Wettability of AlN with different roughness, porosity and oxidation state by commercial Ag-Cu-Ti brazes

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The effects of porosity (about 27%), of roughness (Ra = 0.17-0.20 μm versus Ra = 0.02–0.03 μm) and of pre-oxidation (air, 1250°, 30 min) on wettability and contact interaction of AlN with commercial brazing alloys of Ag-Cu-Ti composition were studied. Wettability was determined by the sessile drop method. The interface interaction was identified by SEM and microprobe analysis. Experimental data for porous, pre-oxidized and rough samples are compared with data for dense samples polished to Ra = 0.02–0.03 μm not subjected to pre-oxidation. The results show that for these systems surface roughness does not influence the contact angle value significantly. Pre-oxidation of the AlN, however, tends to reduce wettability as a result of the replacement of braze/AlN interaction by braze/surface aluminium oxide interaction. Contact angles for porous samples are higher by about 20–30° than for dense samples.

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