A comprehensive evaluation of the strength of AART solder joints

The alternative assembly and reflow technology (AART) process provides a mechanism for the simultaneous reflow soldering of surface mount and through hole components. AART provides for a shorter process sequence that avoids the use of wave and/or manual soldering. The strength of the solder joints that are formed via the AART process needs to be characterized, and is the focus of this paper. This research had two objectives. First, it benchmarked the strength of solder joints formed via the AART process against the traditional wave soldered joint. Second, it characterized the strength of solder joints that result when a less than optimal amount of solder was used. The failure mechanisms that were observed were catalogued for different solder volumes and solder paste types. It was found that the strength of the joint decreases when the solder paste volume deposited is less than 80% of the required volume. A transition in the failure mechanism was also observed as the solder volume decreased. Furthermore, this study showed that the solder joint strength and the failure mechanism were independent of the type of solder paste (water-soluble or no-clean). This investigation reconfirms the profound influence of the solder volume on the mechanical strength of the soldered joints and the predominant failure modes