Effect of soldering temperature on cross-interaction at L-S interface of linear Cu/SAC305/Ni solder joints

In this paper, polycrystalline Cu/SAC305 solder/ polycrystalline Ni linear solder joints were used to study the liquid-solid interfacial reaction mechanism of Cu-Ni cross-interaction under narrow-pitch (120 μm) conditions under 250 and 300°C. The Cu-Ni cross-interaction mechanism was explored by the temperature influence on the IMC growth rate, morphological and type transitions on both sub sides. The results showed that: (1) After Cu/SAC305/Ni linear solder joint reacts at 250 °C for 60 min, (Cu,Ni) 6 Sn 5 type IMC is formed on both sides of the interface. The morphology of IMC grain on Cu side is always scalloped. Average diameter of IMC grains grows from 2.28 μm to 3.68 μm, and IMC layer at the interface reaches 12.39 μm. However, the IMC grain morphology at the Ni interface grows gradually from needle to stick, and the averages thickness of the interface IMC layer is 34.32 μm, which has a faster growth rate than the Cu side. (2) After Cu/SAC305/Ni linear solder joint reacts at 300 °C for 60 min, with the increase of temperature, the (Cu,Ni) 6 Sn 5 IMC appear on both sides interface. The morphologies of IMC grains translated from scallop-like to block. Average diameter of IMC grains increased from 2.57 μm to 7.65 μm, and average thickness of IMC layer reached 10.71 μm. The IMC grain morphology on Ni side interface also gradually increased from needle to block. The large and coarse transition into block, average thickness of IMC layer is up to 30.42 μm, which has a bigger growth rate than that on the Cu side. When the reaction temperature increases, the thickness of IMC layer on both sides do not increase, and even slightly decreases, and the interface morphology of the interface IMC changes toward a more coarse direction. The theoretical study of the Cu-Ni interaction at different temperature with linear Cu/SAC305/Ni solder joints is good for obtaining the good reliability of electronics packaging.