Compared are the ultrasonic bonding, annealing and low temperature aging characteristics of one mil Al-1 pct Si, Al-1 pct Mg, and Al-½ pct Mg bonding wires. Ultimate tensile strengths and average bond pull strengths of these three alloys decrease similarly in the 125° to 200°C temperature range, while dissimilarity was observed in elongation: Al-Mg alloys become more ductile and Al-1 pct Si embrittles. Aging to −65°C showed no changes in the mechanical properties of Al-½ pct Mg but caused embrittlement in Al-1 pct Mg, suggesting GP zone formation.