Effect of Ar reflow atmosphere on the SAC305 solder joint reliability

Lead-free solder alloys are more easily oxygenized and have poor wettability compared to traditional Sn-Pb solder alloys, which affects solder joints reliability. Ar is the most plentiful rare inert gas. It has been accepted that, in Ar atmosphere, the oxidation of lead-free solder joints can be prevented and the wettability of lead-free solder joints can be improved. To date, however, few systemic researches have been reported. The objective of this investigation is to study the effect of Ar atmosphere on the reflow process and solder joint reliability of lead-free solders (SAC305) for SOIC8 package. Reflow process in both Ar and air atmospheres was conducted with OSP-pad PCBs. The IMC formation after reflow process and environmental tests was also investigated. The experimental results indicated that the wetting and reliability performance of the SAC305 solder joint could be greatly improved due to the use of Ar atmosphere.