JP2011133670A - White solder resist composition for spray painting - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide: a white resist composition for spray painting which is excellent in edge covering property while reducing environmental load and prevents sagging, orange peel phenomenon and yellowing due to heat history, and to provide a printed wiring board on which the white resist composition for spray painting is sprayed and painted. <P>SOLUTION: The white resist composition for spray painting contains: (A) a carboxyl group-containing photosensitive resin; (B) silicon dioxide powder and/or metal oxide powder produced by a thermal decomposition; (C) a photopolymerization initiator; (D) a diluent; (E) an epoxy compound; (F) a titanium oxide; and (G) a solvent. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a white solder resist composition for spray coating suitable for a solder resist and various resists that can be used as a permanent mask, and a printed wiring board coated with the same.

  A printed wiring board is used to form a pattern of a conductor circuit on a substrate and to mount electronic components on the soldering land of the pattern by soldering, and the circuit portion excluding the soldering land is used as a permanent protective film. It is covered with a solder resist film. This prevents solder from adhering to unnecessary parts when soldering electronic components to a printed wiring board, and prevents circuit conductors from being directly exposed to air and being corroded by oxidation or humidity. To do.

  In addition, printed wiring boards are also used as mounting substrates for light emitting diode elements (LEDs) and the like, and the solder resist film formed on the mounting surface has a function of improving the reflectance of light from the light source. It has been demanded. Corresponding to such a new application, for example, a solder resist composition capable of forming a solder resist film having a high reflectance in Patent Document 1 is a solder that can form a solder resist film having a small decrease in reflectance in Patent Document 2. A resist composition is disclosed.

  Furthermore, in recent years, solder resist compositions have been required to have high resolution and high precision in response to the demand for improvement in the wiring density (densification) of printed wiring boards, and screen printing methods are applicable to both consumer and industrial boards. Therefore, a liquid photo solder resist method (photographic development method) is proposed which is excellent in positional accuracy and conductor edge coverage. These solder resist compositions are prepared by applying a liquid composition, which is a photosensitive resin composition, onto a printed wiring board using an electrostatic spray coating machine, volatilizing the solvent, and then exposing the unexposed portions to organic. It is removed using a solvent and developed.

  When applying a liquid solder resist composition to a printed wiring board with an electrostatic spray coater, if the solder resist composition has a high solvent content, the viscosity of the solder resist composition will decrease, and sagging and covering properties will be reduced. As a result, the amount of solvent in the exhaust gas during spray application increases, which places a burden on the environment. On the other hand, when the content of the solvent in the solder resist composition is reduced, the finished appearance of the solder resist film such as “skin skin” is deteriorated.

  Therefore, Patent Document 3 discloses that a coating film having a good coating appearance can be formed by improving the sagging property and edge covering property of the solder resist film, and further preventing the deterioration of the coating appearance such as the yuzu skin. A coating method has been proposed in which the temperature of the solder resist composition is 40 ° C. or more and 60 ° C. or less and the apparent viscosity is 30 seconds or more and 100 seconds or less. However, even the method described in Patent Document 3 requires a solvent content in the solder resist composition of 35 to 40% by mass, which causes a problem that the environmental load is large. Furthermore, conventionally, in order to bring out desired viscosity characteristics and thixotropy, hydrogenated castor oil, fatty acid amide, polycarboxylates, such as Anti-Terra-U and Anti-Terra-203 manufactured by Big Chemie Japan Co., Ltd. Anti-Terra-204, polycarboxylic acid amide solution, such as BYK-405 manufactured by Big Chemie Japan, modified urea, such as BYK-410, BYK-411, BYK-420 manufactured by Big Chemie Japan, Various materials such as BYK-425 have been used, but all have a problem that they tend to turn yellow due to thermal history and are not preferable as a composition for a white solder resist composition.

JP 2007-322546 A JP 2008-211036 A JP 2006-351605 A

  In view of the above circumstances, the present invention provides a white solder resist composition for spray coating, which is excellent in edge covering property and can suppress yellowing due to sagging property, wound skin, and thermal history while reducing the environmental load, and the spray. It aims at providing the printed wiring board which spray-coated the white soldering resist composition for coating.

  The first aspect of the present invention includes (A) a carboxyl group-containing photosensitive resin, (B) silicon dioxide powder and / or metal oxide powder produced by a thermal decomposition method, (C) a photopolymerization initiator, (D It is a white solder resist composition for spray coating, which contains a) a diluent, (E) an epoxy compound, (F) titanium oxide, and (G) a solvent. In the present invention, by adjusting the viscosity and thixotropy (thixo ratio) of the white solder resist composition, (B) the silicon dioxide powder and / or the metal oxide powder produced by the thermal decomposition method is used. The present invention provides a white solder resist composition having viscosity characteristics suitable for spray coating, while preventing environmental load by preventing and reducing the solvent content.

  In the second aspect of the present invention, the silicon dioxide powder and / or metal oxide powder produced by the thermal decomposition method (B) is 2 to 100 parts by weight of (A) carboxyl group-containing photosensitive resin. It is a white solder resist composition for spray coating characterized by containing 20 mass parts.

  A third aspect of the present invention is the white solder resist composition for spray coating, wherein the solvent (G) contains propylene glycol monomethyl ether.

  The fourth aspect of the present invention is a white solder resist composition for spray coating, wherein the thixo ratio is 1.4 to 2.2, and the fifth aspect of the present invention has a viscosity of A white solder resist composition for spray coating, which is 1 to 50 dPa · s. The “thixo ratio” means the ratio (η5 / η50) of the viscosity at a rotation speed of 5 rpm and 50 rpm measured by a viscometer under the condition that the temperature of the solder resist composition is 25 ° C.

  According to a sixth aspect of the present invention, there is provided a printed wiring board in which the white solder resist composition for spray coating is spray-coated.

  According to the first aspect of the present invention, since the silicon dioxide powder and / or metal oxide powder produced by the thermal decomposition method (B) is used for adjusting the viscosity and the thixo ratio, the edge covering property is excellent. It is possible to form a solder resist film in which sagging property, crushed skin, film adhesion, and yellowing due to thermal history are suppressed. In addition, the environmental load can be suppressed by reducing the content of the solvent (G). Furthermore, since a viscosity suitable for spray coating can be obtained, production efficiency is improved.

  According to the second aspect of the present invention, (B) the silicon dioxide powder and / or metal oxide powder produced by the thermal decomposition method is 2 parts per 100 parts by mass of (A) the carboxyl group-containing photosensitive resin. By containing -20 mass parts, more suitable viscosity and thixo ratio can be obtained as a white solder resist composition for spray coating.

  According to the third aspect of the present invention, when the solvent (G) contains propylene glycol monomethyl ether, sagging properties and film sticking properties can be further suppressed.

  According to the fourth and fifth aspects of the present invention, it is possible to improve the edge covering property, the low sagging property, the low swell skin property, and the low film sticking property in a well-balanced manner while suppressing yellowing due to thermal history. it can.

  According to the sixth aspect of the present invention, it is possible to obtain a printed wiring board that is coated with a solder resist film that is excellent in edge covering properties and has suppressed sagging properties, crushed skin, film adhesion, and yellowing due to thermal history. it can.

  Next, each component of the white solder resist composition for spray coating of the present invention will be described. The white solder resist composition for spray coating of the present invention comprises (A) a carboxyl group-containing photosensitive resin, (B) a silicon dioxide powder and / or a metal oxide powder produced by a thermal decomposition method, and (C) photopolymerization initiation. Containing the agent, (D) diluent, (E) epoxy compound, (F) titanium oxide and (G) solvent, and each of the above components is as follows.

(A) Carboxyl group-containing photosensitive resin No particular limitation as long as it is a photosensitive resin containing a carboxyl group, for example, a photosensitive carboxyl group-containing resin having one or more photosensitive unsaturated double bonds, photosensitive property And a carboxyl group-containing resin having no unsaturated double bond. As an example of the component (A), a radical polymerizable unsaturated monocarboxylic acid such as acrylic acid or methacrylic acid is reacted with at least a part of the epoxy group of the alicyclic epoxy resin having two or more epoxy groups in the molecule. Subsequently, a product obtained by reacting the produced hydroxyl group with a saturated or unsaturated polybasic acid or polybasic acid anhydride can be exemplified.

  The alicyclic epoxy resin is a resin having an alicyclic skeleton, and the skeleton is an epoxy resin formed by a chain of aliphatic cyclic compounds. Although there is no restriction | limiting in particular of an epoxy equivalent, Usually, 1000 or less, Preferably the thing of 100-500 is used.

Examples of the alicyclic skeleton epoxy resin include “EHPE-3150” (1,2-epoxy-4- (2-oxiranyl) of 2,2-bis (hydroxymethyl) -1-butanol) manufactured by Daicel Chemical Industries, Ltd. Cyclohexene adduct).

  When these epoxy resins are reacted with radically polymerizable unsaturated monocarboxylic acid, the epoxy group is cleaved by the reaction of the epoxy group and the carboxyl group to form a hydroxyl group and an ester bond.

  The radically polymerizable unsaturated monocarboxylic acid to be used is not particularly limited, and examples thereof include acrylic acid, methacrylic acid, crotonic acid, and cinnamic acid. However, at least one of acrylic acid and methacrylic acid (hereinafter referred to as (meth) acrylic). It is sometimes referred to as an acid.), And acrylic acid is particularly preferable.

  Moreover, the reaction method of an epoxy resin and radically polymerizable unsaturated monocarboxylic acid is not specifically limited, For example, it can be made to react by heating an epoxy resin and acrylic acid in a suitable diluent. Examples of the diluent include ketones such as methyl ethyl ketone and cyclohexanone, aromatic hydrocarbons such as toluene and xylene, alcohols such as methanol, isopropanol and cyclohexanol, and alicyclic hydrocarbons such as cyclohexane and methylcyclohexane. Petroleum solvents such as petroleum ether and petroleum naphtha, cellosolves such as cellosolve and butylcellosolve, carbitols such as carbitol and butylcarbitol, ethyl acetate, butyl acetate, cellosolve acetate, butyl cellosolve acetate, carbitol acetate, butyl Examples include acetates such as carbitol acetate. Examples of the catalyst include amines such as triethylamine and tributylamine, and phosphorus compounds such as triphenylphosphine and triphenylphosphate.

  In the reaction between the epoxy resin and the radically polymerizable unsaturated monocarboxylic acid, 0.7 to 1.2 equivalents of the radically polymerizable unsaturated monocarboxylic acid are reacted per 1 equivalent of the epoxy group of the epoxy resin. When at least one of acrylic acid or methacrylic acid is used, it is preferable to carry out a reaction of 0.8 to 1.0 equivalent per equivalent of epoxy group of the epoxy resin. The reaction between the epoxy resin and the radically polymerizable unsaturated monocarboxylic acid is preferably performed in a heated state, and the reaction temperature is particularly preferably 80 to 140 ° C. If the reaction temperature exceeds 140 ° C., the radically polymerizable unsaturated monocarboxylic acid may undergo thermal polymerization and may be difficult to synthesize. If the reaction temperature is less than 80 ° C., the reaction rate becomes slow and the production efficiency decreases. .

  In the reaction of the epoxy resin and the radically polymerizable unsaturated monocarboxylic acid in the diluent, the blending amount of the diluent is preferably 20 to 50% with respect to the total weight of the reaction system. The reaction product of the epoxy resin and the radically polymerizable unsaturated monocarboxylic acid can be subjected to the reaction with the following polybasic acids, if necessary, in the form of a diluent solution without isolation.

  The polybasic acid or polybasic acid anhydride reacts with a hydroxyl group generated by a reaction between an epoxy resin and a radically polymerizable unsaturated monocarboxylic acid to give the resin a free carboxyl group. The polybasic acid or its anhydride is not particularly limited, and either saturated or unsaturated can be used. Examples of the polybasic acid include succinic acid, maleic acid, adipic acid, citric acid, phthalic acid, tetrahydrophthalic acid, 3-methyltetrahydrophthalic acid, 4-methyltetrahydrophthalic acid, 3-ethyltetrahydrophthalic acid, 4- Ethyltetrahydrophthalic acid, hexahydrophthalic acid, 3-methylhexahydrophthalic acid, 4-methylhexahydrophthalic acid, 3-ethylhexahydrophthalic acid, 4-ethylhexahydrophthalic acid, methyltetrahydrophthalic acid, methylhexahydro Examples include phthalic acid, endomethylenetetrahydrophthalic acid, methylendomethylenetetrahydrophthalic acid, trimellitic acid, pyromellitic acid, and diglycolic acid. Examples of polybasic acid anhydrides include these anhydrides. These compounds may be used alone or in combination of two or more.

  The amount of the polybasic acid or polybasic acid anhydride to be reacted is 0.3 to 1.0 mol with respect to 1 mol of the hydroxyl group of the reaction product of the epoxy resin and the radically polymerizable unsaturated monocarboxylic acid. From the point that a highly sensitive resin film can be obtained at the time of exposure, it is preferably 0.4 to 1.0 mol, more preferably 0.6 to 1.0 mol. When the amount is less than 0.3 mol, the dilute alkali developability of the obtained resin may be reduced. When the amount exceeds 1.0 mol, various properties (for example, water resistance) of the finally obtained cured coating film may be reduced. May decrease.

  The polybasic acid is preferably added to the unsaturated monocarboxylic oxide epoxy resin and subjected to a dehydration condensation reaction. The water produced during the reaction is preferably removed continuously from the reaction system, but the reaction is preferably carried out in a heated state. The reaction temperature is preferably 70 to 130 ° C. When the reaction temperature exceeds 130 ° C., those bonded to an epoxy resin and radically polymerizable unsaturated groups of unreacted monomers may easily cause thermal polymerization, making synthesis difficult. The speed is slow, which may be undesirable in actual manufacturing.

  The acid value of the polybasic acid-modified unsaturated monocarboxylic acid epoxy resin, which is a reaction product of the polybasic acid or polybasic acid anhydride and the unsaturated monocarboxylic acid epoxy resin, is preferably 60 to 300 mgKOH / g. The acid value of the reaction product can be adjusted by the amount of the polybasic acid to be reacted.

  In the present invention, the polybasic acid-modified unsaturated monocarboxylic oxide epoxy resin can also be used as a photosensitive resin, but one or more radical polymerizations are carried out on the carboxyl group of the polybasic acid-modified unsaturated monocarboxylic oxide epoxy resin. It is good also as a carboxyl group-containing photosensitive resin which further introduce | transduced the radically polymerizable unsaturated group and made the photosensitivity improved by making the glycidyl compound which has a functional unsaturated group and an epoxy group react.

  In this carboxyl group-containing photosensitive resin with improved photosensitivity, the radically polymerizable unsaturated group is bonded to the side chain of the polymer skeleton of the precursor photosensitive resin by the reaction of the last glycidyl compound. High photopolymerization reactivity and excellent photosensitivity. Examples of the compound having one or more radically polymerizable unsaturated groups and an epoxy group include glycidyl acrylate, glycidyl methacrylate, allyl glycidyl ether, pentaerythritol triacrylate monoglycidyl ether, and the like. In addition, you may have multiple glycidyl groups in 1 molecule. These compounds may be used alone or in combination of two or more.

  The glycidyl compound is added to and reacted with the polybasic acid-modified unsaturated monocarboxylic oxide epoxy resin solution, but usually in a ratio of 0.05 to 0.5 mol with respect to 1 mol of the carboxyl group introduced into the resin. React with. From the viewpoint of the photosensitivity of the white solder resist composition containing the resulting carboxyl group-containing photosensitive resin and the electrical properties such as the thermal management width and electrical insulation, the reaction is carried out at a rate of 0.1 to 0.5 mol. Is preferred. The reaction temperature is preferably 80 to 120 ° C. The photosensitive resin comprising the glycidyl compound-added polybasic acid-modified unsaturated monocarboxylic oxide epoxy resin thus obtained preferably has an acid value of 45 to 250 mgKOH / g.

(B) The silicon dioxide powder produced by the thermal decomposition method and / or the silicon dioxide powder produced by the metal oxide powder thermal decomposition method includes, for example, fumed silica. By adding fumed silica, it is possible to suppress discoloration such as yellowing due to thermal history while imparting thixotropy to the white solder resist composition for spray coating of the present invention to suppress sagging of the solder resist film. Although the fumed silica which can be used by this invention is not specifically limited, For example, what is obtained by hydrolyzing silicon chloride as a raw material at high temperature can be mentioned.

The characteristics of fumed silica such as specific surface area, primary particle size and surface treatment are not particularly limited, but fumed silica having a specific surface area of 50 to ²⁰⁰ m ² / g is preferred from the viewpoint of leveling properties after coating. Examples of the fumed silica include AEROSIL (R) 90, AEROSIL (R) 130, AEROSIL (R) 150, AEROSIL (R) 200, AEROSIL (R) manufactured by Nippon Aerosil Co., Ltd. ) 300, AEROSIL (R) 380, AEROSIL (R) OX50, AEROSIL (R) EG50, AEROSIL (R) TT600, Leorosil QS-09, QS-10L, QS-10, QS-102, manufactured by Tokuyama Corporation CP-102, QS-20L, QS-20, QS-25C, QS-30, QS-30C, QS-40, etc. are mentioned. As the hydrophobic fumed silica, AEROSIL® R972, AEROSIL® R974, AEROSIL® R104, AEROSIL® R106, AEROSIL® R106, AEROSIL® R202, AEROSIL (R) manufactured by Nippon Aerosil Co., Ltd. ) R805, AEROSIL (R) R812, AEROSIL (R) R816, AEROSIL (R) R7200, AEROSIL (R) R8200, AEROSIL (R) R9200, AEROSIL (R) RY50, AEROSIL (R) NY50, AEROSIL (R) RY200 , AEROSIL (R) RY200S, AEROSIL (R) RX50, AEROSIL (R) NAX50, AEROSIL (R) RX200, AEROSIL (R) RX300, AEROSIL (R) R504, AEROSIL (R) DT4, Toroyama Co., Ltd. MT-10, MT-10C, DM-10, DM-10C, DM-20S, DM-30, DM-30S, KS-20S, KS-20SC, HM-20L, HM-30S, PM-20L, etc. It is done. These compounds may be used alone or in combination of two or more.

  Examples of the metal oxide powder produced by the pyrolysis method include fumed metal oxide. By adding a fumed metal oxide, it is possible to impart thixotropy to the white solder resist composition for spray coating of the present invention as in the case of the fumed silica, and to suppress discoloration such as yellowing due to thermal history. Although the fumed silica which can be used by this invention is not specifically limited, For example, what is obtained by hydrolyzing a metal chloride as a raw material at high temperature can be mentioned.

The characteristics of the fumed metal oxide such as the specific surface area, the primary particle diameter, and the surface treatment are not particularly limited, but a fumed metal oxide having a specific surface area of 50 to ²⁰⁰ m ² / g is preferable from the viewpoint of leveling properties after coating. Examples of the fumed metal oxide include AEROXIDE® Alu, AEROXIDE® TiO ₂ , AEROXIDE® TiO ₂ P25S, VP AEROPERL® P25 / 20, VP Zirconium Oxide 3 manufactured by Nippon Aerosil Co., Ltd. -YSZ, VP Zirconium Oxide PH, AEROXIDE® TiO ₂ T805, AEROXIDE® AluC805 and the like. These compounds may be used alone or in combination of two or more. In particular, the oxide of titanium can improve white hiding power and can be used as a color pigment.

  Further, two or more of the above fumed oxides may be mixed, but from the viewpoint of workability, silicon dioxide (for example, new silica) powder produced by pyrolysis and metal oxidation produced by pyrolysis A material (for example, fumed metal oxide) powder previously mixed may be used. Examples of the mixture of fumed silica and fumed metal oxide include AEROSIL (R) MOX80, AEROSIL (R) MOX170, and AEROSIL (R) COK84 manufactured by Nippon Aerosil Co., Ltd.

  The blending amount of the silicon dioxide powder and / or metal oxide powder produced by the pyrolysis method is 100% by weight of the carboxyl group-containing photosensitive resin, and the lower limit thereof increases thixotropy to prevent sagging. It is 2 parts by mass from the point, and preferably 7 parts by mass from the viewpoint of reliably preventing sagging. Moreover, the upper limit is 20 parts by mass from the viewpoint of maintaining the smoothness of the solder resist film after application and preventing it from becoming a crusty skin, and from the point of reliably maintaining the smoothness of the solder resist film. Part by mass.

(C) Photopolymerization initiator It is not particularly limited as long as it is a photopolymerization initiator that is generally used. For example, oxime initiator, benzoin, acetophenone, 2-hydroxy-2-methyl-1-phenylpropane-1 -One, 1-hydroxycyclohexyl phenyl ketone, benzophenone and the like. These photopolymerization initiators may be used alone or in combination of two or more. The compounding quantity of a photoinitiator is 1-30 mass parts with respect to 100 mass parts of carboxyl group-containing photosensitive resin, Preferably it is 5-20 mass parts.

(D) Diluent diluent is, for example, a photopolymerizable monomer, and is used to obtain a coating film having acid resistance, heat resistance, alkali resistance, etc. by sufficiently photocuring a carboxyl group-containing photosensitive resin. To do. Examples of the photopolymerizable monomer include 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, and the like. Can be mentioned. These diluents may be used alone or in combination of two or more. The compounding quantity of a diluent is 20-300 mass parts with respect to 100 mass parts of carboxyl group-containing photosensitive resin, Preferably it is 2.0-40 mass parts.

(E) Epoxy compound In the white photosensitive resin composition, the epoxy compound increases the cross-linking density of the cured coating film, and is a resin cured film with little discoloration of the white coating film due to UV irradiation and thermal history and a decrease in reflectance. For example, an epoxy resin is added. Examples of the epoxy resin include bisphenol A type epoxy resin, novolak type epoxy resin (phenol novolak type epoxy resin, o-cresol novolak type epoxy resin, p-tert-butylphenol novolak type, etc.), bisphenol F and bisphenol S with epichlorohydrin. Bisphenol F-type and bisphenol S-type epoxy resins obtained by reaction, alicyclic epoxy resins having cyclohexene oxide groups, tricyclodecane oxide groups, cyclopentene oxide groups, and the like, tris (2,3-epoxypropyl) isocyanurate , Triglycidyl isocyanurate having a triazine ring such as triglycidyl tris (2-hydroxyethyl) isocyanurate, dicyclopentadiene type epoxy resin, Adama It can be exemplified Tan type epoxy resin. These compounds may be used alone or in combination of two or more.

  The compounding quantity of an epoxy compound is 1-75 mass parts with respect to 100 mass parts of carboxyl group-containing photosensitive resin from the point which obtains a sufficient coating film after hardening, and improves solder heat resistance, and coating film hardening 20 to 60 parts by mass is preferable from the viewpoint of the balance between the heat resistance and the solder heat resistance.

(F) Titanium oxide Titanium oxide is anatase-type titanium oxide particles and titanium oxide particles having a rutile crystal structure, and is used to whiten the coating film. From the viewpoint of whiteness, rutile type titanium oxide is preferable. Examples of rutile titanium oxide include “TR-600”, “TR-700”, “TR-750”, “TR-840” manufactured by Fuji Titanium Industry Co., Ltd., and “R-550” manufactured by Ishihara Sangyo Co., Ltd. ”,“ R-580 ”,“ R-630 ”,“ R-820 ”,“ CR-50 ”,“ CR-60 ”,“ CR-90 ”,“ CR-93 ”, manufactured by Titanium Industry Co., Ltd. “KR-270”, “KR-310”, “KR-380” and the like can be mentioned. The compounding quantity of a rutile type titanium oxide is 30-200 mass parts with respect to 100 mass parts of carboxyl group-containing photosensitive resin, Preferably it is 50-150 mass parts.

(G) The solvent is for adjusting the drying property of the white solder resist composition for spray coating. Examples of the solvent include ketones such as methyl ethyl ketone and cyclohexanone; aromatic hydrocarbons such as toluene, xylene and tetramethylbenzene; methyl cellosolve, ethyl cellosolve, butyl cellosolve, methyl carbitol, butyl carbitol, propylene glycol monomethyl ether, Glycol ethers such as diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, dipropylene glycol monoethyl ether, triethylene glycol monoethyl ether; ethyl acetate, butyl acetate, cellosolve acetate, diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, propylene glycol Monomethyl ether acetate and glyco Esters such as esters of ethers; ethanol, can be mentioned propanol, ethylene glycol, and alcohols such as propylene glycol.

  In the white solder resist composition for spray coating of the present invention, in addition to the components (A) to (G) described above, various additive components such as an antifoaming agent, various additives and extender pigments may be used as necessary. Etc. can be contained.

  A well-known thing can be used for an antifoamer, for example, a silicone type, a hydrocarbon type, an acrylic type etc. can be mentioned.

  Examples of various additives include dispersants such as coupling agents such as silane, titanate, and alumina, boron trifluoride-amine complex, dicyandiamide (DICY) and its derivatives, organic acid hydrazide, and diaminomaleonitrile (DAMN). ) And derivatives thereof, guanamine and derivatives thereof, melamine and derivatives thereof, latent hardeners such as amine imide (AI) and polyamine, metal salts of acetylacetone such as acetylacetonate Zn and acetylacetonate Cr, enamine, tin octylate, Examples include quaternary sulfonium salts, triphenylphosphine, imidazole, imidazolium salts, and thermosetting accelerators such as triethanolamine borate.

  The extender pigment is for increasing the physical strength of the coated solder resist film, and examples thereof include silica, barium sulfate, alumina, aluminum hydroxide, talc, and mica.

  Although the manufacturing method of the above-mentioned white solder resist composition for spray coating of the present invention is not limited to a specific method, for example, the above components (A) to (G) and other components are blended at a predetermined ratio as necessary. After mixing, if necessary, it is kneaded or mixed by a kneading means such as a triple roll, ball mill or sand mill, or a stirring means such as a super mixer or a planetary mixer to obtain the white solder resist composition for spray coating of the present invention. It is done.

  The white solder resist composition for spray coating of the present invention obtained as described above has a desired thickness on a printed wiring board having a circuit pattern formed by etching a copper foil of a copper-clad laminate, for example, Spray coating is applied at a thickness of 5 to 100 μm. Examples of the spray coating means include an electrostatic spray coating machine, an air spray coating machine, and an airless spray coating machine.

  After spray coating, preliminary drying is performed in a hot-air oven or a far-infrared oven as necessary, and the solvent is volatilized from the white solder resist composition to make the surface of the coating film tack-free. The preliminary drying temperature is preferably about 50 to 100 ° C., and the preliminary drying time is preferably 20 to 25 minutes.

After preliminary drying, exposure by laser direct drawing using LDI (Laser Direct Imaging) or exposure by active energy rays is performed using a negative mask that does not allow passage of active energy rays. As the negative mask, a negative film is used when the active energy ray is ultraviolet, a metal mask is used when it is an electron beam, and a lead mask is used when it is an X-ray, but it can be printed because a simple negative film can be used. In the production of wiring boards, ultraviolet rays are often used as active energy rays. The irradiation amount of ultraviolet rays is 10 to 1000 mJ / cm ² .

  In the case of printed wiring board manufacture, for example, a negative film having a light-transmitting pattern other than the soldering land of the circuit pattern is closely attached and irradiated with ultraviolet rays from above, and then the soldering land is applied to the soldering land. The coating is developed by removing the corresponding non-exposed areas with dilute alkaline aqueous solution. This removal may be any of dissolution, swelling, peeling, etc. of the unexposed part. The dilute alkaline aqueous solution used at this time is generally 0.5 to 5% sodium carbonate aqueous solution, but other alkalis can also be used.

  Next, in the case of containing a thermosetting compound, for example, a post-cure is performed by heating for 20 to 80 minutes with a dryer such as a hot-air oven or a far-infrared oven at 130 to 170 ° C., thereby forming a solder resist film. Can be formed.

  In this way, a printed wiring board coated with a solder resist film is obtained, on which electronic components are connected, fixed and mounted by soldering by a jet soldering method or a reflow soldering method. A circuit unit is formed.

  In the present invention, both the printed wiring board coated with the solder resist film before mounting the electronic component and the printed wiring board mounted with the electronic component on the printed wiring board are included in the object.

  Next, examples of the present invention will be described. However, the present invention is not limited to these examples as long as the gist thereof is not exceeded.

Examples 1-15, Comparative Examples 1-3
Each component shown in the following Table 1 is blended at a ratio shown in the following Table 1, mixed and dispersed at room temperature using three rolls, and spray coating used in Examples 1 to 15 and Comparative Examples 1 to 3 A white solder resist composition was prepared. The numbers in the formulation in Table 1 below indicate parts by mass.

The details of each component in Table 1 are as follows.
(A) Carboxyl group-containing photosensitive resin / Synthesis Example 1: Synthesis of Resin A-1 Acrylic acid was obtained by melting 270 parts by mass of epoxy resin (EHPE-3150 manufactured by Daicel Chemical Industries, Ltd.) in 400 parts by mass of cellosolve acetate. (Unsaturated group-containing monocarboxylic acid) 110 parts by mass was added and reacted under heating and reflux conditions by a conventional method. To this reaction product, 160 parts by mass of tetrahydrophthalic anhydride (polybasic acid anhydride) was reacted by a conventional method, Subsequently, 40 parts by mass of glycidyl methacrylate (ethylenically unsaturated monomer) was reacted by a heating under reflux method to obtain a product (resin A-1).
Synthesis Example 2: Synthesis of Resin A-2 72 parts by mass of acrylic acid was obtained by dissolving 210 parts by mass of cresol novolac type epoxy resin (manufactured by DIC, N-680) as an epoxy resin in 120 parts by mass of diethylene glycol monoethyl ether acetate. The reaction product was reacted with 76 parts by mass of tetrahydrophthalic anhydride (polybasic acid anhydride) by a conventional method to obtain a product (resin A-2). .
Cyclomer P (ACA) Z-300: a carboxyl group-containing resin using a resin having an acrylic copolymer structure manufactured by Daicel Chemical Industries, Ltd.
ZFR-1124: a carboxyl group-containing resin having a bisphenol F type epoxy acrylate structure manufactured by Nippon Kayaku Co., Ltd.
FLX-2089: Nippon Kayaku Co., Ltd., a carboxyl group-containing resin having a urethane-modified epoxy acrylate structure.
(B) Silicon dioxide powder and / or metal oxide powder produced by a thermal decomposition method AEROSIL R974: manufactured by Nippon Aerosil Co., Ltd., hydrophobic fumed silica.
AEROSIL 200: manufactured by Nippon Aerosil Co., Ltd., hydrophilic fumed silica.
-AEROXIDE Alu C: Nippon Aerosil Co., Ltd., fumed metal oxide (aluminum oxide).
AEROXIDE TiO ₂ P25: Nippon Aerosil Co., Ltd., fumed metal oxide (titanium dioxide).
(C) Photopolymerization initiator DAROCURE TPO: Ciba Specialty Chemicals Co., Ltd., 2,4,6-trimethylbenzoyldiphenylphosphine oxide.
(D) Diluent-M-408: Toa Gosei Co., Ltd., ditrimethylolpropane tetraacrylate.
(E) Epoxy compound EPICRON 860: Dainippon Ink and Chemicals, bisphenol A type epoxy resin.
(F) Titanium oxide CR-80: manufactured by Ishihara Sangyo Co., Ltd., rutile titanium oxide.

  In addition, the additive DICY-7 is a curing accelerator made by Japan Epoxy Resin Co., Ltd., melamine is a latent curing agent, and BYK-411 used in Comparative Example 3 is a thixotropic agent made by Big Chemie Japan Co., Ltd. is there.

The test piece preparation process is shown below.
Substrate: Glass epoxy substrate FR-4, plate thickness 1.6mm, conductor thickness 50μm, width 200μm
Substrate surface treatment: acid treatment (3% sulfuric acid aqueous solution)
Coating: Spray coating Coating conditions: Discharge rate (110 cc / min), conveyor speed (2.3 m / min), disk rotation speed (30000 rpm), applied voltage (-35 KV), white solder resist composition liquid for spray coating Wet film thickness is about 60μm
DRY film thickness: 30-35 μm
Predrying: 70 ° C, 20 minutes (25 minutes in BOX furnace)
Exposure: 400 mJ / cm ² on the solder resist composition (OMW HMW-680GW)
Development: 1% Na ₂ CO ₃ , 30 ° C., 0.1 MPa, 60 seconds Post cure: 150 ° C., 60 minutes (70 minutes in BOX furnace)

The evaluation / measurement items are as follows.
(1) Viscosity The viscosity of the prepared white solder resist composition for spray coating was measured at a sample temperature of 25 ° C. using a Malcolm spiral viscometer PC-1C type (φ35 rotor).
(2) Thixo ratio Using the Brookfield viscometer RVT type for the prepared white solder resist composition for spray coating, the thixo is calculated from the ratio of the viscosity of the spindle at 5 rpm and 50 rpm at the sample temperature of 25 ° C. (η5 / η50). The ratio was calculated.
(3) Sag property The coated substrate which is a test piece was visually evaluated.
○: There is no twist or sag in the solder resist film on the surface of the painted substrate.
Δ: The solder resist film on the surface of the painted substrate is slightly twisted or sagged.
X: The solder resist film on the surface of the painted substrate has a twist or sag.
(4) Scratch skin property The painted substrate which is a test piece was visually evaluated.
○: The solder resist film on the coated substrate surface is smooth.
Δ: Some unevenness exists in the solder resist film on the surface of the coated substrate.
X: The solder resist film on the surface of the coated substrate has irregularities.
―: Sagging occurred so much that the specimen could not be prepared and could not be evaluated.
(5) Film sticking property The negative film was contacted after preliminary drying, and the sticking property when exposed was evaluated.
○: No sticking.
Δ: A sticky mark remains on the coating film.
X: Film ink adhered after film peeling.
―: Sagging occurred so much that the specimen could not be prepared and could not be evaluated.
(6) Edge Covering The cross section of the coated substrate, which is a test piece, was observed, and the film thickness of the resist covering the edge portion of the conductor was measured.
(7) Discoloration evaluation Discoloration evaluation: After heating at 260 ° C for 5 minutes, the discoloration of the cured coating film was visually evaluated.
○: No discoloration.
Δ: Some discoloration is observed.
X: Yellowing.
(8) Solder heat resistance A cured coating film of a test piece is immersed in a solder bath at 260 ° C. for 30 seconds in accordance with a test method of JIS C-6481, and then a peeling test using a cellophane tape is defined as one cycle, and this is performed 1-3 times. The coating state after the repetition was observed visually and evaluated according to the following criteria.
A: No change is observed in the coating film even after 3 cycles.
○: Only a slight change is observed in the coating film after repeating 3 cycles.
(Triangle | delta): A change is recognized by the coating film after 2 cycles repetition.
X: Peeling is recognized in the coating film after 1 cycle.

  The measurement results and evaluation results are shown in Table 2.

  As shown in Table 2 above, in Examples 1 to 15 in which 2 to 20 parts by mass of silicon dioxide powder and / or metal oxide powder produced by the thermal decomposition method were mixed, Sticking to the film could be suppressed, and the film thickness of the resist covering the edge portion was also as good as 7 μm or more. This is probably because the white solder resist composition for spray coating has a viscosity range of 1.1 to 3.0 dPa · s and a thixo ratio of 1.4 to 2.2, which is a numerical range suitable for spray coating. Moreover, in Examples 1-15, since the silicon dioxide powder and / or metal oxide powder which were manufactured by the thermal decomposition method are used for adjustment of a viscosity and thixotropy (thixo ratio), the discoloration property by a thermal history is also included. Moreover, the solder heat resistance was good. However, a slight tendency was observed in Example 14 having a viscosity of 55 dPa · s, and a tendency to sag in Example 15 having a viscosity of 0.5 dPa · s.

  From the comparison between Examples 1 to 5 and Examples 9 to 10, both silicon dioxide powder produced by the pyrolysis method and metal oxide powder produced by the pyrolysis method were almost equally prevented from dripping. Generation of skin and sticking to the film could be suppressed. Further, from the comparison of Examples 1 to 5 and Examples 11 to 13, when propylene glycol monomethyl ether was added to the solvent, sagging properties and film stickiness could be further suppressed.

  On the other hand, in Comparative Example 1, the viscosity and the thixo ratio of the white solder resist composition for spray coating were high, and a crushed skin with irregularities on the surface of the coated substrate was observed. In Comparative Example 2, the thixo ratio was low, sagging occurred, and a test piece could not be prepared. In Comparative Example 3 in which a conventional thixotropic agent was used, no sagging occurred and no skin was observed, but the surface of the coating film turned yellow after heating.

  The white solder resist composition for spray coating of the present invention has excellent edge covering properties and can suppress yellowing due to sagging properties, crushed skin, and thermal history, so the field of printed wiring boards, particularly printed wiring for LED mounting. High utility value in the field of boards.

Claims (6)

  (A) carboxyl group-containing photosensitive resin, (B) silicon dioxide powder and / or metal oxide powder produced by thermal decomposition method, (C) photopolymerization initiator, (D) diluent, (E) epoxy compound A white solder resist composition for spray coating, comprising: (F) titanium oxide and (G) a solvent.   The silicon dioxide powder and / or metal oxide powder produced by the thermal decomposition method (B) contains 2 to 20 parts by mass with respect to 100 parts by mass of the (A) carboxyl group-containing photosensitive resin. The white solder resist composition for spray coating according to claim 1.   The white solder resist composition for spray coating according to claim 1, wherein the solvent (G) contains propylene glycol monomethyl ether.   The white solder resist composition for spray coating according to any one of claims 1 to 3, wherein the thixo ratio is 1.4 to 2.2.   The white solder resist composition for spray coating according to any one of claims 1 to 4, wherein the viscosity is 1 to 50 dPa · s.   A printed wiring board, wherein the white solder resist composition for spray coating according to any one of claims 1 to 5 is spray-coated.