(4.2) CORROSION RESISTANCE AND MECHANICAL STRENGTH OF BRAZEDCERAMIC-TO-METAL SEALS FOR IMPLANTABLE MEDICAL DEVICES

摘要

Brazing is used to make hermetic electrical feedthroughs for implantable medical devices such asrnpacemakers, internal defibrillators, and neurostimulators. The feedthroughs need to be strongrnand corrosion resistant in body fluids so that they maintain hermeticity for up to ten years.rnBrazes are the most vulnerable material of feedthroughs to corrosion. In this study, anodicrnpolarization tests were performed on commercial braze materials to compare the corrosionrnresistance of the brazes. The corrosion current density and open circuit potential of commercialrnbrazes melted on alumina, titanium, and niobium substrates were determined from anodicrnpolarization tests. The brazes used were 99.99Au, Gold ABA, Cusil, Ticusil, Cusin-1 ABA,rnIncusil ABA, and 99.99Al. 99.99Au and Cusil were melted on niobium sputtered alumina whilernthe other brazes were melted directly on alumina. 99.99Au (gold) had lower corrosion currentrndensity and was more noble than the other brazes tested. The tensile strengths of joints madernwith alumina brazed to titanium and niobium were determined. The strongest joints were madernby sputtering the alumina with niobium. Gold brazed joints had the best combination of strengthrnand corrosion resistance and therefore gold is the best braze material for making implantablernfeedthroughs that was tested. The active metal brazes tested in this study were inferior to gold,rnbut may be suitable for feedthrough applications in different or less hostile environments.