SOLDER BALL JOINT RELIABILITY WITH ELECTROLESS NI/PD/AU PLATING-INFLUENCE OF PHOSPHORUS CONTENT AND THICKNESS OF ELECTROLESS PD PLATING FILM

摘要

There have been so many reports about the solder joint reliability (SJR) of electroless Ni/Pd/Au plating (ENEPIG) for two decade. In these reports, almost electroless Ni plating is Ni-P and all immersion Au plating is pure gold. But electroless Pd plating has two type, pure Pd and Pd-P. In this study, the both influences of phosphorus content and thickness of electroless Pd plating film of ENEPIG were investigated on the solder-ball joint reliability with using a high-speed solder-ball shear test. In particular, we examined the SJR in the case of ENEPIG finished substrates that had undergone multiple reflow cycles. After reflow, we observed intermetallic compounds (IMCs) of interface between solder and ENEPIG. We consider that the shape of the IMCs is important factor that influences the SJR after multiple reflow cycles. Our results show that SJR of ENEPIG tends to be poorer on the condition of the higher phosphorus content and the thicker electroless Pd. We conclude that pure Pd plating has the widest thickness range, and that the optimum thickness of the pure Pd plating film is 0.05～0.2 μm. On the other hand, the high phosphorus content and thick Pd-P films extremely lower SJR of ENEPIG. We found that the structure of IMCs changed from dendrite type to dome type with the increase of P content in electroless Pd plating. Consequently, we inferred that the high adhesion at the dendrite type IMC/solder interface resulted in excellent solder-ball joint reliability after the reflow cycles.