Improvement of the solder joint strength in a SAC 305 solder ball to a ENIG substrate using LF hydrogen radical treatment

Joint strength between solder ball and pad on the substrate is one of the major factors which have effects on the electronic device reliability. To improve the strength of the solder joint, the efforts evaluation surface cleaning, heat treatment and change of solder composition have been in progress. This paper discussed a solder ball joint strength improvement using low frequency hydrogen radical surface treatment and focused on the effects of surface treatment conditions on the interfacial reaction and the shear strength of the solder ball. The shear strength between the solder ball and the pad increased about 30% in comparison with no treatment under the same reflow condition. Especially, at a treatment time of 5 minutes, the shear strength considerably increased by 70% and the fracture mode of the shear test changed from interfacial fracture to the solder fracture.