Hybrid microcircuit via development

Hybrid microcircuits were designed to interconnect frontside thin-film networks with metallized backside ground planes on 95 by 114 mm square alumina substrates. Manufacturing processes were developed for making holes in alumina substrates, metallizing substrates on both sides and through vias, dry film photolithographing 6 micrometers thick gold to 127 micrometers line widths and spacings, and determining via quality and acceptance. The techniques developed produce vias which exhibit through-hole resistances of less than 10 microhms and are acceptable for radio frequency or logic circuit application. Sample parts were fabricated and evaluated on both test substrates and production substrates to prove in the new techniques. The few problems encountered with initiating a new process into production were solved, and via related technology were used successfully in production.