Microstructural Evolution of Cantilever Wire Probe after Touch-Down Fatigue Cycles for Power Semi-Conductor Wafer Testing

Abstract

As fatigue fracture occurs in the bending area of the wire probe of the probe card owing to fatigue load during the touch-down (T/D) test, the development of wire probe materials with improved fatigue properties according to the wire materials is required. In this study, Tungsten (W), Rhenium-Tungsten (ReW), Beryllium-Copper (BeCu), and P7 (Palladium - Silver - Copper alloy, Pd-Ag-Cu) alloy were used to measure the tensile strength of the cantilever wire which was utilized for testing the electrical property of power semiconductor wafers used in the probe card. Additionally, the fatigue characteristics and microstructure changes of the wire were analyzed according to the T/D fatigue test using a scanning electron microscope, and electron back-scattered diffraction analysis was used for comparative analysis. In W and ReW wire probes with high initial yield strength, the misorientation angle due to grain elongation was smaller than that of P7. Accordingly, the grain deformation due to strain generation was small, whereas in materials with low initial yield strength, the misorientation angle was smaller. However, the amount of strain generated by grain orientation deformation was large. Therefore, under long-term T/D test conditions, it is assumed that ReW, W, and BeCu wire materials, which generate less deformation after long-term use than those with high initial strength, are superior to P7 materials.