Characteristic evaluation of electroless nickel-phosphorus deposits with different phosphorus contents

The surface morphology, electrical property and reaction with solder alloy of two electroless nickel-phosphorus (EN-P) deposits (Ni 7wt.%P and Ni-10wt.%P) were investigated in this study. The P content of the EN-P layer decreased with increasing pH value. The ENP plating layers had an amorphous structure and the electrical resistivity of the layer increased with increasing P content. Reaction layers of Ni3Sn4, Ni2SnP and Ni3P formed at the interfaces between the Sn-3.5Ag solder and the two EN-P deposit layers. The thickness of the interfacial Ni3Sn4 intermetallic compound (IMC) layer in the Sn-3.5Ag/Ni-7wt.`/`P joint was thicker than that in the Sn-3.5Ag/Ni-10wt.%P joint, whereas the thickness of the Ni3P layer increased with increasing P content. These study results confirmed that the interfacial reaction between solder and the EN-P layer is significantly affected by the composition (P content) of the EN-P layer. (C) 2007 Published by Elsevier B.V.