Analysis of Joining Boundary between Ni-P Electroless Plate and Solder by EPMA Scatter Diagram Method (I)

We have developed scatter diagram method to evaluate material structure from the X-ray image data of electron probe micro analyzer (EPMA). The X-ray image data are projected on the two dimensional space of X-ray intensity to make a histogram so called scatter diagram. The analysis of this scatter diagram gives us important information of the material such as distribution of elements in complex compounds.We have applied this method for the study of the bonding interface between Ni-P electroless plate and SnPb solder. We have found the coarse δ (Ni3Sn4) phase and mixture fine (Ni3Sn4)x+Pb(1-x) phase at the bonding interface between Ni-P electroless plate and the Sn-Pb solder. The existence P-rich region at the edge of solder side in the Ni-P electroless plate is confirmed.The analysis of fracture surface revealed that the crack is generated at the interface between P-rich region and δ-phase and proceeds towards the solder.