JP2575815B2 - Manufacturing method of printed circuit board - Google Patents

Description

The present invention relates to a method for manufacturing a printed circuit board, and more particularly, to a method of using a photocurable polyimide resin composition as an improved solder resist. And a method for manufacturing a printed circuit board having excellent solder heat resistance, chemical resistance, electrical characteristics and flexibility.

(Prior Art) Rigid and flexible printed circuit boards used for industrial electronics use solder resists mainly composed of various thermosetting resins. Conventionally, an alkyd / melamine resin, an epoxy / melamine resin, a two-part epoxy resin, or the like is used for the thermosetting solder resist. The protective film of the resist is printed on the surface of a printed circuit board by other methods. And then cured by heating.

However, the above-mentioned thermosetting resin composition requires a considerable amount of time and temperature for heat curing, so that productivity is poor, and because of the high heat curing temperature, substrate warpage and shrinkage occur. There was a drawback that it was easy to do. In order to solve these disadvantages, UV-curable solder resists used in consumer printed circuit boards have been studied. However, in a printed circuit board used for industrial electronics, the thickness of a conductive circuit portion made of silver or copper is as large as 50 to 70 μm. Therefore, the solder resist must be applied thickly to maintain the insulation.However, there is a problem with the curability of a thick film with a commercial UV-cured resist, and when applied to an industrial printed circuit board, the insulation and soldering properties are poor. There is a drawback that the heat resistance is poor and the reliability as a solder protection and insulating protective film cannot be maintained.

Furthermore, in the case of a flexible printed circuit board, in addition to this, extremely good film-forming properties and flexibility are required, so that conventional heat-cured and UV-cured resists could not sufficiently satisfy the characteristics. .

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

[Structure of the Invention] (Means for Solving the Problems) The present inventors have conducted intensive studies to achieve the above object, and as a result, as a base polymer of a solder resist,
By using a solvent-soluble polyimide resin having a methyl group or an ethyl group at a specific ortho position, and having a carbonyl group in the main chain, the heat resistance, photosensitivity and flexibility of the polyimide resin are sufficiently exhibited. It has been found that a method for manufacturing a printed circuit board that can achieve the above object can be obtained, and the present invention has been completed. That is, the present invention relates to (A) (a) 3,3 ', 4,4'-benzophenonetetracarboxylic acid (including its anhydride and lower alkyl ester)
And (b) the general formula (I) or (II) (Where X is CH ₂ , O, SO ₂ , C (CH ₃ ) ₂ , C (C
F ₃ ) a divalent group of ₂ or S, R ¹ and R ² are monovalent groups of CH ₃ , C ₂ H ₅ , OCH ₃ or OC ₂ H ₅ , and R ³ and R ⁴ are C ₂ H the ₅ group, R ⁵ represents respectively a benzene ring or a cyclohexane ring, and R ¹ to R ⁴
Are substituted at the ortho-position of the amino group with respect to R ⁵ ) as the main component, and the amount of the main component aromatic diamine is at least 90 mol% with respect to the component (a). A polyimide resin obtained by reacting with a diamine, (B) a diluent, and (C) a photocurable resin composition containing a sensitizer or a photopolymerization initiator, which is not a polyazide, as essential components, A method for manufacturing a printed circuit board, which comprises coating a predetermined portion, exposing and curing to form a protective film, and then depositing solder on a portion where the protective film is not formed.

 Hereinafter, the present invention will be described in detail.

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

The (a) 3,3 ', 4,4'-benzophenonetetracarboxylic acid can include its anhydride and lower alkyl ester.

(B) As the aromatic diamine having the general formula (I) or (II), 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'-diethoxy-4,4'-diaminodiphenylmethane, 3,3 '-Diethyl-4,4'-diaminodiphenylether,3,3'-diethoxy-4,4'-diaminodiphenylether,3,3'-dimethyl-4,4'-diaminodiphenylsulfone,3,3'-diethyl-4 , 4'-diaminodiphenylsulfone, 3,3'-dimethoxy-4,4'-diaminodiphenylsulfone, 3,3'-diethoxy-4,4'-
Diaminodiphenyl sulfone, 3,3'-dimethyl-4,4 '
-Diaminodiphenylpropane, 3,3'-diethyl-4,
4'-diaminodiphenylpropane, 3,3'-dimethoxy-4,4'-diaminodiphenylpropane, 3,3'-diethoxy-4,4'-diaminodiphenylpropane, 3,3'-dimethyl-4,4 ' -Diaminodiphenyl sulfide, 3,
3'-diethyl-4,4'-diaminodiphenyl sulfide, 3,3'-dimethoxy-4,4'-diaminodiphenyl sulfide, 3,3'-diethoxy-4,4'-diaminodiphenyl sulfide, 4 , 4'-dimethyl-5,5'-diaminodiphenylhexafluoropropane and the like,
These can be used alone or in combination of two or more. In addition to this aromatic diamine, 10 mol% of a diamine can be blended.

The reaction between (a) 3,3 ', 4,4'-benzophenonetetracarboxylic acid and (b) an aromatic diamine is carried out in an organic solvent at a reaction temperature of 30 ° C or lower, preferably 0 ° C or lower. 3 ~
After an addition reaction for 12 hours, a dehydrating agent is added and dehydration cyclization is performed at 100 ° C. to obtain a polyimide resin having the following structural formula.

(Where X is CH ₂ , O, SO ₂ , C (CH ₃ ) ₂ , C (C
F ₃ ) a divalent group of ₂ or S, R ¹ and R ² are monovalent groups of CH ₃ , C ₂ H ₅ , OCH ₃ or OC ₂ H ₅ , and R ³ and R ⁴ are C ₂ H the ₅ group, R ⁵ represents respectively a benzene ring or a cyclohexane ring, and R ¹ to R ⁴
The organic solvent used in both ortho positions are substituted with) the addition polymerization reaction of the amino group relates R ⁵ is, for example dimethyl sulfoxide, N, N-dimethylformamide, N, N-diethylformamide, N, N -Dimethylacetamide, N, N-diethylacetamide, N-methyl-2-pyrrolidone, hexamethylenephosphamide and the like are used. The logarithmic viscosity measured at 30 ° C. as a solution having a concentration of 0.5 g of polyimide resin / 10 ml of N-methyl-2-pyrrolidone is preferably in the range of 0.2 to 4.0, particularly 0.3 to 2.0.

As the diluent (B) used in the present invention, for example, N, N
-Dimethylsulfoxide, N, N-dimethylformamide, N, N-diethylformamide, N, N-dimethylacetamide, N, N-diethylacetamide, N-methyl-2
-Pyrrolidone, hexamethylenephosphamide, diethylene glycol dimethyl ether and the like, and these may be used alone or as a mixture of two or more. The polyimide resin is soluble in an organic solvent, and when used as a material for forming an insulating protective film such as a solder resist, 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 sensitizer or photopolymerization initiator (C) used in the present invention include benzoin, benzoin ethyl ether,
Examples include benzoin alkyl ethers such as benzoin isopropyl ether and benzoin phenyl ether, benzoin thioethers, benzophenone, acetophenone, 2-ethyl-anthraquinone, decyl chloride, and thioxanthone. These may be used alone or as a mixture of two or more. The compounding ratio of the photopolymerization initiator is 0.1 to 10% by weight, preferably 0.5 to 5% by weight based on the polyimide resin.
The range is suitable. If the amount is less than 0.1% by weight, it takes a long time to cure, while if it exceeds 10% by weight, the curability is not further improved and it is uneconomical.

The photocurable resin composition used in the present invention contains the above components as essential components, but if necessary, inorganic fillers such as silica, magnesium carbonate, calcium carbonate, sodium sulfate, talc and bentonite, thixotropic agents, phthalocyanine Green colorants, defoamers, coupling agents,
A leveling agent or the like can be added and blended.

This photocurable resin composition is applied on a flexible printed board or a glass epoxy printed board by screen printing or another method. For screen printing,
Print on the board by a well-known method, and
Heat and dry at ~ 120 ° C for 30-60 minutes to remove diluent. Thereafter, the substrate is exposed to light, for example, ultraviolet light, so that the applied photocurable resin composition is cured to a thickness of 10 to 30 μm.
Is formed. As the ultraviolet lamp used here, those having a dominant wavelength of 1000 to 8000 ° are preferable, and among them, ultraviolet light of 2000 to 4000 ° is particularly suitable, xenon lamp, arc lamp, or low-pressure, medium-pressure or high-pressure. A mercury lamp can be used. The exposure time is
Depending on the composition of the photocurable resin composition, film thickness, lamp strength, distance from the light source to the composition film, for example, 30
The exposure time with a high-pressure mercury lamp having an input of W / cm is 5 to 30 seconds.

(Function) In the method for manufacturing a printed circuit board of the present invention, curing is achieved by forming a protective film with a photocurable resin composition using a polyimide resin. That is, 3,3 ', 4,
By reacting 4'-benzophenonetetracarboxylic acid with an aromatic diamine having a methyl group or an ethyl group substituted at a specific ortho position, a carboxylic group is added to the main chain of the base polymer, and a specific ortho position at the base polymer. Since the carbonyl group has a methyl group or an ethyl group, the carbonyl group is photosensitized, protons are pulled out by the interaction of an alkyl group such as a methyl group or an ethyl group, and radicals are generated. To form an excellent protective film by light.

(Example) Hereinafter, an example of the present invention will be described.

Example 1 After the inside of the flask was replaced with nitrogen by passing dry nitrogen into a three-necked flask, 31.0 g of 3,3 ', 5,5'-tetraethyl-4,4'-diaminodiphenylmethane was added, and N-methyl-2- 253 ml of pyrrolidone (NMP) was added and dissolved. After dissolution, the mixture was cooled to 0 ° C and 32.2 g of 3,3 ', 4,4'-benzophenonetetracarboxylic anhydride (BT) was added with stirring. The reaction was continued by stirring for 6 hours while keeping the reaction heat in ice water. Next, acetic anhydride 4 as a dehydrating agent was added to the reaction solution.
0.8 ml and 4.0 ml of pyridine were added, and a ring closure reaction was performed at 100 ° C. for 3 hours while distilling acetic acid. Thereafter, acetic anhydride / pyridine was distilled off under reduced pressure to complete the imidization. After the imidization reaction, the reaction solution is poured into a mixed solution of methanol and water to precipitate a polyimide resin, and the precipitate is dried and a yellow polyimide resin powder (logarithmic viscosity 0.5) 5
9 g were obtained. 30 g of the obtained polyimide resin powder was dissolved in 70 ml of diethylene glycol dimethyl ether, 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 the inside of the flask was replaced with nitrogen by passing dry nitrogen into a three-necked flask, 36.2 g of 4,4'-dimethyl-5,5'-diaminodiphenylhexafluoropropane was added, and N-
342 ml of methyl-2-pyrrolidone was added and dissolved. After dissolution, the mixture was cooled to 0 ° C and 32.2 g of 3,3 ', 4,4'-benzophenonetetracarboxylic anhydride was added with stirring. The reaction was continued for 6 hours while keeping the heat of reaction in ice water to cause a reaction. Next, 40.8 ml of acetic anhydride and 4.0 ml of pyrisone, which are dehydrating agents, were added to the reaction solution, and a ring closure reaction was carried out at 100 ° C. for 3 hours while distilling acetic acid. Thereafter, acetic anhydride / pyridine was distilled off under reduced pressure to complete the imidization. After the imidization reaction, the reaction solution was poured into a mixed solution of methanol and water to precipitate a polyimide resin, and the precipitate was dried to obtain 64 g of a yellow polyimide resin powder (logarithmic viscosity 0.44). 30 g of the obtained polyimide resin powder was dissolved in 70 ml of diethylene glycol dimethyl ether, 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 (B).

Example 3 After passing dry nitrogen through a three-necked flask and replacing the inside of the flask with nitrogen, 3,3′-dimethyl-5,5′-diethyl-4,
2 ′ g of 4′-diaminodiphenylmethane was added, and N
242 ml of -methyl-2-pyrrolidone was added and dissolved. After dissolution, the mixture was cooled to 0 ° C. and 32.2 g of 3,3 ′, 4,4′-benzophenonetetracarboxylic anhydride was added with stirring. The reaction was continued for 6 hours while keeping the heat of reaction in ice water to cause a reaction. Next, 40.8 ml of acetic anhydride and 4.0 ml of pyridine as dehydrating agents were added to the reaction solution, and a ring closure reaction was carried out at 100 ° C. for 3 hours while distilling acetic acid. Thereafter, acetic anhydride / pyridine was distilled off under reduced pressure to complete the imidization. After the imidization reaction, the reaction solution was poured into a mixed solution of methanol and water to precipitate a polyimide resin, and the precipitate was dried to obtain 56.4 g of a yellow polyimide resin powder (logarithmic viscosity: 0.33). Dissolve 30 g of the obtained polyimide resin in 70 ml of diethylene glycol dimethyl ether, and further add benzophenone.
1 g and 2 g of fine silica powder as a thixotropic agent were added to produce a photocurable resin composition (C).

Comparative Examples 1-2 A commercially available epoxy-based solder resist was used as the photocurable resin composition (D).

The following tests were performed using the photocurable resin compositions (A) to (D) of Examples 1 to 3 and Comparative Examples 1 and 2. Example 1
2 and Comparative Example 1 were glass epoxy copper-clad laminates degreased with tetrachloroethane, and Example 3 and Comparative Example 2 were 280 mesh polyester fibers on the copper foil side of a polyimide flexible printed circuit board degreased with tetrachloroethane. After printing by applying a screen having a pattern formed on a net made of, and then drying at 120 ° C. for 30 minutes, 2
Conveyor speed 0.5m / m from a distance of 10cm in an ultraviolet irradiation furnace equipped with one kW high-pressure mercury lamp (H-2000L / S manufactured by Toshiba)
Irradiation was performed twice at in, and the film was cured to form a protective film, and the electrical characteristics were tested. A rosin-based flux was brush-coated on the protective films obtained in Examples and Comparative Examples, and a cross-cut test, a state of the protective film after immersion in a solder bath, an electrical insulation property, and a flexibility test were performed. The results are shown in Table 1. The protective film of the circuit board according to the present invention showed excellent characteristics.

* 1: In each case, a commercially available epoxy solder resist was used.

* 2: Measured by JIS-C-2103 * 3: Measured by JIS-D-0202 * 4: Comb-shaped electrode 1 shown in Fig. 1 (distance between electrodes: 0.25mm,
Measured according to JIS-Z-3197 using 0.25 mm between conductors, cut dimensions of 50 mm, and conductor thickness of 70 μm) * 5: Folded 180 degrees 10 times [Effect of the Invention] As is clear from the above description and Table 1 According to the method of manufacturing a printed circuit board of the present invention, a circuit board excellent in electrical characteristics, solder heat resistance, and flexibility can be obtained, and the printed circuit board is suitable for industrial electronics.

[Brief description of the drawings]

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 electrodes.

Claims (1)

(57) [Claims] (1) (A) (a) 3,3 ', 4,4'-benzophenonetetracarboxylic acid (including its anhydride and lower alkyl ester) and (b) a compound of the formula (I) or (II) (Where X is CH ₂ , O, SO ₂ , C (CH ₃ ) ₂ , C (C
F ₃ ) a divalent group of ₂ or S, R ¹ and R ² are monovalent groups of CH ₃ , C ₂ H ₅ , OCH ₃ or OC ₂ H ₅ , and R ³ and R ⁴ are C ₂ H the ₅ group, R ⁵ represents respectively a benzene ring or a cyclohexane ring, and R ¹ to R ⁴
Are substituted at the ortho-position of the amino group with respect to R ⁵ ) as the main component, and the amount of the main component aromatic diamine is at least 90 mol% with respect to the component (a). A polyimide resin obtained by reacting with a diamine, (B) a diluent, and (C) a photocurable resin composition containing a sensitizer or a photopolymerization initiator, which is not a polyazide, as essential components, A method for manufacturing a printed circuit board, comprising forming a protective film by coating and exposing and curing a predetermined portion, and then depositing solder on a portion where the protective film is not formed.