Study on Slip Behavior of lead-free Solder Joints under Uniaxial Stress

The samples were soldered using copper pillars and Sn-3.0Ag-0.5Cu solder paste with a typical reflow profile about peak time of 245 degrees C. In order to observe the microstructure and crystal orientations, the sample is grinded and polished to be characterized by scanning electron microscope (SEM) and electron backscattered diffraction (EBSD). By analyzing the microstructure and crystal orientation, the number of grains contained in the sample and grain orientation is obtained. Next, in order to study the relationship between deformation and crystal orientation, the sample was subjected to uniaxial tensile test. The following results were obtained by the experiment: 1) In the process of deformation, the slip system which is activated is closely correlated to the grain orientation; 2) There may be several slip systems that were activated during deformation, though the solder joint is the single crystal structure.