Research On Compressive Creep Bechavior Of The Sn-Cu Lead-free Solder

Along with the implementation of the comprehensive prohibition law of world industry developed countries for containing Pb solder of the production and use on electronic field, the research and development of the lead-free solder has launched vigorously. Up to now, it has been basically form 4 series of lead-free solder: Sn-Ag Sn-Cu Sn-Zn and Sn-Bi. Sn-Cu solder has good mechanical properties and price advantage, so it is considered to the most potential substitutes for Sn-Pb solder.Hereby on the basic of the research on eutectic Sn-0.7Cu lead-free solder, through adding the minim of RE, Ag, In and Bi, the thesis has a research for the influence about structure and resistance compressing creep properties, and obtains the primary research result as follows:(1) Having compressing creep, Sn-0.7Cu lead-free solder generates polygonization at grain boundary, and forms subgrain. Through compressing creep test, there has a relation on Sn-0.7Cu lead-free solder about steady state creep speed rate, temperature and stress in the given range of stress and temperature, as follows(2) Through Sn-0.7Cu lead-free solder compressing creep test, when σ is 9.14MPa, the test sample prepared by quick cooling has highest activation energy. Accompaning increasing of cooling rate, eutectic Sn-0.7Cu lead-free solder can firstly precipitate dendritic crystal. It is close arranging and slender. Cu₆Sn₅ exists in eutectic structure, hindrances dislocation movement and increases resistance compressing creep properties(3) RE contributes to Sn-0.7Cu lead-free solder in resistance compressing creep performance. RE can and metamorphose purge the basal body. Otherwise, RE limite arborescent crystal movement and refine coarse arborescent crystal, through RE fill-up crystals superficial defective. At the same time, it causes irregular phase boundary, hindrances phase boundary deformation and increasing resistance compressing creep performance.(4) Ag contributes to Sn-0.7Cu lead-free solder in resistance compressing creep performance. Ag and Sn form thinnish and non-active Ag₃Sn which chiefly distributes in eutectic structure. The phase is hardy to solution and growing and can prevent formation and movement of the positive hole.(5) Bi contributes to Sn-0.7Cu lead-free solder in resistance compressing creep performance. Bi exists in Sn in the form of solid solution phase. Maximum the percentage compostion of Bi is in Sn-Bi eutectic structure. Bi is difficult to form intermediate compound with Sn and Cu. Bi can reduce fauly energy of material, widen extended dislocation.(6) When σ is 9.14MPa, compressing creep actication energy of the Sn-0.7Cu-0.4RE, Sn-0.7Cu-0.5Bi, Sn-0.7Cu-0.5Ag and Sn-0.7Cu-0.5In is 66.30KJmol-l 65.41KJmol-l 60.39KJmol-l å’Œ 50.09KJmol-l, respectively.