JPH05110216A - Manufacture of double-sided flexible printed circuit board - Google Patents

Abstract

PURPOSE:To provide a two-layer flexible printed circuit board with no adhesive agent layer by completing imidation by heating and pressing specific polyisoimide film which is formed on a mold material and has an opening as required to a conductive foil or a flexible printed circuit board. CONSTITUTION:Using para-phenylene diamine: 4, 4'-and/or aromatic diamine content whose 3, 4'-diamino diphenyl ether mole ratio is 90:10-50:50, both ends are formed with diamine content and a polyisoimide which is produced by isoimidizing polyamic acid whose both ends are sealed with dicarbone acid anhydrous part and/or its derivative is formed in film-shape on a conductive foil and then heated and pressed together with the conductive foil. As a result, a double-sided flexible printed circuit board with a specified thickness is obtained without lowering resistances to alkali, solvent and heat and also electric characteristics inherent with a double-sided flexible printed circuit board with no adhesive agent.

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 double-sided flexible printed circuit board having no adhesive layer using a specific polyisoimide.

[0002]

2. Description of the Related Art In recent years, with the development of the electronic and electric industries, simplification, miniaturization and high reliability of mounting methods for communication and consumer equipment have been demanded, and use of printed circuit boards has been desired. In particular, the use of a flexible printed circuit board which is light in weight and can be mounted three-dimensionally is advantageous and attracts attention.

Conventionally, in order to manufacture a two-layer flexible printed circuit board using a polyimide resin, a method of applying a varnish of polyamic acid on a copper foil and then drying and curing the varnish is generally used. However, this solution of polyamic acid is unstable at room temperature, requires low temperature for storage, and is not suitable for long-term storage. Furthermore, recently, the use of flexible printed circuit boards having a multilayer structure has been strongly desired. However, when these polyamic acids are used for a double-sided flexible printed circuit board, when the drying conditions are mild, when the copper foils are bonded together, water generated during imidization, etc., on the copper foil, Blisters, wrinkles, and the like occur, and conversely, if the drying conditions are too strong, sufficient adhesive strength cannot be obtained. Also, some examples using thermoplastic polyimide have been reported, but they are still insufficient in terms of adhesive strength and heat resistance. Double-sided flexible printed circuit boards that do not have an adhesive layer have been increasingly used as electronic devices have become smaller and lighter.

These conventionally used methods each have drawbacks in heat resistance, adhesion, workability and chemical resistance. First, in a three-layer flexible printed circuit board having an adhesive layer, the adhesive layer has low heat resistance.
Even if polyimide is used for the supporting film, there is a drawback that the heat resistance of the flexible printed circuit board is determined by the heat resistance of the adhesive layer. If the conductor layer is formed by vapor deposition or sputtering, the adhesion between the support film layer and the conductor layer is low, or if the resin layer is thickened, for example, polyamic acid is directly applied and dried to form a thick film. When this is done, the stress due to contraction due to imidization exceeds the supporting force of the conductor layer, and a large curl occurs during drying. On the other hand, if the polyamic acid solution is repeatedly applied and dried directly on the conductor layer, and further imidized, curling during the process is reduced, but heat history is present in the portion near the conductor layer and the portion on the opposite side of the conductor layer. Since they are different, the imidization rate and the residual solvent amount in the film are different, and the curl and dimensional change rate of the film after etching the copper foil are large.

[0005]

SUMMARY OF THE INVENTION The object of the present invention is to provide a double-sided flexible printed circuit board having no adhesive layer, which has the inherent alkali resistance, solvent resistance, and It is intended to provide a double-sided flexible printed circuit board having a predetermined thickness without deteriorating heat resistance and electric characteristics.

[0006]

The present invention provides 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride (hereinafter abbreviated as BPDA) and pyromellitic dianhydride (hereinafter abbreviated as PMDA).
Aromatic carboxylic acid dianhydride component having a molar ratio (BPDA: PMDA) of 90:10 to 50:50, para-phenylenediamine (hereinafter abbreviated as PPD), 4,4′-diaminodiphenyl ether (hereinafter 4 , 4'-DDE), 3,4'-diaminodiphenyl ether (hereinafter abbreviated as 3,4'-DDE) among three aromatic diamines, PPD: 4,4'-DDE and / or 3, An aromatic diamine component having a molar ratio of 4'-DDE of 90:10 to 50:50, the diamine component forming both ends, and the both ends being sealed with a dicarboxylic acid anhydride and / or a derivative thereof. Polyisimide obtained by isoimid polyamic acid is formed into a film on the conductor foil, and then the conductor foil is heated and pressure-bonded by matching the polyisoimide film surfaces to each other or the polyisoimide film surface.
It is a method for producing an imidized double-sided flexible printed circuit board.

In the present invention, a small amount of another tetracarboxylic dianhydride or diamine may be added to the tetracarboxylic dianhydride or diamine component.

As the tetracarboxylic dianhydride component,
For example, 2,3,3 ', 4'-biphenyltetracarboxylic dianhydride, 3,3', 4,4'-benzophenonetetracarboxylic dianhydride, 3,3 ', 4,4'-P-tere Phenyltetracarboxylic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 3,
3 ', 4,4'-benzophenone tetracarboxylic dianhydride, 3,
3 ', 4,4'-P-terphenyltetracarboxylic dianhydride, 4,
4'-hexafluoroisopropylidene bis (phthalic anhydride) etc. can also be used together.

Examples of the diamine component include 4,4'-diaminodiphenylmethane, 3,3'-dimethylbenzidine, 4,
4'-diamino-P-terphenyl, 4,4'-diamino-P-quaterphenyl, 2,8-diaminodiphenylene oxide and the like can also be used together.

As the dicarboxylic acid anhydride, maleic anhydride, phthalic anhydride, naphthalene dicarboxylic acid anhydride and the like are usually used.

BPDA and P used in the present invention
The molar ratio of MDA is preferably 90:10 to 50:50, and more preferably 80:20 to 60:40. PM as an acid component
When DA is used, the addition of 50 mol% or more decreases the adhesiveness of the film. If it is 10 mol% or less, the value of the dimensional change becomes worse.

On the other hand, PPD used as an aromatic diamine
And the molar ratio of 4,4'-DDE or 3,4'-DDE is 90: 10-
50:50 is preferable, and more preferably 80:20 to 60:40.
Is. If the amount of 4,4'-DDE or 3,4'-DDE added exceeds 50 mol%, heat resistance and dimensional stability will be reduced. on the other hand,
If it is less than 10 mol%, sufficient adhesive force cannot be obtained.

The reaction of the tetracarboxylic dianhydride component, the diamine component and the dicarboxylic acid anhydride component is carried out in the following manner: acid dianhydride component / diamine component / acid anhydride component (molar ratio) = 0.9 / 1.0
/0.2 to 0.99 / 1.0 / 0.02 is preferable. When the acid dianhydride component is lower than 0.90, the degree of polymerization does not increase and the film properties after curing are poor. If it is greater than 1.00, gas is generated during curing, and a smooth film cannot be obtained.

The reaction is usually carried out in an organic polar solvent which does not react with the tetracarboxylic dianhydride or diamines. Besides being inert to the reaction system and being a solvent for the products, this organic polar solvent must be a good solvent for at least one, preferably both, of the reaction components. Typical examples of this type of solvent include N, N-dimethylformamide, N, N-dimethylacetamide, dimethyl sulfone, dimethyl sulfoxide, N-methyl-2-pyrrolidone, etc., and these solvents may be used alone or in combination. used. Other than these, benzene, dioxane,
A non-polar solvent such as xylene, toluene or cyclohexane is used as a dispersion medium of the raw material, a reaction modifier or a volatilization modifier from the product, a film smoothing agent and the like.

The reaction is generally preferably carried out under anhydrous conditions. This is because the tetracarboxylic acid dianhydride may be ring-opened by water and may be inactivated to stop the reaction. Therefore, it is necessary to remove both the water content in the raw material and the water content in the solvent. But on the other hand, it regulates the progress of the reaction,
Water may be added to control the degree of resin polymerization. Further, the reaction is preferably carried out in an inert gas atmosphere. This is to prevent the oxidation of diamines. Dry nitrogen gas is generally used as the inert gas.

The dicarboxylic acid anhydride may be added to the reaction system together with the acid dianhydride component and the diamine component at the same time for reaction, or after the acid dianhydride component and the diamine component are reacted in advance, You may add and make it react. The polyamic acid obtained by the reaction is isoimidized with a catalyst such as dicyclohexylcarbodiimide.

Materials that can be used as the conductor foil include metal foils such as copper, aluminum, constantan and nickel.

In the present invention, the method for forming the polyisoimide film on the conductor foil is 1-100 μm from the upper end of the conductor foil by a known coating means such as a rotary coater, a knife coater, a doctor blade and a flow coater on the conductor foil.
It can be obtained by casting and coating to a uniform thickness, followed by heating and drying. Then, the polyisoimide surfaces on the conductor foil are combined or other conductor foils are combined and pressure-bonded, and imidized to obtain a double-sided flexible printed circuit board. In addition, a semi-cured polyisoimide film is formed on the conductor foil, and a polyisoimide film formed on another release material having the same composition or a different composition is brought into contact with the isoimide film surface. It is also possible to insert a predetermined number of isoimide films into and heat and press-bond two or more simultaneously to form a thick polyisoimide film.

That is, a polyisoimide solution is applied onto a release material and dried until a tack-free state is obtained to form a polyisoimide film. Then, the surfaces of the polyisoimide films are overlapped with each other, and the polyisoimide films are heated and pressure-bonded to each other to prepare a polyisoimide film having an integral multiple of the thickness which was first applied and dried. At this time, a thicker polyisoimide film can be obtained by inserting a predetermined number of polyisoimide films from which the release material has been peeled off so that the surfaces of the polyisoimides can be overlapped with each other as necessary. It is also possible to obtain a thicker product by peeling off the release material on one side after pressure bonding and repeating the same process. At this time,
A double-sided flexible printed circuit board can be obtained by using conductor foils having upper and lower sides at a required thickness.

In the present invention, suitable conditions for drying the polyisoimide solution to form a polyisoimide film are 100 to 180 ° C. and 30 to 200 minutes. If the temperature is lower than this and the time is short, when using double-sided
When pressure-bonded, the fluidity is large, the variation in the film thickness is large, and the dimensional change after imidization is large. In addition, swelling due to the residual solvent occurs. On the other hand, when the temperature is higher and the time is longer than this, the imidization of the isoimide proceeds, the fluidity is too small at the time of heating and pressure bonding, and the peel strength with the conductor foil or the flexible printed circuit board decreases.

As a coating thickness of one sheet of isoimide, a thickness after imidization of 50 μm or less is suitable. When it is thicker than this, the evaporation rate of the solvent is slow and the productivity is remarkably reduced. The conditions for heating and crimping the polyisoimide film on the conductor foil are 200 to 380 ° C and 5 to 150 for the press type.
kg / cm ² , 5 to 30 minutes, 200 to 3 for roll type laminator
Appropriate conditions are 80 ° C., 1 to 50 kg / cm, 0.1 to 10 m / min.

Furthermore, since the film of the present invention does not generate condensed water during heat curing, it can be applied as a multilayer board, and a substrate composed of a conductor foil and polyimide without an adhesive layer. Can be used as a two-layer flexible printed circuit board.

[0023]

According to the present invention, by using a specific polyisoimide film formed on a release material and optionally having openings, heating and pressure bonding with a conductor foil or a flexible printed circuit board to complete imidization. A double-sided flexible printed circuit board can be obtained easily and inexpensively with good productivity and yield.

[0024]

Example 1 A 4-necked flask equipped with a stirrer, a thermometer, and a reflux condenser was charged with PPD as a diamine component.
86.4g (0.8mol), 3,4'-DDE 40.0g (0.2mol)
Then, 3000 g of N-methyl-2-pyrrolidone (hereinafter abbreviated as NMP) was added, and the mixture was stirred well until the diamine was dissolved. After the diamine component was dissolved, the solution was cooled to 15 ° C or lower, and 223.6 g (0.76 mol) of BPDA, PMDA41.4
g (0.19 mol) and 14.8 g (0.1 mol) of phthalic anhydride were gradually added so that the temperature in the system did not exceed 15 ° C, and after the addition was completed, stirring was carried out at 20 ° C for 6 hours.

Then, N dissolved in 600 g of NMP solution,
412.6 g of N'-dicyclohexylcarbodiimide was slowly added dropwise over 8 hours. After completion of dropping, the mixture was stirred at 20 ° C. for 24 hours. After completion of stirring, the reaction mixture was filtered to remove dicyclohexylurea. The resulting solution was precipitated in methanol to give a yellow polyisoimide powder. 50 g of this powder was added to 200 g of dimethylformamide (hereinafter DM
(Abbreviated as F) to obtain a polyisoimide solution.

Example 2 A diamine component was added to a 4-necked flask equipped with a stirrer, a thermometer, and a reflux condenser as PP.
D 75.6 g (0.7 mol) and 4,4'-DDE 60.0 g (0.3 mol) were added, and NMP (3000 g) was further added, and the mixture was stirred well until the diamine was dissolved. After the diamine component is dissolved,
The solution was cooled to 15 ° C or lower, and BPDA 195.6g (0.66mol), PMDA 63.3g (0.29mol), phthalic anhydride 1
4.8 g (0.1 mol) was gradually added so that the temperature in the system did not exceed 15 ° C. After completion of the addition, stirring reaction was carried out at 20 ° C. for 6 hours.

Next, N, dissolved in 600 g of NMP solution,
N'-dicyclohexylcarbodiimide 412.6 g (2 mol)
Was slowly added dropwise over 8 hours. 20 ° C after dropping
The mixture was stirred for 24 hours. After completion of stirring, the reaction mixture was filtered to remove dicyclohexylurea. The resulting solution was precipitated in methanol to give a yellow polyisoimide powder. 50 g of this powder was dissolved in 200 g of DMF to obtain a polyisoimide solution.

Comparative Example 1 A 4-necked flask equipped with a stirrer, a thermometer and a reflux condenser was charged with PP as a diamine component.
D 86.4 g (0.8 mol) and 3,4′-DDE 40.0 g (0.2 mol) were added, and NMP (3000 g) was further added, and the mixture was stirred well until the diamine was dissolved. After the diamine component is dissolved,
The solution was cooled to 15 ° C or lower, and 223.6 g (0.76 mol) of BPDA, 41.4 g (0.19 mol) of PMDA, and phthalic anhydride 1
4.8 g (0.1 mol) was gradually added so that the temperature in the system did not exceed 15 ° C, and after the addition was completed, the reaction was completed by stirring at 20 ° C for 6 hours.

Comparative Example 2 A 4-necked flask equipped with a stirrer, a thermometer and a reflux condenser was charged with PP as a diamine component.
D 108.1 g (1.0 mol) was added, NMP was added 3000 g,
Stir well until the diamine has dissolved. After the diamine component has dissolved, the solution is cooled to 15 ° C or lower and BPDA 27
9.3g (0.95mol), phthalic anhydride 14.8g (0.1mol)
Was gradually added so that the temperature in the system did not exceed 15 ° C, and after completion of the addition, stirring was carried out at 20 ° C for 6 hours.

Then, N dissolved in 600 g of NMP solution,
412.6 g of N'-dicyclohexylcarbodiimide was slowly added dropwise over 8 hours. After completion of dropping, the mixture was stirred at 20 ° C. for 24 hours. After completion of stirring, the reaction mixture was filtered to remove dicyclohexylurea. The resulting solution was precipitated in methanol to give a yellow polyisoimide powder. 50 g of this powder was dissolved in 200 g of DMF to obtain a polyisoimide solution.

COMPARATIVE EXAMPLE 3 A 4-necked flask equipped with a stirrer, a thermometer and a reflux condenser was charged with PP as a diamine component.
D 43.3 g (0.4 mol) and 3,4'-DDE 120.1 g (0.6 mol) were added, and further NMP 3000 g was added, and the mixture was stirred well until the diamine was dissolved. After the diamine component is dissolved,
The solution was cooled to 15 ° C or below, and BPDA 111.8g (0.38mol), PMDA 124.3g (0.57mol), phthalic anhydride 1
4.8 g (0.1 mol) was gradually added so that the temperature in the system did not exceed 15 ° C, and after completion of the addition, stirring was carried out at 20 ° C for 6 hours.

Then, N dissolved in 600 g of NMP solution,
412.6 g of N'-dicyclohexylcarbodiimide was slowly added dropwise over 8 hours. After completion of dropping, the mixture was stirred at 20 ° C. for 24 hours. After completion of stirring, the reaction mixture was filtered to remove dicyclohexylurea. The resulting solution was precipitated in methanol to give a yellow polyisoimide powder. 50 g of this powder was dissolved in 200 g of DMF to obtain a polyisoimide solution.

As described above, the polyisoimide solutions synthesized in Examples 1 and 2 and Comparative Examples 1, 2 and 3 were applied onto a copper foil with a spinner so that the thickness after imidization was 25 μm, and 100
C., 1 hour, 150.degree. C., 30 minutes (for Comparative Example 1, heating at 350.degree. C. for 30 minutes to complete thermal imidization)
A single-sided two-layer flexible printed circuit board was obtained.

Two pieces of the obtained two-layer flexible printed circuit board were pasted together with the film side inside, and 350 ° C., 50 k
After heating and pressure bonding for 15 minutes, a double-sided flexible printed circuit board was obtained. Table 1 shows the values of peel strength, solder heat resistance, and dimensional change rate of the obtained double-sided flexible printed circuit board.

[0035]

[Table 1]

Although all of the products prepared by the method of the present invention have excellent properties, in Comparative Example 1 in which no imidization was carried out,
The peel strength was not sufficient, and the same was true for Comparative Example 2 in which PMDA and DDE were not used. Further, in Comparative Example 3 in which the amount of PMDA or DDE used was too large, the dimensional change was large and it was not suitable as a substrate.

[0037]

According to the present invention, a double-sided flexible printed circuit board having no adhesive layer can be obtained. Furthermore, by using a specific polyisoimide, it is possible to obtain effects such as a reduction in the dimensional change rate and a reduction in curling without impairing other properties even after the completion of imidization.
INDUSTRIAL APPLICABILITY The present invention can be easily applied to a continuous process of a flexible printed circuit board using a continuous sheet, and is suitable as an industrial method for manufacturing a flexible printed circuit board.

Claims (1)

[Claims] 1. A molar ratio (BPDA: P) of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride (hereinafter abbreviated as BPDA) and pyromellitic dianhydride (hereinafter abbreviated as PMDA).
Aromatic carboxylic dianhydride component having MDA of 90:10 to 50:50, para-phenylenediamine (hereinafter abbreviated as PPD), 4,4'-diaminodiphenyl ether (hereinafter 4,4'-
PDE: 4,4'-DDE and / or 3,4'-DDE among three aromatic diamines of DDE) and 3,4'-diaminodiphenyl ether (abbreviated as 3,4'-DDE below) An aromatic diamine component having a molar ratio of 90:10 to 50:50,
The diamine component forms both ends, and polyisoimide obtained by isoimidating polyamic acid whose both ends are sealed with dicarboxylic acid anhydride and / or its derivative is formed into a film on a conductor foil, and then polyisoimide is formed. A method for producing a double-sided flexible printed circuit board, which is formed by imidizing the film surfaces with each other or with a conductor foil on the polyisoimide film surface, followed by heating and pressure bonding.