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
2002-08-07
2004-10-19
Gilliam, Barbara (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
C430S281100, C430S311000
Reexamination Certificate
active
06806028
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to photosensitive conductive pastes which are primarily used for forming desired conductive patterns (circuit patterns, electrode patterns, or the like) on substrate surfaces or ceramic layers forming ceramic multilayer elements when circuit elements, ceramic multilayer elements or the like are formed, to methods for forming conductive patterns using the photosensitive conductive pastes, and to methods for manufacturing ceramic multilayer elements.
2. Description of the Related Art
Recently, concomitant with miniaturization of mobile communication apparatuses, satellite broadcast receivers, computers and the like, miniaturization and improved performance of high-frequency electronic elements used for the apparatuses mentioned above have also been progressing, and in addition, wiring patterns of high-frequency electronic circuit elements have been increasingly required to have higher wiring density and higher signal transmission speed.
In response to the requirements of the higher wiring density and higher signal transmission speed, finer wiring pattern and larger thickness (increase in thickness) thereof must be achieved.
For forming wiring patterns of high-frequency electronic elements, a method is generally used in which a pattern is formed on an insulating substrate using a conductive paste composed of a powdered polyvalent metal such as copper and an organic vehicle such as an organic binder or an organic solvent, and is then dried and fired to form a predetermined wiring pattern.
When wiring patterns are formed, screen printing has generally been used. However, when a fine wiring pattern is formed by using this method, it has been difficult to decrease the wire width and the space between wires (wire pitch) to 50 &mgr;m or less, and in general, it has been understood that the limitation of microfabrication of the wire width and the wire pitch by screen printing is 50 &mgr;m.
In contrast, in Japanese Unexamined Patent Application Publication Nos. 5-287221, 8-227153, and the like, methods in which fine and thick wires are formed by a photolithographic method using a photosensitive conductive paste have been disclosed. In these methods, a photosensitive conductive paste containing a powdered conductive metal, an acrylic copolymer having carboxyl groups and ethylenic unsaturated groups in the side chains thereof, a photoreactive material, a photopolymerization initiator, and the like is applied to an insulating substrate and is then dried, and subsequently, patterning is performed for the film thus formed by a photolithographic method including exposure and development treatment.
In addition, in Japanese Unexamined Patent Application Publication Nos. 6-224538, 8-335757, and the like, methods in which fine and thick wires are formed by a photolithographic method using a photosensitive conductive paste containing powdered glass have been disclosed. In these methods, powdered glass is contained in the photosensitive conductive paste so as to improve the adhesion between the conductive pattern and ceramic.
Recently, it has been increasingly desired in photolithographic methods using photosensitive conductive pastes that development be performed using water or an aqueous alkaline solution in consideration of environmental conservation, and accordingly, an organic binder having acidic groups, such as carboxyl groups, which liberate protons has been used. However, when the organic binder as described above is used and a polyvalent metal, in particular copper, is used as a conductive component in the photosensitive conductive paste, copper ions which dissolve out in the solution component (primarily composed of an organic solvent) of the paste react with anions of the organic binder, which are formed after protons are liberated therefrom, and as a result, a three-dimensional network may be formed by ionic cross-linking, thereby facilitating gelation of the photosensitive conductive paste. When the photosensitive conductive paste gels, in addition to difficult application thereof, a problem of unstable development may arise even when application can be preformed.
In addition, when the photosensitive conductive paste containing the acrylic copolymer having ethylenic unsaturated groups in the side chains is used, sensitivity to exposing light is increased; however, when an unsaturated glycidyl compound is used for forming ethylenic unsaturated groups in the side chains by an addition reaction, since hydroxyl groups which facilitate gelation are formed, a problem in that gelation more easily occurs may arise.
As methods for preventing gelation, for example, a phosphorous compound such as phosphoric acid, a compound having an azole structure such as benzotriazole, and an organic compound having a carboxyl group such as acetic acid have been disclosed, respectively, in Japanese Unexamined Patent Application Publication Nos. 9-218509, 9-218508, and 9-222723 as a gelation inhibitor contained in a photosensitive conductive paste. However, the methods using these gelation inhibitors may only prolong the time for gelation of the photosensitive paste to some extent, and even when these gelation inhibitors are present, difficulties in use of photosensitive conductive pastes have not been solved in practice.
Furthermore, a method has been disclosed in Japanese Unexamined Patent Application Publication No. 10-171107 in which 3-methyl-3-methoxybutanol is used as an organic solvent for preventing gelation. However, a phenomenon similar to gelation occurs in the paste in a dry state, that is, a three-dimensional network is formed by ionic cross-linking, and as a result, the substantial molecular weight is increased. Accordingly, a problem in which non-exposed areas are difficult to dissolve out in a developing solution may arise in some cases.
SUMMARY OF THE INVENTION
The present invention was made to solve the problems described above. Accordingly, an object of the present invention is to provide a photosensitive conductive paste having superior storage stability and adhesion to a substrate, which is unlikely to gel and can be formed into a fine and thick conductive pattern. In addition, another object of the present invention is to provide a method for manufacturing a conductive pattern using the photosensitive conductive paste described above and a method for manufacturing a ceramic multilayer component.
To these ends, the photosensitive conductive paste of the present invention comprises: (a) a powdered base metal processed by surface oxidation treatment; (b) an organic binder having acidic groups; (c) a photosensitive organic component; and (d) a material for forming microgels by reaction with metal hydroxides present on the surface of the powdered base metal.
Since the material for forming microgels by reaction with metal hydroxides present on the surface of the powdered base metal is contained in the photosensitive conductive paste of the present invention, in addition to the powdered base metal processed by surface oxidation treatment, gelation of the paste before application and gelation of the film obtained therefrom by application and drying can be sufficiently suppressed. Accordingly, a fine and thick conductive pattern (such as a circuit or an electrode) can be efficiently manufactured.
The reasons gelation can be prevented in the photosensitive conductive paste of the present invention are believed to be that:
(1) the activity of metal hydroxides present on the surface of the powdered base metal is low since the surface thereof is processed by oxidation; and
(2) material present on the surface of the powdered base metal forms microgels with the metal hydroxides present on the surface of the powdered base metal by complex formation, and these microgels have a steric hindrance effect, thereby interfering with formation of bonds between the powdered base metal and the acidic groups of the organic binder.
REFERENCES:
patent: 4598037 (1986-07-01), Felten
patent: 6531257 (2003-03-01), Kubota
patent: 2001/003
Dickstein Shapiro Morin & Oshinsky LLP.
Gilliam Barbara
Murata Manufacturing Co. Ltd.
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