Selective electrochemical etching for the investigation of solder joint microstructures

Hereby we introduce a method called selective electrochemical etching for the investigation of solder joint microstructures. The aim of this technique is to remove the tin from the solder joint, which enables the examination of the remaining intermetallic microstructures in such a detail, which is unlike to any other previously established method. In our work we discuss the importance of intermetallic compound (IMC) investigation and compare the existing methods with our proposed technique. Pilot measurement results are also presented on selectively etched SAC (Sn-Ag-Cu) alloy solder joints. We present the found relationship between 1) the soldering methods and parameters, 2) the resulting microstructures, 3) the amount of the removed charge/Sn phase during the etching and 4) shear test results on the different solder joints. In our paper we will also investigate the effect of the etching conditions (e.g. etching time, electrolyte concentration, etc.) in order to reach the optimal etching depth, considering the detail and integrity of the intermetallic structures.