JPS62208690A - Flexible printed circuit and manufacture of the same - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a flexible printed circuit board made of a polyimide metal clad plate with excellent heat resistance, electrical properties and mechanical properties, and a method for manufacturing the same.

[Conventional technology]

4. Flexible printed circuit boards are used to produce printed circuits with flexible f[. (It is a board, and its use has increased in recent years as the cases in which printed circuits are housed have become more compact.) Such flexible printed circuit boards have conventionally been made by using polyimide film on copper foil. It is manufactured by sticking together using adhesive.

In this substrate, the polyimide film has good heat resistance, electrical resistance, and mechanical properties within 1-minutes, but since the properties of the adhesive are not within 1-minutes, there is a problem that the properties of the polyimide film are not fully utilized. there were.

[Problem that the invention seeks to solve]

Therefore, methods of manufacturing flexible printed circuit boards made of polyimide metal clad plates without using an adhesive layer have been studied, for example, U.S. Pat.
No. 79,634, Japanese Patent Publication No. 4! J-129862, JP-A-58-190091, JP-A-58-190092, etc. However, a flexible printed circuit board with sufficient heat resistance, adhesiveness, and flexibility has not been obtained.

The present invention has been made in view of the above problems, and its purpose is to improve heat resistance, electric current +J[, and contact 7f+t].
, a flexible printed circuit made of a polyimide metal clad plate that has excellent mechanical properties such as flexible paper, Jl (Flexible printed circuit board and its manufacturing method, Nitoji).

[Means for solving problems]

That is, the present invention uses a symmetric aromatic para-substituted primary amine and a symmetric aromatic para-substituted primary amine in an equivalent ratio of 10.
A flexible method in which metal foil is directly coated with an organic solvent solution of polyamic acid, which is a precursor of polyimide, by mixing at a ratio of ~60:90 to 40 and reacting with aromatic tetracarboxylic anhydride, followed by heating and dehydration. A method for manufacturing a printed circuit board, or an organic solvent solution of polyamic acid (A) produced by reacting a symmetric aromatic meta-substituted primary amine with an aromatic tetracarboxylic acid anhydride, and a symmetric aromatic para-substituted primary amine. An organic solvent solution of polyamic acid (1) produced by reacting a class amine and an aromatic tetracarboxylic acid anhydride is mixed in an equivalent ratio of 10 to 60:90 to 40, and then directly coated on metal foil, The present invention also provides a method for manufacturing a flexible printed circuit board that involves heating and dehydration, and a flexible printed circuit board manufactured by these methods.

Furthermore, the present inventors have also found that when the heating and dehydration described in 1-- are carried out in an inert +1 slag, excellent properties ++1 are exhibited.

In addition, after directly coating metal foil with a solvent solution of polyamide]~acid 4, drying it to a substantially tack-free state, winding it up into a roll, and leaving the rolled product in a roll shape) It has been found that when heated and dehydrated in an inert +' gas, a flexible printed circuit board can be produced in a comparatively small amount t1i and moreover economically.

The symmetrical aromatic meta-substituted primary amine (hereinafter abbreviated as m-diamine) used in the present invention can be represented by a general formula not shown below.

(In the above general formula, X is 0, so, , s, c
o, Ni112, C(Clh)2. C(CF3)2
, and each X may be the same. ) Examples of m-diamines represented by the above general formula are 3.
3°-diaminodiphenyl ether, 3.3'-diaminodiphenyl sulfide, 3,3-diaminodiphenyl sulfone, 3.3"-diaminobenzophenone,
Bis(4-(3-aminophenoxy)phenyl)methane, 2,2-bis(/I-(3-aminophenoxy)phenyl)propane, 2,2-bis(4-(:]-aminophenoxy)phenyl) -1,1,1,:1,3.3-
Hexafluoropropane, 1,3-bis(3-aminophenoxy)hensen, 4,4-bis(:)-aminophenoxy)biphenyl, bis(4-(:l-aminophenoxy)phenyl)ketone, his(4- (:l-aminophenoxy)phenyl] sulfide, bis(4-(3-
aminophenoxy)phenyl]sulpone, bis[4-(
3-aminophenoxy)phenyl]ether, 4.4-
Bis(3-aminophenylsulfonyl) diphenyl ether, 4,4°-bis(3-aminothiophenoxy)
Examples include diphenylsulfone, 1,4-bis(4-(3-aminophenoxy)benzoyl)benzene, and these may be used alone or in combination of two or more.

In addition, symmetric aromatic para-substituted primary amines (hereinafter p-
(abbreviated as diamine) can be represented by the general formula shown below.

(In the general formula, I (X kL ”, 811.
,S ,t:fl,CI+, ,C([11,,),
, [:(C1i3), and each X may be the same or different. ] Examples of p-cyamine generally represented by 1- are 4,4'-diaminodiphenyl ether, 4.4'-diaminodiphenyl sulfide, 4.4'-diaminodiphenylsulfone,
4.4“-diaminobenzophenone, bis(4-(4-
aminophenoxy)phenyl)methane, 2,2-bis(
4-(4-aminophenoxy)phenyl]propane, 2
．． 2-bis(4-(4-aminophenoxy)phenyl)
-1,1,1,3,3,3-hexafluoropropane, 1,3-bis(4-aminophenoxy)benzene,
4,4゛-bis(4-aminophenoxy)biphenyl,
Bis(4-(4-aminophenoxy)phenyl)ketone, Bis(4-(4-aminophenoxy)phenyl)sulfoxide, His(4-(4-aminophenoxy)phenyl)sulfone, His(4-(4-aminophenoxy)phenyl)sulfoxide, phenoxy)phenyl]needle, 4,4°-V's(4-aminophenylsulfonyl)sifgonylneedle, 4,4゛-bis(4-aminothiophenoxy)diphenylsulfone, 1,4-bis[4- Examples include (:(-aminophenoxy)benzoyl)benzene, etc., and these can be used alone or in combination of two or more.

The monocarboxylic acid anhydride to be reacted with the diamine is pyromellitic dianhydride, 3,3°.

4.4°-hensiphenotetracarboxylic dianhydride,
2,2°, 3.3°-benzophenonetetracarboxylic dianhydride, 3,3°, 4,4°-biphenyltetracarboxylic dianhydride, 2,2°, 3,3″-biphenyltetracarboxylic acid dianhydride, 2,2-bis(3,4-dicarboxyphenyl)propanihydride, 2,2-bis(2
, 3-dicarboxyphenyl)brovani anhydride, bis(3,4-carboxyphenyl)ether dianhydride,
Bis(3,4-dicarboxyphenyl)sulfone dianhydride, 1,1-bis(2,:I-dicarboxyphenyl)
Ethane anhydride, his(2,:l-dicarboxyphenyl)methane-anhydride, his(:l,4-dicarboxydiphenyl)methane-anhydride, 2. :l, 6.7-naphthalenetetracarboxylic dianhydride, 1.4.5,11-
Naphthalenetetracarboxylic dianhydride, 1,2,5. l
i-Naphthalenetetracarboxylic dianhydride, 1,2,3
．． 4-Hensendetracarboxylic dianhydride, 3,4,
9.10-Helylenedetracarboxylic dianhydride, 2,3
, 6.7-anthracentetracarboxylic dianhydride, 1
, 2,7.8-phenanthrenetetracarboxylic dianhydride, etc. are used. These may be used alone or in a mixture of two or more.

Examples of organic solvents used during polymerization and coating include N-methyl-2-pyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide,
1.3-dimethyl-2-imidazolidinone, N.

N-diethylacetamide, N,N-dimethylmethoxyacetamide, dimethyl sulfoxide, pyridine, dimethyl sulfone, hexamethyl phosphoramito, te]-ramethyl urea, N-methyl caprolactam, tetrahydrolane, ■-dioxane, p-dioxane, 1.2-dimethoxyethane, his(2-methoxyedyl) ether,
1.2-bis(2-methoxyethoxy)ethane, bis-
[-(2-mel-xyethoxy)ethyl]ether and the like.

The polyamic acid used in the present invention is prepared by adding m-cyamine and p-diamine in an organic solvent in advance.
The h1 ratio of m-diamine and p-diamine is 0.1 to 0.
6: 0.9 to 0.4, particularly preferably 0.2 to
0.4: After mixing at 0.8 to 0.6, it is reacted with aromatic tetracarboxylic anhydride (method 1), or it is produced by reacting m-diamine and aromatic tetracarboxylic anhydride. The resulting polyamic acid (A) and the polyamic acid (1) produced by reacting p-diamine and aromatic tetracarboxylic acid anhydride were mixed in an equivalent ratio of 0.
1 to 0.6: 0.9 to 0.4, particularly preferably 0.2 to 0.4: 0.8 to 0.6 (
Obtained by method 2). Among these methods, from the viewpoint of mechanical properties and the like, particularly preferable results can be obtained when manufacturing by method 1. When m-diamine is 60% or more in terms of equivalent ratio among diamines, the produced polyimide has strong thermoplasticity, and it is difficult to directly touch the polyimide film with a r111 iron (:H] 0 to 150℃). If the
, the film may be damaged or damaged in a high-temperature bath (280
If the film is floated at a temperature higher than 1), the film may be deformed and the appearance of the printed wiring board may be damaged, resulting in the drawback that it is difficult to handle as a printed wiring board.

In addition, when m-diamine is 10% or less in equivalent ratio,
The adhesion of the produced polyimide film to the metal foil is weak, and the circuit of the flexible printed circuit easily peels off from the film, resulting in a drawback that it cannot be put to practical use.

Furthermore, among the combinations of diamines used in producing polyamic acid, the diamine represented by the formula (1) described in claim 9 is particularly preferable as m-diamine, and as p-diamine, 4,4°-diaminodiphenyl ether and/or 4,4°-bis(4
-aminophenoxy)biphenyl is particularly preferably used, and as the aromatic tetracarboxylic acid anhydride, pyromellitic dianhydride and/or 3.3'', /1,4
It is particularly preferable to use '-benzophenonetetracarboxylic acid anhydride, which improves heat resistance, electrical properties, and adhesion P[
It is possible to manufacture flexible printed circuits 16 (boards) with excellent mechanical properties such as flexible PL.

When coating metal foil with polyamic acid solution,
It contains polyamic acid in an amount of 5 to 40 percent by weight, particularly preferably 10 to 30 percent by weight, and has a logarithmic viscosity of 0.5 to 6 dl/g (15°C, concentration 0.5 g/g).
100 x+1. It is preferable to use a solution having a concentration of 0.1 to 4 mol/g (measured with N,N-dimethylacetamide), especially from the viewpoint of the physical properties of the produced polyimide and the economical efficiency of coating and drying steps.

As the metal foil to be coated with polyamic acid, copper foil or aluminum foil is generally used, or other conductive metal foil such as nickel foil can also be used.

The operation of coating the metal foil with the polyamic acid solution is preferably carried out by casting, and the following method is used for the IL coating.

The uniform thickness obtained by discharging a polyamic acid solution onto the surface of a metal foil through a film forming slit is generally 30 to 3.
00μ) coating ++q layer is formed. Other coating stages include roll coater,
knife coater, comma coater, doctor blade,
It is also possible to use other known means such as a flow coater.

35 layers of polyamic acid coating prepared as above,
Next, the mixture is heated to perform solvent removal and dehydration condensation reactions. This operation can be carried out under any conditions such as normal pressure, reduced pressure, or increased pressure. Generally, the required time is 100-20
Heat to 0°C, preferably 100-150°C to remove most of the solvent. Furthermore, 180 to 350°C, preferably 2
Heating to 00-300° C. completely removes the solvent and converts the polyamic acid into a more stable polyimide. During these desolvation and dehydration steps, if the metal foil surface is exposed to a temperature higher than the temperature at which it is oxidized, the metal foil surface will be oxidized and the mechanical properties of the metal foil may deteriorate. Since F may be more likely to occur, use metal foil 1.
``At temperatures above oxidation of metal foil, carrying out the desolvation and dehydration steps in an inert gas prevents oxidation of the metal foil surface.
- Particularly preferred for In this case, being in an inert +'1 gas means that the surface of the metal foil is in a gas atmosphere that does not substantially undergo an oxidation reaction that adversely affects electrical properties or adhesive strength during heating for a predetermined period of time. Although it depends on the heating temperature, in most cases it means a gaseous atmosphere in which the oxygen concentration is preferably 6% or less.

These heating and drying processes are generally carried out with the sheet spread out, but in the case of the present invention, the metal foil is directly coated with an organic solvent solution of polyamic acid and then dried to a substantially tack-free state. (The amount of solvent is 40% by weight or less)
After that, it is possible to wind it up into a roll and heat the rolled product in N inert gas to remove the solvent and dehydrate it.

The flexible printed circuit board made of the polyimide metal-clad sheet according to the present invention, represented by the method described above, does not contain an adhesive layer, and has the following advantages:1. Due to the use of , it has excellent heat resistance, electrical +1, and mechanical P1.

〔Example〕

Next, the present invention and its effects will be specifically explained by referring to Examples and Comparative Examples of the present invention.

The logarithmic viscosity in the examples is 35°C, 0.5g/l00nL
The N,N-dimethylacetamide viscosity is a value measured at 25°C using a high viscosity rotor of an E-type viscometer. Various performances as a printed circuit board were measured by the methods shown below.

(1) Foil peeling strength It was carried out according to the method of TPC-FC-24 1A.

(2) Surface resistance It was conducted according to JIS C-6481.

(3) Soldering resistance, 115 [Conducted according to 'Knee 64 old. 2 samples
After immersion in a half-in bath at 80° C. for 60 seconds for 7 rt, deformation of the polyimide film was observed.

(4) 4 bristles "r-II+ +1 't': Curvature r'-diameter of tip of ITI iron 0.5m
The angle of the tip of m, = J is 10°. The 11 trowel was adjusted so that the load on the tip was 10 or 1003r. Adjust the temperature at the tip to 325±25℃1
7. 25μ thick film 1- made of polyimide
For more than 5 seconds, hold the 'I'-III trowel for more than 5 seconds.
If the film was not torn, it was marked as ○, and if it was torn within 5 seconds, it was marked as ×.

(5) Folding strength According to JIS P-8115, measurements were carried out at a curvature radius of 0.8 mm on the folded surface and a static 11-load of 500 gr.

(6) Dielectric constant and dielectric loss tangent, conducted according to 115C-6481. The measurement frequency was 1 kllz.

Example 1 In a container equipped with a stirrer, a reflux condenser and a nitrogen introduction tube, 1
．． 3-bis(3-aminophenoxy)benzene 23.4
g (0.08 mol) and 24.0 g (0.12 mol) of 4,4°-diaminodiphenyl ether were dissolved in N,N-dimethylacetamide t'' 420+n! in a nitrogen atmosphere]. 1, :l'', 4
, 4°-Hensif J nondetracarfonic acid anhydride 6
4.4 g (0.20 mol) was added and stirred at 10° C. for 24 hours to obtain a polyamic acid solution of 1/jl. The logarithmic viscosity of the polyamic acid solution thus obtained was 1.5 dl/g. This polyamic acid solution was diluted to 15% with N,N-dimethylacetamide, the viscosity was adjusted to 25,000 cps, and rolled copper foil (thickness 35
μ) was coated uniformly. This coated copper foil was dried by heating at 130° C. for 60 minutes, and then heated for 60 minutes in a nitrogen atmosphere (oxygen concentration: 4%) at 260° C. to obtain a polyimide-coated copper foil. The film thickness was 25μ. The characteristics of this wiring board were as shown in Table-1.

Example 2 In a container equipped with a stirrer, a reflux condenser and a nitrogen inlet tube, 4
．． 4°-bis(3-aminophenoxy)biphenyl 22
．． 1 g (0.06 mol) and 28.0 g (0.14 mol) of 4.4°-diaminodiphenyl ether were
Dimethylacetamide:] Dissolved in 5On+1 and heated to 0℃
Cool to near f.1, and then remove pyromellitic acid in a nitrogen atmosphere. 1-Aqueous product 4: ilig (0.20 mol) was added and molded at 0°C for 2 hours. Next, the L solution was returned to room temperature and stirred in a nitrogen atmosphere for about 20 hours. .

The logarithmic viscosity of the polyamic acid solution prepared in this way is 1.
7dl/gtea). This polyamic acid solution was mixed with N, N-
Dilute to 19% with dimethylacetamide and reduce the rotational viscosity to 12
It was adjusted to 0.000 cps.

This solution was uniformly cast onto a rolled copper foil (thickness: 35 μm), heated and dried at 130°C for 10 minutes, and further at 160°C for 10 minutes, and then heated for 10 minutes in a nitrogen atmosphere (oxygen concentration 3%) at 270°C. The copper foil coated with polyimide was obtained by heating for a minute. The film thickness was 25μ. The characteristics of this wiring board are shown in Table-1.
It was as follows.

Example 3 A copper foil coated with polyimide was obtained in the same manner as in Example 2, except that the oxygen concentration was 8% during heat drying at 270°C. The characteristics of this wiring board are shown in Table 1.

Practical hIIi Example 4 Same as Example 2 except that 51.63 (0.14 mol) of 4.4°-his(4-aminophenoxy)biphenyl was used instead of 28.0 g of 4.4°-diaminodiphenyl ether. A polyamic acid solution was prepared. The logarithmic viscosity of the polyamic acid solution thus obtained was 1.6 d.
It was l/g. This polyamic acid solution was diluted to 18% with N,N-dimethylacetamide, and the rotational viscosity was adjusted to 105%.
．． Adjusted to 0OOcps.

This solution was uniformly cast onto a rolled copper foil (thickness 35 μm), heated and dried at 130°C for 20 minutes, and further at 160°C for 20 minutes, and then heated and dried in a nitrogen atmosphere (oxygen concentration 3%) at 270°C for 20 minutes. The copper foil coated with polyimide was obtained by heating for a minute. The film thickness was 25μ. The characteristics of this wiring board are shown in Table-1.
It was as follows.

Example 5 31.7 g (0-08 mol) of bis(4-(3-aminophenoxy)phenyl coketone) and 4,4°- 24.0 g (0-12 mol) of diaminodiphenyl ether was dissolved in N,N-dimethylacetamide 4011al, and pyromellitic acid anhydride 4 was dissolved in nitrogen atmosphere F.
:1. Add Iig (0.20 mol) and vr for about 24 hours.
I did it. The logarithmic viscosity of the polyamic acid solution thus determined is 1. It was l1d173. This polyamide]・
The acid solution was diluted with N,N-shimedylacetamide 1-1 to 1:1%, the rotational viscosity was reduced to 25,000 cps, and IITE electrolytic copper 7i (J-zosa 1) was added using a doctor blade.
8μ, 3)] manufactured by Metal Mining Co., Ltd.) was uniformly coated. This coated copper foil was heated to 130℃ for 10 minutes, and then
After drying by heating at 160° C. for 10 minutes, heating was performed for 10 minutes at 270° C. in a nitrogen atmosphere (oxygen concentration: 3%) to obtain a polyimide-coated copper foil. The film thickness was 25μ. The characteristics of this wiring board are as shown in Table 1.Example 6 Bis(4-(3-aminophenoxy)phenyl)sulfide 24 .0g (0,06 mol) and 4.4°-
Bis(4-aminophenoxy)biphenyl 51.6g (
0,N mol) to N,N-dimethylace]amide 420
Resistant to dissolution 17, pyromellitic acid ice-free material 4:1 in nitrogen atmosphere. tig (0.20 mol) and about 21
1 u,', the stirring stroke became '4i. 32 then(:?
The logarithmic viscosity of the polyamic acid solution is ',! ,ldl
/g-C available. This polyamide 1 was diluted to 12% with an acid solution of N,N-dimethylacetamide and the rotational viscosity was adjusted to 4r.
+, 0 fTOcps, and coated uniformly onto If T IX' copper foil (thickness 35 μm, manufactured by Mitsui Mining & Smelting Co., Ltd.) using a doctor blade. After heating and drying this coated copper foil at 130°C for 10 minutes and then at 160°C for 10 minutes, it was placed in a nitrogen atmosphere at 270°C (oxygen concentration 3%).
) for 10 minutes to obtain polyimide-coated copper foil. The film thickness was 50μ. The characteristics of this wiring board were as shown in Table-1.

Example 7 25.9 g (0.06 mol) of bis(4-(3-aminophenoxy)phenyl)sulfone was added to bis(4-(3-
Aminophenoxy)phenyl]sulfite 24. Og
A polyamic acid solution was obtained in the same manner as in Example 6 except that . The logarithmic viscosity of this solution is 2. c+dl/g
There was. This solution was diluted to 13% with N,N-dimethylacetic acid amide and the rotational viscosity was adjusted to 40.000 cps. Thereafter, in the same manner as in Example 6, the polyimide was removed and the copper foil was removed. This wiring, L board special P1
゛ was as shown in Table-1.

Example 8 2.2-His(4-(3-aminophenoxy)phenyl)-1,1,1,3,:],:] 311 g (0.06 mol) of l-hexafluoropropane was dissolved in bis(4- (3
-Aminophenoxy)phenyl]sulfite 24.0
A polyamic acid solution was obtained in the same manner as in Example 6, except that g was used instead of g. The logarithmic viscosity of this solution is 1.2 dl/
It was g. This solution was diluted to 18% with N,N-dimethylacetamide and the rotational viscosity was adjusted to 45.0 OO cps. Thereafter, a copper foil coated with polyimide was obtained in the same manner as in Example 6. The characteristics of this wiring board were as shown in Table-1.

Example 9 In a vessel equipped with a stirrer, a reflux condenser and a nitrogen inlet tube, 1.
3-bis(3-aminophenoxy)benzene 23.4g
(0.08 mol) to N,N-dimethylacetamide 2
To this solution in a nitrogen atmosphere was added 25.71<(0.08 mol) of 4,4'-hensophenone de] cyclophonic dianhydride, and the solution was stirred at room temperature. A polyamic acid solution was obtained by stirring for 24 hours.

The logarithmic viscosity of the polyamide acid solution thus obtained was 1.
It was 1 dl/g. This solution will be referred to as Solution A.

Also, 4.4'-diaminodiphenyl ether z4.
og (o, +2 mol) was dissolved in 250 ml of N,N-dimethylacetamide, and 38.7 g of 3.3', 4.4'-benzophenonetetracarboxylic dianhydride ( 0.12 mol) was added thereto and stirred at room temperature for 24 hours to obtain a polyamic acid solution. The logarithmic viscosity of the polyamic acid solution thus obtained was 1.6 dl/
It was g. This solution will be referred to as Solution B.

Next is liquid A! 9 g of liquid B and 74 g of liquid B were mixed, and the ratio of amic acid in liquid A to amic acid in liquid B was adjusted to 40:60. This solution was diluted to 14% with N,N-dimethylacetamide.
The viscosity was adjusted to 26,000 cps and uniformly coated on rolled copper foil (J size 35 pn) using a doctor blade. After drying this coated copper foil at 150°C for 60 minutes, it was dried in a nitrogen atmosphere (acid, +2
Copper foil coated with polyimide was coated with polyimide by heating for 30 minutes at a concentration of 3'4). The film thickness was 2511 m+.

The characteristics of this wiring board are shown in Table 1.

Example 10 4. In a vessel equipped with a stirrer, a reflux condenser and a nitrogen inlet tube.
4'-bis(3-aminophenoxy)biphenyl22.
1 g (0.06 mol) was dissolved in 150 nl of N,N-dimethylace]amide, and pyromellitic dianhydride + 3.1 g (0.06 mol) was added to this solution under a nitrogen atmosphere.
was added and stirred at room temperature for 24 hours to obtain a polyamic acid solution. The logarithmic viscosity of the polyamic acid solution thus obtained was 1.7 dl/g. This solution will be referred to as Solution C.

Also, 4,4'-diaminodiphenyl ether28.
0 g (0.14 mol) was dissolved in 240 tel of N,N-dimethylacetamide, and 10.5 g (0.14 mol) of pyromellitic dianhydride was added to this solution under a nitrogen atmosphere. After stirring at room temperature for 24 hours, the polyamic acid solution was diluted to 1:1. The logarithmic viscosity Iη of the polyamic acid solution obtained in this manner was 1.6 dl/g. This solution will be referred to as Solution D.

Next, 44 g of liquid C and 713 g of liquid D were mixed 17, and the ratio of the amic acid of liquid C and the amic acid of liquid D was: l O: 70
Adjusted to. This solution was diluted to 5% I with N,N-dimethylacetamide, and the viscosity was adjusted to 3000 Or, ps.
using a doctor blade to remove rolled copper foil (thickness 3
5p) was uniformly coated. This coated copper foil was dried at 150° C. for 60 minutes, and then heated in a nitrogen atmosphere (oxygen concentration 3%) at 260° C. for 30 minutes to obtain a polyimide-coated copper foil. The film thickness was 25 μm.

The characteristics of this wiring board are shown in Table-1.

Comparative Example 1 In a container equipped with a stirrer, a reflux condenser, and a nitrogen introduction tube,
3-bis(3-aminophenoxy)benzene 58.4g
(0.20 mol) to N,N-dimethylacetamide 4
It was dissolved in 30nffi. To this solution was added 64.4 g (0.20 mol) of 3,3°,4,4°-benzophenonetetracarboxylic acid dianhydride under a nitrogen atmosphere.
．． The mixture was stirred at 10° C. for 24 hours to obtain a polyamic acid solution.

The monthly viscosity of the polyamic acid in the obtained solution was 1.4 dl.
/g was there. This polyamic acid solution, N,N-dimethylacetamide CPS, was applied to the solution and coated uniformly onto rolled copper foil (J!; 1 3511) using a doctor blade. This cope ink copper foil was dried by heating at 130° C. for 60 minutes, and then heated for 60 minutes in a nitrogen atmosphere (oxygen concentration: 4%) at 240° C. to obtain a polyimide-coated copper foil. The film thickness was 25μ. Table 2 shows the characteristics of this wiring board.
It was as follows.

Comparative Example 2 4.
4'-bis(4-aminophenoxy)biphenyl73.
6g (0.20mol) was dissolved in 400ffifi of N,N-dimethylacetamide, cooled to around 0°C,
Pyromellitic dianhydride 43.6 under nitrogen atmosphere
g (0.20 mol) and stirred at around 0°C for 2 hours.

Next, the solution in 1- was returned to room temperature and subjected to type 1'1' for about 20 hours under a nitrogen atmosphere. The logarithmic viscosity of the polyamic acid solution thus obtained was 1.6 dl/g. This polyamic acid solution was diluted to fi'1% N,N-dimethylacetoamide, and the rotational viscosity was expressed as 1 Nl, 000 t:ps.

This solution Tsukinobu copper foil (J'/Sa: +5/7) 1.
：Y-uniformly cast and further coated at 130℃ for 10 minutes.
After drying by heating with lill-C for 10 minutes, it was heated for 10 minutes at 270° C. in a nitrogen atmosphere (oxygen concentration 3%) to obtain a polyimide-coated copper foil. The film thickness was 25μ. The characteristics of this wiring board were as shown in Table-2.

〔Effect of the invention〕

As can be seen from Example 1, the flexible printed circuit 1 according to the present invention. (The board is made by laminating a polyimide film directly onto metal foil such as copper foil without using an adhesive, and it has heat resistance, electrical properties, adhesive properties, and flexibility that could not be achieved with conventional methods.) This is a flexible printed circuit board that exhibits good mechanical properties in all aspects such as flexibility, and is extremely useful in electronic circuits where heat resistance, insulation, dielectric properties, adhesive strength, and bending durability are increasingly required. It is something that can be provided.

Claims (9)

[Claims] (1) After mixing a symmetrical aromatic meta-substituted primary amine and a symmetrical aromatic para-substituted primary amine in an equivalent ratio of 10 to 60:90 to 40, the mixture is reacted with an aromatic tetracarboxylic anhydride. A flexible printed circuit board characterized in that a polyimide film produced by this process is directly bonded to metal foil. (2) Polyamic acid (A) produced by reacting a symmetrical aromatic meta-substituted primary amine and an aromatic tetracarboxylic acid anhydride, a symmetrical aromatic para-substituted primary amine, and an aromatic tetracarboxylic acid After mixing polyamic acid (1) produced by reacting with an acid anhydride in an equivalent ratio of 10 to 60:90 to 40, the reaction is further advanced and the produced polyimide film is directly bonded to the metal foil. A flexible printed circuit board characterized by: (3) The flexible printed circuit board according to claim 1 or 2, wherein the polyimide layer has a thickness of 10 μm to 1 mm. (4) A symmetric aromatic meta-substituted primary amine and a symmetric aromatic para-substituted primary amine are mixed in an equivalent ratio of 10 to 60:90 to 40, and the mixture is reacted with an aromatic tetracarboxylic anhydride. A method for producing a flexible printed circuit board, which comprises directly coating a metal foil with an organic solvent solution of polyamic acid, which is a precursor of polyimide, and then heating and dehydrating it. (5) An organic solvent solution of polyamic acid (A) produced by reacting a symmetrical aromatic meta-substituted primary amine and an aromatic tetracarboxylic anhydride, a symmetrical aromatic para-substituted primary amine, and an aromatic After mixing an organic solvent solution of polyamic acid (B) produced by reacting with a group tetracarboxylic acid anhydride at an equivalent ratio of 10 to 60:90 to 40, the mixture is directly coated on metal foil, and further heated and dehydrated. A method for manufacturing a flexible printed circuit board characterized by: (6) The method for manufacturing a flexible printed circuit board according to claim 4 or 5, wherein the heating and dehydration are performed in an inert gas. (7) A substrate obtained by directly coating metal foil with the organic solvent solution of the polyamic acid is dried until it is substantially tack-free, wound up into a roll, and the rolled substrate is placed in an inert gas. Claim 4: By heating, the solvent is removed and the polyamic acid is imidized.
A method for manufacturing a flexible printed circuit board as described in Section. (8) A substrate obtained by directly coating metal foil with a mixture of the organic solvent solution of the polyamic acid (A) and the organic solvent solution of the polyamic acid (B) is dried to a substantially tack-free state. The method for producing a flexible printed circuit board according to claim 5, wherein the polyamic acid is imidized by removing the solvent and imidizing the polyamic acid by winding the board into a roll and heating the rolled board in an inert gas. (9) The symmetric aromatic meta-substituted primary amine has the formula (1
) ▲There are mathematical formulas, chemical formulas, tables, etc.▼(1) (However, in the above formula, X is O, SO_2, S, Co,
The flexible printed circuit board according to any one of claims 1 to 3, which is CH_2, C(CH_3)_2, C(CF_3)_2 or direct connection).