The Study of Void Formation in Ag Sinter Joint

In this study, the influence of solvents, Ag powder, sintering profile on the void formation of sinter joint was investigated. The result indicated that the size of Ag powder used in sinter paste has a significant impact on the void performance. Two types of Ag powder were compared, powder A(~0.2um-1.3um) and powder B(~1-11um). Paste A (using powder A) has higher risk of forming void in Ag joint than paste B (using powder B). Crack line was formed on the open pad after Ag paste was dried under the same sintering profile even without placing die, the crack line was related to the void in silver joint to some degree. Paste B does not have crack and void issue no matter with or without die on top. Under a fixed sintering profile, sinter paste using different types of solvents has different void results. The study of sintering profile showed that ramp up rate and ramp up time were critical to the formation of void, the void was created during the ramp up stage due to the evaporation of the solvent. The mechanism of void formation in sinter paste is different from that of the traditional solder paste.