Stress and Fracture Analyses of Solar Silicon Wafers During Suction Process and Handling

Solar wafer/cell breakage depends on the combination of the stresses generated in the handling and the presence of structural defects such as cracks. Suction process is a common loading during silicon wafer handling. This paper presents a systematic static and dynamic analysis of the suction process. Optimum suction pad diameter and locations are obtained by minimizing the stress distribution under both static and dynamic loading, and the effect of the impact time on the crack driving force is also investigated in this optimum situation. The results show that the four pads configuration with diameter of 20 mm placed in a rhombus shape with 18 and 38 mm diagonal lengths yields lowest maximum principle stress among the cases analyzed. In the dynamic fracture analyses, the maximum J integral appears at 800 and 1400 μs for continued holding and unloading cases after reaching the maximum load, respectively. The J integral for the unloading cases are always smaller than the holding cases. It has been found that when the impact time is longer than 3 s and 5600 μs the dynamic fracture mechanics analysis of the suction impact process can be replaced by a static fracture mechanics analysis for the holding and unloading cases, respectively.