Application of ultrasonic waves during brazing of alumina/copper using Z[lc]n-S[lc]n filler

Abstract

Ultrasonic waves were applied during the brazing of alumina to copper. The aim of this work is to study the effect of ultrasonic waves and filler composition on the properties of the braze joint between alumina and copper using Zn-Sn alloys as filler metal. First alumina was metallized by applying ultrasonic waves to the Zn-Sn braze bath. Then the metallized alumina was brazed with copper using the same filler alloy. The joining mechanism was investigated by measuring the joining strength, hardness and analyzing the microstructure at the interface of the joint. The weight percent of tin in the filler ranged between 0, 30, 60 and 91 percent. The shear strength and microstructure of the joint strongly depend on the filler composition. The effect of ultrasound was assessed primarily from acoustic cavitations, impact and friction between filler and alumina ceramic, to improve the wetting between alumina and the filler, and reflect improved joint strength. Another ultrasonic advantage causes reduction of the joining temperature and means that thermal stress as in the braze joint are reduced.