JPH08150687A - Preparation of easily removable polyimide resin film - Google Patents

Abstract

PURPOSE: To remove a polyimide simply, efficiently, and economically by a method in which a polyamide acid resin is coated with a polyamide acid resin incorporated with the salt of a metal selected from Cu, Cr, Ni, and Fe. CONSTITUTION: A polyimide film is formed after a polyimide acid is applied on copper foil and heated. The solution of a polyamide acid metal salt in which about 10 g of CuCl2 .2H2 O was added into about 100 g of a polyamide acid varnish and which was stirred for about 4 hr at room temperature is applied on the polyimide film to adjust its thickness at about 360 mm by a doctor blade and allowed to stand at room temperature. The polyimide film is further heated in a vacuum oven to complete the imidization.

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 resin film which can be easily removed.

[0002]

2. Description of the Related Art Polyimide resin has excellent mechanical properties and electrical properties, and also has excellent resistance to chemicals. Therefore, a multi-chip module (Multi-chip module:
MCM), Flexible printed cir
cuit: FPC) and Tape automatic bondin
g: TAB) is widely used.

When manufacturing MCM, FPC or TAB, especially a multi-layer substrate, with a polyimide resin, it is necessary to make a large number of small holes (vials) through the layers and to embed an electrically conductive material in the holes. As a means for forming such a hole, it is necessary to remove the polyimide film corresponding to the position of the hole.

However, since completely imidized polyimide has excellent chemical resistance, it is difficult to remove it by etching. The imidization here means a reaction of converting a polyamic acid precursor into a final product, polyimide.

Although a dry etching method has been proposed in which the polyimide film is directly removed by using a laser beam, it has drawbacks such as high equipment cost and low etching rate.

Another method is a wet etching method in which the partially imidized film is etched and then the imidization is completed. However, this wet etching method requires a soft baking process to remove the used solvent, and also needs a photoresist when selectively etching the polyimide film to form a pattern. Have.

Among various wet etching methods, there is a traditional chemical etching method in which a photoresist is applied and then etching is performed with an etching solution. As an etching solution which is less harmful to the environment, for example, US Pat.
426, 253 (1984), No. 4,431,479.
(1984), 4,436,583 (1984) and 4,848,929 (1989). However, the types of polyimides that can be etched with these solutions with good efficiency are limited. For example, Kapton (trade name) and its precursor Pyralin disclosed in US Pat. Nos. 4,436,583 and 4,848,929.
(Product name) is widely used.

To produce the adhesive-free TAB, it is necessary to coat the polyimide film with a conductive metal layer. There are also reports on a technique for forming a thin metal layer by depositing a metal on Kapton, such as U.S. Pat. No. 4,863,808, but since a metal layer deposition process is required,
High cost.

As a method for producing the adhesive-free TAB, there is also a die casting method in which a polyimide thin film is die-cast on a metal foil (DIE-CAST). However, die casting TAB
In addition to being difficult to etch, it has the drawback that the smoothness and tackiness of the finished product are not compatible.

Another method for improving the etching efficiency is to use commercialized photosensitive polyimide or soluble polyimide. However, it is also known that such a special substance has poor mechanical and electrical properties and chemical resistance.

[0011]

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a method for producing a polyimide film which can be easily and economically removed by a traditional etching method or a mechanical method. .

[0012]

SUMMARY OF THE INVENTION In its broadest sense, the present invention relates to a method for producing a polyimide film which is easy to remove, including the steps shown below.

(1) A step of coating a substrate with a first layer of a polyamic acid resin. (2) Cu, C on the first layer of polyamic acid resin
coating a second layer of polyamic acid resin mixed with a salt of a metal selected from the group consisting of r, Ni and Fe.

(3) A step of heating the first layer and the second layer to cyclize the polyamic acid to form a polyimide film.

The substrate may be selected according to the purpose, but normally an electrically conductive metal foil such as gold foil, silver foil or copper foil is used. Depending on the purpose of use, this conductive metal film can be etched separately from the polyimide film to form an electrically conductive pattern.

Polyamic acid (POLYAMIC ACID) is a precursor of polyimide, and the general formula of its imidization reaction is shown below.

[0017]

Embedded image

Here, R represents an aromatic tetravalent organic group,
R'represents an aromatic or aliphatic diamine divalent group having at least two carbon atoms. However, the two amino groups on the diamine are each bonded to different carbon atoms of the divalent group.

The polyamic acid used in the first layer and the polyamic acid used in the second layer may be the same or different, but they can be synthesized by the reaction of a diamine and a dianhydride. The general formula of the reaction is shown below.

[0020]

Embedded image

The meanings of R and R'herein are as before. A typical dianhydride is US Pat. No. 3,853,81
There is one disclosed in No. 3. In the present invention, bis- (3,4-dicarboxyphenyl) ether dianhydride is used as the dianhydride.
dianhydride, ODPA), 3,3'-4,4'-benzophenone tetracarboxylic dianhydride (3,3'-4,4 ')
-Benzophenonetetracarboxylic dianhydride, BTDA)
And 3,3'-4,4'-biphenyltetracarboxylic dianhydride (3,3'-4,4'-biphenyltetracarboxyli
C dianhydride, bpda) is particularly preferred.

Examples of typical diamines are ethylenediamine, propylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, 2-ethylhexylenediamine, nonamethylenediamine, decamethylenediamine, 2,11-diamino-dodecane. And its analogs; meta-phenylenediamine, para-phenylenediamine, 2,2'-naphthalenediamine, 4,4'-biphenylenediamine, methylenedianiline- (4,4'-diaminodiphenylmethane), ethylenedianiline- ( 4,4'-diaminodiphenylethane), propylenedianiline- (4,4'-diaminodiphenylpropane), bis- (para-amino-cyclohexyl) N-phenylamine, bis- (para-amino-
Cyclohexyl) N-methylamine, hexafluroisopropylidene-bis- (4-phenylamine), 4,
4'-diamino-diphenylmethane, 4,4'-diamino-diphenylethane, 4,4'-diamino-diphenylpropane, 4,4'-diamino-diphenylbutane,
2,6-diamino-pyridine, bis- (4-amino-phenyl) diethylsilane, bis- (4-amino-phenyl) diphenylsilane, bis- (4-amino-phenyl) ethylphosphine oxide, bis- (4 -Amino-phenyl) phenylphosphine oxide, bis- (4-amino-phenyl) -N-phenylamine, bis- (4-amino-phenyl) -N-methylamine,
3,3'-dimethyl-4,4'-diamino-biphenyl, 3,3'-dimethoxy-benzidine, 2,4-bis (b-amino-t-butyl) toluene, bis- (para-
b-amino-t-butyl-phenyl) ether, para-
Bis- (2-methyl-4-amino-phenyl) benzene, para-bis- (1,1-dimethyl-5-amino-pentyl) benzene, m-xylylenediamine, p-xylylenediamine, oxydianiline- ( 4,4'-diaminodiphenyl ether), ketodianiline, 4,
4'-diamino-diphenyl sulfide, 3,3'-
Diamino-diphenyl sulfide, 4,4'-diamino-diphenyl sulfone, 3,3'-diamino-diphenyl sulfone, bis- (para-amino-cyclohexyl) methane, bis- (para-amino-cyclohexyl) ethane, bis- ( Para-amino-cyclohexyl) propane, bis- (para-amino-cyclohexyl) sulfide, bis- (para-amino-cyclohexyl) sulfone, bis- (para-amino-cyclohexyl) ether, bis- (para-amino-cyclohexyl) Diethylsilane, bis- (para-amino-cyclohexyl) diphenylsilane, bis- (para-amino-cyclohexyl) ethylphosphine oxide, bis-
(Para-amino-cyclohexyl) phenylphosphine oxide, 1,2-bis- (3-amino-propoxy) ethane, 2,2-dimethylpropylenediamine, 3
-Methoxy-hexamethylenediamine, 2,5-methylheptamethylenediamine, 5-methylnonamethylenediamine, 1,4-diamino-cyclohexane, 1,2-diamino-octadecane and 2,5-diamino-1,
There is 3,4-oxadiazol.

In the present invention, as the diamine, 4,
4'-diaminodiphenyl ether (4,4'- diami
nodiphenyl ether, 4,4'-ODA), 3,3'-diamino diphenyl sul
fone, 3,3'-SO2DA) and para-phenylene diamine (PDA) are particularly preferred.

Bismalimide (BMI) may be further added to improve the tackiness.

A suitable solvent for the reaction mixture is, for example, N 2.
-Methyl-2-pyrrolidone (NMP) and diethylene glycol dimethyl ether (DEGDE).

The polyamic acids used in the first layer and the second layer do not always have the same composition.

The metal salt premixed with the polyamic acid in the second layer is a salt of Cu, Cr, Ni or Fe. Preferred salts according to the invention are CuCl ₂ .2H ₂ O, NiCl
₂ · 2H ₂ O, it is FeSO ₄ and CuSO _4. The weight ratio of polyamic acid to metal salt is preferably between 0.05 and 20. The polyamic acid and the metal salt must be thoroughly mixed, and mechanical stirring for 0.5 to 24 hours is preferable.

The heating in the step (3) of the present invention is also called baking. The step of baking the polyamic acid in the first and second layers is necessary for the cyclization of the polyamic acid and the formation of the polyimide. After baking, it is necessary to remove the solvent used. Baking temperature is 100 ℃
To 400 ° C is preferred, and a more preferred temperature range is 10
The temperature is from 0 ° C to 200 ° C.

Compared with the first layer, the polyamic acid in the second layer contains a metal salt and therefore has low tackiness and is easily removed after cyclization.

The polyimide film thus produced has a characteristic that it can be easily removed by a traditional chemical etching method or a mechanical method.

In the chemical etching method, the substrate is coated with a double-layered polyimide film and baked, and then immersed in the chemical etching solution for 1 to 2 minutes, and further immersed in deionized water.
After soaking for 0 to 50 seconds, the polyimide film can be etched. Until the desired etching result is obtained
Repeat the above method several times. The etching solution used may be one that can etch the polyimide film. As an example, 6-35 wt% KOH, 5-
An etching solution composed of 20 wt% H ₂ O and 55 to 89 wt% ethanol can be used. A suitable temperature range for this etching solution is 55 to 75 ° C.
It is also possible to replace KOH with NaOH and ethanol with polypropyl alcohol.

[0032]

As is apparent from the examples described below, the polyimide film prepared according to the present invention has an advantage that it is easily adhered to a substrate and is easily etched. Since other properties are the same as those of the conventional polyimide film, the present invention makes it possible to realize a high degree of etching property without sacrificing other properties of the product. According to the present invention, a polyimide film can be etched easily and efficiently. For example, in the present invention,
It does not require a costly dry etching method and, in the traditional wet etching method, also eliminates the need for a partial imidization procedure prior to etching, allowing direct etching to complete imidization. On the other hand, the prior art etching method using a photosensitive polyimide film and a soluble polyimide film has poor overall performance.

The advantages and improvements of the present invention will be more apparent from the following examples.

[0034]

【Example】

Preparation of polyamic acid varnish Polyamic acid varnish 1 3,3′-4,4′-biphenyltetracarboxylic dianhydride (BPDA), 3,3′-4,4′-benzophenone tetracarboxylic dianhydride (BTDA) , Para-phenylenediamine (PDA) and 4,4'-diaminodiphenyl ether (ODA) were mixed at a molar ratio of 1: 1: 1: 1, stirred at room temperature for 4 hours, and after adding bismalimid (BMI), The mixture was stirred for another hour to form a polyamic acid. The obtained varnish had a viscosity of 5000-6000 CPS and a polyamic acid content of 15-16 wt%.

Polyamic acid varnish 2 4,4'-diaminodiphenyl ether (4,4-ODA
, 0.08 mol), bis- (3,4-dicarboxyphenyl) ether dianhydride (ODPA, 0.08 mol), diethylene glycol dimethyl ether (DEGDE, 130 m)
l) and N-methyl-3-pyrrolidone (NMP, 70 ml)
Was mixed and stirred at room temperature for 6 hours to synthesize a polyamic acid. The viscosity of the obtained varnish was 450 cps.

Polyamic acid varnish 3 3,3'-diaminodiphenyl sulfone (3,3'-
SO2DA (0.08 mol), bis- (3,4-dicarboxyphenyl) ether dianhydride (ODPA, 0.08 mol)
And diethylene glycol dimethyl ether (DEGDE, 1
30 ml) was mixed and stirred at room temperature for 6 hours to synthesize a polyamic acid. The viscosity of the obtained varnish was 300 cps.

Solution of Polyamic Acid and Metal Salt 1 100 g of polyamic acid varnish 2 and 10 g of CuCl ₂
· 2H ₂ O was added, at room temperature and stirred for 4 hours.

Polyamic acid and metal salt solution 2 100 g of polyamic acid varnish 3 and 10 g of FeSO ₄
Was added, and the mixture was stirred at room temperature for 4 hours.

Experimental Method For the adhesion to copper foil, see I. P. C. No.
The test was conducted according to the method of 2.4.9.

The etching cycle was performed as follows. That is, while alternately stirring the test membrane, potassium hydroxide (13 wt%), distilled water (11 w
t%) and ethanol (76 wt%) in water (60 ° C. for 1 minute) and deionized water (60 ° C. for 30 seconds). Each treatment of the membrane with potassium hydroxide / ethanol solution and deionized water is a cycle. Such a cycle is repeated until the film is effectively etched. The number of etching cycles is an index of the degree of difficulty of etching the polyimide film.

Example 1 A copper foil was coated with a polyimide acid and heated at 80 ° C. for 1 hour to form a polyimide film. The solution 1 was applied onto the film with a doctor blade to a thickness of about 360 mm, and then the solution 1 was applied at room temperature.
Let stand for 0 minutes and 1 hour at 80 ° C. The membrane was further heated in a vacuum oven as follows. That is, heating to 150 ° C. within 1 hour and maintaining for 1 hour, heating to 250 ° C. within 1 hour and maintaining for 1 hour, further heating to 350 ° C. within 1 hour, and maintaining for 2 hours 2. 1 within 5 hours
It cooled to 50 degreeC and completed imidization. As a result of the experiment, the adhesiveness to the copper foil was 0.3 lb / in or less, and the etching cycle by chemical etching was 8.

[Example 2] The operation is the same as in Example 1, but Solution 2 was used in place of Solution 1. results of the experiment,
The adhesiveness to copper foil is 0.3 lb / in or less,
The etching cycle by chemical etching is 8.

[Comparative Example A] A doctor blade was used to apply a polyamic acid having a thickness of 360 mm to a copper foil, and the temperature was set to 80 ° C.
After being left at room temperature for 1 hour, it was heated as in Example 1 to obtain an imidized film. As a result of the experiment, the adhesiveness to the copper foil was 8 lb / in or more, and the etching cycle by chemical etching was more than 50.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) What is the inventor What is the name of the inventor?

Claims (10)

[Claims] 1. A step of (1) coating a substrate with a first layer of a polyamic acid resin, and (2) Cu on the first layer of the polyamic acid resin,
Coating a second layer of a polyamic acid resin mixed with a salt of a metal selected from the group consisting of Cr, Ni and Fe, (3) by heating the first layer and the second layer And a step of forming a polyimide film by cyclizing a polyamic acid. 2. The method for producing a polyimide film, which is easy to remove, according to claim 1, wherein the heating is performed at a temperature of 100 ° C. to 400 ° C. 3. The method for producing a polyimide film, which is easy to remove, according to claim 1, wherein the heating is performed at a temperature of 100 ° C. to 200 ° C. 4. The metal salt is selected from the group consisting of copper chloride, nickel chloride, ferrous sulfate and copper sulfate.
The method for producing a polyimide film according to claim 1, which is easily removed. 5. The method for producing a polyimide film, which is easy to remove, according to claim 1, wherein the polyamic acid is a reaction product of a dianhydride and a diamine. 6. The dianhydride is bis- (3,4-dicarboxyphenyl) ether dianhydride, 3,3′-4,
The method for producing a polyimide film according to claim 5, which is selected from the group consisting of 4'-benzophenone tetracarboxylic dianhydride and 3,3'-4,4'-biphenyltetracarboxylic dianhydride. 7. The easily removable polyimide film according to claim 5, wherein the diamine is selected from the group consisting of 4,4′-diaminodiphenyl ether, 3,3′-diaminodiphenyl sulfone and para-phenylenediamine. Method. 8. The substrate is an electrically conductive metal foil,
The method for producing a polyimide film according to claim 1, which is easily removed. 9. The method for producing an easily removable polyimide film according to claim 8, wherein the substrate is a copper foil. 10. A polyimide film produced by the method of claim 1, which is easy to remove.