Estimating the Strength of Annular Glass-to-Metal Seals in Microelectronic Packages: An Experimental Study

The resistance of annular glass-to-metal seals, in microelectronic packages, to a sudden change in temperature is tested through the thermal shock test. In order to predict or evaluate the failure of the seal under thermal shock, the strength of the seal has to be known. A lower bound for the strength of such seals is evaluated by subjecting samples made of a circular lead sealed to a TO-8 eyelet through an annular glass seal, to various levels of thermal shock and calculating the corresponding maximum thermal stresses in the glass. This procedure is repeated in four thermal shock test fluids: water, oil, fluorocarbon, and liquid nitrogen. A lower bound of approximately 7600 Ibf/in²is estimated for the strength of the glass-to-metal interface.