THICK-FILM WIRING SUBSTRATE

PURPOSE: To obtain a thick film wiring substrate with improved contact bonding properties between a Cu conductor layer and a ceramic substrate and improved solder wetting properties by forming an oxidized Cu conductor layer on the surface of a ceramic substrate and by laminating a Cu conductor layer which is not oxidized on the oxidized Cu conductor layer.

CONSTITUTION: A Cu conductor layer 2 which is subjected to oxidation is formed on the surface of a ceramic substrate 1 and a Cu conductor layer 3 which is not subjected to oxidation is laminated on the oxidized Cu conductor layer 2. For example, Cu pasts is printed in a first printing process 4 and the Cu conductor layer 2 is formed on an alumina substrate 1a. Thus, the Cu conductor layer 2 is heated and dried in a first drying process 5 and the Cu conductor layer 2 is subjected to oxidation process. Then, in a second printing process 6, Cu paste is printed on the lower-layer Cu conductor layer 2, the surface side Cu conductor layer 3 is laminated. Then, the surface side Cu conductor layer 3 is dried under normal drying conditions which do not deteriorate solder wetting properties in a second drying process 7. After that, two-layer Cu conductor layers 2 and 3 are simultaneously calcined in a calcining process 8.

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