JP3193468B2 - Manufacturing method of printed circuit board - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a method of manufacturing a printed circuit board, and more particularly to a solder protective film of a photocurable polyimide resin having good heat resistance, chemical resistance, insulation and flexibility. Solder resist).

[0002]

2. Description of the Related Art Conventionally, rigid and flexible printed circuit boards are used in industrial electronics.
The formation of solder resist is one of the most necessary steps when assembling a printed circuit board. Conventionally, alkyd / melamine resin, epoxy /
Melamine resin, a thermosetting solder resist composition such as a two-part epoxy resin is used, and these thermosetting solder resists are applied to the surface of a printed circuit board by printing or other methods, and then heat-cured. To form a protective film.

However, the above-mentioned conventional solder resist is
There is a problem that productivity is poor because a considerable time and temperature are required for heat curing after application, and there is a problem that the substrate is easily warped or shrunk due to a high heat curing temperature. To solve these problems, ultraviolet (UV) -cured solder resists used in consumer printed circuit boards have been studied. However, printed circuit boards used in industrial electronics have been developed using silver or copper conductor circuits. The thickness of the part is very thick (about 50 to 70 μm) and must be applied thickly to maintain the insulating properties of the solder resist. However, there is a problem with the curability of thick UV-curable resist for consumer use.
On the other hand, it has been found that when the film thickness is reduced, when applied to an industrial printed circuit board, insulation and solder heat resistance are poor, so that reliability cannot be maintained as solder protection and insulation protection. Furthermore, in the case of flexible printed circuit boards, in addition to the above-mentioned reliability, extremely good film-forming properties and flexibility are required, so that conventional heat-cured and UV-cured solder resists have sufficient characteristics. I cannot be satisfied. Therefore, there has been a demand for the development of a UV-curable solder resist used for industrial printed circuit boards and flexible printed circuit boards.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and utilizes a solder resist excellent in electrical insulation, solder heat resistance, film forming property, flexibility and chemical resistance. And a method of manufacturing a printed circuit board.

[0005]

Means for Solving the Problems As a result of intensive studies aimed at achieving the above object, the present inventors have developed a novel photocurable resin composition having a vinyl ether group in the side chain of a polyimide base polymer, and It has been found that the above object can be achieved by using the resist, and the present invention has been completed.

That is, the present invention relates to (A) a polyimide polymer containing at least one structural unit represented by the following general formula:

[0007]

Embedded image (Wherein, R ¹ represents a tetravalent organic group, R ² represents a trivalent aromatic group, and R ³ represents a divalent organic group.) (B) Diluent and (C) sensitization A photocurable resin composition containing an agent or a photopolymerization initiator as an essential component is coated and exposed and cured on a circuit board to form a protective film, and then a solder is deposited on a portion where no protective film is formed. This is a method for manufacturing a printed circuit board.

Hereinafter, the present invention will be described in detail.

The (A) novel polyimide polymer used in the present invention comprises, for example, (a) an imide molecular chain composed of tetracarboxylic dianhydride and diamine and a carboxyl side chain represented by the general formula (3). A polyimide resin having at least one structural unit having

[0010]

Embedded image (Wherein R ¹ represents a tetravalent organic group and R ² represents a trivalent aromatic group) (b) hydroxyalkyl vinyl ether represented by the general formula

[0011]

[Image Omitted] The compound is obtained by reacting with HOR ³ OCHＣＨCH ₂ (wherein R ³ represents a divalent organic group).

(A) a structural unit represented by the general formula 3
The polyimide resin having a carboxyl group only needs to be soluble in an organic solvent.

(B) As shown in the general formula 4,
Examples of the hydroxyalkyl vinyl ether include 2-hydroxyethyl vinyl ether and 1-hydroxyethyl vinyl ether, and others include 4-hydroxymethylphenyl vinyl ether. These can be used alone or in combination.

The reaction between the (a) polyimide resin containing the structural unit represented by the general formula (3) and the (b) hydroxyalkyl vinyl ether is carried out in a solvent in the presence of a condensing agent.
It can be carried out by contacting both in the presence of a base.

As the solvent used here, dimethyl sulfoxide, N, N-dimethylformamide, N, N-
Diethylformamide, N, N-dimethylacetamide, N, N-diethylacetamide, N-methyl-2-pyrrolidone, hexamethylenephosphamide and the like;
These can be used alone or in combination of two or more. Examples of the condensing agent include dicyclohexylcarbodiimide, diphenyl 2,3-dihydro-2-thioxo-3-benzoxazolylphosphonate, 1-methyl-3- (3-dimethylaminopropyl) carbodiimide, and the like. Alternatively, two or more kinds can be used in combination. Examples of the base include pyridine, dimethylaminopyridine, triethylamine and the like, and these can be used alone or as a mixture of two or more.

The reaction temperature between the polyimide resin and the hydroxyalkyl vinyl ether is not particularly limited, but is preferably in the range from room temperature to 100 ° C. Also, hydroxyalkyl vinyl ethers are preferably used in a chemically calculated amount based on the carboxy equivalent of the polyimide resin,
May be more. Usually, it is used so that the ratio of the constitutional unit containing a vinyloxyalkyloxy group to the constitutional unit not containing the group is in the range of 100: 0 to 5:95.

The thus obtained novel polyimide polymers, absorption of 1785 cm ^-1 and 1727 cm ^-1 based on the imide group in an infrared absorption spectrum of a white powder, 1257Cm based on 1720 cm ^-1 and ether groups based on ester group ^{- One} absorption is seen. This polyimide polymer has a vinyloxy group having high reactivity with Lewis acids, proton acids and cations in its side chains, and is soluble in aprotic polar solvents.

As the diluent (B) used in the present invention, dimethyl sulfoxide, N, N'-dimethylformamide, N, N'-diethylformamide, N, N'-dimethylacetamide, N, N'-diethylacetamide,
Examples thereof include N-methyl-2-pyrrolidone, hexamethylenephosphamide, cyclohexanone, and γ-butyl lactone, and these can be used alone or as a mixture of two or more. 5-40% by weight, preferably 15-30% by weight of the polyimide polymer (A) is added to this diluent for reasons of film formation.
It is desirable to dissolve so that

Examples of the sensitizer or photopolymerization initiator (C) used in the present invention include various onium salts, and these can be used alone or as a mixture of two or more.
As onium salts, for example, diphenyliodonium tetrafluoroborate, 4-methoxydiphenyliodonium tetrafluoroborate, tetrafluoroborate-4,
4'-dimethyldiphenyliodonium, and 4,4'diisopropyldiphenyliodonium tetrafluoroborate. The compounding ratio of the sensitizer or the photopolymerization initiator is 0.5 to 20% by weight based on the polyimide polymer, preferably
It is desirable to mix 2.0 to 10% by weight. 0.5
If it is less than 20% by weight, it takes a long time to cure, and if it exceeds 20% by weight, the curability cannot be further improved and it is uneconomical.

The photocurable resin composition of the present invention comprises the polyimide polymer (A), the diluent (B) and the sensitizer or photopolymerization initiator (C) as essential components. To the extent not contrary to the purpose, and if necessary, inorganic fillers such as silica, magnesium carbonate, calcium carbonate, sodium sulfate, talc, bentonite, coloring agents such as thixotropic agents, phthalocyanine green, defoaming agents, and coupling agents. And a leveling agent.

In order to form a solder protective film using the photocurable resin composition thus obtained, it is applied on a flexible printed board or a glass epoxy printed board by screen printing or another method. In the case of screen printing, a pattern is printed on a board by a well-known method, and the printed board is printed.
Heat at 80-120 ° C for 30-60 minutes to remove diluent. Next, the substrate is exposed to light, for example, ultraviolet light, and cured. The protective coating obtained by this series of operations is 10 to 30
It has a thickness of μm. The ultraviolet rays to be irradiated here preferably have a dominant wavelength between 1000 and 8000 angstroms, and among them,
An ultraviolet ray of 000 angstroms is suitable, and a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, a long-high-pressure mercury lamp, a xenon lamp, or the like can be used. The exposure time depends on the composition of the composition, the film pressure, the lamp intensity, the distance from the light source, and the like. For example, the exposure time with a high-pressure mercury lamp having an input of 30 W / cm is 5 to 30 seconds.

[0022]

According to the method of manufacturing a printed circuit board of the present invention,
By using the novel photocurable resin composition having excellent film forming properties, a printed circuit board excellent in electrical insulation, solder heat resistance and flexibility can be manufactured.

[0023]

Next, the present invention will be described with reference to examples, but the present invention is not limited to these examples.

Example 1 After replacing the inside of a three-necked flask with dry nitrogen through the flask, 76.1 g of 3,5-diaminobenzoic acid was added, and N-
1200 ml of methyl-2-pyrrolidone (NMP) was added and dissolved. After dissolution, the mixture was cooled to 0 ° C and 222 g of hexafluoroisopropylidene-2,2-diphthalic anhydride was added with stirring. Continue stirring while suppressing the heat generated by the reaction in ice water,
The reaction was allowed to proceed for 6 hours. Then, xylene was added to the reaction solution.
350 g was added, and a ring closure reaction was performed for 1.5 hours while azeotropically removing water generated at 150 ° C. Thereafter, xylene was distilled off under reduced pressure to complete the imidization. After the reaction, the reaction solution was poured into a mixed solution of methanol and water to precipitate a polyimide resin. The precipitate was dried to obtain 280 g of a white polyimide resin powder (logarithmic viscosity: 0.5 dl / g).

The obtained polyimide resin (201 g) was further added with N
The resulting solution was dissolved in 1100 ml of MP, and 70.4 g of 2-hydroxyethyl vinyl ether, 15 g of 4-diaminopyridine and 124 g of dicyclohexylcarbodiimide were added to the solution and reacted at room temperature for 4 hours. After the completion of the reaction, dicyclohexylurea, a by-product, was removed by suction filtration, and the reactor was poured into a mixed solution of methanol and water to precipitate a vinyl etherified polyimide polymer, and the precipitate was dried and dried. Vinyl etherified polyimide polymer powder (logarithmic viscosity 0.55dl
/ G) 220 g were obtained. 30 g of this polyimide polymer was dissolved in 70 ml of diglyme, and 3 g of diphenyliodonium tetrafluoroborate and 2 g of fine silica powder as a thixotropic agent were added and uniformly mixed to prepare a photocurable resin composition.

The prepared photocurable resin composition was degreased with tetrachloroethane and printed on the copper foil side of a glass epoxy copper-clad laminate by applying a pattern formed on a 280 mesh polyester fiber net, After drying at 120 ° C for 30 minutes, irradiation was performed twice at a conveyor speed of 0.5 m / min from a distance of 10 cm in an ultraviolet irradiation furnace equipped with one 2 kW high-pressure mercury lamp H-2000L / S (trade name, manufactured by Toshiba Corporation). Cured to produce a printed circuit board.

Example 2 After the inside of the three-necked flask was purged with dry nitrogen, 38 g of 3,5-diaminobenzoic acid and 3,3'-dimethyl-
70.5 g of 5,5'-diethyl-4,4'-diaminodiphenylmethane (MED) was added, and 1200 ml of N-methyl-2-pyrrolidone (NMP) was added thereto and dissolved. 0 ℃ after melting
Then, 155.1 g of 3,3 '-, 4,4'-biphenylethertetracarboxylic dianhydride (ODPA) was added thereto while cooling and stirring. The stirring was continued while suppressing the heat generated by the reaction in ice water, and the reaction was allowed to proceed for 6 hours. Then, 350 g of xylene was added to the reaction solution, and a ring-closing reaction was performed at 150 ° C. for 1.5 hours while azeotropically removing generated water. Thereafter, xylene was distilled off under reduced pressure to complete the imidization. After the reaction, the reaction solution was poured into a mixed solution of methanol and water to precipitate a polyimide resin. The precipitate was dried to obtain 256 g of a white polyimide resin powder (logarithmic viscosity: 0.5 dl / g).

[0028] 211 g of the obtained polyimide resin was further
MP985ml, and 35.2g of 2-hydroxyethyl vinyl ether and 7.5g of 4-dimethylaminopyridine were added to this solution.
Then, 61.9 g of dicyclohexylcarbodiimide was added and reacted at room temperature for 4 hours. After the completion of the reaction, dicyclohexylurea, a by-product, was removed by suction filtration, and the reactor was poured into a mixed solution of methanol and water to precipitate a vinyl etherified polyimide polymer, and the precipitate was dried and dried. Vinyl etherified polyimide polymer powder (logarithmic viscosity
0.55 dl / g) 215 g was obtained. This polyimide polymer 30
g was dissolved in 70 ml of diglyme, and 3 g of diphenyliodonium tetrafluoroborate and 2 g of fine silica powder as a thixotropic agent were added and uniformly dissolved to prepare a photocurable resin composition.

The prepared photocurable resin composition was used in Example 1
In the same manner as in the above, printing, drying and curing were performed by irradiating ultraviolet rays to produce a printed circuit board.

Example 3 After replacing the inside of a three-necked flask with dry nitrogen through a flask, 38 g of 3,5-diaminobenzoic acid and 3,3'-dimethyl-
70.5 g of 5,5'-diethyl-4,4'-diaminodiphenylmethane (MED) was added, and 1200 ml of N-methyl-2-pyrrolidone (NMP) was added thereto and dissolved. 0 ℃ after melting
179 g of 3,3 '-, 4,4'-biphenylsulfonetetracarboxylic dianhydride (OSDA) was added thereto while cooling and stirring. The stirring was continued while suppressing the heat generated by the reaction in ice water, and the reaction was allowed to proceed for 6 hours. Then, 350 g of xylene was added to the reaction solution, and a ring closure reaction was carried out at 150 ° C. for 1.5 hours while azeotropically removing generated water. Thereafter, xylene was distilled off under reduced pressure to complete the imidization. After the reaction, the reaction solution was poured into a mixed solution of methanol and water to precipitate a polyimide resin. The precipitate was dried to obtain 246 g of a white polyimide resin powder (logarithmic viscosity: 0.5 dl / g).

[0031] 230 g of the obtained polyimide resin was further
MP was dissolved in 1060 ml, and 35.2 g of 2-hydroxyethyl vinyl ether and 7.5 ml of 4-dimethylaminopyridine were added to this solution.
g and 61.9 g of dicyclohexylcarbodiimide were added, and the mixture was reacted at room temperature for 4 hours. After completion of the reaction, dicyclohexylurea, a by-product, was removed by suction filtration, and the furnace solution was poured into a mixed solution of methanol and water to precipitate a vinyl etherified polyimide resin.The precipitate was dried, and white vinyl ether was dried. Polyimide polymer powder (logarithmic viscosity
0.55 dl / g) 238 g was obtained. 30 g of this polyimide polymer
Was dissolved in 70 ml of diglyme, and 3 g of diphenyliodonium tetrafluoroborate and 2 g of fine silica powder as a thixotropic agent were added and uniformly mixed to prepare a photocurable resin composition.

The prepared photocurable resin composition was prepared in Example 1
In the same manner as in the above, printing, drying and curing were performed by irradiating ultraviolet rays to produce a printed circuit board.

Comparative Example 1 A commercially available glass epoxy printed circuit board treated with a general-purpose epoxy solder resist was obtained.

Comparative Example 2 A commercially available flexible printed circuit board treated with a general-purpose epoxy solder resist was obtained.

A rosin flux was applied to the protective coating of the printed circuit board manufactured or obtained in Examples 1 to 3 and Comparative Examples 1 and 2 and immersed in a solder bath melted at 260 ° C. for 10 seconds. A cross-cut test, an electrical insulation property, and a flexibility test were performed on the protective coating after boiling. The results are shown in Tables 1 and 2, and the remarkable effects of the present invention could be confirmed.

[0036]

[Table 1] * 1: Measured according to JIS-C-2103

[0037]

[Table 2] * 1: Measured according to JIS-D-0202 * 2: Distance between electrodes 0.25 mm as shown in Fig. 1, between conductors
Measured in accordance with JIS-Z-3197 using a comb-shaped electrode 1 with 0.25 mm, cut size of 50 mm, and conductor thickness of 70 μm * 3: 180 ° bending 10 times

[0038]

As is clear from the above description and Tables 1 and 2, according to the method for manufacturing a printed circuit board of the present invention, solder heat resistance and chemical resistance are obtained despite a thin solder resist film. Excellent in electrical properties, electrical insulation and flexibility,
A printed circuit board suitable for industrial electronics can be manufactured.

[Brief description of the drawings]

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

[Explanation of symbols]

 1 Comb electrodes

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G03F 7/038 G03F 7/027 H05K 3/28

Claims (1)

(57) [Claims] (A) a polyimide polymer containing at least one structural unit represented by the following general formula: (Wherein, R ¹ represents a tetravalent organic group, R ² represents a trivalent aromatic group, and R ³ represents a divalent organic group.) (B) Diluent and (C) sensitization A photocurable resin composition containing an agent or a photopolymerization initiator as an essential component is coated and exposed and cured on a circuit board to form a protective film, and then a solder is deposited on a portion where no protective film is formed. Printed circuit board manufacturing method.