Abstract:

The Au-Sn/Ni joints are prepared by the reflow bonding process, and the microstructure and phase composition are investigated by scanning electron microscope(SEM) with energy dispersive X-ray spectroscopy(EDS), the shear strength of the Au-Sn/Ni joint is detected by fatigue testing technology, the influence of the reflow process parameters on the microstructure and mechanical property of Au-Sn/Ni joint is researched. The results show that, the solder forms a (Au₅Sn+AuSn) eutectic microstructure after soldering at 310 ℃ for 1 min with water-cooling and air-cooling, and the (Ni, Au)₃Sn₂ intermetallic compound (IMC) is formed and distributes in the solder matrix, while the (Ni, Au)₃Sn₂ IMC layer is formation at the AuSn20/Ni interface. However, as to the furnace-cooling joints, the mass fraction of Ni increases in the solder matrix due to the lower cooling rate. The (Ni, Au)₃Sn₂ grows abnormally due to the consuming of (Au, Ni)Sn phase, which leading to the disappearence of eutectic microstructure in solder matrix. The thickness of IMC layer increases gradually with extension of reflow time, because of the continually diffusion of Ni atoms from the substrate to solder matrix. The shear strength of the Au-Sn/Ni joints decreases slightly with the increasing of the reflow time, and the failure mold is brittle fracture at the solder/Ni interface. In a word, the Au-Sn/Ni joint gets the best mechanical properties by reflow at 310 ℃ for 1 min, with the water-cooling process.

Key words: interfacial reaction, intermetallic compound(IMC), shear strength, Au-Sn/Ni joint