a feedthrough terminal assembly for an active implantable medical device includes a conductive terminal pin or lead wire which extends through a conductive ground plane of the aimd in non - conductive relation . a feedthrough capacitor associated with the terminal pin or lead wire has first and second sets of electrode plates coupled , respectively , to the conductive pin or lead wire and to the ground plane . a breathable electromechanical connection material conductively couples the capacitor &# 39 ; s electrode plates to respective components of the aimd , which allows helium gas to pass freely therethrough during a standard pressurized or vacuum pull helium leak detection test . a breathable washer may be disposed between an alumina insulator and a surface of the capacitor . an additional further breathable coating or conformal coating may be placed over a surface of the feedthrough capacitor disposed toward the interior of the aimd .