Rate controlling processes in anodic bonding of boroslicate glass-to-Kovar alloy coated with Al film

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ÎÄÕÂÒ³Â룺826 - 830

Key words£ºanodic bonding; kinetics; elastic deformation; viscous flow; charge transfer; activation energy; joint strength

Abstract: The Kovar alloy disks coated with Al film were anode-bonded to the glass at temperatures of 513¡«713K under the static voltage of 500V. The kinetics of enlargement of intimate contact area between the Kovar alloy and the glass was examined, and the joint strength was determined by the shear tests. It is suggested that a critical temperature of about 663K exists. The enlargement of intimate contact area is achieved mainly by elastic deformation of the glass at temperature lower than the critical temperature. The estimated activation energy is close to that of conductivity of the glass. Whereas, the enlargement of intimate contact area is achieved mainly by viscous flow of the glass, and the corresponding activation energy is higher than the former and is a combination of the activation energies of conductivity and viscous flow of the glass. Examination of joint strength reveals that the chemical bond or complete bonding is formed as soon as the surfaces are brought into intimate contact, and rateª²controlling process in anodic bonding is considered to be the rate of enlargement of intimate contact area.