Effect of ultrasonic Ni-sprayed Cu substrates on the microstructures and properties of composite interconnection joints

Since during the soldering process via solder doping, the doped particles require more energy to interact with the interface layer, excessive energy consumption thus needs to be avoided. The process of Ni spraying Cu substrates prior to soldering offers a highly effective solution for reducing energy transfer. This study focused on the performance of composite solder (Sn58Bi/SAC105) on Cu- xNi (Cu substrates subjected to x minute Ni spraying), with the aim of conducting an in depth investigation into the effects of different Ni spraying durations on solder joints. To achieve the research aim, the changes in the microstructure of the solder joints and the growth of the intermetallic compound (IMC) layer were analyzed. Compared with soldering on plain Cu substrates, soldering on Ni sprayed Cu substrates led to a different situation. The Bi phase, which had previously formed a continuous network across a large area, began to disperse into fine particles due to the Ni spraying. Simultaneously, the precipitation of (Cu,Ni) 6 Sn 5 grains was promoted, thereby enhancing solder joint performance through the pinning effect. Ni spraying also suppressed the growth of the IMC layer and refined the IMC grains. In addition, the shear strength of the solder joints prepared on Ni sprayed Cu substrates was 38.42 MPa, which is approximately 10% higher than that of solder joints on Cu substrates. It is hoped that these findings will provide valuable insights for the field of electronic packaging and facilitate the wider application of surface treatment technologies in soldering.