JPS62171185A - Manufacture of flexible printed circuit - 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 (Industrial Field of Application) This paper #4 relates to a method for manufacturing a flexible printed circuit board by a direct coating method.

(Conventional technology) A flexible printed circuit board is a flexible wiring board with a conductor circuit formed on the surface of a polymeric insulating film, and it effectively achieves the miniaturization of electronic devices, which has become noticeable in recent years. Among them, aromatic polyimide is becoming mainstream as an insulating film.

Conventionally, general flexible printed circuit boards have been manufactured by integrating a ready-made polyimide film and @foil via an adhesive. Unfortunately, I was unable to take full advantage of polyimide's strong and flexible properties.

A method to solve this problem is to directly cast a polyamic acid varnish with a thermal expansion coefficient similar to that of the metal foil onto the metal foil, remove the solvent, and cause an imidization reaction (hereinafter referred to as the direct coating method). omitted) was proposed,
It's coming.

(Problems to be Solved by the Invention) This method not only solves the above-mentioned problems with customization due to adhesives, but also enables a significant simplification of the manufacturing process. However, according to this method, depending on the method of surface treatment of the metal foil, sufficient adhesion strength between the polyimide and the metal foil may not be obtained, which may seriously impede reliability.

The present invention aims to provide a flexible printed circuit board which does not have such drawbacks and has very good adhesive strength and is produced by a direct coating method.

(Means and Effects for Solving the Problems 2) The present inventors have developed a coupling agent that effectively acts on the adhesive direction between polyimide and metal foil of a flexible printed circuit board obtained by the above-mentioned direct coating method. As a result of studies, it was discovered that a significant improvement in adhesive strength could be obtained when a coupling agent having both mercapto and silanol ester groups was used, leading to the present invention.

That is, the present invention directly applies a polyamic acid face to the conductor,
In the production of a flexible printed circuit board obtained by drying and imidization, a coupling agent having both mercapto and silanol ester groups is used.

The flexible printed circuit board according to the present invention is made of polyamide L having a coefficient of thermal expansion comparable to that of the metal foil on a metal foil such as a porcelain.
! It can be manufactured by applying fRyt, removing the solvent, and imidizing it.

The polyimide finally formed on the metal foil is a polymer represented by the following general formula r, which has a rear unit (here, R1
) ].

f as R1! p, m, 0-phenyl diamine, 2
゜4-diaminotoluene, 2,5-diaminotoluene,
2,4-diamino-cow sirene, diamino durene, 1,5
-diaminonaphthalene, 2,6-diaminonaphthalene,
benzidine, 4.4'-diaminotaphenylene, 4.
4"'-Diaminoquaterphenyl, 4.4'-diaminodiphenylmethane, 1,2-bis(anilinoneethane, 4.4'-diaminodiphenyl ether, diaminodiphenylsulfone, 2,2-bis(p-aminophenyl)furopane, 2 , 2-bis(p-aminophenyl hexafluoropropane, 2,6-diaminonaphthalene,
5.6'-dimethylbenzidine, 5.5'-dimethoxybenzidine, 5.5'-dimethyl-4,4'-diaminodiphenyl ether, 5.5'-dimethyl 4.4'
-diaminodiphenylmethane, diaminotoluene.

Diaminobencitrial olide, 1,4-bis(p-
aminophenoxy)benzene, 4,4'-bis(p-aminophenoxy)biphenyl, 2,2-bis(4-(p
-aminophenoxy)phenyl)propane, diaminoanthraquinone, 4,4'-bis(6-amituphenoxyphenylnodiphenylsulfone, 1,5-bis(anilino)hexafluoropropane, 1,4-bis(anilino) Octafluorobutane, 1,5-bis(anilino)decafluoropentane, 1,7-bis(anilino)tetradefluorohebutane, 2,2-bis(4-(p-
aminophenoxy)phenyl)hexafluoropropane, 2,2-bis(4-(5-aminophenoxy2phenyl)hexafluoropropane, 2,2-bis(4-(2
-Aminophenokidinphenyl)hexafluoropropane, 2゜2-bis(4-(4-aminoneenoxy)-6
゜5-dimethylphenyl)hexafluoropropane, 2
,2-bis(4-(4-aminophenoxif-3,5-
ditrifluoromethylphenyl)hexafluoropropane, p-bis(4-amino-2-trifluoromethylphenoxy)benzene, 4,4'-bis(4-amino-2
-trifluoromethylphenoxy)biphenyl, 4.4
'-bis(4-amino-6-trifluoromethylphenoxy)biphenyl, 4,4'-bis(4-amino-2-
trifluoromethylphenoxy) diphenyl sulfone,
4,4'-bis(5-amino-5-trifluoromethylphenoxy)diphenylsulfone, 2,2-bis(4-
Diamines such as (4-amino-5-trifluoromethylphenoxy)phenyl)hexafluoropropane, as well as diisocyanates obtained by the reaction of diamines such as phosgene and the like, such as triclean diisocyanate, There are aromatic diisocyanates such as diphenylmethane diisocyanate, naphthalene diisocyanate, diphenyl ether diisocyanate, and phenylene-1,5-diisocyanate. In addition, examples of tetracarboxylic acids and their rust conductors include the following:
.

Ru. Here, it is exemplified as a tetracarboxylic acid, but this
Of course, esters, acid anhydrides, and acid chlorides of , can also be used. Pyromellitic acid, 2,3°5',4'-tetracarboxydiphenyl, 5. Name 4.4'-tetracarboxydiphenyl, 3.5',4.4'-tetracarboxydiphenyl ether, 2,3,5',4'-tetracarboxydiphenyl ether s 515'94.4'-
Tetracarboquinbenzoneenone, 2,5°5',4
'-Tetracarboxybenzophenone, 2,5°6.7
-Tetracarboxynaphthalene, ? , 4,5.7-titracarboxynaphthalene, 1,2,5.6-f tracarboxynaphthalene, 5.5',4.4'-tetracarboxydiphenylmethane, 2,2-bis(6゜4 -dicarboxyphenyl)propane, 2,2-bis(5,4-dicarboxyphenyl)hexafluoropropane, s,
3<4.4'-tetracarboxydiphenyl sulfone,
5,4,9,10 -f Tora force, boxyperylene, 2,2-bis(4-(5,4-dicarboxyphenoxy)phenyl)propane, 2,2-bis(4-(5,4
-dicarboxyphenoxy)phenyl)hexafluoropropane, butanetetracarboxylic acid, cyclopentanetetracarboxylic acid, etc.

Further, the polyamic acid solution to be applied to the metal foil does not have to be a single solution, but a mixture or co-condensation of two or more types can also be used. Rather, it is desirable to suitably modify the coefficient of thermal expansion of the polymer to match that of the metal foil. For example, when using copper mt for metal foil, polyimide at 50°C, 5250°C to prevent curling of the board.
It is necessary to design the molecule after the average thermal expansion coefficient t-2

The synthesis reaction consists of N-methyl-2-pyolidone (NMP),
N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), dimethyl sulfate, sulfolane, γ-butyrolactone, cresol, phenol, halogenated phenol.

0 to 12 in solutions such as cyclohexanone and dioxane
It is carried out in the range of 0℃.

1. Used as a metal conductor foil in the present invention. Copper, aluminum, iron, gold, silver, nickel palladium, chromium, molybdenum, etc. These alloys may be subjected to mechanical treatment such as corona discharge sanding in order to increase their adhesion to polyimide.

The coupling agent used in the present invention has both a mercapto group and a silanol ester group in its molecule71. For example, γ-mercaptopropyltrimethoxysilane, γ-mercaptopropyltriethoxysilane, γ-mercaptopropyltriethoxysilane,
-Mercaptoglobil trip Ωboxysilane, γ-)t
Examples include lucatopropyl tributoxysilane, γ-mercaptopropylmethyldimethoxysilane, γ-mercaptopropylmethyljethoxysilane, γ-mercaptopropylmethyldiproboxysilane, γ-mercaptopropylmethyldibutoxysilane, etc. Shin-Etsu Kagaku K
It may also be an oligomer such as P-591 (trade name). There are two ways to use it: one is to pre-apply it to the metal foil to be coated, and the other is to blend it into the festival. When used by coating on metal foil, the coupling agent is added to a solvent such as acetone, toluene, alcohol, or water at 0.00%.
1~20we% desirably 0.1~10W [% commonly understood,
Coat it on metal foil in advance, let it dry, and then completely coat it with polyamic acid. The method of kobada blending is to add 0.1 to 10 wt% of the coupling agent to the nonvolatile content of the polyamic acid.
Hope! <+zQ, 1 to 5 wt% 210, stir thoroughly before use. The latter method of blending is more effective in improving adhesion.

In the present invention, the entire polyimide film layer is formed on the metal foil by uniformly coating the surface of the gold pA foil with a solution of 8 to 40% polyamic acid by discharging it from a film-forming slit.

Examples of this coating method include those using a roll coater, comma coater, knife coater, doctor blade flow coater, sealed coater, etc.

Next, the solvent of the polymer solution directly applied to the gold M foil as described above is removed by heating at 60 to 200°C. At this time, it is also possible to remove under reduced pressure. Finally 200-450℃
Imidization is performed by heating to .

At this time, the final curing temperature is important. This is because even if a polyimide having a coefficient of thermal expansion approximately the same as that of the MII metal conductor is formed, shrinkage stress occurs due to solvent evaporation and imidization reaction during heating. This stress may cause warping or screwing of the flexible printed circuit board.

These stresses can be easily relaxed if the final heating temperature is higher than the glass transition temperature of the entire polymer. In this way, a polyimide film layer of 10 to 160 μm is formed on the metal foil.

In the present invention, the atmosphere in which coating, solvent removal, and imidization are performed is important. For example, when a polyimide film layer is formed on a copper foil by carrying out the series of operations described above in the atmosphere, deterioration is observed in the polyimide film obtained by etching out the copper foil later. The cause is the reaction between copper ions and amide groups in the presence of oxygen, and deterioration can be greatly suppressed by blocking oxygen. After imide formation, deterioration is unlikely to occur even if thermal history is lost. i
The deterioration reaction of octopus progresses the most during ignition during curing, and the greatest effect is obtained when oxygen is completely cut off at this point. It is also desirable to block oxygen during polymer bath solution application and solvent removal. A vacuum atmosphere or an inert gas atmosphere is used as a method for blocking oxygen, and examples of the inert gas include helium, neon, argon, nitrogen, metal bright annealing gas, and a mixture of these gases.

(Example) Next, the present invention will be explained based on examples.

Synthesis Example 1 About 500 ml of dry nitrogen per minute was poured into a 50J stainless steel reaction pot equipped with a thermocouple, a stirrer, and a nitrogen inlet nozzle.◆-Phenylenediamine 614, 1 gr, 4.4
'-diaminodiphenyl ether 280.4gr and N-
A total of 17 kg of methyl-2-pyrrolidone was added and stirred to completely dissolve the diamine. 20 in this bath Wiwo water jacket
While cooling to below .degree. C., 2105.4 gr of 5.5'4.4'-biphenyltetracarboxylic dianhydride was gradually added to carry out a weight reaction, thereby obtaining a viscous polyamic acid varnish. In order to improve the subsequent coating workability, this varnish was completely coated at 85°C in a case where the rotational viscosity of the varnish was approximately 500 poise.

1.0 wt of γ-mercaptopropyltrimethoxysilane solid content was added to the polyamic acid varnish synthesized in Synthesis Example 1.
% and stirred optically. This varnish is manufactured by Nippon Mining Co., Ltd.
Coating was performed on copper foil (trade name: 65μm'tJi defoiling, hereafter abbreviated as JTC foil) using a coating machine, dried in a forced circulation drying oven, and then dried in a turn-roll type continuous atmosphere curing oven.
The imidization reaction was completed at 0°C to obtain a flexible copper-clad board. By etching the copper of this flexible copper clad board, the width Q
, a complete flexible printed circuit board with a 5+nm circuit was fabricated. The beer strength (90°5Qmm-4-9) of this flexible printed circuit board is 2.4 kg-Cm-'/ in the machine direction (hereinafter abbreviated as MD).

Direction perpendicular to mechanical force direction (hereinafter abbreviated as TD) 2.5
kg-cm-1.

Example 2 5 wt-% methanol solution of γ-mercaptopropyltrimethoxysilane/! ! Polyamide varnish 1 synthesized in Synthesis Example 1 was coated and dried on JTC foil. : Coating, drying, and imidization in the same manner as in Example 1.

After etching, a 7 lexiple printed circuit board was obtained.

Due to the beer strength of this flexible printed circuit board, MD
, TD force direction were both 1.9 kg-cr'.

Example 5 A flexible printed circuit board was obtained in the same manner as in Example 11 except that γ-mercaptoglobil triptoxysilane was used. The beer strength of this flexible printed circuit board is
The MD and TD force directions are also 2.5'fJ! , -C1ll-
'Ayyyyyyyyyyyyyyy, :.

Example 4 Example 2 and II, except that γ-mercaptoglobil triptoxysilane was used! A flexible printed circuit board was obtained in the same manner as r1. Beer strength is MD.

The TD force direction was also 1.9.Cll1-1.

Example 5 Shin-Etsu Chemical's KP-591 (product name, mercaptan-silanol ester thread coupling agent, chemical structure unknown, hereinafter abbreviated as KP-591) was used at 2.5 wt% based on the solid content of polyamic acid varnish. Otherwise, a flexible printed circuit board was obtained in the same manner as in Example fl11. Beer 5! i degree is 2゜9 kg -cn+-1 for MDD, 15 for TDD
kg ・Cm-' T th ff, :.

Example 6 A flexible printed group, f
I got it. The strength of the bee is 2.5 kg-c for MDD.
m-", TD direction 2.7 kg -c+n-I
There was a T.

Comparative Example 1 A flexible printed circuit board was obtained in the same manner as in Example 1, except that the #elephant polyamic acid varnish synthesized in Synthesis Example 1 was used. Beer gifi & IMDy5 direction αf3 kg
-cm-1'l' f) Direction 1. Q kg-Cm
-' was carried out except that 5 wt-% methanol elution of trimethoxysilane was used! A flexible printed circuit board was obtained in the same manner as in 2. Beer strength is the same as MD sword 0, 9 kg -
Cm-' T D direction 1. Q kg -crn-' and ivy.

Comparative Example 5 A flexible printed circuit board was obtained in the same manner as in Example 2 except that N-phenyl-γ-aminopropyltrimethoxysilane was used. Beer strength is MD, TD force direction is also i
, o kg-cm” Te Atsuta.

Comparative Example 4 A flexible printed circuit board was obtained in the same manner as in Example 2, except that γ-glycidoxyglobyltrimethoxysilane was used. Beer strength is MD force 4 times 11kg -cm-'
TD direction Q, 8 kg -c+n-IT Arata.

Comparative Example 5 A flexible printed circuit board was obtained in the same manner as in Example 2, except that an acetone solution of CAVCOMOD APG (trade name, zircoaluminate coupling agent) manufactured by Kusumoto Kasei Co., Ltd. was used. Beer strength is 0.6 in both MD and TD force directions.
1(g-cm-"tl'; h.

(Effects of the Invention) As described above in detail, according to the present invention, it has become possible to manufacture a flexible printed circuit board with very good adhesive strength by the direct coating method.

Claims (1)

[Claims] 1. A method for manufacturing a flexible printed circuit board in which a polyamic acid varnish is directly applied to a conductor and imidized, the method comprising using a coupling agent having both mercapto and silanol ester groups.