Advanced glass seals for implantable medical devices

Lanthanum Borate (LaBor) glass is used as the insulating glass seal material in feedthroughs used in implantable medical devices. Guided by finite element analysis modeling, alumina was selected as a promising additive for the LaBor glass to tailor its material properties for glass seals that are better matched with lower CTE pin materials. Thermal expansion and elastic properties were measured for LaBor glass containing up to 20 wt% alumina. Trends for thermal expansion and elastic modulus were reasonably predicted by literature descriptions. As predicted by finite element modeling, the modified glass showed good resistance to crack growth and the hermetic behavior of the seal was confirmed by helium leak detection and fluorescent dye observations.