Low RF loss metal-ceramic bonds

Abstract

Metal-ceramic interfaces in RF circuits of high power microwave tubes can be the source of attenuation, a heat barrier, and lead to thermal failure. Process improvements, leading to a reliable technique for applying Ti-Mo-Cu thin films that have low losses, close dimensional tolerence and high heat transfer, have been optimized over previously reported works. Sputter metallization of beryllia and subsequent diffusion brazing to copper comprise the basic process. Long range failures have been eliminated through strict control of the titanium layer thickness to 250Å. Bond strengths to the order of beryllia's yield stress of 12000 lbf/in2are achievable.