JP5843255B2 - Solder resist composition and metal base circuit board - Google Patents

Description

  The present invention relates to a solder resist composition and a metal base circuit board on which a solder resist layer is formed by this composition. More specifically, the present invention relates to a solder resist composition for mounting an optical semiconductor element such as an LED (Light Emitting Diode) and a metal base circuit board.

  In recent years, liquid crystal display devices have been used in various fields, and in particular, in the electronic industry field such as personal computers and televisions. Among these liquid crystal display devices, those that employ a direct type backlight system have a light source disposed on the back surface of the liquid crystal panel, and light is emitted from the light source to the entire back surface of the liquid crystal panel. .

  On the other hand, the light source is arranged on the side surface of the liquid crystal panel in the case of employing the edge light type backlight system. Then, light emitted from the light source is incident on the light guide plate, and the propagated light is emitted from the surface side of the light guide plate via a prism sheet or the like, so that the entire back surface of the liquid crystal panel is irradiated. ing.

  As a light source for such backlight type and edge light type liquid crystal display devices, CCFL (Cold Cathode Tube) has been mainly used heretofore, but from the consideration of environmental aspects such as high brightness and mercury-free, Those using LEDs as light sources are increasing. In particular, with the increase in the size of liquid crystal display devices for home televisions, the demand for higher brightness of the light source has increased, and there are various methods for effectively using not only the emitted light from the LED as the light source but also the reflected light. Proposed.

  As one of the methods, conventionally, a method of forming a highly reflective solder resist layer highly filled with a white pigment on the outermost layer of a printed circuit board for mounting an LED package has been proposed (for example, Patent Documents 1 to 3). 3). For example, in the solder resist composition described in Patent Document 1, by mixing rutile-type titanium oxide with a carboxyl group-containing resin that does not have an aromatic ring, deterioration of the resin due to light is suppressed, and high reflectance is maintained. ing.

  Moreover, in the metal-based circuit board described in Patent Document 2, a circuit board having both thermal conductivity and light reflection performance by forming a solder resist layer using an epoxy resin containing a white pigment such as titanium dioxide. Is realized. Furthermore, in the metal base circuit board described in Patent Document 3, an inorganic mixture is blended with a mixture of a carboxyl group and (meth) acryloyl group-containing polymer, an acrylic compound, a photopolymerization initiator, and an epoxy compound. By using the solder resist composition, the reflectance is improved.

  On the other hand, along with the thinning of the liquid crystal display device, the thinning of the printed circuit board for LED package mounting is also required. Therefore, conventionally, a metal base substrate has been proposed in which an insulating layer provided in a metal foil shape is formed of a specific epoxy resin so that it can be bent even at room temperature (see Patent Document 4).

JP 2007-322546 A JP 2009-4718 JP 2010-14767 A JP 2006-303082 A

  However, the conventional techniques described above have the following problems. That is, since the thin metal base circuit board described in Patent Document 4 described above is easily warped and twisted in the mounting process, if a solder resist composition highly filled with white pigment is used, the solder There is a problem that cracks are likely to occur in the resist layer.

  Therefore, the main object of the present invention is to provide a solder resist composition and a metal base circuit board in which cracks due to warping or twisting of the substrate are less likely to occur in the solder resist layer even when highly filled with a white pigment.

  The inventor has conducted extensive experiments to solve the above-described problems, and as a result, found that the “tensile modulus” and “breaking elongation” of the solder resist layer affect the occurrence of cracks. And it investigated further about the resin component which comprises a soldering resist layer, and discovered that generation | occurrence | production of a crack could be prevented by implement | achieving a soldering resist layer with a low tensile elasticity modulus and a high fracture elongation.

That is, the solder resist composition according to the present invention contains at least an epoxy resin, an epoxy resin curing agent, a photosensitive prepolymer, a photosensitive monomer, a photopolymerization initiator, and a white pigment, The epoxy resin is (1) a hydrogenated bisphenol A to F type having an epoxy equivalent of 200 to 2000 or a copolymer thereof, and (2) a bisphenol A to F type having an epoxy equivalent of 200 to 10,000 or (3) The main chain contains a siloxane skeleton and a bisphenol A skeleton, the proportion of silicone in the main chain is 30 to 75% by mass, and an epoxy group is introduced at the terminal. (4) the main chain contains a hexamethylene glycol skeleton, a glycerin skeleton and a bisphenol A skeleton, and an epoxy group at the terminal The introduced epoxy resin and (5) at least one selected from the group consisting of polytetramethylene glycol type epoxy resins, wherein the epoxy resin curing agent has one or more amino groups in the molecule And / or a curing agent having one or more carboxyl groups in the molecule.
In the present invention, a specific epoxy resin and a curing agent having one or more amino groups in the molecule and / or a curing agent having one or more carboxyl groups in the molecule are used. Therefore, even if the white pigment is highly filled, the cured product (solder resist layer) maintains a low tensile elastic modulus and a high elongation at break, i.e., flexibility.
In this solder resist composition, the photosensitive prepolymer may contain one or more unsaturated double bonds, carboxyl groups and hydroxyl groups in the molecule.
The photosensitive monomer may contain one or more unsaturated double bonds in the molecule.
Furthermore, as the white pigment, for example, at least one selected from the group consisting of titanium dioxide, barium sulfate, silicon dioxide, zirconia oxide, magnesium oxide, aluminum oxide, and aluminum nitride can be used.

The metal base circuit board according to the present invention includes a metal foil, an insulating layer formed on the metal foil, a conductor circuit locally formed on the surface of the insulating layer, an insulating layer and a conductor circuit. A solder resist layer formed on the surface, and the solder resist layer is formed of the above-described solder resist composition.
In the present invention, since the solder resist layer is formed of the above-described solder resist composition, it exhibits excellent flexibility even when highly filled with a white pigment, and in the mounting process of an optical semiconductor element such as an LED, Even if the substrate is warped or twisted, cracks are unlikely to occur.

  According to the present invention, since a specific epoxy resin and a specific epoxy resin curing agent are used, the occurrence of cracks in the solder resist layer caused by warping or twisting of the substrate is suppressed even when a high amount of white pigment is filled. can do.

It is sectional drawing which shows typically the structure of the metal base circuit board of the 2nd Embodiment of this invention.

  Hereinafter, embodiments for carrying out the present invention will be described in detail. Note that the present invention is not limited to the embodiments described below.

(First embodiment)
First, the solder resist composition according to the first embodiment of the present invention will be described. The solder resist composition of this embodiment contains at least an epoxy resin, an epoxy resin curing agent, a photosensitive prepolymer, a photosensitive monomer, a photopolymerization initiator, and a white pigment.

[Epoxy resin]
As an epoxy resin which is the main component of the solder resist composition of the present embodiment, one or more epoxy resins selected from the following (1) to (5) epoxy resins can be used. .
(1) An epoxy resin which is a hydrogenated bisphenol A type or F type having an epoxy equivalent of 200 to 2000 or a copolymer thereof.
(2) Epoxy resin which is bisphenol A type or F type having an epoxy equivalent of 200 to 10,000 or a copolymer thereof.
(3) An epoxy resin in which the main chain includes a siloxane skeleton and a bisphenol A skeleton, the ratio of silicone in the main chain is 30 to 75% by mass, and an epoxy group is introduced at the terminal.
(4) An epoxy resin in which the main chain includes a hexamethylene glycol skeleton, a glycerin skeleton and a bisphenol A skeleton, and an epoxy group is introduced at the terminal.
(5) Polytetramethylene glycol type epoxy resin.

  Since these epoxy resins have a long molecular chain or a cured product is flexible, flexibility can be imparted to the formed solder resist layer.

[Epoxy resin curing agent]
The epoxy resin curing agent blended in the solder resist composition of the present embodiment can be appropriately selected according to the epoxy resin to be used, but the curing agent having one or more amino groups in the molecule, 1 in the molecule. The curing agent having the above carboxyl group, or these are used in combination. Since the curing agent having an amino group or a carboxyl group reacts with an epoxy group to form a crosslinked structure, a cured product having excellent physical properties can be obtained.

  On the other hand, when a curing agent having no amino group or carboxyl group in the molecule is used, when the white pigment is highly filled, the tensile modulus of the formed solder resist layer is increased or the breaking elongation is decreased. If the flexibility of the solder resist layer is not sufficient, cracks are likely to occur due to warping or twisting of the substrate in the mounting process.

  Further, when using the two kinds of curing agents described above, it is desirable to use a compound that does not have a rigid structure such as an aromatic ring in the main chain in order to impart flexibility to the formed solder resist layer. . Specifically, examples of the curing agent having one or more amino groups in the molecule include trimethylhexamethylenediamine, 2-methylpentamethylenediamine, polyoxypropylenediamine, and the like. Examples of the curing agent having one or more carboxyl groups in the molecule include aliphatic dibasic acid polyanhydrides, esters of aliphatic acid anhydrides and polyalkylene glycols, and the like. In addition, the addition amount of an epoxy resin hardening | curing agent is not specifically limited, According to the kind etc. of epoxy resin, it can select suitably.

[Photosensitive prepolymer]
The photosensitive prepolymer is blended in order to impart photocurability and developability to the solder resist composition and to form a solder resist layer having an arbitrary pattern shape on the metal base circuit board. Although the compounding quantity is not specifically limited, It is desirable that it is 15-40 mass% of the whole soldering resist composition from a viewpoint of developability and photocurability. By setting it within this range, a solder resist composition excellent in both developability and photocurability can be obtained.

  Moreover, it is preferable that the photosensitive prepolymer mix | blended with a soldering resist composition contains one or more of an unsaturated double bond, a carboxyl group, and a hydroxyl group in a molecule | numerator, respectively. Thereby, developability and photocurability can be provided. Furthermore, it is more preferable that the photosensitive prepolymer is soluble in an alkaline aqueous solution, thereby improving workability when forming a solder resist layer having a predetermined pattern shape on the metal base circuit board.

[Photosensitive monomer]
The photosensitive monomer is blended in the solder resist composition for the purpose of imparting photocurability and adjusting the viscosity. Although the compounding quantity is not specifically limited, It is desirable that it is 1-5 mass% of the whole soldering resist composition from a viewpoint of the developability and the physical property after hardening. By setting it in this range, the photocurability can be improved without reducing the physical properties (breaking elongation, etc.) of the formed solder resist layer.

  Moreover, it is preferable that the photosensitive monomer mix | blended with the soldering resist composition of this embodiment contains one or more unsaturated double bonds in a molecule | numerator, and thereby can provide photocurability. Examples of such photosensitive monomers include dipentaerythritol hexaacrylate, phthalic acid monohydroxy acrylate, bisphenol FEO-modified diacrylate, 2,2-bis (4- (methacryloxyethoxy) phenyl) propane, and the like.

[Photopolymerization initiator]
The photopolymerization initiator is blended in the photosensitive prepolymer and the photosensitive monomer in the solder resist composition to initiate a photocuring reaction by irradiating light of a specific wavelength such as photosensitive ultraviolet rays. Although the compounding quantity is not specifically limited, From a reactive and storage stability viewpoint, it is desirable that it is 0.5-4 mass% of the whole soldering resist composition. By setting it within this range, a solder resist composition having excellent photoreactivity and good storage stability can be obtained.

  Examples of the photopolymerization initiator blended in the solder resist composition of the present embodiment include 2,2-dimethoxy-1,2-diphenylethane-1-one, 1-hydroxy-cyclohexyl-phenyl-ketone, and 2-hydroxy. 2-methyl-1-phenyl-propan-1-one, 1- [4- (2-hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propan-1-one, 2-hydroxy- 1- {4- [4- (2-hydroxy-2-methyl-propionyl) -benzyl] phenyl} -2-methyl-propan-1-one, 2-methyl-1- (4-methylthiophenyl) -2- Morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone-1, and 2- (dimethylamino)- Alkylphenone photopolymerization initiators such as-[(4-methylphenyl) methyl] -1- [4- (4-morpholinyl) phenyl] -1-butanone, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide And acylphosphine oxide photopolymerization initiators such as bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide, bis (η5-2,4-cyclopentadien-1-yl) -bis (2,6 A titanocene photopolymerization initiator such as -difluoro-3- (1H-pyrrol-1-yl) -phenyl) titanium or the like can be used.

  In addition, to the solder resist composition of the present embodiment, a photosensitizer such as benzoates may be added together with the photopolymerization initiator described above, and for the purpose of suppressing polymerization inhibition by oxygen, A tertiary amine compound or the like can also be added.

[White pigment]
The white pigment is blended for the purpose of improving the reflectance of the solder resist layer to be formed. The blending amount is not particularly limited, but when a white pigment is highly filled and a solder resist layer having a high reflectance is formed, the white pigment content in the solder resist composition is 20 to 80% by volume. It is desirable to do. Thereby, a reflectance can be raised about the soldering resist layer formed, without reducing a physical property (breaking elongation etc.).

  As a white pigment to be blended in the solder resist composition of the present embodiment, it is preferable to use one or more of titanium dioxide, barium sulfate, silicon dioxide, zirconia, magnesium oxide, aluminum oxide and aluminum nitride. . As a result, a solder resist layer having a high reflectance can be formed.

  When titanium dioxide is used as the white pigment, it is preferable to use a rutile structure with less resin degradation due to photocatalytic action, and the surface is coated with aluminum hydroxide or silicon dioxide. Is more preferable.

  In order to avoid thickening, it is desirable to add two or more types of white pigments having different particle sizes to the solder resist composition. In addition, white pigments are treated with silane coupling to improve wettability and adhesion with resin components such as epoxy resins, epoxy resin curing agents, photosensitive prepolymers and photosensitive monomers, and to improve mechanical properties. It is desirable that The treatment method is not particularly limited, and either the direct treatment method or the integral blend method may be selected in consideration of improvement in workability, cost, mechanical properties, and the like.

[Diluent]
A diluent can be appropriately added to the solder resist composition of the present embodiment as necessary. As the diluent, for example, a photopolymerizable monomer or a solvent can be used. Typical examples of the photopolymerizable monomer include acrylates such as 2-ethylhexyl acrylate, 2-hydroxybutyl acrylate, and benzyl acrylate, and methacrylates corresponding thereto.

  Examples of the solvent include alcohols such as ethanol and isopropanol, 2-methoxyethanol, 1-methoxyethanol, 2-ethoxyethanol, 1-ethoxy-2-propanol, 2-butoxyethanol, 2- (2-methoxy). Ethoxy) ethanol, ether alcohols such as 2- (2-ethoxyethoxy) ethanol and 2- (2-butoxyethoxy) ethanol, ketones such as acetone, methyl ether ketone, methyl isobutyl ketone and diisobutyl ketone ketone, toluene and xylene And the like. These diluents may be used alone or in combination of two or more.

  On the other hand, the addition amount of the diluent is desirably 3 to 30% by mass of the entire solder resist composition. When the addition amount of the diluent is less than 3% by mass, the effect of addition cannot be obtained sufficiently. Particularly, in the case of a high-viscosity solder resist composition, when it is applied on an insulating layer or a conductor circuit, it is not filled. Defects may occur. On the other hand, when an amount of diluent exceeding 30% by mass is added, the solvent remains in the solder resist layer after light / thermosetting, which may cause foaming and the like, which may adversely affect mechanical properties.

  As described above in detail, the solder resist composition of the present embodiment has a specific epoxy resin as a main component and has an epoxy resin curing agent having at least one amino group in the molecule and / or at least one in the molecule. Since the epoxy resin hardening | curing agent which has this carboxyl group is used, even if it fills with a white pigment highly, the soldering resist layer excellent in the flexibility can be formed. As a result, it is possible to form a solder resist layer that has high reflectivity and is less likely to cause cracks due to warping or twisting of the substrate in the mounting process.

(Second Embodiment)
Next, a metal base circuit board according to a second embodiment of the present invention will be described. FIG. 1 is a cross-sectional view schematically showing the configuration of the metal base circuit board of the present embodiment. As shown in FIG. 1, the metal base circuit board 10 of the present embodiment has an insulating layer 2 formed on one surface of a metal foil 1, and a conductor circuit 3 is locally provided on the insulating layer 2. ing. Further, the solder resist layer 4 is formed on the surfaces of the insulating layer 2 and the conductor circuit 3 from the composition of the first embodiment described above. An optical semiconductor element package 5 such as an LED is mounted on the metal base circuit board 10 of the present embodiment by solder 6 or the like.

[Metal foil 1]
For example, aluminum, iron, copper, or an alloy thereof, or a clad foil can be used as the metal foil 1, but in consideration of heat dissipation, aluminum, copper, an alloy or alloy thereof, and a clad foil should be used. Is desirable. Moreover, in order to improve the adhesiveness with the insulating layer 2, the metal foil 1 is subjected to sandblasting, etching, various plating treatments, coupling agent treatment, and oxidation treatment on the adhesive surface side with the insulation layer 2 as necessary. Etc. can be subjected to surface treatment.

[Insulating layer 2]
The insulating layer 2 can be formed of, for example, an epoxy resin composition containing an epoxy resin, an epoxy resin curing agent, an inorganic filler, and the like. The epoxy resin used as the main component of the epoxy resin composition which forms the insulating layer 2 is not particularly limited, and a known one can be adopted.

  Specifically, bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, bisphenol S diglycidyl ether, resorcinol diglycidyl ether, hexahydrobisphenol A diglycidyl ether, polypropylene glycol diglycidyl ether, neropentyl glycol diglycidyl ether, phthalate Acid diglycidyl ester, dimer acid diglycidyl ester, triglycidyl isocyanate, tetraglycidyl diaminodiphenylmethane, tetraglycidyl metaxylenediamine, phenol novolac polyglycidyl ether, tetrabromobisphenol A diglycidyl ether, bisphenol hexafluoroacetone glycidyl ether, etc. Examples include resins containing compounds with epoxy groups It is.

  Moreover, it is preferable that the density | concentration of the chlorine ion and sodium ion contained in an epoxy resin composition is 1000 ppm or less in total, and it is more preferable that it is 500 ppm or less. This is because when the concentration of chlorine ions and sodium ions in the epoxy resin composition is high, migration of ionic impurities occurs at high temperature, high humidity, direct current or alternating current voltage, and the electrical insulation tends to decrease. .

  On the other hand, the hardening | curing agent mix | blended with the epoxy resin composition which forms the insulating layer 2 contains the compound which has a 1 type, or 2 or more types of functional group among the hydroxyl group, amino group, and acid anhydride group which react with an epoxy group. Is preferred. Examples of such a curing agent include polyamines, polyphenols, and acid anhydrides.

  The epoxy resin composition forming the insulating layer 2 may contain a curing accelerator together with these epoxy resin curing agents. As a hardening accelerator, an imidazole compound, a tertiary amine compound, and a phosphorus compound are suitable.

  Examples of imidazole compounds include 2-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, and 2-phenyl-4-methyl. Imidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole, 2,3-dihydro-1H-pyrrolo [1,2-a] benzimidazole, 2-phenyl-4,5-dihydroxymethylimidazole 2,4-diamino-6- [2'-methylimidazolyl- (1 ')]-ethyl-s-triazine, 2,4-diamino-6- [2'-undecylimidazolyl- (1')]- Ethyl-s-triazine, 1-cyanoethyl-2-methylimidazole and the like are desirable.

  As the tertiary amine compound, benzyldimethylamine, 2- (dimethylaminomethyl) phenol, 2,4,6, -tris (diaminomethyl) phenol and the like are desirable. As the phosphorus compound, triphenylphosphine, tributylphosphine, tetraphenylphosphonium bromide and the like are desirable.

  As for the addition amount of the hardening accelerator to the epoxy resin composition which forms the insulating layer 2, it is desirable that it is 0.005-3 mass% of the whole epoxy resin composition. When the addition amount of a hardening accelerator exceeds 3 mass%, there exists a possibility that workability | operativity may fall by thickening. Moreover, when the addition amount is less than 0.005% by mass, it is not desirable from the viewpoint of cost and workability because long-time high-temperature heating is required during curing.

  The inorganic filler contained in the epoxy resin composition forming the insulating layer 2 is preferably an electrically insulating and heat conductive material, such as silicon dioxide, alumina, aluminum nitride, silicon nitride, boron nitride. And magnesium oxide.

  In that case, the chlorine and sodium ion concentration in the inorganic filler is preferably 500 ppm or less, and more preferably 100 ppm or less. When the chlorine and sodium ion concentration in the inorganic filler exceeds 500 ppm, the migration of ionic impurities is likely to occur at high temperature, high humidity, direct current or alternating current voltage, and the electrical insulation may tend to decrease. is there.

  Moreover, as for the content rate of the inorganic filler in the insulating layer 2, it is desirable that an inorganic filler is 40-80 volume% with respect to the total volume of the insulating layer 2. FIG. If the content of the inorganic filler is less than 40% by volume, it will be difficult to obtain the necessary thermal conductivity. On the other hand, when the content of the inorganic filler exceeds 80% by volume, the viscosity becomes high and defects are likely to occur during the formation of the insulating layer, which may adversely affect the withstand voltage and adhesion.

  In order to avoid thickening of the epoxy resin composition by the inorganic filler, it is desirable to mix two or more inorganic fillers having different particle diameters. Moreover, in order to improve the wettability and adhesiveness with an epoxy resin and a hardening | curing agent, it is desirable to process an inorganic filler with a silane coupling agent.

  Furthermore, a solvent can be appropriately added to the epoxy resin composition forming the insulating layer 2 in order to adjust the viscosity. The type of the solvent is not particularly limited as long as the epoxy resin and the epoxy resin curing agent being insulated are soluble.

  Furthermore, additives such as a leveling agent, an antifoaming agent and a wetting and dispersing agent are added to the epoxy resin composition forming the insulating layer 2 in order to improve leveling properties, antifoaming properties, and wettability to the base. May be.

[Conductor circuit 3]
The conductor circuit 3 can be formed of, for example, aluminum, iron, copper, gold, silver, nickel, an alloy thereof, or a clad foil. However, since the wettability with the solder is good, the bonding with the solder is particularly preferable. The surface side is preferably made of copper. Moreover, in order to improve the adhesiveness with the insulating layer 2, the conductor circuit 3 is subjected to sandblasting, etching, various plating treatments, coupling agent treatment, and oxidation treatment on the adhesive surface side with the insulation layer 2 as necessary. Etc. can be subjected to surface treatment.

[Solder resist layer 4]
The solder resist layer 4 is formed of the solder resist composition of the first embodiment described above, and has, for example, a tensile elastic modulus at room temperature of 0.1 to 8000 MPa and a fracture elongation of 0.5 to 30%. . Such a solder resist layer 4 is excellent in flexibility, and cracks are hardly generated even if the substrate is warped or twisted in the mounting process.

[Production method]
The metal base circuit board 10 having the above-described configuration can be manufactured by, for example, the following method. First, an epoxy resin composition for forming the insulating layer 2 is applied on the metal foil 1 so as to have a predetermined thickness, and a conductor layer constituting a conductor circuit is formed on the layer made of the epoxy resin composition. Laminate to make a metal base substrate.

  And about this metal base substrate, after masking a predetermined position with an etching resist and etching a conductor layer, the conductor circuit 3 is formed by removing the etching resist. Then, after apply | coating a soldering resist composition on the insulating layer 2 and the conductor circuit 3, it hardens with a heat | fever and an ultraviolet-ray, the soldering resist layer 4 is formed, and it is set as a metal base circuit board.

  As described above in detail, in the metal base circuit board 10 of the present embodiment, the solder resist layer 4 is formed of a solder resist composition containing a specific epoxy resin as a main component and using a specific epoxy resin curing agent. Therefore, even if the white pigment is highly filled, the flexibility is maintained. This realizes a metal base circuit board that is less likely to crack in the solder resist layer even when the board is warped or twisted in the mounting process of an optical semiconductor element such as an LED while increasing the reflectance of the solder resist layer. be able to.

  Hereinafter, the effects of the present invention will be specifically described with reference to Examples and Comparative Examples of the present invention. In the present example, the solder resist compositions of Examples 1 to 9 and Comparative Examples 1 and 2 were prepared by changing the formulation, and the characteristics were evaluated. The composition of each solder resist composition of Examples and Comparative Examples is shown in Table 1 below.

The following materials were used for each solder resist composition shown in Table 1 above.
(Epoxy resin)
A1: Hydrogenated bisphenol A type epoxy resin ("YX8034" manufactured by Mitsubishi Chemical Corporation, epoxy equivalent = 270 g / eq)
A2: Bisphenol F type epoxy resin (“JER4010P” manufactured by Mitsubishi Chemical Corporation, epoxy equivalent = 4400 g / eq)
A3: Epoxy resin whose main chain includes a siloxane skeleton and a bisphenol A skeleton (“Nobiflex 348” manufactured by Nanoresins, epoxy equivalent = 1150 g / eq)
A4: Epoxy resin in which the main chain includes a hexamethylene glycol skeleton, a glycerin skeleton, and a bisphenol A skeleton and an epoxy group is introduced at the terminal (“EXA-4816” manufactured by DIC, epoxy equivalent = 403 g / eq)
A5: Polytetramethylene glycol type epoxy resin ("SR-PTMG" manufactured by Sakamoto Pharmaceutical Co., Ltd., epoxy equivalent = 413 g / eq)
A6: Bisphenol A type epoxy resin (“JER828” manufactured by Mitsubishi Chemical Corporation, epoxy equivalent = 190 g / eq)

(Epoxy resin curing agent)
B1: A curing agent having two amino groups in the molecule (“Jeffamine D-400” manufactured by Mitsui Chemical Fine Co., Ltd.)
B2: a curing agent having two carboxyl groups in the molecule (“HF-08” manufactured by Shin Nippon Rika Co., Ltd.)
B3: a curing agent having one or more hydroxyl groups in the molecule (phenol novolak resin “HF-1M” manufactured by Meiwa Kasei Co., Ltd.)

(Photosensitive prepolymer)
C: Photosensitive prepolymer containing one unsaturated double bond, one carboxyl group and one hydroxyl group in the molecule (“ACA 200M” manufactured by Daicel Cytec Co., Ltd.)

(Photosensitive monomer)
D: Photosensitive monomer containing 6 unsaturated double bonds in the molecule (“Light acrylate DPE-6A” manufactured by Kyoeisha Chemical Co., Ltd.)

(White pigment)
E1: Titanium dioxide (“CR-90” manufactured by Ishihara Sangyo Co., Ltd.)
E2: Barium sulfate (“B-30” manufactured by Sakai Chemical Industry Co., Ltd.)
E3: Silicon dioxide (“A-1” manufactured by Tatsumori)
E4: Zirconia oxide (“EP” manufactured by Daiichi Rare Element Chemical Industries, Ltd.)
E5: Magnesium oxide (“SMO” manufactured by Sakai Chemical Industry Co., Ltd.)
E6: Aluminum oxide ("AO-802" manufactured by Admatechs)
E7: Aluminum nitride (“H grade” manufactured by Tokuyama)

(Photopolymerization initiator)
F: Acylphosphine oxide-based photopolymerization initiator (Ciba Japan “DAROCURE TPO”)

(Diluent)
G: 1-methoxy-2-propanol ("MMPG" manufactured by Daicel Chemical Industries)

  The solder resist compositions of Examples 1 to 9 and Comparative Examples 1 and 2 shown in Table 1 above were evaluated by the method shown below.

<Tension modulus and elongation at break>
Evaluation of the tensile modulus and elongation at break were performed by applying each solder resist composition of Examples and Comparative Examples on a PET (polyethyleneterephthalate) film, curing it with heat and ultraviolet rays, and then peeling the PET film. It carried out using the obtained sample. At that time, the thickness of each sample was set to 100 μm. Moreover, the measurement was performed by the method prescribed | regulated to JISK7161 using Shimadzu autograph AG-5kNX by Shimadzu Corporation.

<Crack generation>
In the evaluation of crack occurrence, the metal base circuit board 10 shown in FIG. 1 was prepared using each solder resist composition of the example and the comparative example, and this was used as a sample for evaluation. And about each metal base circuit board, the bending test was done and the presence or absence of the crack generation was confirmed.

[Production method of metal base circuit board]
An aluminum foil having a thickness of 200 μm was used as the metal foil 1, and an epoxy resin composition for forming the insulating layer 2 was applied thereon so that the thickness after curing was 100 μm. At that time, the epoxy resin composition is bisphenol A type epoxy resin (“EPICLON-840” manufactured by DIC Corporation) and an amine-based curing agent diaminodiphenylmethane (“H84B” manufactured by Nippon Gohsei Co., Ltd.) as a curing agent. Furthermore, crushed coarse particles of silicon oxide having an average particle size of 1.2 μm (“A-1” manufactured by Tatsumori) and crushed coarse particles of silicon oxide having an average particle size of 10 μm (“SQ” manufactured by Hayashi Kasei Co., Ltd.) -10 ") was blended so that the total amount contained in the insulating layer 2 was 50% by volume. The spherical coarse particles and the spherical fine particles were made to have a mass ratio of 6: 4.

  Next, a copper foil having a thickness of 35 μm is laminated on the layer made of the epoxy resin composition, and then heated to thermally cure the epoxy resin composition to form the insulating layer 2 to obtain a metal base substrate. It was. Thereafter, the copper foil was etched by masking a predetermined position of the metal base substrate with an etching resist, and then the etching resist was removed to form the conductor circuit 3. Next, a liquid solder resist composition having the composition shown in Table 1 above was applied on the insulating layer 2 and the conductor circuit 3, and then cured with heat and ultraviolet rays to form the solder resist layer 4. Example 1 To 9 and Comparative Examples 1 and 2 were obtained.

[Bending test]
The bending test was performed using a cylindrical mandrel manufactured by BYK-Gardner with a curvature radius of 0.5 to 20 mm. And by this bending test, the thing which the crack generate | occur | produced in the soldering resist layer 4 was set as x, and the thing which did not generate | occur | produce a crack was set as (circle).

  The above results are summarized in Table 2 below.

  As shown in Table 2 above, the solder resist composition of Comparative Example 1 whose main component is a bisphenol A type epoxy resin having an epoxy equivalent of less than 200 g / eq has a high tensile elastic modulus of 9500 MPa and a fracture elongation of 0.41. %, And cracking occurred in the bending test. The solder resist composition of Comparative Example 2 using a curing agent other than the curing agent having one or more amino groups in the molecule and the curing agent having one or more carboxyl groups in the molecule has a tensile modulus of 8300 MPa. It was high and the elongation at break was as low as 0.45%, and cracks occurred in the bending test.

  In contrast, the solder resist compositions of Examples 1 to 9 had a low tensile elastic modulus of 22.1 to 31.1 MPa and a high value of 11.8 to 17.2%. Furthermore, in the bending test, no crack was generated, and the result was good.

  From the above results, according to the present invention, the flexibility is maintained even when the white pigment is highly charged, and cracks are generated in the solder resist layer 4 even when the bending test is performed at a curvature radius of 0.5 to 20 mm. It has been confirmed that a metal base circuit board is obtained.

  The metal base circuit board of the present invention is less likely to cause cracks due to warping and twisting of the board in the LED mounting process, even if a solder resist layer highly filled with white pigment is formed on the surface of the metal base board on which the LED package is mounted, It is extremely useful industrially as a metal base circuit board for LED.

1 Metal foil 2 Insulating layer 3 Conductor circuit 4 Solder resist layer 5 LED package 6 Solder joint 10 Metal base circuit board

Claims (6)

At least an epoxy resin, an epoxy resin curing agent, a photosensitive prepolymer, a photosensitive monomer, a photopolymerization initiator, and a white pigment,
The epoxy resin is
(3) An epoxy resin in which the main chain includes a siloxane skeleton and a bisphenol A skeleton, the ratio of silicone in the main chain is 30 to 75% by mass, and an epoxy group is introduced at the terminal.
A solder resist composition, wherein the epoxy resin curing agent is a curing agent having one or more amino groups in the molecule and / or a curing agent having one or more carboxyl groups in the molecule.   2. The solder resist composition according to claim 1, wherein the photosensitive prepolymer contains one or more unsaturated double bonds, carboxyl groups, and hydroxyl groups in the molecule.   The solder resist composition according to claim 1 or 2, wherein the photosensitive monomer contains one or more unsaturated double bonds in the molecule. The solder resist composition according to claim 3, wherein the photosensitive monomer contains six of the unsaturated double bonds in the molecule. The white pigment, characterized in that at least one selected titanium dioxide, barium sulfate, silicon dioxide, zirconium oxide, magnesium oxide, from the group consisting of aluminum oxide and aluminum nitride, any of claims 1 to 4 The solder resist composition according to claim 1. Metal foil,
An insulating layer formed on the metal foil;
A conductor circuit locally formed on the surface of the insulating layer;
A solder resist layer formed on the surface of the insulating layer and the conductor circuit,
The metal base circuit board in which the said soldering resist layer is formed with the soldering resist composition of any one of Claims 1-5 .

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