A comparative study between pure Pd and Pd(P) films on the solderability was performed. In the Sn-3Ag0.5Cu/Au/Pd/Ni(P) system (pure Pd case), (Cu,Ni)(6)Sn-5 and Ni3P were the predominant intermetallic species at the interface after the removal of the Au/Pd dual layer in soldering. We found that a significant growth of (Ni,Cu)(3)Sn-4 occurred between (Cu,Ni)(6)Sn-5 and Ni3P after aging at 180 degrees C for 500 h. This phenomenon was not observed in the reference case, in which a Pd(P) film had replaced the pure Pd layer before the reaction. The (Cu,Ni)(6)Sn-5/(Ni, Cu)(3)Sn-4 interface provided a crack initiation site, seriously deteriorating the high-speed ball shear resistance of the solder joints. The retarded growth of (Ni,Cu)(3)Sn-4 in the Pd(P) case was attributed to the presence of an additional Ni2SnP nanolayer between (Cu,Ni)(6)Sn-5 and Ni3P that prevented the outward diffusion of Ni, thereby inhibiting the formation of the undesired (Cu, Ni)(6)Sn-5/(Ni, Cu)(3)Sn-4 structure. The results of this study indicate Pd(P) film is more beneficial to the solderability than pure Pd. (C) 2012 Elsevier B.V. All rights reserved.