Fatigue of SMT solder joint including torsional curvature and chip location optimization

Abstract

The objective is to find whether fatigue of the solder joint or the location of the chip is related to the curvature and torsional curvature when SMT solder joints are under vibration or shock condition. However, the torsional curvature is always omitted. In this paper the relationship of curvature and torsional curvature is argued, and it is found that the quantity of the curvature is closer to that of the torsional curvature and shows that omitting the torsional curvature is not accurate. Also, the fatigue of the solder joint including torsional curvature is obtained. One kind of SMT printed circuit board (PCB) used in aviation and spaceflight has been obtained to test its modes. According to the modal results, the location of the SMT assembly is not very suitable and the reliability of SMT solder joints will decrease, which will make an unreasonable catastrophe appear. Meanwhile, the location optimization including curvature and torsional curvature is considered and four areas are obtained in the PCB to locate the chip for increasing the fatigue of solder joints. In this paper the results obtained by assuming the PCB is simply supported in its four boundary. The other fixed condition will be calculated using a similar method.