The Study Of The Effect Of Ni On Sn-0.3Ag-0.7Cu Lead-Free Solder And The Nano-Mechanical Properties Of Solder

Because of the lead and lead contained compounds'toxicity to human body and the environment and the restriction of legislation, It is inevitable that lead-free solder has become the tendency of the electronic packaging materials. New lead-free solders have been used in industry. The effects of Ni on physical properties, mechanical properties and microstructures of Sn-0.3Ag-0.7Cu alloy and that of solder/Cu substrate were studied. Mechanical behavior of Sn-0.3Ag-0.7Cu bulk solder, BGA solder ball and BGA solder joint were also analyzed in the paper.The result shows that the melting point raises a little as Ni is added into the solders. Shorter melting zone indicated that reliable soldered joints can be formed. The wetting property of solder alloy was improved when Ni is added into the solder. When Sn-0.3Ag-0.7Cu solder contains 0.05wt% Ni, the wetting time is shortest. And when the solder contains 0.1%Ni, the value of wetting force is largest. After adding Ni into the solder theβ-Sn phase is refined, which is benefit to the improvement of solders mechanical property. Tensile strength of solder is descended as Ni is added into the solders. But the trend of parabolic curve appeared on the elongation percentage of solder. The effect of Ni on microhardness was a little. But the effect of Ni on IMC of solder joints appears the trend of parabolic. When Sn-0.3Ag-0.7Cu solder contains 0.05wt% Ni, the thickness of IMC was smallest.Nanoindentation tests were performed on the Sn-0.3Ag-0.7Cu bulk solder, BGA solder ball and BGA solder joint. The Young's modulus of bulk solder, BGA solder ball and BGA solder joint were obtained from load-depth curves with Oliver-Pharr method. Depth-time curves were obtained from load-depth curves and the creep rate sensitivity of bulk solder, BGA solder ball and BGA solder joint were obtained by data fitting. The results show that Young's modulus and the creep rate sensitivity exponent of bulk solder were 2.5 times than that of the BGA solder ball and BGA solder joint approximately. When the load-rate is 20mN/s, the Vickers hardness value that was measured by the Berkovich nanoindentation tests was the same as that of microhardness.