Reflow Soldering Using Flux-sprayed Solder Preforms

This research paper investigates the use of flux-sprayed solder preforms as an alternative method to reduce flux outgassing in reflow soldering. The study compares the flux volume, void level, solder balling, and solder spattering between the use of traditional solder pastes and flux-sprayed solder preforms. The flux present in the solder paste functions as removing metal oxidations and ensuring proper solder joint formation. However, the high flux content in solder pastes leads to significant outgassing, resulting in voids, solder balling, and solder spattering around solder joints. The study demonstrates that by using flux-sprayed solder preforms instead of solder paste, the flux volume can be significantly reduced, thereby minimizing the outgassing and associated defects. The solder preforms are customized and the flux deposition is applied using spraying valves, and a controlled reflow soldering process is employed to melt the preforms. Experimental results show that the void level is reduced by using flux-sprayed solder preforms compared to traditional solder pastes. The solder balling and solder spattering are also effectively minimalized. This study provides an alternative assembly material for reflow, addressing the challenges associated with flux outgassing and offering improved solder joint quality.