Submicrometer-sized Al2O3 powders were three-roll mixed with RuO2-based resistor paste (Shoei R-2310) in varying weight ratios (5-20 wt.%), followed by thick-film printing the mixtures onto AlN substrates and fired over 850 degreesC in ambient air. Observation of the interfacial microstructure reveals that the addition of Al2O3, reduced the formation of interfacial pores pronouncedly; whilst, the film changed toward a porous structure as the powder loading approaches toward 20 wt.%. The electrical resistance of the film was found to increase exponentially with the Al2O3 fraction. A critical threshold for the resistance increase was at similar to 10 wt.% of the Al2O3 fraction. (C) 2001 Elsevier Science B.V. All rights reserved.
