A simple and reproducible method towards fabricating defect-free and reliable solder joints

This paper describes a simple and reproducible method to obtain defect-free and reliable solder joints. That is to split the solder joints fabricated from an infrared (IR) reflow soldering process. The characteristics of split solder joints have been critically studied. It is found that the method of splitting is effective in eliminating pore formation (both gas and shrinkage pores) and inclusions in solder joints. The method is applicable to various solder pastes whether it be no-clean or water-soluble. Thermal and mechanical fatigue cycling tests show that fatigue life of the solder joints can be prolonged by more than 60% as compared to that without splitting. Fractographs illustrate that the fractured section in the fatigued joints occurs quite often at the interfaces of printed circuit board (PCB) and copper pads after splitting has been applied to the joints. This strongly testifies the solder portion has been strengthened by splitting. The proposed method is specially suitable for specimens with large pad area in each joint or where the pores or inclusions most likely appear.