed circuit board,
The present invention has been reached.

Therefore, the object of the present invention, when directly coating the polyimide precursor resin solution on the conductor, is excellent in workability without curling, industrially excellent flexibility that can be continuously manufactured. It is to provide a method for manufacturing a printed circuit board.

[Means for Solving the Problems] That is, the present invention is to apply a polyimide-based precursor resin solution directly onto a conductor, then dry and cure to produce a flexible printed circuit board, at a drying temperature of 110 ° C. or higher, 1
This is a method for producing a flexible printed circuit board, which is dried under a condition of less than 40 ° C. until the amount of the solvent becomes 50 parts by weight or less with respect to 100 parts by weight of the resin, and then cured.

In the present invention, examples of the polyimide-based precursor resin include a polyimide precursor resin, a polyamideimide precursor resin, a polyimide ester precursor resin, and the like, which does not substantially contain a closed imide ring in its molecule. And preferably the following general formula (1) (In the formula, R1 to R8 are any of hydrogen, halogen, a lower alkoxy group, and a lower alkyl group, and at least one of them is a lower alkoxy group). Or the general formula (2) It is a polyimide precursor resin having a structural unit represented by.

The polyamide resin precursor of the general formula (1) includes pyromellitic dianhydride and the following general formula (3). (However, R1 to R8 in the formula are the same as in the above case), and can be obtained by reacting with a diaminobenzanilide derivative.

The diaminobenzanilide derivative must have at least one lower alkoxy group as a substituent. The term "lower" as used herein means that the number of carbon atoms is 10 or less, and if the number of carbon atoms exceeds 10, the heat resistance decreases, which is not preferable. The lower alkoxy group is preferably a methoxy group or an ethoxy group, and more preferably an alkoxy group is present at the ortho position of the amide bond from the viewpoint of improving water absorption. More preferably, the formula is Is 2'-methoxy-4,4'-diaminobenzanilide.

The polyamide precursor resin of the general formula (2) is obtained by reacting biphenyltetracarboxylic acid anhydride with para-phenylenediamine.

The synthesis reaction of such a polyimide-based precursor resin is generally performed by using N-methylpyrrolidone (NMP), dimethylformamide (DMF), an amide solvent of dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), Dimethyl sulfate, sulfolane, butyrolactone, cresol, phenol, halogenated phenol, cyclohexanone,
The reaction is carried out in a solvent such as dioxane, tetrahydrofuran or diglyme at a reaction temperature of 0 to 200 ° C, preferably 0 to 100 ° C. A precursor solution of the polyimide resin can be obtained by mixing the diamine compound and the acid anhydride compound which react with the above general formula in these solvents in approximately equimolar amounts.

In the present invention, it is necessary to contain at least 30 mol% or more, preferably 50 mol% or more of the structural unit represented by the general formula (1) or the general formula (2). If it is less than 30 mol%, the coefficient of thermal expansion of the resin becomes large, the flexible printed circuit board is greatly curled, and practical application becomes difficult.

Further, in the present invention, the physical properties such as the coefficient of linear expansion can be adjusted by using other components together.

For the other components, various diamines, tetracarboxylic acids, tricarboxylic acids or copolymerization using derivatives of these acid anhydrides, or polyimide obtained separately by synthesis or its precursor and polyamideimide Etc. can be blended.

Specific examples are p-phenylenediamine, m-
Phenylenediamine, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylmethane, 3,3'-dimethyl-4,4'-diaminodiphenylmethane, 2,2'-bis [4 -(4-aminophenoxy) phenyl] propane, 1,2-bis (anilino) ethane, diaminodiphenyl sulfone, diaminobenzanilide, diaminobenzoate, diaminodiphenyl sulfide, 2,2'-bis (p-aminophenyl) propane, 2,2-bis (p-aminophenyl) hexafluoropropane, 1,5-diaminonaphthalene, diaminotoluene, diaminobenzotrifluoride, 1,4
-Bis (p-aminophenoxy) benzene, 4,4'-bis (p-aminophenoxy) biphenyl, diaminoanthraquinone, 4,4'-bis (3-aminophenoxyphenyl) diphenyl sulfone, 1,3-bis (anilino ) Hexafluoropropane, 1,4-bis (anilino) octafluorobutane, 1,5-bis (anilino) decafluoropentane, 1,7-bis (anilino) tetradecafluoroheptane, the following general formula Or (However, in the formula, R10 and R12 represent a divalent organic group, and R9 and
R11 represents a monovalent organic group, and p and q represent integers greater than 1), 2,2-bis [4- (p-aminophenoxy) phenyl] hexafluoropropane, 2,2-bis [4- (p-aminophenoxy) phenyl] hexafluoropropane, 2-bis [4- (3-aminophenoxy) phenyl] hexafluoropropane, 2,2-bis [4- (2-aminophenoxy) phenyl] hexafluoropropane, 2,2-bis [4- (4-amino) Phenoxy) -3,5-dimethylphenyl] hexafluoropropane, 2,2-bis [4- (4-aminophenoxy) -3,5-
Ditrifluoromethylphenyl] hexafluoropropane, p-bis (4-amino-2-trifluoromethylphenoxy) benzene, 4,4'-bis (4-amino-2-
Trifluoromethylphenoxy) biphenyl, 4,4'-
Bis (4-amino-3-trifluoromethylphenoxy) biphenyl, 4,4'-bis (4-amino-2-trifluoromethylphenoxy) diphenyl sulfone, 4,
4'-bis (3-amino-5-trifluoromethylphenoxy) diphenyl sulfone, 2,2-bis [4- (4-
Amino-3-trifluoromethylphenoxy) phenyl] hexafluoropropane, benzidine, 3,3 ′, 5,
5'-tetramethylbenzidine, octafluorobenzidine, 3,3'-dimethoxybenzidine, o-tolidine,
Diamines such as m-tolidine, 2,2 ', 5,5', 6,6'-hexafluorotrizine, 4,4 "-diaminoterphenyl, and 4,4-diaminoquaterphenyl, and these diamines and phosgene There are diisocyanates obtained by such reactions.

Moreover, the following are mentioned as tetracarboxylic acid and its derivative (s). Although tetracarboxylic acid is exemplified here, ester compounds, acid anhydrides and acid halides thereof can of course be used. Pyromellitic acid, 3,3 ′, 4,4′-biphenyltetracarboxylic acid, 3,
3 ', 4,4'-benzophenone tetracarboxylic acid, 3,3',
4,4'-diphenylsulfone tetracarboxylic acid, 2,3,
3 ', 4'-diphenyl ether tetracarboxylic acid, 2,3,
3, ', 4'-benzophenone tetracarboxylic acid, 2,3,6,7
-Naphthalene tetracarboxylic acid, 1,4,5,7-naphthalene tetracarboxylic acid, 1,2,5,6-naphthalene tetracarboxylic acid, 3,3 ', 4,4'-diphenylmethane tetracarboxylic acid, 2,2 -Bis (3,4-dicarboxyphenyl) propane, 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane, 3,4,9,10-tetracarboxyperylene, 2,2-bis [4 -(3,4-dicarboxyphenoxy)
Phenyl] propane, 2,2-bis [4- (3,4-dicarboxyphenoxy) phenyl] hexafluoropropane,
Examples thereof include butanetetracarboxylic acid and cyclopentanetetracarboxylic acid, and also trimellitic acid and its derivatives.

It is also possible to introduce a crosslinked structure or a ladder structure by modifying with a compound having a reactive functional group.

For example, there are the following methods.

A pyrrolone ring, an isoindoloquinazolinedione ring, or the like is introduced by modifying with a compound represented by the following general formula.

[Wherein, R 13 represents a 2 + z-valent (z is 1 or 2) aromatic organic group, and B is —NH ₂ group, —CONH ₂ group or —SO.
₂ A substituent selected from the NH ₂ group and in the ortho position with respect to the amino group] Modified with an amine, diamine, dicarboxylic acid, tricarboxylic acid, or tetracarboxylic acid derivative having a polymerizable unsaturated bond, and cured Sometimes it forms a bridge structure. As the unsaturated compound, maleic acid, nadic acid, tetrahydrophthalic acid, ethynylaniline and the like can be used.

A network structure is formed by modifying with an aromatic amine having a phenolic hydroxyl group or a carboxylic acid and using a crosslinking agent capable of reacting with the hydroxyl group or the carboxyl group.

The linear expansion coefficient of the polyimide resin of the present invention can be adjusted by modifying it with each of the above components. That is, a polyimide resin having only the structure of the general formula (1) or (2) or 1 × 10 6
An insulator having a linear expansion coefficient of ^-5 (1 / K) or less can be formed, and the linear expansion coefficient can be arbitrarily increased by modifying the insulator by using each of the above components.

It is also possible to modify it for the purpose of further improving various physical properties such as adhesiveness and bending resistance.

In the present invention, such a polyimide-based precursor resin solution is applied directly on the conductor, but any method can be used as an application method, for example, a barcode method, a gravure coating method, a roll coating method, A die coating method and the like can be mentioned. The die coating method is preferable because bubbles are not caught in the resin solution.

In the drying step, the drying temperature must be 110 ° C or higher and lower than 140 ° C, preferably 120 to 140 ° C. Drying temperature is 15
If it exceeds 0 ° C, it is difficult to reduce the thermal expansion, and if the drying temperature is less than 120 ° C, the evaporation rate is slow and it is difficult to put it into practical use. Drying may be performed at multiple temperatures.

In this drying step, the amount of solvent is polyimide-based precursor resin 10
It is necessary to dry to 50 parts by weight or less, preferably 30 parts by weight or less with respect to 0 parts by weight. When cured in the presence of a solvent exceeding 50 parts by weight, it is difficult to achieve low thermal expansion.

The curing here means a step of forcibly promoting the imidization reaction to promote the curing of the resin. This imidization reaction is usually
Proceeds rapidly at temperatures above 150 ° C, especially above 160 ° C.

After evaporating a certain amount or more of the solvent in this way, curing is performed at a temperature exceeding 150 ° C, but the maximum curing temperature is 250 ° C or higher, preferably 3 ° C in order to sufficiently perform the imidization reaction.
It is more than 00 ℃. In this curing step, it is preferable to carry out a multi-step heat treatment or a continuous temperature rising heat treatment because the resin may foam when the temperature is rapidly raised.

Although any process can be adopted for such a drying process and a curing process, it is necessary to keep the substrate flat without losing the stress due to the shrinkage of the resin layer during these treatment processes, and continuous heat treatment is required. In order to prevent the edge from being lifted when performing, an air support method in which the substrate is held in a wavy shape by wind pressure from the upper and lower nozzles is preferable. The heating atmosphere can be selected from air, nitrogen, carbon gas, inert gas such as argon, and the like.

The conductor used in the flexible printed circuit board according to the present invention includes copper, aluminum, iron, silver, palladium,
Examples thereof include nickel, chromium, molybdenum, tungsten, and alloys thereof. Copper is preferred. Further, the conductor, for the purpose of improving its adhesive force, siding, nickel plating, copper-zinc alloy plating, or chemical such as aluminum alcoholate, aluminum chelate, silane coupling agent, anchor coating with a good adhesive resin, etc. Mechanical surface treatment may be performed.

[Examples] Hereinafter, the present invention will be specifically described based on Examples and Comparative Examples, but it goes without saying that the present invention is not limited thereto.

The coefficient of thermal expansion is obtained by applying a polyimide-based precursor resin solution on a copper foil, drying it, and then using a sample in which the imidization reaction has been sufficiently completed at the maximum heat treatment temperature of 350 ° C., and etching copper with a ferric chloride solution. Then, the obtained film is heated to 250 ° C by a thermal mechanical analyzer (TMA) and then heated to 10 ° C / m.
After cooling with in, the average linear expansion coefficient from 240 ° C to 100 ° C was calculated and obtained.

For coating, a commercially available electrolytic copper foil with a thickness of 35 μm (JTC manufactured by Nippon Mining Co., Ltd.) was attached to a 20 cm square SUS frame using a heat-resistant adhesive tape, and a resin with a solid content of 15% by weight was applied using an applicator. The solution was coated on the rough surface of the copper foil.

The residual amount of solvent after drying was determined by the following formula.

{(C−A) ÷ 0.15 (B−A) −1} × 100 (where A is the weight of the frame and copper foil before coating, B is the weight of the frame and copper foil after coating) And C is the weight of the frame and the copper foil after drying.) Further, the abbreviations in Examples and Comparative Examples are as follows.

PMDA: pyromellitic dianhydride BPDA: 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride DDE: 4,4'-diaminodiphenyl ether PPD: paraphenylenediamine MABA: 2'-methoxy-4, 4'-Diaminobenzanilide DMAc: Dimethylacetamide Synthesis Example 1 MABA 944.0 g, DDE 6 while flowing 1 nitrogen per minute into a reaction vessel having an internal volume of 35 l equipped with a thermometer, a stirrer and a nitrogen inlet.
Charge 01.1 g and DMAc17Kg, dissolve under stirring, and cool the reaction system to 15 ° C or less with cold water in the jacket while PMDA14
When 54.9 g was gradually added and reacted, the polymerization reaction proceeded while generating heat, and a viscous polyamide-imide precursor resin solution (solid content concentration 15% by weight) of 120,000 cps was obtained with a B-type viscometer. It was

Synthesis Example 2 DDE 146.1 g, PPD 709.1 g and BPDA 2144.8 g were reacted in DMAc 17 Kg in the same manner as in Synthesis Example 1 above, and the reaction was conducted with a B-type viscometer at 100,000.
A cps polyimide precursor resin solution (solid content concentration 15%) was obtained.

Example 1 The rough surface of an electrolytic copper foil was coated with the resin solution of Synthesis Example 1 so that the final resin layer had a thickness of 25 μm, and dried in a circulating hot air oven at 130 ° C. for 10 minutes. The solvent residual ratio at this time was 22% by weight. Add this to 165 ℃
2 minutes at 200 ° C., 2 minutes at 250 ° C., 2 minutes at 250 ° C., 2 minutes at 300 ° C., and 2 minutes at 350 ° C. for 2 minutes.

The obtained flexible printed board was flat without curling, and the coefficient of thermal expansion of the film after etching was 8 × 10 ⁻⁶ (1 / K).

Comparative Example 1 A flexible printed circuit board was produced in the same manner as in Example 1 except that the drying condition was 155 ° C. for 10 minutes. The obtained flexible printed board was greatly curled with the radius of curvature of 30 mm inside the resin layer. The coefficient of thermal expansion of the film is
It was 18 × 10 ^-6 (1 / K).

Examples 2 to 10 and Comparative Examples 2 and 3 Using the polyimide-based precursor resin solution obtained in Synthesis Example 1, it was dried under the drying conditions shown in Table 1 to the solvent residual rate shown in Table 1, and A flexible printed board was prepared in the same manner as in 1. The curled state and the coefficient of thermal expansion of the obtained flexible printed circuit board were examined in the same manner as in Example 1. The results are shown in Table 1.

Examples 11 to 18 and Comparative Examples 4 to 6 Using the polyimide-based precursor resin solution obtained in Synthesis Example 2 and drying under the drying conditions shown in Table 1 to the solvent residual rate shown in Table 1, A flexible printed board was prepared in the same manner as in 1. The curled state and the coefficient of thermal expansion of the obtained flexible printed circuit board were examined in the same manner as in Example 1. The results are shown in Table 1.

Examples 19 and 20 The polyimide-based precursor resin solution obtained in Synthesis Example 1 or 2 was used and continuously coated on an electrolytic copper foil having a width of 540 mm by a die method so that the final resin layer had a thickness of 25 μm. Then, using an air support type dryer having a length of 6 m, it was continuously dried while being sent at a line speed of 0.6 m.

During this drying process, there was no lifting of the copper foil edge and the vehicle ran smoothly. Furthermore, the same dryer can be used at 165 to 350 ° C.
The temperature was raised up to, and heat treatment was sequentially performed under the same processing conditions as in Example 1 to cure. The flexible printed board obtained was almost flat without curling.

[Effects of the Invention] According to the method of the present invention, it is possible to easily manufacture a flexible printed circuit board having no curl and excellent workability.

Claims (5)

[Claims] 1. A method for producing a flexible printed circuit board by directly applying a polyimide-based precursor resin solution containing substantially no imide ring closed in the molecule on a conductor and then drying and curing the solution to produce a flexible printed circuit board at a drying temperature of 110 ° C. A method for producing a flexible printed circuit board, which is characterized in that it is dried at a temperature of less than 140 ° C. until the amount of solvent becomes 50 parts by weight or less with respect to 100 parts by weight of resin, and then cured. 2. The amount of solvent is resin at a drying temperature of 120 to 140 ° C.
The method for producing a flexible printed circuit board according to claim 1, wherein drying is performed until the amount becomes 30 parts by weight or less based on 100 parts by weight. 3. A polyimide-based precursor resin represented by the following general formula (1): (In the formula, R1 to R8 are any of hydrogen, halogen, a lower alkoxy group, and a lower alkyl group, and at least one of them is a lower alkoxy group). The method for manufacturing a flexible printed circuit board according to claim 1, wherein 4. A polyimide-based precursor resin represented by the following general formula (2): The method for producing a flexible printed circuit board according to claim 1, which is a polyimide precursor resin having a structural unit represented by: 5. The method for producing a flexible printed circuit board according to claim 1, wherein the solvent is an amide solvent.