Preparation of silver-based solder foils by low-voltage magnetic pulsed compaction

Abstract

Cadmium-free silver-based solder foils were fabricated using mechanically alloyed powders containing 56% silver–22% copper–17% zinc–5% tin by low-voltage magnetic pulsed compaction (LV-MPC) followed by liquid-phase sintering. The effects of processing parameters, such as discharge voltage, capacitance, coil turns, diameter–height ratio and compacting times, of LV-MPC on both the green density and the sintered density of compacts were analysed. The results showed that the green density increased with increasing discharge voltage, capacitance and coil turns. The green density also increased with increasing compacting times and diameter–height ratio, but the effect was relatively small because of the small filling height of the powder. The minimum thickness of solder foils fabricated by LV-MPC was approximately 0·2 mm. After sintering for 0·5 h at 480°C, the changing tendency of sintered density with different processing parameters was similar to that of green density with the same processing parameters. However, antidensification occurred and the sintered density declined slightly. The maximum relative densities of the samples after LV-MPC and liquid sintering were approximately 89 and 87% respectively.