The influence of surface roughness and pre-oxidation state on the wettability of aluminium nitride by commercial brazes

摘要

The effects of roughness (Ra = 0.17-0.20 mum) and of pre-oxidation of the AlN ceramic surface on its wettability and contact interaction with commercial brazing alloys CB4 and CB5 of Ag-Cu-Ti composition have been studied. Wettability has been determined by the sessile drop method at three holding temperatures (810, 900 and 950degreesC). Particularities of the interface interaction have been identified by microprobe analysis for pre-oxidized samples. Experimental data are compared with data for samples polished to Ra = 0.02-0.03 mum not subjected to pre-oxidation. The results show that, for the systems under study, surface roughness does not influence the contact angle value significantly. Pre-oxidation of the AlN in air at 1250degreesC, however, tends to reduce wettability as a result of the replacement of braze-aluminium nitride interaction by braze-surface aluminium oxide interaction. (C) 2004 Kluwer Academic Publishers.