Research On Al-containing Low-Ag Lead-free Solder

In the past few decades, the Pb-containing solders have been widely used, especially Sn-Pb eutectic solder. With the understanding of the harm of Pb and its compounds on the environment an human beings, Pb-containing solders have gradually banned. As one of the potential lead- free solders, Sn-Ag-Cu alloys have excellent mechanical properties are widely used in industrial, because of the high content of Ag, which have increase the costs and easy to long-term development. Therefor, the development of low silver Sn-Ag-Cu lead- free solder is the focus of current research direction.Through reducing the content of Ag to obtain a low silver Sn-Ag-Cu solder while lowering costs, but also decrease the wettability and the melting point of the more serious problems. The subject chooses Sn-0.3Ag-0.7Cu lead- free as a reference, by studying feasibility of micro-alloying of 0.49~1.49wt%Al element,as well as the microstructure of the solder alloy, melting characteristics, wetting spread ability, physical properties, shear properties of solder joints are tested and compared.This study find, micro-allying Al element in Sn-0.3Ag-0.7Cu solder alloys can effectively refine the organization, and inhibits the coarse β-Sn phase formation, also create the better plastic IMCs.Compared with the Sn-0.3Ag-0.7Cu lead-free solder, which micro-alloying Al element is not much impact in the melting temperature, doped more than 0.81wt%, the melting point and melting range increase larger, welting spread ability is reduced and the ability of soluble Cu is increased. The results show, micro-alloying 0.49wt%Al can improve the melting characteristics, and balance the dissolution rate of Cu. The results of the test of physical performance show that, after the addition of Al element, can effectively reduce the density and hardness of the solder, but has little significant effect on the solder resistivity. It has a very good improvement in reducing the cost of the solder. The reducing of the hardness shows the improving of plastic, also changes the anti-drop performance.This study shows that by micro-alloying Al element to change the problems due to the Ag decrease, is entirely feasible and can effectively improve the performance of the solder. In this paper, through the experimental work carried out in this paper, study the alloying method to change the new lead- free solder and properties of doped Al have certain reference and practical value.