Mechanism of enlargement of intimately contacted area in anodic bonding of Kovar alloy to borosilicate glass

Abstract

The effects of the bonding temperature and voltage on the rate of the enlargement of intimately contacted area in the anodic bonding of the Kovar alloy to borosilicate glass have been studied systematically in order to obtain better understanding of the rate controlling factor of the process. It was suggested that the attainment of intimate contact was controlled by two factors having different activation energies depending on the bonding temperature. At bonding temperatures higher than 669-687 K (depending on the bonding voltage), the estimated activation energy was close to that of the viscous flow of the glass. At lower bonding temperatures, the estimated activation energy was close to that of the conductivity of the glass. A mechanism of the enlargement of intimately contacted area during the anodic bonding is proposed to explain these results.