Influence of Micro-Additives on Lead-Free Solder Joints

The change of solder materials is driven by ever new requirements and legislations. Thus, lead-free tin based solders like tin-silver-copper (SAC) have become a standard in the electrical industry, especially in high-power modules. In terms of processing and behavior, they are still different to lead-based solders. In order to obtain lead-free solders with the familiar behavior and proven performance of lead-based solders, their development continues. Micro-additives in conventionally used SAC solder can improve mechanical properties, processability and durability. To evaluate these properties, we soldered different solder alloys with three individual micro-additives each and compare them with standard SAC solder. Following shear tests and optical inspection of the solder joints provide information about the differences in reliability, durability and phase growth caused by the individual micro-additives. By comparing two solders with combined micro-additives, the interaction of the additives can be estimated. In conclusion, it is clear that micro-additives can improve the standard solder. By adding different micro-additives, solder can be adapted to the requirements of different applications.