The application of parallel-gap welding for bonding 5-mil annealed Pt wire to a 5000-AA Pt pad (with an underlying base of Ti, Mo, and W) sputter deposited on a sapphire substrate has been systematically examined. Optimum bonding parameters-force, voltage, duration, gap, and electrode width-have been developed for Cu-Cr and Mo-carbide electrodes which attain bond pull strengths approaching the tensile strength of the Pt wire without sapphire substrate microcracking. The Mo-carbide electrodes produced stronger bonds with less oxidation and pitting, and exhibited less electrode-wire adhesion than the Cu-Cr electrodes.>
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Fendrock et al. (1990) studied this question.