Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Compositions to be polymerized by wave energy wherein said...
Reexamination Certificate
2001-11-13
2003-03-04
Buttner, David J. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Compositions to be polymerized by wave energy wherein said...
C522S100000, C522S102000, C522S103000, C524S406000, C524S437000, C524S784000, C524S786000, C523S442000, C523S458000, C523S459000
Reexamination Certificate
active
06528552
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a resist composition excellent in flame resistance for permanent protective coating of a printed wiring board. More specifically, it relates to a resist composition for permanent protective coating of a printed wiring board which resist composition contains almost no halogen, almost no phosphorus and almost no antimony and is excellent in flame resistance. A printed wiring board obtained by applying the resist composition of the present invention, drying the applied resist composition and curing the dried resist composition is suited mainly for use in a semiconductor plastic package as a high-density and small-sized printed wiring board. The resist composition of the present invention is applied on a printed wiring board surface having copper circuits formed, a solvent is removed from the applied composition by heating as required, and then the resist composition is thermally-cured or photically-cured. Otherwise, the resist composition is selectively photically-cured, not-cured portions are developed and removed, and the resist composition is thermally post-cured. The thus-obtained coating is used as a permanent protective coating for a printed wiring board.
RELATED ARTS OF THE INVENTION
Conventionally, a thermosetting type resist, a photo-setting type resist and a photo-setting/thermosetting type resist used as a permanent protective coating for a printed wiring board are a resin composition having no self-extinguishing properties in itself. The above resin composition is applied to the surface of a laminate containing a bromine compound and the applied resin composition is dried and then cured. When the laminate fires, the bromine compound contained in the laminate burns and decomposes to generate a bromine gas and the bromine gas prevents the permanent protective coating as the external layer from burning. In this case, as a result, the laminate as a whole can attain V-0 (self-extinguishing properties) in the UL 94 standard. However, when the above resin composition having no self-extinguishing properties is applied to a halogen-free, phosphorus-free and antimony-free laminate containing no bromine, dried and then cured, the resultant laminate naturally has an inflammable permanent protective coating as an external layer. In this case, since water and a gas which generate when the laminate burns do not prevent so much the permanent protective coating as an external layer from burning, the laminate as a whole shows inflammability. Further, attempts have been made to impart flame retardancy to a permanent protective coating itself as an external layer. As a method for improving the flame resistance of a laminate as a whole by increasing the flame resistance of a flame-retardant permanent protective coating itself, it is necessarily required to incorporate halogen, phosphorus, antimony, etc., into a coating agent for the above permanent protective coating. However, the coating agent containing halogen, phosphorus, antimony, etc., has problems. Therefore, developments of a coating agent which does not contain the above compounds are expected. For this reason, there has not been produced a printed wiring board comprising a halogen-free, phosphorus-free and antimony-free permanent protective coating having self-extinguishing properties (UL flame resistance V-0).
Further, a resist generally contains a color pigment. In most cases, the color pigment is green. The green pigment is generally phthalocyanine green. The molecule of the phthalocyanine green has chlorine in a large amount. Therefore, the phthalocyanine green has a problem in view of the generation of dioxin.
For imparting flame resistance and for avoiding decreasing the characteristic properties of a resist, a phosphoric compound is added in some cases. However, in order to obtain flame resistance, it is required to add a phosphoric compound in an amount of 1 to 5% by weight. Further, some additives generate a toxic substance such as phosphine during burning. Many of the resists containing a phosphoric compound have problems. Further, antimony is not preferred in view of toxicity.
As a resin for a liquid photo-setting/thermosetting coating composition which is developed with an aqueous solution containing an organic solvent or a dilute alkaline aqueous solution, there are known a resin composition (JP-A-1-139619) prepared by incorporating an aromatic epoxy compound into an unsaturated resin obtained by reacting a carboxyl-group-containing acrylate resin with a glycidyl (meth) acrylate, a resin composition (JP-A-61-243869) prepared by adding a diluent into a compound obtained by reacting a saturated or unsaturated polybasic acid anhydride with a reaction product of a novolak type epoxy resin and an unsaturated carboxylic acid, and a resin composition (JP-A-8-41150) prepared incorporating a cresol novolak type epoxy resin into a resin obtained by reacting an alicyclic epoxy-group-containing (meth)acrylate with some of carboxyl groups of a vinyl copolymer having as essential components a (meth)acrylic acid and a lactone-modified hydroxyl (meth)acrylate.
However, a resist containing the above resin composition is not a resist which itself has self-extinguishing properties (flame resistance V-0) so that imparting flame resistance has been required. In recent years, a printed wiring board is becoming denser and denser. An external-layer permanent protective coating on a high-density printed wiring board has insufficient heat resistance and anti-migration properties. Therefore, conventional resists have problems from the viewpoint of reliability also.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a resist composition for a permanent protective coating of a printed wiring board which resist composition itself has self-extinguishing properties and is excellent in flame resistance.
It is another object of the present invention to provide a halogen-free, phosphorus-free and antimony-free resist composition for a permanent protective coating of a printed wiring board which resist composition has self-extinguishing properties and is excellent in flame resistance.
It is further another object of the present invention to provide a resist composition for a permanent protective coating of a printed wiring board which resist composition is excellent in reliability such as anti-migration properties.
According to the present invention, there is provided a resist composition for permanent protective coating of a printed wiring board, which resist composition is excellent in flame resistance and is obtained by incorporating as essential components a flame retardant containing 100 to 140 parts by weight of (a) aluminum hydroxide, 0.1 to 15 parts by weight of (b) amolybdenum compound and 0.1 to 10 parts by weight of (c) a zinc stannate type compound into 100 parts by weight of a resin.
According to the present invention, further, there is provided a resist composition according to above, wherein the resin is at least one selected from the group consisting of a thermosetting resin, a photo-setting/thermosetting resin and a photo-setting resin.
According to the present invention, further, there is provided a resist composition according to above, wherein the photo-setting/thermosetting resin is a resin containing 5 to 35% by weight of (d) an epoxy resin, 20 to 90% by weight of (e) an unsaturated-group-containing polycarboxylic acid resin, 1 to 30% by weight of (f) ethylenic unsaturated monomer and 0.1 to 20% by weight of (g) a photopolymerization initiator as essential components.
According to the present invention, further, there is provided a resist composition according to above, wherein the unsaturated-group-containing polycarboxylic acid resin is a resin having an acid value of 40 to 200 mgKOH/g and obtained by reacting a reaction product of 100 parts by weight of epoxy acrylate and 5 to 40 parts by weight of a polyfunctional cyanate ester compound, with 10 to 90 parts by weight of a polybasic acid anhydride.
DETAILED EXPLANATION OF THE INVENTION
The resis
Harada Toru
Ikeguchi Nobuyuki
Ishii Kenji
Omori Takabumi
Buttner David J.
Mitsubishi Gas Chemical Company Inc.
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