Drop reliability study of PBGA assemblies with SAC305, SAC105 and SAC105-Ni solder ball on Cu-OSP and ENIG surface finish

Lead free SnAgCu solder joints used in surface mount packages like Ball Grid Array (BGA) have a great impact on the reliability of the end product. The mechanical properties of the solder are important factors. By changing the concentration of silver and copper, or by doping a very low portion of the fourth element (e.g. Ni), the strength of solder can be optimized. In this work, the board-level drop test reliability performance of different PBGA soldered assemblies with three different solder ball alloys (SAC305, SAC105 and SAC 105-Ni200ppm ) and two surface finishes (Cu-OSP and NiAu) were studied. We found that SAC105-Ni showed the best impact reliability performance among the 3 types of materials, followed by SAC105 and SAC305 for either OSP or NiAu surface finish. OSP surface finish showed better drop lifetime than NiAu surface finish regardless of the type of solder used in the assemblies.