JP2779907B2 - Polyimide film and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyimide film and a method for producing the same, and more particularly to a polyimide film which is easily removed and a method for producing the same.

[0002]

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

[0003] 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 (vias) through the layers and embed an electric conductive material in the holes. As a means for forming such a hole, it is necessary to remove the polyimide film hitting the position of the hole.

[0004] However, completely imidized polyimide has excellent chemical resistance and is therefore difficult to remove by etching. The imidization here means a reaction for converting a polyamic acid precursor into a polyimide as a final product.

A dry etching method for directly removing a polyimide film by using a laser beam has been proposed, but has disadvantages such as a high cost of the apparatus and a low etching rate.

[0006] As another method, there is a wet etching method in which a partially imidized film is etched and then imidization is completed. However, this wet etching method requires a soft baking step to remove the used solvent, and also requires a photoresist when selectively etching the polyimide film to form a pattern. Having.

[0007] Among the 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 that 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 good efficiency with these solutions are limited. For example, Kapton (trade name) and its precursor Pyralin disclosed in U.S. Patent Nos. 4,436,583 and 4,848,929.
(Trade name) is widely used.

In order to produce the adhesive-free TAB, it is necessary to cover the polyimide film with a conductive metal layer. There is also a report 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 of producing the adhesive-free TAB, there is 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 resulting product cannot have both smoothness and tackiness.

As another method for improving the etching efficiency, there is a method using a commercially available photosensitive polyimide or soluble polyimide. However, it is also known that such special substances have poor mechanical / electrical properties and poor chemical resistance.

[0011]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a polyimide film and a method for producing the same, which can be easily and economically removed by a conventional etching method or a mechanical method with high efficiency. I have.

[0012]

SUMMARY OF THE INVENTION In its broadest sense, the present invention relates to a method for producing a polyimide film including the following steps and a polyimide film produced by the method.

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

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

The substrate may be selected according to the purpose, but usually, an electrically conductive metal foil such as a gold foil, a silver foil or a copper foil is used. The conductive metal film can be etched separately from the polyimide film depending on the purpose of use to form an electric 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 a divalent group of an aromatic or aliphatic diamine having at least two carbon atoms. However, the two amino groups in the diamine are each bonded to a separate carbon atom of the divalent group.

The polyamic acid used for the first layer and the polyamic acid used for the second layer may be the same or different, but 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 'are as described above. Typical dianhydrides are disclosed in U.S. Pat. No. 3,853,81.
No. 3 discloses this. In the present invention, bis- (3,4-dicarboxyphenyl) ether dianhydride (bis- (3,4-dicarboxyphenyl) ether) is used as the dianhydride.
dianhydride, ODPA), 3,3'-4,4'-benzophenonetetracarboxylic 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 include ethylenediamine, propylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, 2-ethylhexylenediamine, nonamethylenediamine, decamethylenediamine, and 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, hexafluoroisopropylidene-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'-diaminodiphenyl sul
fone, 3,3'-SO2DA) and para-phenylenediamine (PDA) are particularly preferred.

In order to improve the tackiness, bismalimide (BMI) can be further added.

Suitable solvents for the reaction mixture are, for example, N 2
-Methyl-2-pyrrolidone (NMP) and diethylene glycol dimethyl ether (DEGDE).

The polyamic acids used for the first and second layers do not always have the same composition.

The metal salt premixed in the polyamic acid of the second layer is a salt of Cu, Cr, Ni or Fe. Preferred salts of the present 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 need to be mixed well, for example, mechanical stirring for 0.5 to 24 hours is preferred.

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

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

The polyimide film thus formed has a characteristic that it is easily removed by a traditional chemical etching method or a mechanical method.

In the chemical etching method, a substrate is coated with two layers of polyimide film and baked, then immersed in a 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 any solution that can etch the polyimide film. As an example, 6-35 wt% KOH, 5-
An etching solution composed of 20 wt% of H ₂ O and 55 to 89 wt% of ethanol can be used. A suitable temperature range for this etching solution is 55-75C.
KOH can be replaced by NaOH and ethanol by polypropyl alcohol.

[0032]

As will be apparent from the examples described later, the polyimide film prepared according to the present invention has an advantage that it is easily etched while having excellent adhesion to a substrate. Since the other properties are not different from the conventional polyimide film, the present invention makes it possible to realize a high etching property without sacrificing other properties of the product. According to the present invention, it is possible to easily and efficiently etch a polyimide film. For example, in the present invention,
There is no need for costly dry etching methods, and in traditional wet etching methods there is no need for a partial imidization procedure before etching, and direct imidization can be performed completely. On the other hand, the etching method using the photosensitive polyimide film and the soluble polyimide film of the prior art has poor overall performance.

The advantages and improvements of the present invention will become 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'-benzophenonetetracarboxylic 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 added with bismalimide (BMI). Stirring was continued for an additional hour to form the 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'-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'-diaminodiphenylsulfone (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.

Polyamic acid and metal salt solution 1 10 g of CuCl ₂ was added to 100 g of polyamic acid varnish _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 was added to 10 g of FeSO ₄
Was added and stirred at room temperature for 4 hours.

Experimental Method The adhesion to copper foil was determined according to I. P. C. No.
The test was performed according to the method of 2.4.9.

The etching cycle was performed as follows. That is, potassium hydroxide (13 wt%) and distilled water (11 w
t%), an aqueous solution of ethanol (76 wt%) (at 60 ° C for 1 minute) and deionized water (at 60 ° C for 30 seconds). Treating the membrane once with a potassium hydroxide / ethanol solution and deionized water is one cycle. Such a cycle is repeated until the film is effectively etched. The number of etching cycles is an index of the 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 above solution 1 was applied on the film with a doctor blade so as to have a thickness of about 360 mm.
Leave for 0 minutes and 1 hour at 80 ° C. The membrane was further heated in a vacuum oven as follows. 1. heating to 150 ° C. within one hour and maintaining for one hour; heating to 250 ° C. within one hour and maintaining for one hour; heating to 350 ° C. within one hour and maintaining for two hours; 1 in 5 hours
It was cooled to 50 ° C. to complete imidization. As a result of the experiment, the adhesion to the copper foil was 0.3 lb / in or less, and the etching cycle by chemical etching was 8.

Example 2 The operation was the same as in Example 1, except that Solution 2 was used instead of Solution 1. results of the experiment,
Adhesion to copper foil is 0.3 lb / in or less,
The etching cycle by chemical etching is 8.

[Comparative Example A] A 360 mm-thick polyamic acid was applied to a copper foil using a doctor verade,
, And then heated as in Example 1 to obtain an imidized film. As a result of the experiment, the adhesion to the copper foil was 8 lb / in or more, and the etching cycle by chemical etching was more than 50.

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int.Cl. ⁶ , DB name) B32B 15/00-15/20 B32B 27/00-27/42 C08J 7/00-7/02 H01L 1 / 03

Claims (9)

(57) [Claims] 1. A step of (1) coating a first layer of a polyamic acid resin on a substrate; and (2) a step of coating a first layer of the polyamic acid resin with Cu,
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; and (3) heating the first layer and the second layer. Cyclizing the polyamic acid to form a polyimide film. 2. The method according to claim 1, wherein the heating is performed at a temperature of 100 ° C. to 400 ° C. 3. The metal salt is selected from the group consisting of copper chloride, nickel chloride, ferrous sulfate and copper sulfate.
A method for producing a polyimide film according to claim 1. 4. The method according to claim 1, wherein the polyamic acid is a reaction product of a dianhydride and a diamine. 5. The dianhydride is bis- (3,4-dicarboxyphenyl) ether dianhydride, 3,3′-4,
The method for producing a polyimide film according to claim 4, wherein the polyimide film is selected from the group consisting of 4'-benzophenonetetracarboxylic dianhydride and 3,3'-4,4'-biphenyltetracarboxylic dianhydride. 6. The method according to claim 4, wherein said diamine is selected from the group consisting of 4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenylsulfone and para-phenylenediamine. 7. The substrate according to claim 1, wherein the substrate is an electrically conductive metal foil.
A method for producing a polyimide film according to claim 1. 8. The method according to claim 7, wherein the substrate is a copper foil. 9. Produced by the method of claim 1,
Polyimide film.