Abstract
The interfacial morphologies for the Sn-3Ag-0.5Cu/Ni-P joint were investigated using a field emission electron probe microanalyzer (FE-EPMA). As the Ni-Sn-P formed, several layers of P-rich layers including Ni 3 P, Ni 12 P 5 , and Ni 2 P were observed. The relationship between Ni-Sn-P formation and the evolution of P-rich layers was quantitatively analysed by FE-EPMA and by using the phase diagram of binary Ni-P. It was also proposed that once the Ni 2 P phase was formed, Sn atoms diffused from the solder matrix into Ni 2 P. As a result, the original Ni 2 P transformed to Ni 2 SnP due to the in-diffusion of Sn. © 2006 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.