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
1999-11-10
2001-10-09
Ashton, Rosemary E. (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
C430S330000, C156S272200
Reexamination Certificate
active
06300037
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a photosensitive resin composition which can be formed into a patterned film by exposing the composition to light through a photomask and then developing the exposed composition, and to an adhesive in the form of a patterned film formed from the composition.
BACKGROUND OF THE INVENTION
It has been proposed to use a patterned adhesive in various electronic parts, for example, for bonding a semiconductor element to a lead frame, bonding a semiconductor element to a circuit board, or bonding circuit boards to each other. Such an adhesive is generally obtained by applying a photosensitive resin composition to a semiconductor element, lead frame, circuit board, or the like as one adherend to first form a coating film of the composition, exposing the coating film to light through a photomask, and then developing the coating film to impart a given pattern thereto. Thereafter, the other adherend is superposed on the patterned adhesive to bond the adherends to each other by hot pressing.
In general, conventional adhesives such as the above one soften in hot pressing and penetrate into rugged surfaces of adherends to produce an anchoring effect. Thus, an adhesive strength is obtained.
However, such an adhesive does not have sufficient flowability in hot pressing although it softens, because it has a crosslinked structure formed during pattern formation through exposure and development. This adhesive hence penetrates insufficiently into the rugged surface of an adherend. As a result, vacant spaces remain on part of the bonding surface and a sufficient adhesive strength cannot be obtained.
Incidentally, recent electronic parts contain electronic elements in which the wirings, terminals, and other components have various shapes. The bonding surfaces of these components are not merely flat but rugged, and such rugged bonding surfaces tend to become more complicated and finer.
Consequently, use of adhesives such as the above-described one in bonding electronic elements results in bonding failures.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a photosensitive resin composition capable of forming a patterned film by being exposed to light through a photomask and then developed, wherein the patterned film melts upon heating. Another object of the present invention is to provide an adhesive in the form of a pattern film which is obtained from the photosensitive resin composition and exhibits satisfactory adhesive properties even when used for electronic parts of various shapes having a rugged surface.
The term “rugged surface” used above includes surfaces having a roughness on the order of millimeter or micrometer or a finer roughness. Namely, it includes adherends which apparently have a flat surface.
The present invention provides a photosensitive resin composition capable of forming a patterned film by being exposed to light through a photomask and then developed, said patterned film melting upon heating. Especially preferred as the photosensitive resin composition is a photosensitive polyimide resin precursor.
The present invention further provides an adhesive in the form of a patterned film which is obtained by forming a coating film of the photosensitive resin composition on a surface of an adherend, exposing the coating film to light through a photomask, and then developing the coating film. This adhesive is characterized by melting upon heating and preferably having a melt viscosity at 250° C. of from 1,000 to 1,000,000 Pa·s.
DETAILED DESCRIPTION OF THE INVENTION
Examples of the photosensitive resin composition of the present invention include a photosensitive polyimide resin precursor, a photosensitive polyethersulfone, and the like. Especially preferred is a photosensitive polyimide resin precursor.
The photosensitive polyimide resin precursor can be obtained by reacting an acid dianhydride ingredient with a diamine ingredient in a substantially equimolar proportion in an appropriate organic solvent, e.g., N,N-dimethylacetamide or N-methyl-2-pyrrolidone, to yield a polyamic acid (for example, the polymerization is effected at room temperature and under dry and nitrogen atmosphere to provide a concentration of polyamic acid of 15 to 30% by weight) and mixing this polymer with a photosensitizer. An epoxy resin, nadic imide, maleimide, or the like may be added thereto if desired.
Examples of the acid dianhydride ingredient include 3,3′,4,4′-biphenyltetracarboxylic dianhydride, 2,2 ′, 3,3′-biphenyltetracarboxylic dianhydride, 3,3′,4,4′-benzophenonetetracarboxylic dianhydride, 2,2′,3,3′-benzophenonetetracarboxylic dianhydride, 4,4′-hydroxydiphthalic dianhydride, 2,2-bis(2,3-dicarboxyphenyl)hexafluoropropane dianhydride, 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA), bis(2,3-dicarboxyphenyl)methane dianhydride, bis(3,4-dicarboxyphenyl)methane dianhydride, bis(2,3-dicarboxyphenyl) sulfone dianhydride, bis(3,4-dicarboxyphenyl) sulfone dianhydride, pyromellitic dianhydride, and ethylene glycol bistrimellitate dianhydride. These dianhydrides may be used alone or in combination of two or more thereof.
Especially preferred for use in the present invention is 6FDA, represented by the following general formula (2) , ethylene glycol bistrimellitate dianhydride, represented by the following general formula (5), 4,4′-hydroxydiphthalic dianhydride, or 3,3′,4,4′-benzophenonetetracarboxylic dianhydride.
Examples of the diamine ingredient include diamines such as 4,4′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, 3,3′-diaminodiphenyl ether, m-phenylenediamine, p -phenylenediamine, 4,4′-diaminodiphenylpropane, 3,3′-diaminodiphenylpropane, 4,4′-diaminodiphenylmethane, 3,3′-diaminodiphenylmethane, 4,4′-diaminodiphenyl sulfide, 3,3′-diaminodiphenyl sulfide, 4,4′-diaminodiphenyl sulfone, 3,3′-diaminodiphenyl sulfone, 1,4-bis(4-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, 1,3-bis(3-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)-2,2-dimethylpropane, hexamethylenediamine, 1,8-diaminooctane, 1,12-diaminododecane, and 4,4′-diaminobenzophenone. These diamines may be used alone or in combination of two or more thereof.
Preferred for use in the present invention is 4,4′-diaminodiphenyl ether, 1,3-bis(4-aminophenoxy)benzene, 1,3-bis (3-aminophenoxy)benzene, represented by the following general formula (4), or a diamine represented by the following general formula (3). Especially preferred is the diamine represented by general formula (3) wherein n=1 (bisaminopropyltetramethyldisiloxane).
(n is an integer of 1 to 10.)
The photosensitizer is preferably a 1,4-dihydropyridine derivative represented by the following general formula (1):
wherein R
1
to R
5
each independently is a hydrogen atom or an organic group having 1 to 4 carbon atoms (e.g., methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, and tert-butyl).
Examples of the above photosensitizer include 1-ethyl-3,5-dimethoxycarbonyl-4-(2-nitrophenyl)-1,4-dihydropyridine, 1,2,6-trimethyl-3,5-dimethoxycarbonyl-4-(2-nitrophenyl)-1,4-dihydropyridine, 2,6-dimethyl-3,5-diacetyl -4-(2-nitrophenyl)-1,4-dihydropyridine, and 1-carboxyethyl -3,5-dimethoxycarbonyl-4-(2-nitrophenyl)-1,4-dihydropyridine. These may be used alone or in combination of two or more thereof. Especially preferred of these is 1-ethyl-3,5-dimethoxycarbonyl-4-(2-nitrophenyl)-1,4-dihydropyridine or 1,2,6-trimethyl-3,5-dimethoxycarbonyl-4-(2-nitrophenyl)-1,4-dihydropyridine.
The photosensitizer is used generally in an amount of from 0.1 to 1.0 mol per mol of the sum of the acid dianhydride ingredient and the diamine ingredient. If the amount thereof exceeds 1.0 mol, the excess photosensitizer remaining in hot pressing decomposes and volatilizes, leading to a decrease in adhesive strength. If the amount thereof is smaller than 0.1 mol, the ability to form a pattern is impaired.
The adhesive of the present invention is produced from t
Fujii Hirofumi
Tanigawa Satoshi
Ashton Rosemary E.
Nitto Denko Corporation
Sughrue Mion Zinn Macpeak & Seas, PLLC
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