Adhesion study of silver films deposited from a hot hollow‐cathode source

A study of the adhesion of silver films deposited from a hot hollow cathode source was undertaken. The coating process consisted of two stages: an ’’ion‐bombardment’’ cleaning phase followed (continuously) by a vapor deposition phase. Effects of four process parameters were investigated: chamber pressure; substrate bias during ion bombardment; substrate current during ion bombardment; and duration of the ion bombardment. Substrate materials investigated were beryllium and aluminum tensile coupons. Pairs of coated coupons were subsequently solid‐state bonded and then tensile tested. Tensile strength data provided a measure of the silver film adhesion, as well as a measure of the integrity of a solid‐state joint. ’’Thresholds’’ of total ion bombardment energy have been established for ensuring minimum adhesion strengths of approximately 0.28 GPa (40 000 psi) for silver on beryllium and aluminum.