Influence of Heat-Treatment Schedule on Glass-to-Metal Sealing Behavior

The influence of heat-treatment schedule including sealing temperature and holding time on glass-to-metal sealing behavior in terms of average pore diameter and porosity was examined by optical microscopy. Results show that with the increasing sealing temperature, the average value of pore diameter firstly increases, then decreases, and at last increases. However, the porosity increases at first and becomes constant above 980 degrees C. Moreover, as the holding time prolonging, the average pore diameter increases gradually at first, and then decreases rapidly. While the porosity increases greatly, then increases slowly and decreases rapidly with increasing holding time. Additionally, the increases of both sealing temperature and holding time result in the increase of the thickness of bubble-free layer. A spatially varying bubble structure was presented by relating profiling to processing conditions.