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
1998-11-10
2001-05-29
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, C522S057000
Reexamination Certificate
active
06238840
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a photosensitive resin composition suitable for use as a solder resist composition applicable to the manufacture of rigid and flexible printed circuit boards or LSI packages such as BGA (ball grid array), CSP (chip size package), etc.
Solder resist is used in the manufacture of printed circuit boards, and in the recent years it is used also in the field of new LSI packages such as BGA, CSP, etc. A solder resist is indispensably necessary as a protective film for protecting the solder-evading portions from adhesion of solder, or as a permanent mask. Sometimes, soldering is practiced by printing a thermosetting solder according to the screen printing process, and the present invention is applicable to such a method, too. In the recent years, however, photo solder resist method or the method of forming pattern by photography has become more prevalent, because the screen printing method is limited in resolving power and cannot cope with the trend of enhancing the density of wiring. Of the photo solder resists, alkali-development type photo solder resist which can be developed with a solution of weak alkali such as sodium carbonate and the like is predominantly used from the viewpoint of securing the working environment and earth environment. As such alkali-development type photo solder resist, those disclosed in JP-A 61-243869 and JP-A 1-141904 can be referred to. The alkali-development type photo solder resist, however, is yet unsatisfactory in durability. That is, it is inferior to prior thermosetting type or solvent development type of solder resists in chemical resistance, water resistance and heat resistance. This is for a reason that the main ingredient of an alkali-development type photo solder resist composition must be a compound having hydrophilic groups facilitating the permeation of chemical solutions, water and water vapor necessary for alkali-development, due to which adhesiveness between resist film and copper is low. Especially in semiconductor packages such as BGA, CSP, etc., a high resistance to PCT (pressure-cooker test property which may be considered as a wet heat resistance) is needed. The existing alkali-development type photo solder resist, however, can endure such a test of severe condition only for about several hours to ten-odd hours.
SUMMARY OF THE INVENTION
An object of the present invention is to solve the problems mentioned above and to provide a photosensitive resin composition suitable for use as a solder resist composition excellent in adhesiveness between a resist film and substrate made of copper or the like and in wet heat resistance.
Thus, the present invention provides a photo-sensitive resin composition comprising (A) a carboxyl group-containing photosensitive resin, (B) an epoxy curing agent represented by the following formula (I), and (C) a photopolymerization initiator:
wherein R
1
, R
2
, R
3
and R
4
are independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms or an aryl group having 6 to 10 carbon atoms, provided that at least one of R
1
, R
2
, R
3
and R
4
is an alkyl group having 1 to 4 carbon atoms or an aryl group having 6 to 18 carbon atoms; R
5
and R
6
are independently a hydrogen atom or an alkyl group having 1 to 2 carbon atoms; and n is 0, 1, 2 or 3.
DETAILED DESCRIPTION OF THE INVENTION
The present inventors have conducted extensive studies with an aim of solving the problems mentioned above. As a result, it has been found that a photosensitive resin composition comprising a photosensitive resin using a specified epoxy curing agent and a photopolymerization initiator and a photosensitive resin composition further comprising a triazine compound in addition to the above-mentioned ingredients are excellent in adhesiveness to copper substrate and other substrates, and in durability. Based on this finding, the present invention has been accomplished.
The photosensitive resin composition of the present invention comprises (A) a carboxyl group-containing photosensitive resin, (B) an epoxy curing agent represented by the following formula (I), and (C) a photopolymerization initiator:
wherein R
1
, R
2
, R
3
and R
4
are independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms or an aryl group having 6 to 10 carbon atoms, provided that at least one of R
1
, R
2
, R
3
and R
4
is an alkyl group having 1 to 4 carbon atoms or an aryl group having 6 to 18 carbon atoms; R
5
and R
6
are independently a hydrogen atom or an alkyl group having 1 to 2 carbon atoms; and n is 0, 1, 2 or 3.
As the carboxyl group-containing photosensitive resin (A) used in the present invention, preferred are compounds formed by esterifying an epoxy compound (a) with an unsaturated monocarboxylic acid and then adding thereto an acid anhydride of a saturated or unsaturated polybasic acid.
As said epoxy compound (a), preferred are novolak type epoxy compounds obtained by reacting an aldehyde with phenol, cresol, halogenated phenol or alkylphenol in the presence of an acid catalyst to form a novolak and then reacting said novolak with epichlorohydrin. Commercially available articles made of such compounds (a) include YDCN-701, -704, YDPN-638 and -602 of Tohto Kasei Co., Ltd., DEN-431 and -439 of Dow Chemical Co., EPN-1259 of Ciba Geigy AG., N-730,-770,-865,-665,-673, VH-4150 and -4240 of Dainippon Ink and Chemicals Inc., EOCN-120 and BREN of Nippon Kayaku Co., Ltd., etc. Apart from the novolak type epoxy compounds, the epoxy compounds obtained by reacting salicylaldehyde with phenol or cresol and then with epichlorohydrin such as EPPN502H, FAE2500, etc. manufactured by Nippon Kayaku Co., Ltd, are also usable successfully. Further, epoxy compounds of Bisphenol A type, Bisphenol F type, hydrogenated Bisphenol A type, brominated Bisphenol A type, amino group-containing type, alicyclic type and polybutadiene modified type such as Epikote 828, 1007 and 807 of Yuka Shell Co., Epiclon 840, 860 and 3050 of Dainippon Ink and Chemicals Inc., DER-330,-337 and -361 of Dow Chemical Co., Celloxide 2021 of Daicel Chemical Industries, Ltd., TETRAD-X and -C of Mitsubishi Gas Chemical Co., Ltd., EPB-13 and -27 of Nippon Soda Co., Ltd. GY-260,-255 and XB-2615 of Ciba Geigy AG, etc. are also usable satisfactorily. Among these compounds, especially preferred are the epoxy compounds obtained by reacting salicylaldehyde with phenol or cresol and then with epichlorohydrin.
As the unsaturated monocarboxylic acid, (meth)acrylic acid (i.e. acrylic acid and methacrylic acid), crotonic acid and cinnamic acid can be referred to. Further, reaction products obtained by reacting a saturated or unsaturated polybasic acid anhydride with a (meth)-acrylate having one hydroxyl group in one molecule or with a half ester formed between a saturated or unsaturated dibasic acid and an unsaturated monoglycidyl compound can also be referred to, of which examples are reaction products obtained by reacting phthalic acid, tetrahydrophthalic acid, hexahydrophthalic acid, maleic acid or succinic acid with hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, tris(hydroxyethyl) isocyanurate di(meth)acrylate or glycidyl methacrylate at an equimolar ratio in the usual manner. These unsaturated monocarboxylic acids may be used either alone or as a mixture thereof. Of these unsaturated monocarboxylic acids, preferred is acrylic acid.
As said saturated or unsaturated polybasic acid anhydride, anhydrides of phthalic acid, tetrahydrophthalic acid, hexahydrophthalic acid, maleic acid, succinic acid, trimellitic acid and the like can be used.
Acid value (KOH mg/g) of said carboxyl group-containing photosensitive resin (A) is preferably 40 to 250 and more preferably 50 to 150, from the viewpoint of balance between alkali developability and other characteristic properties such as electrical properties.
If desired, the carboxyl group-containing photo-sensitive resin (A) may be further reacted with a reaction product obtained by reacting isocyanatoethyl (meth)acrylate, tolylene diisocyanate or isophorone diisocyanate with
Hirakura Hiroaki
Hirayama Takao
Ito Toshihiko
Sato Kuniaki
Yoshino Toshizumi
Antonelli, Terry & Kraus, LLP
Hamilton Cynthia
Hitachi Chemical Company Ltd.
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