Abstract
This study investigated novel ternary Pb-free solder systems. The purpose was to develop novel ternary Pb-free solders to replace conventional Sn-Pb eutectic solder. The components of the novel ternary solders were designed based on Sn-base ternary phase diagrams, melted, homogenized and studied with X-ray powder diffractionmeter, thermal analyzers, SEM, pendant drop analyzer, wetting balance, …ect. were applied to. The experimental results showed that the solidus-liquidus temperature range of the designed Al-In-Sn alloys (76.4~84.4wt%Sn-0.35wt%Al-15.2~23.2%In) meets the demand of alloy design. The resistivity and hardness are similar to those of the Sn-Pb eutectic solder. But mechanical properties and surface tension were much worse than the Sn-Pb eutectic solder. The designed Ga-Sn-Zn alloys (85.5~89.8wt%Sn-2.5~6.6wt%Ga-7.7~8wt%Zn) are very brittle. The solidus-liquidus temperature range meets the demand of alloy design. Because of the inferior mechanical properties, the designed Ga-Sn -Zn alloys are unsuitable for solder alloy. The designed Bi-Sn-Zn alloys (81.3~90.2wt%Sn-5.3~12.9wt%Bi-1.3~7.5Zn), the resistivity (8~14mWcm), hardness (Hv23.3~26.5) and mechanical properties (42.6~73.5MPa) are superior to those of the Sn-Pb eutectic solder (14.5~17.5mWcm、Hv10.5~10.7、49.5MPa). At 87.09wt%Sn-5.48wt%Bi-7.43wt%Zn and 85.59wt%Sn-8.87wt%Bi -5.55wt%Zn the surface tension (350~425erg/cm2) and the results of wetting balance (0.573~0.647mN) are also comparable with the Sn-Pb eutectic solder (325~375erg/cm2、0.623~0.647mN). It is thus concluded that the designed Bi-Sn-Zn alloys at 81.3~87.1wt%Sn-5.4~12.7wt%Bi-5.4~7.5Zn composition range are suitable Pb-free solders.