Joining of metal to ceramic plate using super-spread wetting

Abstract

Ceramic-metal composites with novel performance are desirable materials; however, differences in their properties result in difficulties in joining. In this study, the joining of metal to ceramic is investigated. We recently succeeded in causing super-spread wetting on the surface fine crevice structures of metal surfaces produced by both laser irradiation and reduction-sintering of oxide powders. In this work, joining copper onto an Al2O3 plate was achieved by taking advantage of super-spread wetting. Fe2O3 powder was first sintered under reducing conditions to produce a microstructure which can cause super-spread wetting of liquid metal on an Al2O3 plate. A powder-based surface fine crevice structure of metallic iron with high porosity was well-formed due to the bonding of the reduced metallic iron particles. This structure was joined on an Al2O3 plate with no cracking by the formation of an FeAl2O4 layer buffering the mismatch gap between the thermal expansion coefficients of iron and Al2O3. We successfully achieved metalizing of the Al2O3 surface with copper without interfacial cracks using super-spread wetting of liquid copper through the sintered metallic iron layer on the Al2O3 plate. Then, laser irradiation was conducted on the surface of the copper-metalized Al2O3 plate. A laser-irradiated surface fine crevice structure was successfully created on the copper-metalized Al2O3 plate. Moreover, it was confirmed that the super-spread wetting of liquid tin occurred on the laser-irradiated surface fine crevice structure, finally accomplishing the joining of a copper block and the copper-metalized Al2O3.