JPH03148657A - Alkaline developable photosetting type resin composition for solder mask - Google Patents

Abstract

PURPOSE:To improve the storage stability, alkali developability and definition of the compsn. by incorporating a specific alkali-soluble resin into the compsn. CONSTITUTION:This compsn. is formed by incorporating the alkali-soluble epoxy resin (A) having a carboxyl group and/or hydroxyl group into the compsn. The resin A is produced by a method of adding an acid anhydride (e.g.: maleic anhydride) to a desired epoxy resin and half-esterifying the same. A photodecomposition type cation polymn. initiator is preferably incorporated in addition to the resin A into the compsn. Further, an alkali-insoluble resin (e.g.: epoxy resin) is preferably incorporated into the compsn.

Description

[Detailed description of the invention]

∪Industrial Application Fields] The present invention provides an alkali-developable photocurable resin composition for a single-wave solder mask that has excellent stability as an ink and has extremely good electrical properties as well as resolution and durability. Regarding. [Prior Art] In the production of printed wiring boards, various resin compositions for solder masks have been used depending on the purpose of the wiring board. For example, in consumer wiring boards, ultraviolet curable resin compositions mainly composed of acrylate resins and thermosetting resin compositions mainly composed of epoxy/melamine resins are mainstream, and these are applied by screen printing. Then, a solder mask is formed by patterning. On the other hand, industrial wiring boards often use thermosetting resin compositions that combine epoxy resin with imidazole or amine-based curing agents, and this is applied by screen printing to form patterns. By doing so, a solder mask is formed. However, solder masks made from these resin compositions are
Since it is formed by a screen printing method, there is a limit to its resolution, and it is no longer possible to keep up with the fine patterns required for higher density printed wiring boards and surface mounting. In addition, some industrial wiring boards use solder masks made by laminating films and forming patterns using a photographic method. However, although this kind of solder mask has excellent resolution because the pattern is formed using a photographic method, it has poor ability to follow the unevenness of the copper foil etching area, so fine patterns may cause poor adhesion or poor soldering. It becomes easier to get angry. As a solution to these drawbacks, there is a photo-developable resin composition for coated solder masks that has excellent resolution and followability to etched areas of copper foil. This is called a liquid photoresist, and it has come to be used in the field of high-density wiring. Among these liquid photoresists, the non-contact exposure type is preferred in terms of equipment cost and resolution.
The use of contact exposure type and alkali development type is increasing rather than solvent development type from the viewpoint of cost and safety. The liquid photoresist is made by adding an ultraviolet sensitizer and imidazole to crosslink the epoxy groups to a modified epoxy resin by introducing an unsaturated group capable of radical polymerization, and making the resin into a liquid state. This is what I did. Liquid photoresists are applied to the substrate surface, then irradiated with ultraviolet rays through a patterned film to radically polymerize and crosslink the double bonds, and then the non-irradiated areas are dissolved and removed to form a pattern. , which exhibits superior resolution compared to screen printing methods.

[Issues to be solved by the invention 1i1 However, even in contact exposure/alkaline development type liquid photoresists, the reaction rate between epoxy groups and imidazole etc. at room temperature is high and it is difficult to prepare them in advance. All commercially available products are of the two-wave type.The viscosity after mixing the two liquids decreases and then increases, making viscosity control during coating work complicated.The appropriate range of solvent volatilization temperature and time after coating is narrow. There are problems such as sticking to the film due to poor drying and poor development due to overdrying, which requires strict control of drying conditions, and to improve this point, it is natural to use a curing agent with a slow reaction rate. However, post-curing requires high temperatures and long periods of time, resulting in an interlayer. Furthermore, when double bonds are radically polymerized and hardened,
Because large distortions remain in the coating film due to the volumetric shrinkage at that time, the adhesion to the substrate is still not satisfactory. [Means for Solving the Problems] In order to solve the above problems, the present inventors have conducted intensive research focusing on epoxy resin, which has excellent electrical properties and heat resistance, and is widely used as an electrical insulating material. As a result, by introducing a carboxyl group into the epoxy resin and crosslinking and curing it using a reaction mechanism different from that of conventional liquid photoresists, that is, cationic polymerization of the epoxy group, it has improved storage stability and stability against thermal history during the annealing process. The present inventors have discovered that it is possible to provide a resin composition for a solder mask that can solve all of the problems of conventional liquid photoresists, such as properties, and have completed the present invention. That is, the present invention relates to an alkali-developable photocurable resin composition for a solder mask containing an alkali-soluble epoxy resin having a carboxyl group or a carboxyl group and a hydroxyl group. 1 Example] An alkali-soluble epoxy resin is used in the present invention. A substance that dissolves when heated. The alkali-soluble epoxy resin has a carboxyl group, but its acid value is 40 to 140, more preferably 50 to 1.
Preferably it is 10. If the acid value is less than 40, the solubility in alkali tends to decrease, and if it exceeds 140, the water resistance and alkali resistance of the cured coating film will decrease. In addition, in the alkali-soluble epoxy resin, a hydroxyl group may be present together with a carboxyl group in order to improve solubility, and in that case, the acid value is 50-11.
A range of 0 is preferred. The method for producing the alkali-soluble epoxy resin, that is, the method for introducing carboxyl groups into the epoxy resin in order to make the epoxy resin soluble in alkali, is not particularly limited. For example, (a) adding an acid anhydride to the epoxy resin. ,
Methods include (1) graft polymerization of acrylic acid to an epoxy resin, (3) adding a polybasic acid to the epoxy group of a polyfunctional epoxy resin, and the like by ring-opening an acid anhydride to half-esterify it. In the method (a) of adding an acid anhydride to an epoxy resin, the reaction can be easily carried out by simply adding the acid anhydride to the epoxy resin and heating, and a carboxyl group can be introduced into the epoxy resin. The epoxy resin is not particularly limited, and specific examples thereof include epoxy resins having a hydroxyl group in the molecule, such as bisphenol A type, bisphenol F type, brominated bisphenol A type, and hydrogenated bisphenol A type. . The acid anhydride is not particularly limited, and specific examples thereof include maleic anhydride, succinic anhydride, itaconic anhydride, phthalic anhydride, hexahydrophthalic anhydride, methylnadic anhydride, and chlorendic anhydride. , het acid anhydride, etc. The ratio of the epoxy resin containing a hydroxyl group to the acid anhydride is 0.2 to 0 per mole of the hydroxyl group from the viewpoint of solubility in alkali, reaction rate, and reduction of unreacted substances. .9 mol, even 0.3~
0.8 mol is preferred. Although the ring-opening rate varies depending on the type of acid anhydride and the molar ratio of hydroxyl group to acid anhydride, the reaction is usually completed in 30 minutes to 2 hours when heated to 80 to 180°C. In addition, since the ring-opening reaction is an exothermic reaction, in order to control the reaction rate, it is recommended to heat it in an organic solvent that has no reactivity with epoxy groups and does not participate in the ring-opening reaction, esterification reaction, or transesterification reaction. . As such organic solvents, aromatic hydrocarbons, alicyclic hydrocarbons, and ketones are preferable, and alcohols and esters are not preferable. In the method (c) of adding a polybasic acid to a polyfunctional epoxy resin, the reaction can be carried out by heating at 80 to 180 ° C. in the same manner as in the case of ring-opening addition of acid anhydrides. Carboxyl groups can be introduced into epoxy resins. The polyfunctional epoxy resin is not particularly limited, and specific examples thereof include epoxy resins such as cresol tuborafuku type, phenol novolac type, and polybutadiene epoxide. Further, the polybasic acid is not particularly limited, and specific examples thereof include succinic acid, maleic acid, itaconic acid, oxalic acid, orthophthalic acid, isophthalic acid, and terephthalic acid. Among these, polybasic acids with large steric hindrance between carboxyl groups, such as orthophthalic acid, are preferred from the viewpoint of controlling the reaction rate and stability of the addition-produced resin. One type of alkali-soluble epoxy resin may be used,
Two or more types may be used in combination. The alkali-soluble epoxy resin is used in an amount of usually 40% (wt%) or more, preferably 50% or more of the resin solid content in the composition of the present invention. The ratio is 4
If it is less than 0%, the alkali solubility tends to be low. In addition to an alkali-soluble epoxy resin, the resin composition for a solder mask of the present invention includes an alkali-insoluble epoxy resin in order to improve the ribboning reaction rate, the softening temperature of the cured resin, the crosslinking density, etc. A resin can be blended to form a binder. Furthermore, it is expected that the alkali developability of the solder mask will decrease due to the addition of the alkali-insoluble resin.
Acid value of alkali-soluble epoxy resin, parent wood group content,
By selecting the softening temperature, etc., it is possible to prevent the near-alkali developability from being substantially inhibited. Specific examples of alkali-insoluble resins include all alkali-insoluble St epoxy resins, as well as polyester polyols, polyether polyols,
Examples include polyols such as alicyclic polyols and polybutadiene polyols, acrylates such as trimethylolpropane acrylate and pentaerydrift acrylate, and vinyl ethers. Among these, epoxy resins and polyols that react together with the epoxy resin during cationic polymerization are particularly preferred from the viewpoint of reaction rate, crosslinking density, and the like. Further, the blending ratio of the alkali-insoluble resin is not particularly limited and can be arbitrarily selected depending on the required physical properties, but is usually 5D% or less in the resin solid content. A photodegradable cationic polymerization initiator is blended into the resin composition for a solder mask of the present invention. Since the composition of the present invention is cured by cationic polymerization of epoxy groups, the shrinkage rate due to the curing reaction is smaller than that caused by conventional radical polymerization, and the strain remaining in the coating film is small, resulting in improved adhesion. A good solder mask is formed. The initiator is not particularly limited, and specific examples include:
Examples include PFs, sulfonium salts of SbFs(ell)e, and iodonium salts. The blending ratio of the photodegradable cationic polymerization initiator is preferably 1 to 8%, more preferably 2 to 7%, based on the resin solid content. When the ratio exceeds 8%, the curing of the coating film surface progresses rapidly, which tends to delay internal curing and reduce resolution, while when it is less than 1%, the curing speed decreases,
Curing tends to be insufficient. Furthermore, the resin composition for a solder mask of the present invention may contain a pigment for coloring, an extender pigment for controlling workability during application, and improving the physical properties of a cured film. As the pigment for coloring, both organic pigments and inorganic pigments can be used, but those having excellent chemical resistance, heat resistance, and high transparency are preferred. Specific examples of the colored pigments include organic pigments such as phthalocyanine green, phthalocyanine blue, and quinacridone left, as well as inorganic pigments such as transparent iron oxide. The blending ratio of the coloring pigment is usually 0.2 to 2.0% of the solid content.
5%, more preferably 0.5 to 1.5%. If the proportion is less than 0.2%, the coloring power is insufficient and it tends to be difficult to identify when applying the solder mask, and if it exceeds 2.5%, the transmission of ultraviolet rays is inhibited and the inside of the coating film is not sufficiently cured. Tend. Specific examples of the extender pigment include those having chemical resistance and a particle size of ◎, 1 to 20. Examples include barium sulfate, talc, silica, and kaolin clay. The blending ratio of the extender pigment is usually 70% or less based on the solid content, and preferably 10 to 1%. When the ratio exceeds 70%, the ultraviolet transmittance tends to decrease. The resin composition for a solder mask of the present invention may further contain a viscosity control agent, a surface conditioner, an antifoaming agent, etc. as appropriate within a range that does not impair the object of the present invention. The method for preparing the resin composition for a solder mask of the present invention is not particularly limited, and includes, for example, a solution of the alkali-soluble epoxy resin in the following solvent, a photodegradable cationic polymerization initiator, and an alkali-insoluble type. It can be prepared by adding a resin, pigment, etc. and dispersing it by a normal method such as a roll mill. Examples of the solvent used include ketones, esters, alcohols, glycol ethers, and aromatic hydrocarbons. The amount of the solvent to be used may be appropriately adjusted depending on the viscosity, solid content, etc. of the composition, but is usually 10 to 50% in the composition of the present invention. The composition of the present invention prepared in this way has a long pot life of δ to lh months at 20° C. and has excellent storage stability. Next, an example of a method for forming a solder mask using the resin composition of the present invention will be explained. First, the composition of the present invention is applied onto a substrate by a conventional method, and then dried to a thickness of 15 to 40 mm. Forms a coating film of some degree. The drying conditions do not need to be particularly strictly controlled, and may be, for example, in a hot air circulation oven at 70 to 100°C for 20 to 60 minutes. The solder mask obtained by the present invention exhibits excellent adhesion to any substrate, including but not limited to, glass epoxy substrates, paper phenol substrates, ceramic substrates, polyimide substrates, etc. Next, a negative film is applied. 250~400 after applying
Irradiate with nanometer ultraviolet light. The dried coating film of the composition of the present invention has a high softening temperature of about 50"C or more, so it does not stick to the negative film. Next, a 1% aqueous solution of sodium carbonate and a 1% aqueous dimethylethanolamine solution were prepared. The unexposed areas are removed from the container by immersing it for 1 to 3 minutes at 20 to 50°C using a developing solution such as one in which 0.5 to 3.0% of glycol ether or the like is added to these alkaline aqueous solutions. You can move around in a clear pattern.
By post-curing for a few minutes, a solder mask with excellent adhesion to the substrate, electrical properties, physical properties, and chemical properties, and which can maintain its performance for a long period of time, can be obtained. Next, the present invention will be explained in more detail based on examples, but the present invention is not limited to these examples. Example 1 In a reactor equipped with a stirrer and a reflux device, Epotote Y
DB-500 (epoxy resin manufactured by Tobu Kasei ■) 284g
, 100 g of cyclohexanone and 100 g of xylene were added, heated and dissolved to form a homogeneous solution, and 36 g of maleic anhydride (1st grade reagent) was added to 150-IG.
Heated for 40 minutes at Oc. After cooling, 100 g of cellosolve acetate was added to obtain a solution with a solid content of 50%. The resin acid value was 85.1. Next, 100 g of the resin liquid, 30 g of barium sulfate powder (average particle size 1 sub, the same applies hereinafter), talc (average particle size 5a +
) and 0.5 g of phthalocyanine green were dispersed in a roll mill, and then Adeka Buttomer SP-150 (manufactured by Asahi Denka Kogyo ■) was added as a photodegradable cationic polymerization initiator.
2 g was added to prepare a resin composition for a solder mask. The following evaluation tests were conducted using the obtained composition. The results are shown in Table 1. (Storage Stability) The obtained composition is stored in a thermostat at 40C, and evaluated for the period until the viscosity increases to twice that before storage. (Alkali developability) The resulting composition has a dry film thickness of 15. After drying at 80° C. for 30 minutes, a negative film was adhered and 500 sJ of ultraviolet rays was irradiated using a high-pressure mercury lamp of 80 W/cIl. Next, remove the negative film and
After 2 minutes of immersion in 1% sodium carbonate aqueous solution of C.
Wash with warm water at 50°C, develop, and observe the state of elution in the non-exposed areas. A case where no elution is observed in the exposed area and elution is observed in the unexposed area is considered good. (Resolution) After alkali development, the presence or absence of elution of the pattern in the exposed area and the accuracy when compared with a negative film pattern (width of the exposed area: 150 mm, width of the non-exposed area: 600 aa) are observed. The width of the undissolved part (exposed part) is 200. It is considered good if it does not exceed. (Adhesion) The composition obtained on the cleaned surface of the copper foil of the glass epoxy substrate was coated to a film thickness of 15. 3 at 110℃.
After drying for 0 minutes, ultraviolet rays of t,ooo■'' are irradiated using a high-pressure mercury lamp manufactured by IIOW. Next 120℃
Heat for 30 minutes to harden. Using the test piece thus obtained, the adhesion is examined according to JIS K 5400 Paint General Test Method 6.15 Substrate Mouth Test, and evaluated as the number of spots remaining without peeling/100. (Hardness) Evaluation is performed in accordance with JIS K 5400 6.14 pencil scratch test using test pieces prepared in the same manner as those used for adhesion evaluation. (Acid resistance) A test piece prepared in the same manner as that used for adhesion evaluation is immersed in 10% sulfuric acid at 20°C for 2 hours, and then observed for abnormalities such as blistering, peeling, cracking, discoloration, and softening. . (Alkali resistance) A test piece prepared in the same manner as that used for adhesion evaluation was immersed in a 5% aqueous sodium hydroxide solution at 20°C for 2 hours.
Observe for any abnormalities such as blistering, peeling, cracking, discoloration, or softening. (Trichlorethylene resistance) A test piece prepared in the same manner as that used for adhesion evaluation is immersed in trichlorethylene at 20°C for 2 hours, and then observed for abnormalities such as blistering, peeling, cracking, discoloration, and softening. (Solder heat resistance) A test piece prepared in the same manner as that used for adhesion evaluation was placed in a solder bath heated to 280°C! After dipping for 5 seconds, observe the sample and pass if there is no blistering, peeling, cracking, discoloration, or softening. (Insulation resistance) Measure with the pattern of IPCSN-140Test coupon B (IPC is The Institute
Fore Interconnecting and Packaging Electronic Circuits (The
Instrument for Interconn
ectingand Packaglng Elect
ronic Clreults). (Insulation resistance after moisture test (■)) Evaluated by conducting IPC8M-840 Todoroki class 3 cycle test. (Insulation resistance after moisture test (■)) Evaluated according to IPC3M-1140 Todoroki Class 2. (Breakdown voltage) Evaluated according to IPC3M-840A. (Thermal shock resistance) Evaluated according to IPC5M-840A. (Permittivity) Evaluated according to JIS Z 6911. (Dielectric loss tangent) Evaluated according to JIS Z 3197. Example 2 Epototo VDC in a reactor equipped with a stirrer and a refluxer
M-702 (epoxy resin manufactured by Tobu Kasei ■) 225,
Methyl ethyl ketone (long) and 100 g of toluene were put therein, and after heating and dissolving, 45 g of orthophthalic acid (1st grade reagent) was added and heated at ~85°C for 6 hours. After cooling, add 80 g of cyclohexanone and 2 g of isopropyl alcohol.
0 g was added to make a solution with a solid content of 50%. The resin acid value was 47.2. Next, 30 g of barium sulfate powder, 5 g of talc, and 0.5 g of phthalocyanine green were dispersed in a mixture of 40 g of the resin liquid and 1 g of the resin liquid of Example 1 using a roll mill. A resin composition for a solder mask was prepared by adding 1.2 g of SP-140 (manufactured by Asahi Denka Kogyo ■). Each evaluation test was conducted in the same manner as in Example 1 using the obtained composition. The results are shown in Table 1. Example 3 Epicoat to
ot (epoxy tree N manufactured by Shell Kagaku ■) 262.5g
, 100g of cyclohexanone and xylene! 00g
After heating and dissolving, add succinic anhydride (1st grade reagent).
After cooling, 80 g of cyclohexanone and 2 [1 g of isopropyl alcohol] were added to make a solution with a solid content of 50%. The resin acid value was 66.4. Next, add Evototo YDCN 704 to 70g of this resin liquid.
(manufactured by Tobu Kasei ■) 15g and cyclohexanone 15g
After adding and dissolving 25 g of silica powder (average particle size 5 #II+), 5 g of talc, and 0.5 g of phthalocyanine green using a roll mill, Adeka Butomer sp-tso was added as a photodegradable cationic polymerization initiator.
A resin composition for a solder mask was prepared by adding 2 g of the following. Each evaluation test was conducted in the same manner as in Example 1 using the obtained composition. The results are shown in Table 1. Example 4 Araldite 6 was added to a reactor equipped with a stirrer and a reflux device.
084 (Epoxy resin manufactured by Ciba Geigy) 252
g and 200 g of cyclohexanone were added, heated and dissolved, and then 48 g of itaconic anhydride (1st grade reagent) was added.
Heated at 155-160°C for 40 minutes. After cooling, 80 g of cyclohexanone and 20 g of methanol were added to make a solution with a solid content of 50%. The resin acid value was 87.2. Next, add Epote to 65g of this resin liquid) VDCI-70
13g of 4, 4.5g of Ebiko) 1127 (epoxy resin manufactured by Shell Chemical Co., Ltd.) and Schiff a hexanone IT-
Add 5g of silica powder to make a homogeneous solution, add 25g of silica powder
g1 Talc lOg and Phthalocyanine Green 0.5
g was dispersed in a roll mill, and then 1.2 g of Adeka Optomer SP-170 (manufactured by Asahi Denka Kogyo ■) was added as a photodegradable cationic polymerization initiator to prepare a solder mask resin composition. Each evaluation test was conducted in the same manner as in Example 1 using the obtained composition. The results are shown in Table 1. Example 5 65 g of resin liquid of Example 4, Evototo YDCN-704
To a homogeneous solution obtained by mixing 10 g of Desmofene 800 (polyester resin manufactured by Sumitomo Bayer Urethane ■) and 17.5 g of butyl acetate, was added 10 g of barium sulfate powder with an average particle size of 10.5 g. A resin composition for a solder mask was prepared by dispersing 15 g of kaolin clay (Cat) and 5 g of mica powder with an average particle size of 5jIm using a roll mill, and adding thereto 2 g of ADEKA BUTOMER SP-150 as a photodegradable cationic polymerization initiator. Each evaluation test was conducted in the same manner as in Example 1 using the obtained composition. The results are shown in Table 1. Example 5 30 g of resin liquid of Example 2, 40 g of resin liquid of Example 4
10 g of Epicoat 1001 and 5 g of trimethylolpropane acrylate were mixed to make a homogeneous solution, and 25 g of silica powder, 10 g of talcum powder, and 0.5 g of phthalocyanine blue were dispersed using a roll mill, and Adeka Optoma-SP was added as a photodegradable cationic polymerization initiator. -17
A resin composition for a solder mask was prepared by adding 1.5 g of 0. Each evaluation test was conducted in the same manner as in Example 1 using the obtained composition. The results are shown in Table 1. Comparative Example 1 30g of Ebiko) fool, Epotote VDCM
20g of -704, 25g of cyclohexanone, 10g of xylene were mixed to make a homogeneous solution, and 30g of barium sulfate powder, 5g of talcum powder, and 0.5g of phthalocyanine blue were dispersed in a roll mill, and then the photodegradable cationic polymerization initiator As Adeka Optomer SP-1502
, 0g was added to prepare a resin composition for a solder mask. Each evaluation test was conducted in the same manner as in Example 1 using the obtained composition. The results are shown in Table 1.

【Effect of the invention】

The alkali-developable solder mask resin composition of the present invention contains an epoxy resin into which a carboxyl group has been introduced, and therefore has excellent alkali-developability. In addition, it has excellent thermal stability and little increase in viscosity during storage, making it easy to control during application. In addition, the curing reaction in unexposed areas may progress due to temperature rise during exposure or left unused until development ((), and defects due to undeveloped areas may occur). Because it is crosslinked by cationic polymerization, it shrinks less during curing than radical polymerization types, and it adheres to substrates very quickly, and has sufficient adhesion even with thin patterns of 100 am or less. Needless to say, it fully retains the characteristics of epoxy resins, such as electrical properties, heat resistance, and chemical resistance.

Claims (1)

[Scope of Claims] 1. An alkali-developable photocurable resin composition for a solder mask comprising an alkali-soluble epoxy resin having a carboxyl group or a carboxyl group and a hydroxyl group. 2. An alkali-developable photocurable resin composition for a solder mask, comprising one or more of the alkali-soluble epoxy resins according to claim 1 and a photodegradable cationic polymerization initiator. 3. An alkaline-developable photocurable solder mask comprising one or more of the alkali-soluble epoxy resins according to claim 1, an alkali-insoluble resin, and a photodegradable cationic polymerization initiator. mold resin composition. 4. The resin composition according to claim 2 or 3, containing a pigment.