The Mechanism and Bonding Process of Field-Assisted Bonding of Borosilicate Glass to Kovar Alloy

The paper mainly investigates the field-assisted bonding process of Kovar alloy to Pyrex glass, the bonding is achieved at 350–450°C applying a voltage of 500–800v, and SEM EDS are used to analyze the bonding interface structure and the elements distribution. The experimental results indicate that there is a clear transitional area between the interface of the glass and the alloy. Owing to the formation of the transition area, the glass and the alloy are bonded together. The zigzag morphology in the interface of glass/alloy also indicates the diffusion of the elements. In the bonding process, the Na⁺ depletion zone, which gives birth to a electrostatic force is yielded in the glass. Due to the electrostatic force, the glass contacts with the Kovar alloy intimately. A model is built to analyze the dominant factor of the electrostatic force. Temperature, roughness of the sample and voltage are also the basic factors that influence the field-assisted bonding. The effects of these factors on the bonding process are analyzed in this paper. The experimental results suggest that the bonding area enlarges dramatically, if the voltage is increased. The bonding area enlarged from the initial contacting point and expands quickly. The influence of the time is small according to our experiments.