Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Radiation sensitive composition or product or process of making
Reexamination Certificate
2002-07-11
2004-04-27
Hamilton, Cynthia (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Radiation sensitive composition or product or process of making
C522S100000, C522S103000, C430S311000
Reexamination Certificate
active
06727042
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a photosensitive resin composition which is used as a solder resist in printed circuit boards, can be satisfactorily developed in a dilute basic aqueous solution and can yield a cured film that is excellent in flexibility, water resistance, adhesion, solder heat resistance, electroless gold plating resistance, pressure cooker test (PCT) resistance and other properties.
BACKGROUND ART
To pattern resists on printed circuit boards, screen printing has been conventionally used in many cases. However, a photosensitive resin that can be developed in a dilute basic solution as described in Japanese Examined Patent Application Publication No. 1-54390 is now used to improve productivity. This photosensitive resin is a novolak epoxy (meth)acrylate that has a carboxyl group in a side chain and is obtained by allowing acrylic acid as an unsaturated monobasic acid to react with a novolak epoxy resin and allowing a saturated or unsaturated polybasic acid anhydride to react with the resulting hydroxyl group.
With increasing performances of electronic equipment, further downsized semiconductor packages have been launched in mass production. For example, ball grid arrays (BGAs), chip size packages (CSPS) and other semiconductor packages are now commercially available.
These BGAs, CSPs and other parts are packed by heating a whole work with infrared ray irradiation and reflowing solder to fix the parts. In this procedure, conventional solder resist films as described in Japanese Examined Patent Application Publication No. 1-54390 may cause defects such as cracking due to heat shock. Demands are therefore made on resist films that have improved impact resistance, adhesion, solder heat resistance, electroless gold plating resistance, PCT resistance and other properties.
Japanese Unexamined Patent Application Publication No. 6-324490 discloses a photosensitive resin which is obtained by allowing a novolak epoxy resin to react with dimethylolpropionic acid having two or more hydroxyl groups per molecule and acrylic acid as an unsaturated monobasic acid, and allowing the resulting product to react with a saturated or unsaturated polybasic acid anhydride. A cured product of this type of photosensitive resins may comprise hydroxyl groups in excess and may therefore exhibit insufficient PCT resistance due to its deteriorated water resistance, since the amount of the added saturated or unsaturated polybasic acid anhydride is less than that of the hydroxyl group of dimethylolpropionic acid, although it has excellent adhesion, solder heat resistance and electroless gold plating resistance. If the amount of saturated or unsaturated polybasic acid anhydride is increased to relatively decrease the amount of hydroxyl groups, the carboxyl groups are in excess to thereby cause insufficient PCT resistance in some cases. The use of an acid having two or more hydroxyl groups, such as dimethylolpropionic acid, induces excess of one of the hydroxyl group and carboxyl group over another and is not preferred.
Accordingly, an object of the present invention is to provide a photosensitive resin composition which is used as a solder resist in printed circuit boards, can be satisfactorily developed in a dilute basic aqueous solution and can yield a cured film that is excellent in flexibility, water resistance, adhesion, solder heat resistance, electroless gold plating resistance and pressure cooker test (PCT) resistance.
SUMMARY OF THE INVENTION
After intensive investigations, the present inventors have solved the conventional problems.
Specifically, the present invention provides a photosensitive resin composition comprising:
(A) a photosensitive resin;
(B) an epoxy resin;
(C) a photopolymerization initiator; and
(D) a polymerizable unsaturated compound and/or a solvent,
in which the photosensitive resin (A) is obtained by allowing an epoxy resin (a) to react with a compound (b) having one primary alcoholic hydroxyl group and one functional group selected from a carboxyl group and a secondary amino group per molecule, and an unsaturated monobasic acid (c) to yield a reaction product (I) and allowing a saturated or unsaturated polybasic acid anhydride (d) to react with the hydroxyl group of the reaction product (I).
The photosensitive resin (A) in the photosensitive resin composition may be obtained by allowing from 0.6 mole to 1.0 mole inclusive of the saturated or unsaturated polybasic acid anhydride (d) to react with 1 mole of the primary hydroxyl group of the reaction product (I).
In the photosensitive resin (A) of the photosensitive resin composition, 0.8 to 1.2 equivalent weight in total of the compound (b) and the unsaturated monobasic acid (c) including 0.05 to 0.5 equivalent weight of the compound (b) may be allowed to react with 1 equivalent weight of epoxy groups of the epoxy resin (a).
The photosensitive resin composition may comprise 1% to 50% by weight of the epoxy resin (B) based on the total weight of the composition.
The photosensitive resin composition may comprise 0.5% to 20% by weight of the photopolymerization initiator (C) based on the total weight of the composition.
Preferably, the photosensitive resin composition comprises 5% to 80% by weight of the polymerizable unsaturated compound and/or solvent (D) based on the total weight of the composition.
DISCLOSURE OF THE INVENTION
The present invention will be illustrated in further detail below.
Photosensitive resins (A) for use in the present invention are obtained by allowing an epoxy resin (a) to react with a compound (b) having one primary alcoholic hydroxyl group and one functional group selected from a carboxyl group and a secondary amino group per molecule, and an unsaturated monobasic acid (c) to yield a reaction product (I) and allowing a saturated or unsaturated polybasic acid anhydride (d) to react with the hydroxyl group of the reaction product (I).
Examples of the epoxy resin (a) include epoxy resins such as cresol novolak epoxy resins, phenol novolak epoxy resins, dicyclopentadiene-phenol polyaddition epoxy resins and combinations of these resins. These novolak epoxy resins may be halogenated.
Part of such cresol novolak epoxy resins, phenol novolak epoxy resins, dicyclopentadiene-phenol polyaddition epoxy resins may be substituted with other epoxy resins within ranges not deteriorating the advantages of the present invention. Such other epoxy resins include, but are not limited to, bisphenol A epoxy resins, bisphenol F epoxy resins, hydrogenated bisphenol A epoxy resins, phenol-cresol co-condensation epoxy resins, bisphenol A novolak epoxy resins, bisphenol F novolak epoxy resins, triphenylolmethane epoxy resins, tetraphenylolethane epoxy resins and other epoxy resins prepared by allowing polyfunctional phenols to react with epichlorohydrin, epoxy resins prepared by allowing polyfunctional hydroxynaphthalenes to react with epichlorohydrin, silicone-modified epoxy resins, &egr;-caprolactone-modified epoxy resins, glycidylamine epoxy resins prepared by allowing epichlorohydrin to react with primary or secondary amines, triglycidyl isocyanate and other heterocyclic epoxy resins.
Examples of the compound (b) having one primary alcoholic hydroxyl group and one functional group selected from a carboxyl group and a secondary amino group include glycolic acid, 16-hydroxyhexadecanoic acid and other compounds each having a primary alcoholic hydroxyl group and a carboxyl group; N-benzylethanolamine and other compounds each having a primary alcoholic hydroxyl group and a secondary amino group, of which glycolic acid is typically preferred.
The alcoholic hydroxyl group of the compound (b) is a primary hydroxyl group and has a higher reactivity with respect to the saturated or unsaturated polybasic acid anhydride (d) than a secondary hydroxyl group. Such a secondary hydroxyl group is formed by the reaction of the epoxy group of the epoxy resin (a) with the carboxyl group or secondary amino group of the compound (b) or with a carboxylic acid radical of the unsaturated monobasic acid (c). The saturated o
Saitou Takeshi
Takagi Toru
Yada Mitsuhiro
Hamilton Cynthia
Showa Highpolymer Co. Ltd.
Sughrue & Mion, PLLC
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