High power discrete package commonly uses high lead (Pb) solder paste as die attach and interconnect material. Voiding in solder joint is an on-going problem especially for power electronics. Void, caused by lack of solder or poor wetting in the solder bonds, will slow down or limit the heat dissipation of the power discrete packages, which can lead to thermal failure.
By increasing the soldering profile peak temperature or prolong the soldering time, voids reduction can be achieved. However, this leads to an increase in the flux activity during reflow soldering process and resulted flux hardening condition.
Proper cleaning of the discrete packages is essential after reflow soldering to remove the flux residue generated from die attach and clip attached (DACA).
To find out the impact of cleaning effectiveness against the different peak reflow temperatures on the discrete packages, the authors had developed a series of test plan to evaluate the cleaning effectiveness for the discrete packages soldered with the common high lead solder pastes that available in the market.