JPS61275834A - Photosensitive resin composition - Google Patents

Abstract

PURPOSE:To form a cover coat high in hardness and prevented from peeling by adding silica powder coated with a silane coupling agent to a photosensitive resin to be used for the heat-resistant protective coat of a printed circuit base. CONSTITUTION:The silica powder, preferably, of 0.5-1,000mum particles diameter, coated with a silane coupling agent is added, preferably, in an amt. of 1-80wt% to a photosensitive resin to be used for the heat-resistant protective cot of a printed circuit base, thus permitting the obtained cover coat to be hardened with exposure of a small amount of energy, made unsubject to peeling, and high in hardness by addition of such a powder.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a photosensitive resin suitable for use in a cover coat layer such as a so-called solder resist, which is formed as a solder mask or an insulating material on a printed wiring board. The present invention relates to a composition.

[Summary of the invention]

The present invention adds silica powder coated with a silane coupling agent to a photosensitive resin, which is a heat-resistant protective coating material for printed wiring boards, to form a cover coat layer with high hardness and no peeling. This is what we are trying to achieve.

[Conventional technology]

Generally, in printed wiring boards, a cover coat layer such as a solder resist is applied to the surface of the printed wiring board to protect and insulate the wiring pattern formed by pattern etching copper foil, and to act as a solder mask during solder dipping. It is formed.

In this cover coat layer, it is necessary to provide a window portion to expose a predetermined portion of the wiring pattern so that the solder adheres only to the connection land portion, for example. A photosensitive resin composition that can be developed by pattern exposure is widely used as a material for the cover coat layer.

However, in the conventionally used photosensitive resin compositions,
The hardness of the resulting coating film and its adhesion to the copper foil or substrate are not sufficient, for example, the thickness of the coating film is 20 μm.
In this case, there is a problem in that when external press processing or the like is performed, cracks occur around the cut portion, and when a tape peel test is performed, the cover coat layer peels off at that portion.

Alternatively, when the hardness of the coating film is evaluated by measuring the pencil hardness, it is about 3H at most, and there is also the problem that scratches occur during the production process or during the transportation process.

Conventionally, attempts have been made to treat the surface of the copper foil with a coupling agent or to use thermal hazing to alleviate the stress on the cover coat layer in order to prevent the above-mentioned cranking and peeling. In this case, productivity decreases due to the complexity of the process, deterioration of the copper foil, and warping of the board due to heat.

Twisting is a problem.

Furthermore, attempts have been made to improve the adhesion of the coating by mixing surface-treated talc into the photosensitive resin.
In this case, the photocurability, that is, the sensitivity to light, decreases, and there is a risk that the strength and chemical resistance of the coating film will decrease.

[Problem that the invention seeks to solve]

In this way, with the photosensitive resin composition conventionally used as a solder resist, cracks and peeling of the coating film are unavoidable, especially when the coverco=1 layer is formed into a thick film, and as a result, the print The quality of the wiring board has deteriorated.

The present invention was proposed in view of the situation in the technical field, and provides a photosensitive resin composition that has high coating hardness and is capable of forming a cover coat layer that does not peel or scratch. The purpose is to provide.

[Means for solving problems]

The inventors of the present invention have conducted intensive research over a long period of time to achieve the above-mentioned objectives, and have found that silica powder whose surface is coated with a silane coupling agent has a great effect on coating film strength. They discovered that the curability of the photosensitive resin does not decrease and have completed the present invention. It is characterized by the addition of

In the present invention, a normal photosensitive resin material can be used as the photosensitive resin as the base resin, and an acrylic oligomer or a methacrylic oligomer is used for -r.

Among these, preferred are phenol noborasocueboxy acrylate or methacrylate, or their halfesters, bisphenol A type epoxy acrylate or methacrylate, alicyclic epoxy acrylate or methacrylate, and the like.

These compounds are components that become a skeleton when the photosensitive resin composition of the present invention is cured, and a diluent monomer is usually added to further adjust the viscosity and physical properties of the formed coating film.

As this diluting monomer, polyfunctional acrylate (or methacrylate), bifunctional acrylate (or methacrylate), monofunctional acrylate (or methacrylate), etc. are used, and depending on the purpose, these may be used alone or in combination of two or more. Ru.

Specifically, oligoester acrylates (for example, manufactured by Toagosei Co., Ltd., M8060.M8030.M7100, M8
100) and trimethylolpropane triacrylate,
Pentaerythritol triacrylate, dipentaerythritol hexaacrylate, tetrahydrofurfuryl acrylate, 1,3-butanediol diacrylate, 1,6-hexanediol diacrylate, diethylene glycol diacrylate, neopentyl glycol diacrylate, polyethylene glycol diacrylate, Examples include hydroxypivalate neopentyl glycol diacrylate, citroxyethyl acrylate, and hydroxyethyl methacrylate.

The proportion of these photosensitive resin components is preferably within the range of 1 to 90 ffi%.

Furthermore, a photopolymerization enhancer may be added to the photosensitive resin component so that it is photoexcited when irradiated with ultraviolet rays or the like and easily initiates a photopolymerization reaction.

The photopolymerization increaser may be any material that is generally used as a polymerization initiator, and the amount added is about 0.1 to 20%.

On the other hand, as the silica powder added to these photosensitive resin components, crystalline silica, cristogalite, fused silica, silica sand, etc. are used, and the particle size thereof is 0.5 to 1.
The thickness is preferably within the range of 000 μm. Further, the amount added is preferably within the range of 1 to 80%.

These silica powders are surface-treated with a silane coupling agent, and examples of the silane coupling agent used include the following compounds.

■Vinyltrichlorosilane CHg=CH3iCII 3 ■Vinyltriethoxysilane CHz=CH3i (OCJs) 3 ■Vinyl-tris-(β-methoxyethoxy)-silane CL=CH5i (OCLCHzOCL) 3 ■γ-methacryloxypropyl monotrimethoxysilane CBr2・CCH3-Coo(CL)zsi(OC
H3) 3■β-(3,4-epoxycyclohexyl)
-Ethyltrimethoxysilane-Trimethoxysilane C, Hz-CHCII□0(CH2) 3si (OC
H3) 3■Vinyltriacetoxysilane CHz=CIISi (OOCCTo) z■γ-Mercaptopropyltrimethoxysilane II S CII□
C112CH2SI (OCH3) 3■γ-Aminopropyltriethoxysilane Nozcozcn. CIl□
Si (OC2H5) 3 [phase] r-(bis(β-hydroxyethyl)]-aminopropyltriethoxysilane (1-10C112CH2) 2N (C11°) ssi(
OC2Hs) ■N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane NthCHz
CHzCHzSi (OCzHs) 3@γ-β-(aminoethyl)aminopropyl-dimethoxysilane NL(CL)JH(C1l.)*Si (OCH43)
2CH3@N=(trimethoxysilylpropyl)-ethylenediamineNHK (CH2) 2Nl((CH2) zsi (
OCH13) 3■N-(dimethoxymethylsilylisobutyl)-ethylenediamine (CBr4) zsi (CI43)C112CH(C
H3) CHJtl (CH2) JHz These silane coupling agents have a part in the molecule that has a high affinity for the photosensitive resin and a part that has a high affinity for the silica powder. The treatment improves the dispersibility of the silica powder into the photosensitive resin.

[Effect]

In this way, by mixing silica powder whose surface has been treated with a silane coupling agent into the photosensitive resin, a cover coat layer that is hard to peel off and has high hardness is formed by being cured by low energy exposure.

The details of the reason are unknown, but the inclusion of silica with a high specific gravity expands the wetted area between the resin and the base material and improves the adhesion, the hardness of silica is superior to talc, etc. , is considered to be highly transparent to ultraviolet rays.

〔Example〕

Hereinafter, specific examples of the present invention will be described, but the present invention is not limited to these examples.

Example.

A solder resist layer was formed on a printed wiring board using a photosensitive resin composition as shown in Table 1.

That is, first, as shown in FIG. 1A, a photosensitive resin composition (3 )
was applied.

Next, for this photosensitive resin composition (3),
As shown in , parallel light is irradiated through a glass mask,
Pattern exposure was performed.

Furthermore, as shown in FIG. 1C, after development and removal of a predetermined portion of the photosensitive resin composition (3), as shown in the first diagram, after-curing was performed using heat or ultraviolet rays.

When a solder resist layer was formed according to the above-described method, the ultraviolet irradiation energy required for curing the photosensitive resin composition (3) was extremely low at 24 mJ/cJ.

In addition, when the coating thickness of the solder resist layer was changed and the amount of peeling after pressing was investigated, as shown by curve a in Figure 2, even when the coating thickness was 60 μm, peeling did not occur most of the time. I found out that there isn't. The amount of peeling was measured as the width of the area where peeling occurred at the periphery of the substrate after pressing.

Furthermore, when the hardness of the obtained solder resist layer was measured as a pencil hardness, it showed an extremely high value of 7H.

Table 1 (Part 1) Table 1 (Part 2) % high % Comparative example.

A solder resist layer was formed using a photosensitive resin composition having the composition shown in Table 2 in the same manner as in the previous example.

In this case, the ultraviolet irradiation energy required to cure the photosensitive resin composition (3) was about 48 mJ/cJ, which is about twice as much energy as in the previous example. When the coating thickness of the resist layer was changed and the amount of peeling after pressing was investigated, as shown by the curve in Figure 2, peeling started to occur when the coating thickness was about 20 μm, and when it reached 60 μm, the amount of peeling was 0. It turns out that it can be as long as 8 mm.

Furthermore, when the hardness of the obtained solder resist layer was measured as a pencil hardness, it was as low as 3H.

Table 2 (Part 1) Table 2 (Part 2) From these Examples and Comparative Examples, it can be seen that mixing silica powder that has been surface-treated with a silane coupling agent is effective for improving hardness, adhesion, etc. it is obvious.

〔Effect of the invention〕

As is clear from the above description, in the present invention,
Since the photosensitive resin is mixed with silica powder that has been surface-treated with a silane coupling agent, the thickness of the coating film can be reduced to 60 μm.
Even if you do the above, peeling will not occur, and
It is possible to significantly improve the hardness of the coating film.

Furthermore, the photosensitive resin composition of the present invention can be cured with about 1/2 of the exposure energy of conventional compositions in the exposure process, making it possible to save irradiation energy and to avoid problems caused by insufficient curing. There is no risk of a decrease in coating film strength or chemical resistance.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing an example of the process of forming a solder resist layer using the photosensitive resin composition of the present invention, and FIG. 1A is a photosensitive resin composition coating process, and FIG. B
1C shows a pattern exposure process, FIG. 1C shows a development process, and the first diagram shows an after-cure process. FIG. 2 is a characteristic diagram showing the amount of peeling of a solder resist layer formed using the photosensitive resin composition of the present invention in comparison with that of a comparative example.

Claims (1)

[Claims] A photosensitive resin composition characterized in that silica powder coated with a silane coupling agent is added to a photosensitive resin that is a heat-resistant protective coating material for printed wiring boards.