Field-assisted bonding below 200°C using metal and glass thin-film interlayers

Abstract

Bonding between similar or dissimilar surfaces with metal and glass thin-film interlayers as well as bulk glass plates using an electric field assisted bonding technique at 160°C or less is described. This low-temperature field-assisted bonding is achieved using, e.g., few μm thick glass films rf magnetron sputter deposited from Na or Li silicate glasses, and 0.05-1.0 μm thick Al, Sn, Mg, and Hf films. The bond strength thus achieved is found to be greater than the cohesive strength of the glass used. Results from x-ray photoelectron spectroscopy analyses confirm the migration across the glass layer and the plating out on the cathode surfaces of mobile ions such as Na+ or Li+ during field-assisted bonding. The migration and plating out of mobile ions can be detected in 10 s after the potential is applied and whether actual bonding between the metal and glass occurs or not. The possible bonding mechanism based on these XPS results is proposed.