Abstract
A voltage in the opposite direction to that of anodic bonding was applied to anodically-bonded joints of Fe and Kovar alloy (Fe-Ni-Co alloy) to borosilicate glass at a temperature at which thermal diffusion of the alkali ions in the glass was activated. Disjunction of the bond interfaces occurred in the Kovar/glass joints. On the other hand, the Fe/glass joints retained cohesion of their bond interface after a long application of reverse voltage. At the bond interface in an as-bonded Kovar/glass joint, a reaction layer of a crystalline Fe oxide formed by the reaction between Fe from Kovar alloy and O from glass. The content of Fe in Kovar alloy adjacent to the bond interface decreased. In an Fe/glass joint the reaction layer of amorphous Fe-Si oxide formed. This layer was much thicker than the reaction layer in the Kovar/glass joint. The Kovar alloy adjacent to the bond interface in the Kovar/glass joint was rich in Ni and Co content. This result suggested that properties of the Kovar/glass bond interface were similar to those of Ni/glass or Co/glass bond interface in some instances. For this reason, effects of reverse voltage on anodically-bonded Ni/glass and Co/glass joints were examined. Disjunction occurred in both joints, and it was suggested that the disjunction of anodically-bonded Kovar/glass interface was caused by alloying elements of Ni and Co.
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