Study On Compressive Creep Properties Of The Sn-Zn Lead-free Solder

In this paper, the development and research on Sn-9Zn as well as Sn-9Zn based on lead-free which were added some Bi Al RE. The main contents and results are as follows:(1) Within the test condition of temperature(in the range of 55℃- 100℃) and compressive stress(in the range of 9.3Mpa-18.6MPa), the compressive creep deformation and compressive creep rate of Sn-9Zn Sn-8Zn-3Bh Sn-8.55Zn-0.45 Ah Sn-9Zn-0.5RE were changed increased with the increasing of temperature and compressive stress, the steady creep rate obeys an empirical equation (ε|·)_s=Aσ~n exp[-Q_c/(RT)].(2) For Sn-9Zn Sn-8Zn-3Bh Sn-8.55Zn-0.45Al and Sn-9Zn-0.5RE lead-free solder, the stress exponents (n) are between 3 and 6 at different temperatures, and the apparent creep activation energies are similar under different stresses, the creep mechanism are controlled by dislocation glide and dislocation climb, and the grain boundary contributed for it in some degree.(3) Bi solutes inβ-Sn matrix, form the group of solute non-uniform, which increase the dislocation gliding during creep, impede the entity of diffusion distortion, consequently improve the creep resistance of Sn-8Zn-3Bi.(4) Adding RE to Sn-9Zn lead-free solder, on the one hand, complex thermal stability compound are formed and located in grain boundary, strengthened the grain boundary, which effectively hinder the diffusion of Sn atoms, restrain the growth and gliding of dendritic at high temperature. So, the creep resistance is improved. On the other hand, minute amount of RE atoms solute in 6-Sn matrix which restrict the dislocation moving, so the creep resistance is improved.(5) Adding Al to Sn-9Zn lead-free solder, the structure of Sn-8.55Zn-0.45Al is refined, and formed complex compound of Al. The thermal stability compound are located in grain boundary of 8-Sn, formed discontinuation network distribution, which effectively hinder the diffusion of Sn atoms, restrain the growth and gliding of dendritic at high temperature, so the creep resistance is improved.(6) Invigoration effect of the particle non-deforming is inverse the relationship of interparticle distance, the interparticle distance of Al compound smaller than RE compound, the activation energy of dislocation slipping and climbing increased. So, the steady creep rate of Sn-8.55Zn-0.45Al is lower than Sn-9Zn-0.5RE, the apparent creep activation energy is higher than Sn-9Zn-0.5RE.