JPH01313992A - Manufacture of printed wiring board - Google Patents

Abstract

PURPOSE:To improve electric characteristics, solder heat resistance and flexibility by containing, as main components, 3,3',4,4'-benzophenone tetracalboxylic acid (containing its anhydride and lower alkyl ester) and specified aromatic diamine. CONSTITUTION:The main components of polyimide resin are 3, 3',4,4'- benzophenone tetracalboxylic acid (containing its anhydride and lower alkyl ester) and aromatic diamine shown by formula I and formula II. The resin is obtained by reacting diamine where the main component aromatic diamine amount is at least 90mol% with reference to 3,3',4,4'-benzophenone tetracalboxylic acid. In the formulas I, II, each notation shows the following: X shows one of bivalent radicals of CH2, O, SO2, C(CH3)2, C(CF3)2, and S; R<1>, R<2> show one of monovalent radical of CH3, C2H5, OCH3 and OC2H5; R<3>, R<4> show C2H5 radical; R<5> shows benzen ring or cycrohexane ring. Thereby, solder heat resistance, electric characteristics and flexibility are improved.

Description

Detailed Description of the Invention [Object of the Invention] (Industrial Field of Application) The present invention relates to a method for manufacturing a printed circuit board, and more particularly, to a method for manufacturing a printed circuit board, and more specifically, a method for manufacturing a printed circuit board using a photocurable polyimide resin composition as an improved solder resist. , relates to a method for manufacturing a printed circuit board with excellent solder heat resistance, chemical resistance, electrical properties, and flexibility.

(Prior Art) Solder resists containing various thermosetting resins as main components are used for rigid and flexible printed circuit boards used in industrial electronics. Conventionally, alkyd/melamine resin, epoxy/melamine resin, two-component epoxy resin, etc. have been used for this thermosetting solder resist, and the protective film of this resist can be applied by printing or other methods on the surface of the printed circuit board. It was formed by applying a resist and then heating and curing it.

However, the above-mentioned thermosetting resin composition requires a considerable amount of time and temperature for heating and curing, resulting in poor productivity, and the high heating and curing temperature causes warpage and shrinkage of the substrate. The drawback was that it was easy to do. UV is being used in consumer printed circuit boards to solve these drawbacks.
A hardened solder resist was considered. However, printed circuit boards used in industrial electronics are
The thickness of the conductor circuit part made of silver or copper is 50 to 70 μm.
Therefore, solder resist must be applied thickly to maintain insulation properties, but consumer U■ hardening resists have problems with hardening in thick films, so they cannot be applied to industrial printed circuit boards. In some cases, the insulation properties and solder heat resistance are poor, and the reliability as a solder protection and insulating protective film cannot be maintained.

Furthermore, in the case of flexible printed circuit boards, extremely good film-forming properties and flexibility are required, and conventional heat-curing and UV-curing resists cannot fully satisfy these properties. It was.

(Problems to be Solved by the Invention) The present invention has been made in view of the above circumstances, and uses a solder resist made of a photocurable resin composition, which has excellent soldering heat resistance, chemical resistance, and electrical properties. , it is an object of the present invention to provide a method for manufacturing a printed circuit board with excellent flexibility.

[Structure of the Invention (Means for Solving the Problem) As a result of extensive research to achieve the above object, the present inventor has developed a methyl group or ethyl group at a specific ortho position as a base polymer for a solder resist. By using a solvent-soluble polyimide resin that has a carbonyl group in the raw bait, the heat resistance, photosensitivity, and flexibility of the polyimide resin can be fully exhibited, and a printed circuit board that can achieve the above objectives can be created. discovered that a manufacturing method could be obtained,
This completes the present invention. That is, the present invention provides (A) (a) 3.3', 4.4'-benzo7znontetracarboxylic acid (including its anhydride and lower alkyl ester), (b) general formula (I) or (If) (wherein, X is CH2,01SO,,C(CHx
)2, C(CF3)2 or S divalent group, R'
, R' is cHi, 02 R5, OCH, or QC2H
, R' is C2H.

group, R5 represents a benzene ring or a cyclohexane ring, and R1 to R4 are all substituted at the ortho position of the amino group with respect to R5), and the main component is A polyimide resin obtained by reacting a diamine having an aromatic diamine content of at least 90 mol % based on component (a), (B) a diluent, and (C) a light whose essential components are a sensitizer or a photopolymerization initiator. A method for manufacturing a printed circuit board, which comprises applying a curable resin composition to a predetermined portion of a circuit board, curing it with exposure to light to form a protective film, and then depositing solder on areas where the protective film is not formed. .

The present invention will be explained in detail below.

The polyimide resin (A) used in the present invention includes (a)3.
3', 4,4'-benzophenonetetracarboxylic acid anhydride and lower alkyl ester), and (b
) The main component is an aromatic diamine having the general formula (I) or (II), which is reacted with a diamine in which the amount of the main aromatic diamine is at least 90 mol % based on component (a). .

The (a) 3.3', 4.4'-benzophenone tetracarboxylic acid can include its anhydride and lower alkyl ester.

(b) As the aromatic diamine having the general formula (I> or (If), 3,3'-dimethyl-5,5'
-diethyl-4,4″-diaminodiphenylmethane, 3
．． 3', 5,5'-tetraethyl-4,4'-diaminodiphenylmethane, 3,3'-dimethyl-4,4'-
Diaminodicyclohexylmethane, 3.3'-dimethoxy-4,4'-diaminodiphenylmethane, 3.3'-
Jetoxy-4゜4'-diaminodiphenylmethane, 3
．． 3'-diethyl-4,4'-diaminodiphenyl ether, 3.3'-jethoxy-4,4'-diaminodiphenyl ether, 3゜3'-dimethyl-4,4'-diaminodiphenyl sulfone, 3.3'-diethyl -4,4
'-Diamino diphenyl sulfone, 3,3'-dimethoxy-4,4'-diaminodiphenylsulfone, 3,3'
-Jethoxy-4,4'-diaminodiphenylsulfone, 3,3'-dimethyl-4,4'-diaminodiphenylpropane, 3,3'-diethyl-4,4'-diaminodiphenylpropane, 3,3'-dimethoxy -4゜4'-
Diaminodiphenylpropane, 3,3'-jethoxy-
4,4'-diaminodiphenylpropane, 3,3'-dimethyl-4,4'-diaminodiphenyl sulfide,
3.3'-diethyl-4,4'-diaminodiphenylsulfide, 3.3'-dimethoxy-4,4'-diaminodiphenylsulfide, 3,3'-jethoxy-4
, 4'-diaminodiphenyl sulfide, 4,4'-
Examples include dimethyl-5,5'-diaminodiphenylhexafluoropropane, and these can be used alone or in a mixture of two or more. In addition to this aromatic diamine, 10 mol% of diamine can be blended.

The reaction between (a) 3.3', 4.4'-benzophenonetetracarboxylic acid and (b) aromatic diamine is carried out by using approximately equimolar amounts in an organic solvent at a reaction temperature of 30°C or lower, preferably 0'C or lower. After addition reaction for 3 to 12 hours, a dehydrating agent is added and cyclodehydration is carried out at 100°C to obtain polyimide 181Jm having the following structural formula.

・・・・・・(1) ・・・・・・(1v) (However, in the formula, X is CH,, o, SO2, c (CH,
)2, C(CF3)2 or a divalent group of S, R',
R' is CH, , C, H, , OCH, or QC, H, 1
The valence group is R', R' is C2H.

group, R1+ represents a benzene ring or a cyclohexane ring, and R1-R4 are all substituted at the ortho position of the amino group with respect to R5) Examples of the organic solvent used in this addition polymerization reaction include dimethyl sulfoxide, N,N-dimethylformamide, N,N-diethylformamide, N,N-dimethylacetamide,
N,N-diethylacetamide, N-methyl-2-pyrrolidone, hexamethylene phosphoamide, etc. are used.

The logarithmic viscosity measured at 30°C as a solution with a concentration of polyimide resin 0.50/N-methyl-2-pyrrolidone 101 is 0.2-4. It is particularly preferable that Ol is within the range of 0.3 to 2.0.

Examples of the diluent (B) used in the present invention include N, N
-dimethylsulfoxide, N,N-dimethylformamide, N,N-diethylformamide, N,N-dimethylacetamide, N,N-diethylacetamide, N-
Examples include methyl-2-pyrrolidone, hexamethylene phosphoamide, diethylene glycol dimethyl ether, and these may be used alone or in combination of two or more. Polyimide resin is soluble in organic solvents, and when used as a material for forming an insulating protective film such as a solder resist, it is used as a solution dissolved in a diluent at a ratio of 5 to 40% by weight, preferably 15 to 30% by weight. .

Examples of the (C) sensitizer or photopolymerization initiator used in the present invention include benzoin, benzoin alkyl ethers such as benzoin ethyl ether, benzoin isopropyl ether, benzoin phenyl ether, benzointhioethers, benzophenone, acetophenone,
Examples include 2-ethyl-anthraquinone, decyl chloride, and thioxanthone, and these may be used alone or in combination of two or more. The blending ratio of the photopolymerization initiator is 0.1 to 10% by weight, preferably 0.5 to 5% by weight based on the polyimide resin.
A weight percent range is suitable. If the amount is less than 0.1% by weight, it will take a long time to cure, and if it exceeds 10% by weight, the curability will not improve any further and it will be uneconomical, both of which are not preferred.

The photocurable resin composition used in the present invention has each of the above components as essential components, but if necessary, inorganic fillers such as silica, magnesium carbonate, calcium carbonate, sodium sulfate, talc, bentonite, thixotropic agent, phthalocyanine, etc. Coloring agents such as green, antifoaming agents, coupling agents, leveling agents, etc. can also be added and blended.

This photocurable resin composition is applied onto a flexible printed circuit board or a glass epoxy printed circuit board by screen printing or other methods. For screen printing,
Printed on the substrate by a well-known method, and the printed substrate was
The diluent is removed by heating and drying at 0 to 120°C for 30 to 60 minutes. Thereafter, the applied photocurable resin composition is cured by exposing the substrate to light, such as ultraviolet light, to form a protective film having a thickness of 10 to 30 μt. The ultraviolet lamp used here preferably has a dominant wavelength between 1,000 and 8,000, and especially
~4000X ultraviolet light is suitable, xenon lamp,
Arc lamps or low, medium or high pressure mercury lamps can be used. The exposure time depends on the composition of the photocurable resin composition, film thickness, lamp intensity, distance from the light source to the composition film, etc., but for example, the exposure time with a high-pressure mercury lamp with an input of 30 W/cll is 5. ~30 seconds.

(Function) The method for manufacturing a printed circuit board of the present invention performs curing by forming a protective film with a photocurable tM composition using a polyimide resin.

That is, by reacting 3.3', 4,4'-benzophenonetetracarboxylic acid with an aromatic diamine having a methyl group or ethyl group substituted at a specific ortho position, a carboxyl group is added to the main chain of the base polymer. Also, because the pace polymer has a methyl group or ethyl group at a specific ortho position, the carbonyl group becomes photosensitized, and proton abstraction occurs due to interaction with alkyl groups such as methyl or ethyl groups, resulting in radical formation. This causes the polyimide resin to exhibit photosensitivity and forms an excellent protective film when exposed to light.

(Example) Examples of the present invention will be described below.

Example 1 After purging the inside of the flask with nitrogen by passing dry nitrogen into a three-ring flask, 3.3', 5.5'-te1-laethyl-4
,4'-diaminodiphenylmethane31. Put OQ,
To this, N-methyl-2-pyrrolidone (NMP) 25
3 ml was added and dissolved. After dissolving, the mixture was cooled to 0° C. and 3.3″, 4.4′-benzophenonetetracarboxylic anhydride (BT>32.2111) was added while stirring.

The reaction was allowed to continue for 6 hours with stirring while suppressing the reaction heat in ice water. Next, anhydrous vinegar #, which is a dehydrating agent, is added to the reaction solution.
40.81 and pyridine 4.01 were added thereto, and a ring-closing reaction was carried out for 3 hours while distilling acetic acid at IOOO°C. Thereafter, acetic anhydride/pyridine was removed by distillation under reduced pressure to complete imidization. After the imidization reaction, the reaction solution is poured into a mixed solution of methanol and water to precipitate the polyimide resin, and the precipitate is dried to form a yellow polyimide resin powder (
A logarithmic viscosity of 0.5)59Q was obtained. The obtained polyimide resin powder 300 was dissolved in diethylene glycol dimethyl ether 7o11, and 1 g of benzophenone and 2 g of fine silica powder as a thixotropic agent were added to produce a photocurable resin composition (A).

Example 2 After replacing the inside of the flask with nitrogen by introducing dry nitrogen into a three-ring flask, 36.2 g of 4,4'-dimethyl-5,5'-diaminodiphenyl hexafluoropropane was added,
N-methyl-2-pyrrolidone 3421 was added to this and dissolved. After dissolving, cool to 0℃ and stir while stirring.
．． 32.29 g of 3', 4,4'-benzophenone tetracarboxylic anhydride was added. The reaction was continued with stirring for 6 hours while suppressing the reaction heat in ice water.

Next, 40.8 ml of acetic anhydride as a dehydrating agent was added to the reaction solution.
and pyridine 4.01 were added, and a ring-closing reaction was carried out for 3 hours while distilling off acetic acid at 100"C. Thereafter, acetic anhydride/pyridine was distilled off under reduced pressure to complete imidization. Imide After the reaction, the reaction solution is poured into a mixed solution of methanol and water to precipitate the polyimide resin.
The precipitate was dried to obtain 64 g of yellow polyimide resin powder (logarithmic viscosity: o, 44). 30 g of the obtained polyimide resin powder was dissolved in diethylene glycol dimethyl ether 701, and then 1 g of benzophenone and 2 g of fine silica powder as a thixotropic agent were added to produce a photocurable resin composition <8).

Example 3 After purging the inside of the flask with nitrogen by passing dry nitrogen into a three-loaf flask, 3,3'-dimethyl-5,5'-diethyl-
28.20 g of 4,4'-diaminodiphenylmethane was added, and 2421 g of N-methyl-2-pyrrolidone was added and dissolved. After dissolving, cool to 0°C and stir while stirring 3.3
', 32.2 g of 4,4'-benzophenonetetracarboxylic anhydride was added. The reaction was continued with stirring for 6 hours while suppressing the reaction heat in ice water. Next, dehydrating agents acetic anhydride 4 (1,8if) and pyridine 4.01 were added to the reaction solution, and a ring-closing reaction was carried out for 3 hours while distilling acetic acid at 100°C. Thereafter, acetic anhydride/pyridine was mixed under reduced pressure. After the imidization reaction, the reaction solution was poured into a mixed solution of methanol and water to precipitate the polyimide resin, and the precipitate was dried to form a yellow polyimide resin powder (logarithmic Viscosity 0.33) 56
．． Get 40.

The obtained polyimide resin 30Q was dissolved in diethylene glycol dimethyl ether 701, and 1 g of benzophenone and 2 g of fine silica powder were added according to the thixotropic rule to produce a photocurable resin composition (C).

Comparative Examples 1 and 2 A commercially available general-purpose epoxy solder resist was used as a photocurable resin composition (D).

The following tests were conducted using the photocurable resin compositions (A) to (D> of Examples 1 to 3 and Comparative Examples 1 to 2. Example 1
~2 and Comparative Example 1 are glass epoxy copper i8i laminates degreased with tetrachloroethane, Example 3 and Comparative Example 2
was printed by applying a screen with a pattern formed on a 280-mesh polyester fiber net to the copper foil side of a polyimide flexible printed circuit board that had been degreased with tetrachloroethane, and then dried at 120°C for 30 minutes. 2 kW high-pressure mercury lamp (Toshiba H-2000
L/S) was irradiated twice at a conveyor speed of 0.5i/iin from a distance of 10C11 in an ultraviolet irradiation furnace equipped with one UV irradiation tube to form a protective film, and the electrical properties were tested.

Further, rosin-based flux was applied on the protective films obtained in Examples and Comparative Examples, and a cross-cut test, the state of the protective film after immersion in a solder bath, electrical insulation properties, and flexibility tests were conducted. These results are shown in Table 1, and the protective film for circuit boards according to the present invention does not exhibit excellent properties.

*1: Commercially available general-purpose epoxy solder resists were used in both cases.

*2: Measured according to JIS-C-2103 *3: JT
Measured by SD-0202 *4: Interdigital electrode 1 shown in Fig. 1 (distance between electrodes 0.25 mi, distance between conductors 0.2
5 nm, cutting dimension 501Il, conductor thickness 70μm)
Measured according to JI 5-Z-3197 using 5: 180 degree bending 10 times [Effects of the Invention] As is clear from the above explanation and Table 1, according to the method for manufacturing a printed circuit board of the present invention. A printed circuit board with excellent electrical properties, solder heat resistance, and flexibility can be obtained, and is suitable for industrial electronics.

[Brief explanation of the drawing]

FIG. 1 is a plan view of a comb-shaped electrode used for electrical insulation of a printed circuit board according to the present invention. 1...Comb-shaped electrode. Figure 1

Claims (1)

[Scope of Claims] 1(A) (a) 3,3',4,4'-benzophenonetracarboxylic acid (including its anhydride and lower alkyl ester); (b) general formula (I) or ( II) ▲There are mathematical formulas, chemical formulas, tables, etc.▼(I) ▲There are mathematical formulas, chemical formulas, tables, etc.▼(II) (However, in the formula, X is CH_2, O, SO_2, C(CH
_3)_2, C(CF_3)_2 or a divalent group of S,
R^1, R^2 are CH_3, C_2H_5, OCH_3
Or the monovalent group of OC_2H_5, R^3, R^4 are C
_2H_5 group, R^5 represents a benzene ring or a cyclohexane ring, and R^1 to R^4 are all R^
(substituted at the ortho position of the amino group with respect to 5) as a main component, and the amount of the main aromatic diamine is at least 90 mol % based on component (a). A photocurable resin composition containing as essential components a polyimide resin, (B) a diluent, and (C) a sensitizer or photopolymerization initiator is applied to a predetermined portion of a circuit board and cured by exposure to protect the circuit board. A method for manufacturing a printed circuit board, comprising forming a film and then depositing solder on areas where a protective film is not formed.