Radiation imagery chemistry: process – composition – or product th – Imaged product – Including resin or synthetic polymer
Reexamination Certificate
2001-11-16
2004-07-27
Hamilton, Cynthia (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Imaged product
Including resin or synthetic polymer
C430S311000, C430S280100, C430S282100, C430S281100, C430S283100, C430S284100, C430S285100, C430S287100, C430S288100, C522S085000, C522S121000
Reexamination Certificate
active
06767678
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a photosolder resist composition which can be alkali developed, and also to a solder resist film formed using the composition.
2. Related Art
As a method for applying a solder to predetermined pares of a printed circuit board, generally employed is a method for forming a solder resist pattern on a printed circuit board. A solder resist is for applying a solder to the parts where the pattern is not formed and preventing solder from applying to the parts where the pattern is formed, and at the same time protecting the circuit in the parts where the pattern is formed.
Mounting electronic parts on a printed circuit board has recently been densified and a solder resist is required to be fine. Hence, a method for patterning a solder resist by photolithographic method tends to become a general method and for such a purpose, a liquid photosolder resist has been employed.
As such a photosolder resist composition, Japanese Patent No. 2868190 discloses a modified epoxy resin obtained by adding acrylic acid to a polyfunctional epoxy resin and adding an acid anhydride to a hydroxyl group produced by the reaction is used.
However, such a modified epoxy resin has a problem that the resin is inferior in acid resistance and alkaline resistance since the resin contains an ester bond easy to be hydrolyzed in a molecule. Therefore, there occurs a problem that defects are easily caused in a gold plating process to be carried out thereafter. Further, since brittleness is high, there is another problem of inferior thermal impact resistance. Furthermore, owing to the epoxy-modified resin, a high cost is also a problem.
Japanese Patent Laid-Open No. 191737 (2000) proposes an acrylic resin-based photosolder resist. However, since the acrylic resin-based resist has high hydrophilicity, the resist has a problem that it is inferior in water resistance and electric properties
SUMMARY OF THE INVENTION
The purpose of the invention is to provide a photosolder resist composition excellent in gold plating resistance, thermal impact resistance, and electric insulating properties and to provide a solder resist film formed using the composition.
The photosolder resist composition of the invention contains (A) a resin containing radical polymerization groups and carboxyl groups obtained by adding a cyclic ether group of a cyclic ether group-containing vinyl monomer to a carboxylic group of a radical polymer containing at least isobornyl (meth)acrylate and a carboxyl group-containing vinyl monomer as monomer units; (B) an inorganic filler; and (C) a photocurable mixture of a polyfunctional acrylic monomer (c1), compound containing a cyclic ether group (c2), and a photopolymerization initiator (c3).
The photosolder resist composition of the invention is excellent in acid resistance and alkaline resistance, and consequently excellent in gold plating resistance and at the same time in thermal impact resistance and electric insulating properties since the composition contains the above-described resin (A), inorganic filler (B) and photocurable mixture (C).
The resin (A) is preferable to have double bonds of 0.1×10
−3
to 3.0×10
−3
mol/g. In addition, the content of the carboxyl group (acid value) is preferably 30 to 200 mgKOH/g.
The ratio of the carboxyl group in the resin (A) and the cyclic ether group in the photocurable mixture (C), that is, in the compound (c2) is preferably (1.3/0.7) to (0.7/1.3) by mole.
Further, the solder resist composition of the invention may further contain a coloring pigment.
The content of the inorganic filler (B) is preferably 5 to 75 parts by weight in 100 parts by weight of solid content of the entire photosolder resist composition of the invention.
Further, in the invention, the resin (A) may be neutralized by a base and made water-soluble.
The solder resist film of the invention is obtained by applying the photosolder resist composition of the invention to a substrate, drying at 50 to 90° C., exposing by activation energy beam, removing and developing non-exposed parts with an alkaline washing solution, and heating and curing the photocured parts at 140 to 170° C.
Hereinafter, detailed description will be given respectively for the resin (A), i.e. the first component, the inorganic filler (B), i.e. the second component, and the photocurable mixture (C), i.e the third component, of the photosolder resist composition of the invention.
(A) The Resin Containing a Radical Polymerization Group and a Carboxyl Group
The first component contained in the photosolder resist composition of the invention is a resin containing a radical polymerization group and a carboxyl group, and can be obtained by ring-opening addition of a cyclic ether group of a cyclic ether group-containing vinyl monomer to a carboxylic group of a radical copolymer containing at least isobornyl (meth) acrylate and a carboxyl group-containing vinyl monomer as monomer units. The content of isobornyl (meth)acrylate contained in the resin (A) is preferably 10 to 50% by weight and further preferably 15 to 35% by weight. If less than 10% by weight, the tack property and the thermal resistance may be insufficient and if more than 50% by weight, the brittleness may become too high.
Examples of the carboxyl group-containing vinyl monomer are acrylic acid, methacrylic acid and the like. As an example of the cyclic ether group-containing vinyl monomer, glycidyl methacrylate is typical one and also usable is 3,4-epoxycyclohexyl methacrylate, disclosed in Japanese Patent Laid-Open No. 191737(2000). However, from a viewpoint of an addition reactivity, the material cost and the like, glycidyl methacrylate is especially preferable to be used.
The resin (A) containing a radical polymerization group and a carboxyl group contains at least one radical polymerization group and carboxyl group in one molecule, in which the double bonds are preferably 0.1×10
−3
to 3.0×10
−3
mol/g and further preferably 1.0×10
−3
to 3.0×10
−3
mol/g, and the content of the carboxyl group is preferably 30 to 200 mgKOH/g. If the double bonds are less than 1.0×10
−3
mol/g, the photocurable property of the obtained resist may become insufficient so that there is possibility to result in deterioration of adhesion and thermal resistance at the time of development, and if they are more than to 3.0×10
−3
mol/g, not only the film strength may become brittle but also the resolution property may be deteriorated. Further, if the content of the carboxyl group is less than 30 mgKOH/g, the alkaline development property may be deteriorated, and if it more than 200 mgKOH/g, even the exposed parts may be dissolved. The double bonds are further preferably 1.5×10
−3
to 2.7×10
−3
mol/g and the content of the carboxyl group is further preferably 70 to 120 mgKOH/g.
The number average molecular weight of the resin (A) is preferably 2,000 to 40,000. If it is less than 2,000, the heat resistance of the obtained resist may be insufficient, and if it is more than 40,000, the viscosity may become too high and there sometimes occurs a problem on the workability at the time of producting the composition.
In the invention, a base may be added to the resin (A) to neutralize the carboxyl group so as to use the resin (A) as an aqueous solution. The above-described base is not particularly restricted and usable are well-known neutralization agents for carboxylic group, for example, inorganic substances such as sodium hydroxide, potassium hydroxide, and lithium hydroxide; and amine compounds such as triethylamine and dimethylethanolamine. The amount of the above-described base is properly determined corresponding to the molecular weight of the resin (A) and the content of the carboxyl group and may be proper to make the resin (A) water soluble and, for example, the amount may be set to be sufficient to neutralize 30 to 200% (0.3 to 2 mole) of that of carboxyl group.
(B) Inorganic Filler
The
Fujita Minoru
Namba Osamu
Okajima Keiichi
Yabuuchi Naoya
Hamilton Cynthia
Nippon Paint Co. Ltd.
Townsend and Banta
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