JPH05105755A - Polyisoimide and its film - Google Patents

Abstract

PURPOSE:To obtain a polyisoimide free from the lowering tendency of the dimensional change ratio and the generation of curl by isoimidating a polyamic acid obtained by reacting a specific aromatic carboxylic acid dianhydride component with an aromatic diamine component. CONSTITUTION:The objective polyisoimide suitable for the manufacture of double-layer flexible printed circuit board, etc., is produced by reacting (A) an aromatic carboxylic acid dianhydride component consisting of (i) 3,3',4,4'- biphenyltetracarboxylic acid dianhydride and (ii) pyromellitic acid dianhydride at a molar ratio (i:ii) of 90:10 to 50:50 with (B) an aromatic diamine component produced by mixing (iii) p-phenylenediamine, (iv) 4,4'-diaminodiphenyl ether and (v) 3,4'-diaminodiphenyl ether at a molar ratio [(iii):(iv) and/or (v)] of 90:10 to 50:50 and isoimidating the obtained polyamic acid in the presence of a catalyst such as dicyclohexyl carboimide.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a specific polyisoimide, a film using the same, optionally provided with openings, and a two-layer flexible printed circuit board having no adhesive layer obtained from this film. Is. Further, the present invention can be applied to a multi-layer board or a coverlay film having no adhesive layer.

[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, if the drying conditions are mild, when the copper foils are bonded together, the 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.

A two-layer flexible printed circuit board having no adhesive layer is used as electronic devices are becoming smaller and lighter.
The application is expanding more and more, the film cover lay without adhesive layer is also developed, and recently, not only the conventional wiring board, but also the board with holes in the supporting film such as TAB carrier tape is used. Is also increasing.

As a method of manufacturing a cover lay having no adhesive layer for a two-layer flexible printed circuit board, a method of directly applying and drying a polyimide precursor ink on the two-layer flexible printed circuit board by a screen printing method or the like. However, in order to use the polyimide precursor varnish as an ink, it is necessary to mix a filler or the like in order to improve the thixotropy, and a polyimide film layer and a filler that do not have a filler as a base material are included. Since it was difficult to balance between the polyimide coverlay layers, the flexible printed circuit board with a coverlay obtained could not have sufficient folding endurance.

On the other hand, as a method of manufacturing a flexible printed circuit board having a conductor film and a supporting film layer used for TAB or the like, a supporting film layer is preliminarily perforated by punching or the like to form an adhesive. After bonding the conductor layer using, the method of forming a wiring circuit, or by directly applying a polyamic acid solution to the conductor layer, and then drying and imidizing, or the conductor layer by vapor deposition or sputtering method on the support film layer. After forming the film, a hole is formed in the supporting film layer with a laser or a strong alkaline solution, and then a wiring circuit is formed.

However, 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 heat resistance of the adhesive layer is low, so even if polyimide is used for the supporting film, the heat resistance of the flexible printed circuit board is It has the drawback of being determined by sex. 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. If so, the stress due to the contraction accompanying the 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 directly and repeatedly applied to the conductor layer several times and dried, and further imidization reduces curl during the process, thermal history is generated 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. Further, when using a laser, especially when using an excimer laser is excellent in fine workability and less damage to the copper foil, but a strong imide bond must be cut, which requires time to process and low productivity, It has a problem of high running cost. Alternatively, a polyimide having a molecular structure capable of being alkali-etched after imidization has a drawback that the solvent resistance is slightly deteriorated, the danger is high because a strong alkaline solution is used as an etching solution, and waste liquid cannot be easily treated. ing.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a polyisoimide which overcomes the above-mentioned drawbacks and an alkali resistance inherent to a two-layer or multilayer flexible printed circuit board having no adhesive layer using the same. A polyisoimide film having a predetermined thickness and having holes formed as necessary without deteriorating solvent resistance, heat resistance, and electrical characteristics, and a flexible printed circuit board made from the film. Is.

[0009]

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 and para-phenylenediamine (hereinafter abbreviated as PPD), 4,4′-diaminodiphenyl ether (hereinafter 4, 4'-DDE), 3,4'-diaminodiphenyl ether (hereinafter abbreviated as 3,4'-DDE) 3
Among the aromatic diamines of the species, an aromatic diamine component having a molar ratio of PPD: 4,4′-DDE and / or 3,4′-DDE of 90:10 to 50:50 is used, A polyisoimide which is formed by imidizing a polyamic acid whose both ends are sealed with a dicarboxylic acid anhydride and / or a derivative thereof at both ends, and which is formed on a mold release material and is provided with a predetermined opening portion if necessary And a method for producing a flexible printed circuit board in which this film is attached to a conductor foil and imidized.

In the present invention, a small amount of another tetracarboxylic dianhydride or diamine may be added to the tetracarboxylic dianhydride component 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 by 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 at the same time with the acid dianhydride component and the diamine component to react, 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 release material include plastic films such as polypropylene, polyester, polyether sulfone, polyimide and polyethylene, and metal foils.

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

In the present invention, a method for forming a polyisoimide film on a release material is carried out by a known coating means such as a rotary coater, knife coater, doctor blade, flow coater or the like on the release material from 1 to 100 μm from the upper end of the release material.
It can be obtained by casting and coating to a uniform thickness, followed by heating and drying. In addition, a semi-cured polyisoimide film is formed on a release material, and a polyisoimide film formed on another release material having the same composition or a different composition is aligned with the isoimide film surface, and if necessary Insert a predetermined number of isoimide film into
It is also possible to obtain a thick polyisoimide film by simultaneously heating and pressing two or more sheets.

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.

Next, the polyisoimide film with the mold release material is perforated by a conventional method such as punching, cutting, alkali etching, laser or the like together with the mold release material or by opening only the polyisoimide film. I do. After the hole processing is completed, the polyisoimide film is heated and pressure-bonded to the conductor foil or the flexible printed circuit board, and then the release material is peeled off to sufficiently perform imidization.

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, the fluidity is large when heating and crimping with the conductor foil, the bleeding and bleeding at the opening is large, the variation in the film thickness is also large, and the dimensional change after imidization Will grow. Further, when used as a multilayer board, swelling due to the residual solvent occurs. On the other hand, if the temperature is higher and the time is longer than this, the imidization of isoimide proceeds, and the fluidity is too small when heating and pressure bonding with the conductor foil, and the peel strength with the conductor foil or the flexible printed circuit board decreases. ..

The suitable coating thickness of one sheet of isoimide is 50 μm or less after imidization. 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 70 to 200 ° C and 5 to 100k for the press type.
g / cm ² , 5 to 30 minutes, 70 to 200 for roll type laminator
C., 1 to 50 kg / cm, 0.1 to 10 m / min are suitable conditions.

Further, 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.

[0028]

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. Thus, it is possible to easily and inexpensively obtain a two-layer flexible printed circuit board having a hole in the supporting film layer and a flexible circuit board with a coverlay with good productivity and high yield.

[0029]

【Example】

(Example 1) To a 4-necked flask equipped with a stirrer, a thermometer, and a reflux condenser, 86.4 g of PPD was added as a diamine component.
(0.8 mol) and 3,4'-DDE 40.0 g (0.2 mol) were added,
Furthermore, N-methyl-2-pyrrolidone (hereinafter abbreviated as NMP) 3
000g was added and stirred well until the diamine component 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, PMDA 41.4
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 4-necked flask equipped with a stirrer, a thermometer and a reflux condenser was charged with PP as a diamine component.
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 195.6 g (0.66 mol) of BPDA and 63.3 g (0.29 mol) of PMDA were added to the system at a temperature of 15 ° C.
After the addition was completed, the reaction mixture was stirred at 20 ° C. for 5 hours. Then phthalic anhydride 14.8g
(0.1 mol) was added, and the mixture was further reacted at 20 ° C. for 2 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 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 further NMP of 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 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.

Next, 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 coated on a commercially available polyester film with a spinner so that the thickness after imidization was 25 μm, and 100 ° C. Cured for 1 hour at 150 ° C. for 30 minutes (heated at 350 ° C. for 30 minutes to complete thermal imidization for Comparative Example 1) and cured to give a polyisoimide film (comparative example 1 is a polyimide film). ) Got.

Next, this polyisoimide film was perforated using a mold, the release film on one side was peeled off, and the polyisoimide film surface was superposed on the roughened surface of a commercially available copper foil, 90 degreeC, 40 kg / cm < ² >, 15 minutes heating-pressing was performed. Then, the release film was peeled off, and heating was performed at 380 ° C. for 1 hour to imidize the isoimide.

The characteristics of the two-layer flexible printed circuit board obtained by the method of the present invention have the same or higher characteristics as those prepared by direct coating, drying and imidization on a copper foil by a usual method. Was there. On the other hand, in Comparative Example 1 not isoimidized, the peel strength was not sufficient, and Comparative Example 2 in which PMDA and DDE were not used was similar. Also PMDA, D
In Comparative Example 3 in which the amount of DE used was too large, the dimensional change was large and it was unsuitable as a substrate.

Table 1 shows the peel strength, solder heat resistance and dimensional change rate of the obtained two-layer flexible printed circuit board.

[0042]

[Table 1]

[0043]

According to the present invention, by using a specific polyisoimide, it is possible to obtain effects such as a reduction in dimensional change rate and a reduction in curling without impairing other properties even after completion of imidization. Furthermore, the film of the present invention can be used to obtain a two-layer flexible printed circuit board having holes in the support film, a two-layer flexible printed circuit board with a coverlay, and a multilayer flexible printed circuit board if necessary. 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 a method for industrially manufacturing a flexible printed circuit board having holes.

Claims (4)

[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 acid 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,
A polyisoimide obtained by isoimidating a polyamic acid in which the diamine component forms both ends and the both ends are capped with a dicarboxylic acid anhydride and / or a derivative thereof. 2. A polyisoimide film having the polyisoimide of claim 1 formed on a release material. 3. The polyisoimide film according to claim 2, which is provided with predetermined openings. 4. A method for producing a flexible printed circuit board, which is obtained by attaching the film according to claim 2 or 3 to a conductor foil and imidizing the film.