Sumitomo Metal Industries, Inc.

Sumitomo Metal Ceramics Inc.

Syozo Otomo

Koichi Uno

Kazunari Tanaka

Yoshikazu Nakata

A process for forming fine thick-film conductor patterns on a ceramic substrate which comprises the steps of forming grooves in a positive-working photoresist layer on the substrate by the photolithographic technology, filling the grooves with a conductive paste by squeezing with a squeegee, removing the photoresist layer by a wet process, and firing the remaining conductive paste pattern is improved. By the improvements, the conductive paste is squeezed into the grooves by the screen printing technique using a mask, and/or the solvent in the conducive paste consists essentially of one or more hydrocarbons, and/or the squeegee is made of a material having a flexural modulus in a range of 30-200 kgf/mm.sup.2. The formation of the grooves may be accomplished by laser beam machining; in this case a negative-working photoresist or any other soluble resin may be used to form the grooves therein. Also provided are a process for forming a fine thick-film conductor pattern by means of transfer of a conductive paste pattern formed on a support film to a green sheet, as well as a process for forming bumps on a ceramic circuit substrate.

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Asa-gun, Japan

Syozo Otomo