KR20060020098A - Uv curable composition - Google Patents

Abstract

The present invention relates to a UV curable resin composition, comprising a UV curable resin, an initiator, a UV-responsive acrylic or vinyl monomer, and an inorganic powder, but a thermal initiator capable of generating radicals effectively by heat generated in an ultraviolet curing process as an initiator. The present invention provides an ultraviolet curable resin composition that can be preferably used as a lower filler in a printed circuit board by increasing the curability by mixing with a photoinitiator to impart adhesion to the lower substrate.

Description

UV curable resin composition

The present invention relates to an ultraviolet curable resin composition, and more particularly, to an ultraviolet curable resin composition suitable for use as an internal filling material in the field of printed circuit boards and packaging processes.

In general, the outermost layer of a printed circuit board protects the solder layer from solder-independent parts during soldering and also coats the copper layer with the copper layer by soldering resists. It is possible to prevent a short circuit problem due to ion-migration. However, in the case of electronic products used in automobiles, the thickness of the copper layer is high, so that it is difficult to coat the copper layer with the copper layer properly by the general solder resist coating method. Resistance is required. In addition, the printed circuit board is soldered at a temperature of 260 ° C or higher during component mounting, and thus various physical properties such as high temperature stability and electrical insulation are required.

Currently, the thermosetting resin composition is used in the art, and the thermosetting resin composition has advantages of excellent adhesion, desired color, and high temperature stability.

However, the thermosetting resin composition for the purpose of the existing lower filling is composed of a two-component type requires sufficient agitation before use, and there is inconvenience in use because the available time after mixing is short within 1 day. In addition, since the thermosetting resin composition uses an organic solvent and the organic solvent used is volatilized in the curing process, there is an environmental problem, and the curing process is longer than the ultraviolet curing method and has a complicated problem in applying an automatic process.

Therefore, development of the ultraviolet curable resin composition which improves the problem of the thermosetting resin composition currently used is needed.

By the way, the general ultraviolet curable resin composition shows a severe shrinkage phenomenon in the curing process compared to the thermosetting resin composition, and deep curing at the thickness of 100㎛ or more is not good. In addition, the urethane-based acrylic resin used to compensate for crack resistance has a problem in thermal stability at the soldering temperature of 260 ~ 280 ℃.

Accordingly, the present inventors further use a peroxide-based compound as a thermal initiator in addition to a photoinitiator in order to maintain a balance between crack resistance and thermal stability and to maintain lower curability even at a thickness of 100 μm or more, and additionally, a urethane-based acrylic as an ultraviolet curable resin. When the resin and the epoxy resin having good thermal stability are mixed, the present invention has been found to improve the balance between crack resistance and thermal stability.

Accordingly, an object of the present invention is to cure the deep core even in the thick film up to 350㎛ and to strengthen the crack resistance to physical or thermal impact, due to improving the inconvenience and environmental problems of the existing thermosetting resin composition Printed circuit boards, especially for electrical components with thick copper layers An ultraviolet curable resin composition suitable for various fillers coated with a lower filler and a thick film of a product.

The ultraviolet curable resin composition of the present invention for achieving the above object includes an ultraviolet curable resin, an initiator, an ultraviolet-responsive monomer and an inorganic powder, wherein the initiator is characterized in that the mixture of a photoinitiator and a thermal initiator.

The present invention will be described in more detail as follows.

(A) UV curable resin

In the ultraviolet curable resin composition of the present invention, the ultraviolet curable resin is a resin capable of reacting with ultraviolet rays by including an acrylic group and a vinyl group at both ends of the chain or side chains of the chain. Such ultraviolet curable resins are typical of epoxy type acrylic resins, ether type acrylic resins, ester type acrylic resins and urethane type acrylic resins.

Epoxy-based acrylic resins can be divided into bisphenol A type, bisphenol F type, phenol novolak type and cresol novolak type according to the starting materials. Of these, bisphenol F type has excellent comparative flexibility and cresol novolak type. The high temperature stability has an advantage. However, epoxy-based acrylic resins generally have severe curing shrinkage, and thick films have a problem in that they are poor in crack resistance against physical impact.

On the other hand, the urethane-based acrylic resin can be subdivided into aliphatic and aromatic based on the structure. Aliphatic urethane-based acrylic resins have the advantages of excellent flexibility, low shrinkage and high elongation during curing. Aromatic urethane-based acrylic resins are less flexible or elongated than aliphatic, but are advantageous for relatively high temperature stability. Disadvantages of the urethane-based acrylic resin is that the stability at the soldering process temperature of 260 ~ 280 ℃ is weak and the adhesion to the printed circuit board is weak compared to the epoxy-based acrylic resin.

The ultraviolet curable resin can be used within the range of 10 to 70% by weight in the total composition, and preferably used within the range of 15 to 35% by weight. If the content of the ultraviolet curable resin is less than 15% by weight, curing shrinkage occurs severely, and adhesion to the printed circuit board is degraded. If the content is more than 35% by weight, the stability at the soldering temperature is deteriorated. Problems may arise.

Epoxy type acrylic resin and urethane type acrylic resin can be used individually or can be mixed, Preferably it is mixed. When mixed, it is preferable to use the urethane-based acrylic resin so that 50 to 80% by weight of the total ultraviolet curable resin content.

When mixed with epoxy-based acrylic resin, if the content of urethane-based acrylic resin is less than 50% by weight of the total UV-curable resin content, the hardness of the cured film is high, so that the resistance to cracking becomes a problem, and the content of urethane-based acrylic resin exceeds 80% by weight. If this happens, the crack resistance is excellent, but the film may be lifted during the soldering process.

The urethane-based acrylic resin that can be used has an average molecular weight of about 5,000 ~ 25,000, and when elongated and cured after mixing with 2-hydroxyethyl acrylate in a weight ratio of 6: 4, the elongation at break is preferably in the range of 150 to 300%. Since the urethane-based acrylic resin is an ultraviolet curable resin and serves as a main chain of the entire cured product, and needs to complement flexibility, it is necessary to maintain a certain molecular weight or more. In general, when the average molecular weight is less than 5,000, there is a problem causing a problem in the soldering process and low elongation, when the average molecular weight is more than 25,000 may be a problem for compatibility with the entire composition. This is because the higher the molecular weight, the worse the compatibility with the UV-responsive monomer which serves as a diluent in the composition. In addition, the elongation of the urethane-based acrylic resin to be used cannot be overlooked because it is associated with resistance to cracking. As a whole, when the elongation at break is less than 150%, it is difficult to compensate for the crack resistance of the cured film, and in the case of urethane-based acrylic resin having an elongation of more than 300%, the film is often lifted during the soldering process. Therefore, the selection and the content of the urethane-based acrylic resin in the ultraviolet curable resin should be determined in elongation, molecular weight and content in consideration of the resistance to cracking of the cured film and the lifting problem of the film in the soldering process.

(B) initiator

The ultraviolet curable resin composition of this invention mixes a thermal initiator with an ordinary photoinitiator as an initiator.                     

Compounds useful as photoinitiators that form radicals by ultraviolet light include 2-methyl-1- [4- (methylthio) phenyl] -2- (4-morpholinyl) -1-propaneone, 2-benzyl-2- (Dimethylamino) -1- [4- (4-morpholinyl) phenyl] -1-butanone, bis (eta 5-2,4-cyclopentadien-1-yl) bis [2,6-difluoro Benzoin alkyl ethers such as rho-3- (1H-pyrrole-1-yl) phenyl] titanium, phosphine oxide phenyl bis (2,4,6-trimethyl benzoyl), benzoin, benzoin methyl ether, 2 Anthraquinones such as ethyl anthraquinone or 1-chloro anthraquinone, thioxanthones such as isopropyl thioxanthone or 2,4-diethyl thioxanthone, benzophenone or 4-benzoyl 4'-methyldiphenyl sulfone There is a benzophenone system such as a feed, and one or two or more thereof may be used in combination. In addition, tertiary amines such as ethyl 4- (dimethylamino) benzoate, 2-ethylhexyl 4- (dimethylamino) benzoate, 2- (dimethylamino) ethyl benzoate and triethanol amine for the photopolymerization rate or sensitizing effect of the photoinitiator. Etc. can be used.

The content of the photoinitiator has appropriate photoactivity against ultraviolet rays when used within the range of 0.1 to 20% by weight, preferably 1 to 10% by weight of the total composition. If the content of the photoinitiator is less than 0.1% by weight, there is a problem that the hardness of the cured product is weak, and if the content of the photoinitiator is greater than 20% by weight, the physical properties of the cured product are lowered.

The use of a thermal initiator in combination with such a photoinitiator is intended to increase core hardenability. As the thermal initiator, a peroxide system may be used. Peroxide-based thermal initiator is a material that forms a radical by heat, it can solve the problem of deep curing that occurs when only the photoinitiator is used. An initiator such as ethyl peroxide or benzyl peroxide may be used as the peroxide initiator, but ethyl peroxide that generates radicals at a lower temperature than the general ultraviolet ray curing group is preferable. A typical UV curing machine uses one of a high pressure mercury lamp, a mercury lamp, and a metal halide lamp, which emits not only ultraviolet light but also a small amount of infrared wavelengths. In this case, the generated infrared wavelength has a temperature of 60 to 70 ° C., and ethyl peroxide may be initiated in this temperature range to compensate for deep sclerosis.

The content of the thermal initiator is 0.01 to 10% by weight, preferably 0.5 to 3% by weight of the total composition. When the content of the thermal initiator is less than 0.01% by weight of the total composition, problems with deep curing occur in coatings having a thickness of 200 μm or more, and when it exceeds 10% by weight, problems with storage stability may occur.

(C) UV-responsive monomer

The ultraviolet curable resin composition of this invention is an ultraviolet reactive monomer reacted by ultraviolet irradiation, and contains an acryl or vinyl monomer. Usable ultraviolet or acrylic monomers of the vinyl type include 2-hydroxy ethyl (meth) acrylate, 2-hydroxy propyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, 2-phenoxyethyl ( Meta) acrylate, glycidyl (meth) acrylate, isobornyl (meth) acrylate, caprolactone (meth) acrylate, ethoxylated (meth) acrylate, propoxylated (meth) acrylate, Ethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, polyethylene glycol di (meth) acrylic Latex, polypropylene glycol di (meth) acrylate, ethoxylated bisphenol A di (meth) acrylate, propoxylated bisphenol A di (meth) acrylate, caprolactone modified yes Pentyl glycol hydroxypivalate ester diacrylate, trimethylolpropane tri (meth) acrylate, ethoxylated trimethylolpropane tri (meth) acrylate, propoxylated trimethylolpropane tri (meth) acrylate, glycerol Reyl tri (meth) acrylate, ethoxylated glyceryl tri (meth) acrylate, propoxylated glyceryl tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, ditrimethylolpropane tetra ( Meta) acrylate, ethoxylated pentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, and the like, and urethane acrylates may be used. .

The content of the UV-responsive monomer is 1 to 50% by weight, preferably 10 to 30% by weight in the total composition. If the content is less than 1% by weight, UV curability is insufficient, the coating film strength is low and the viscosity is not easy to use high, if more than 50% by weight may be a problem in the crack resistance of the coating.

(D) inorganic powder

Inorganic powders usable in the present invention include barium sulfate, titanium dioxide, silica, talc, aluminum oxide, calcium carbonate, titanium barium, zinc oxide, bentonite, and the like. The mixture is mixed with the ultraviolet curable resin sufficiently to be used. Most inorganic powders have excellent thermal stability, electrical insulation and physical properties, so it is advisable to use as much amount as possible without affecting the coating property.

(E) Other

In addition, colorants such as phthalocyanine green, phthalocyanine blue, diazo yellow, insoluble azo pigments, crystal violet, carbon black, and silicone or acrylic antifoaming agents and thixotropic agents such as leveling agents and flow preventing agents can be used.

In order to apply the ultraviolet curable resin composition of the present invention to a printed circuit board, a screen printing method, a spray, a curtain and a roller printing machine may be used, and the most frequently used method is a screen printing method.

Moreover, the titration method for using the composition of this invention for an electric printed circuit board is as follows.

First, the screen printing method is used to fill the space between the circuits and irradiate ultraviolet rays. The amount of ultraviolet irradiation light is suitably 1,000 to 1500 mJ / cm 2. Deep light may be insufficient in light quantity of 1,000 mJ / cm 2 or less, and light quantity of 1,500 mJ / cm 2 or more may lower the hardening property of the composition. In addition, the temperature in the ultraviolet irradiation process is preferably 50 ℃ or more for the proper reaction of the peroxide-based thermal initiator contained in the composition. The surface of the cured composition coated on the upper surface of the copper circuit layer is removed using a suitable polishing apparatus. After removal, the solder resist is coated and cured to match the characteristics of the solder resist. The printed circuit board thus manufactured undergoes a copper surface treatment and then mounts the component through a soldering process.                     

The production method and examples of the present invention are described below. However, the present invention is not limited to these examples.

Example  1 to 6 and Comparative example  One

In the composition shown in Table 1 below, the ultraviolet curable resin (A), the initiator (B), the ultraviolet reactive acrylic or vinyl monomer (C), the inorganic powder (D), and the additives were put in a container, respectively, and the inorganic powder was the ultraviolet curable resin ( A) or it was stirred to fully wet the ultraviolet-ray acrylic or vinyl monomer (C). The stirred composition was dispersed using a three-roll milling device, a bead milling device, or the like. The reason for using the milling apparatus is to maintain a particle size of 15㎛ or less in order to have an even printability in the coating process and to evenly disperse the powder raw material and the liquid raw material. The dispersed composition was used after sufficiently stirring again.

The photo solder resist coating film was obtained through the following processes about the liquid photo solder resist solution thus obtained.

1) Application (printing)

Each prepared ultraviolet curable resin composition was applied with a screen printing machine so as to sufficiently fill the space between the copper circuit layers.

2) hardening

The composition was cured at an amount of light of 1,000 to 1500 mJ / cm 2 using an ultraviolet curing machine.

3) polishing                     

A suitable polishing apparatus was used to remove the cured composition applied to the surface of the copper circuit layer.

The obtained coating film was evaluated for printability, curability, curing shrinkage, crack resistance, adhesion and solder heat resistance, and the results are shown in Table 2 below. Specific evaluation method is as follows.

<Printability>

When the ultraviolet curable resin composition was filled between a copper layer and a copper layer using the screen printing machine, the surface antifoaming and pinhole state were observed. Excellent anti-foaming and no pinhole, "○", good anti-foaming, and pinholes generated "△", bad antifoaming and pinholes were marked with "x".

<Curability>

The ultraviolet curable resin composition was printed on a printed circuit board with a thickness of 350 μm, and after UV curing at a light amount of 1,300 mJ / cm 2, the state between the substrate and the cured composition was observed. If there is adhesion and there is no sticky "○", bad adhesion and some stickiness occurs "△", stickiness occurs largely and when the composition is pushed out when the finger is weakly pushed out and labeled "x".

<Hardening shrinkage>

The ultraviolet curable resin composition was printed on a flat glass plate with a thickness of 350 μm, and after UV curing at a light amount of 1,300 mJ / cm 2, the state between the substrate and the cured composition was observed. If there is no distortion of the cured composition and the surface is flat, "○". If there is a slight distortion or a weak curvature of the cured surface is detected, "△". If the warpage is severely observed and the curvature of the cured surface is largely observed with the naked eye, "×" "And separated.

<Crack resistance>

The ultraviolet curable resin composition was printed between the copper layer and the copper layer formed by the circuit of 350 micrometers in thickness, and ultraviolet curing was performed at the light quantity of 1,300mJ / cm <2>. And after hardening the board | substrate after cooling to room temperature, the board | substrate was about 20 degrees and the grade of the crack of the resin composition was observed. When there was no crack in the cured composition, "○", when a small amount of weak cracks were generated, "△", and when a crack occurred severely, it was classified as "x".

<Adhesiveness>

The ultraviolet curable resin composition was printed on an epoxy substrate with a thickness of 350 μm, and ultraviolet curing was performed at a light amount of 1,300 mJ / cm 2. And the cured composition was cross-cut adhesion test. According to JIS (Japan industrial Standard) D 0202, "○" if any one lattice is not detached from the board, "△" if one to ten lattices are detached, and 10 or more When the grid is detached, it is indicated by "x".

Solder Heat Resistance

The ultraviolet curable resin composition was printed between the copper layer and the copper layer formed by the circuit of 350 micrometers in thickness, and ultraviolet curing was performed at the light quantity of 1,300mJ / cm <2>. After curing, the surface of the copper layer was polished to remove the cured composition from the surface of the copper layer. The cured composition is then only between the copper layer and the copper layer. On the polished substrate, "Chemite 177" manufactured by Cheongsol Chemical Co., Ltd., a low residue solder flux, was applied and immersed in a molten solder bath at 288 ° C for 10 seconds. At this time, each composition was immersed in the solder bath twice in flux application, and the floating of the photo solder resist was observed. "○" is a case where there is no lifting of the hardened composition, "△" is a case where some lifting is appeared, and "x" is a case where lifting is severely shown.

Composition Example Comparative example One 2 3 4 5 6 UV curable resin UX-4101 - - 292.0 175.0 146.0 - 146.0 UX-7101 - - - - - 146.0 - EAM-2160 - 234.0 292.0 117.0 88.0 88.0 88.0 R-190 234.0 - - - - - - UV Responsive Acrylic Monomer DPHA 12.0 12.0 10.0 12.0 12.0 12.0 12.0 SR-368 14.0 14.0 10.0 14.0 14.0 14.0 14.0 HX-620 48.0 48.0 20.0 48.0 48.0 48.0 48.0 TMP (3EO) TA 29.0 29.0 - 29.0 29.0 29.0 29.0 HEMA 54.0 54.0 34.0 54.0 54.0 54.0 54.0 SC-1400 6.0 6.0 6.0 6.0 6.0 6.0 6.0 Photoinitiator IRGACURE-907 9.0 9.0 9.0 9.0 9.0 9.0 15.0 DETX 6.0 6.0 6.0 6.0 6.0 6.0 9.0 EHA 3.0 3.0 3.0 3.0 3.0 3.0 4.0 Ten initiators Ethyl peroxide 2.0 10.0 10.0 10.0 10.0 25.0 - Dispersant Disperbyk-111 7.0 7.0 7.0 7.0 7.0 7.0 7.0 Pigment Green # 9500 0.1 0.1 0.1 0.1 0.1 0.1 0.1 Inorganic fillers B-30 243.0 243.0 171.0 205.0 243.0 243.0 243.0 BF-1 132.0 132.0 44.0 132.0 132.0 132.0 132.0 Crystalite 5X 117.0 117.0 44.0 117.0 117.0 117.0 117.0 EXTRA IT 58.0 58.0 44.0 58.0 58.0 58.0 58.0 Total 990.1 1000.1 1000.1 1000.1 1000.1 1000.1 1000.1

* UX-4101: Urethane-based acrylic resin of Nippon Kayaku of Japan, which has two acrylic groups in the molecule and has a weight average molecular weight of 6,200 to 8,200, and cured after mixing with 2-hydroxyethyl acrylate in a weight ratio of 6: 4. Elongation at break is 220% It is about resin.

* UX-7101: Urethane-based acrylic resin manufactured by Nippon Kayaku of Japan, which has two acrylic groups in its molecule and has a weight average molecular weight of about 8,000 to 10,000. Elongation at break is about 230%.

* EAM-2160: Cresol epoxy-based acrylic resin manufactured by Nippon Kayaku of Japan, which has 4.1 acrylic groups in the molecule and excellent theoretical high temperature resistance with a theoretical weight average molecular weight of 650.

* R-190: Bisphenol A epoxy resin of Nippon Kayaku of Japan, which has two acrylic groups in the molecule and has a weight average molecular weight of about 1950.

* DPHA: dipentaerythritol penta or hexa acrylate from Nippon Kayaku of Japan.

* SR-368: Tris [2-hydroxyethyl] isocyanurate triacrylate from "Satomer" of the United States.

* HX-620: Caprolactone modified neopentyl hydroxypivalate ester diacrylate monomer of Nippon Kayaku, Japan.

* TMP (3EO) TA: Acryl monomer of tri-ethoxylated trimethylolpropane triacrylate structure manufactured by Miwon Corporation

* HEMA: Acrylic monomer of 2-hydroxyethyl methacrylate structure of "Junsei Chemical" of Japan

* SC-1400: The hydroxy ethyl methacrylate phosphate monomer by the "MY Corporation".

* IRGACURE-907: Photoinitiator of 2-methyl-1- [4- (methylthio) phenyl] -2- (4-morpholinyl) -1-propanone structure of "Ciba Geigy Corp.".

* DETX: Photoinitiator of 2, 4- diethyl thioxanthone structure of "LAMBSON Corp.".

* EHA: Photopolymerization sensitizer of 2-ethylhexyl-4- (dimethylamino) benzoate structure from "LAMBSON Corp.".

* Disperbyk-111: Dispersant from "BYK chemie".

* Green # 9500: Green pigment of brominated phthalocyanine green, manufactured by Daehan Swiss Chemical.

* B-30: Barium sulfate manufactured by Japan "sakai chemical".

* BF-1: Barium sulfate manufactured by Japan "sakai chemical".

* Cystalite 5X:: Silica from Japan "Tatsumoril"

* EXTRA IT:: Norwegian Talc Mineral AS "fine particle size talc.

Test Items Example Comparative example  One 2 3 4 5 6 Printability ○ ○ △ ○ ○ ○ ○ Curable △ ○ ○ ○ ○ ○ × Curing shrinkage △ △ ○ ○ ○ ○ △ Crack resistance △ △ ○ ○ ○ ○ △ Adhesion △ △ ○ ○ ○ ○ × Solder heat resistance × ○ △ ○ ○ ○ ×

From the results of Table 2, it can be seen that the ultraviolet curable resin composition (Examples 1 to 6) according to the present invention in particular, the adhesion is improved compared to the comparative example, which can effectively form radicals by the heat generated in the ultraviolet curing process It is considered that the use of a peroxide-based initiator can increase the curability and impart adhesion to the underlying substrate. In addition, it can be seen that the crack resistance is further improved when a urethane-based acrylic resin having a small curing shrinkage property and high elongation is used in combination (Examples 3 to 6).

As described in detail above, the ultraviolet curable resin composition comprising a peroxide-based initiator capable of generating radicals effectively by heat generated in the ultraviolet curing process according to the present invention can increase the curing properties and give adhesion to the lower substrate. In the case where a urethane acrylic resin is mixed with an epoxy-based acrylic resin as an ultraviolet curable resin, crack resistance is improved due to the use of a urethane-based acrylic resin having a small curing shrinkage property and a high elongation, and thus can be preferably used as a lower filler of a printed circuit board.

Claims (7)

In the ultraviolet curable resin composition containing an ultraviolet curable resin, an initiator, an ultraviolet-responsive acrylic or vinyl monomer, and an inorganic powder, UV initiator curable resin composition, characterized in that the initiator is a mixture of a photoinitiator and a thermal initiator. The ultraviolet curable resin composition according to claim 1, wherein the thermal initiator is a peroxide initiator. The ultraviolet curable resin composition according to claim 2, wherein the peroxide initiator is ethyl peroxide. The ultraviolet curable resin composition according to claim 1, wherein the thermal initiator is contained in 0.5 to 3.0% by weight of the total composition. The ultraviolet curable resin composition according to claim 1, wherein the ultraviolet curable resin comprises a urethane-based acrylic resin at 50 to 80% by weight in the total ultraviolet curable resin. The ultraviolet curable resin composition according to claim 5, wherein the urethane-based acrylic resin has a weight average molecular weight in the range of 5,000 to 25,000. The ultraviolet curable resin according to claim 5, wherein the urethane-based acrylic resin has an elongation at the determination point of 150 to 300% when ultraviolet cured after mixing with 2-hydroxyethyl acrylate in a weight ratio of 6: 4. Composition.