Effect Of Ni On Interfacial Reaction And Mechnical Properties Of SAC0307 Joint

Exploring new types of Lead-free solders have become one of the main contents on studying the electronic packaging materials. The property of Sn-Ag-Cu solders performed well, but they still exist some problems in industry. The paper is based on Sn-0.3Ag-0.7Cu low silver solders, then adding microelement Ni (0-0.15wt%) to alloys inorder to improve properties. After aging at 180℃for different time, the effect of Ni on the IMC morphology of solder joints, the growth rate and the shear strength of joint were studied. The IMC and the shear strength of Sn-0.3Ag-0.7Cu-XNi/Cu after multi-reflow were also analyzed in this paper.The results show that the microstructure are refined and there is (Cu1-xNix)6Sn5 phase dispersion in it when adding Ni. When the Ni content is 0.05wt%, the thickness of IMC is smallest, the restrain effect is obviously. On the Cu pad, the relation of the thickness of IMC and rhe square root of aging time is nearly linear, and a new Cu3Sn layer appears. On the Ni pad, the IMC (Cu1-xNix)6Sn5 is storm-like. After aging, the type of IMC doesn't change but the chemical composition changes, and the thickness of IMC increased lightly. However, which is smaller than that on Cu pad, the thickness of IMC and the growth rate are smallest of all when adding 0.05Niwt%. Thickness of residual Ni layer for Sn-0.3Ag-0.7Cu/Ni is also smaller than that for Sn-0.3Ag-0.7Cu-0.05Ni/Ni obviously after aging.The shear strength increases then decreases with the increasing of Ni content, when it is 0.05Niwt%, the shear strength is highest. After aging, the shear strength of Sn-0.3Ag-0.7Cu-XNi/Cu decrease along with increase of aging time, which is still highest when adding 0.05Niwt%. The fracture position of solder joints changes from solders to between sloders and IMC, and fracture types change from ductile fracture to ductile-brittle fracture after aging. The thickness of IMC increases along with the increase of reflow times. The addition of 0.05wt%Ni to the solder can decrease the thickness of IMC effectively regardless of the reflow cycles. Furthermore, shear strength didn't change apparently after the cycles of reflow, which was found decreased slisghtly after five-time reflow. The fracture surface are found largely partn in the bulk solder and partly at the interface between the solder and IMC after five reflow cycles, and fracture types change from ductile fracture to ductile-brittle fracture.