Effect of isothermal storage on the microstructure and grain orientation of Cu/Cu₃Sn/Cu solder joint

Abstract

Purpose This study aims to analyse the changes in the microstructure and grain orientation of the full Cu3Sn solder joint (Cu/Cu3Sn/Cu) during isothermal aging at 420°C. Design/methodology/approach The Cu3Sn solder joint was fabricated through soldering Cu/Sn/Cu structure and then aged at 420°C. The microstructure evolution and grain orientation were studied by observing the cross-section and top-view surfaces of solder joints. Findings Original Cu3Sn solder joint initially transformed into the full Cu41Sn11solder joint (Cu/Cu41Sn11/Cu) at 10 h and finally into the full α(Cu) solder joint (Cu/α(Cu)/Cu) at 150 h during aging. Micro-voids formed in the center of the solder joint interface during the conversion of Cu41Sn11to α(Cu), resulting in lower reliability of the solder joint. Cu3Sn and Cu41Sn11 grains presented a column-like shape, while α(Cu) presented an irregular shape. The average grain sizes of interfacial phases first increased and then decreased during aging. Original Cu3Sn solder joint exhibited two main textures: [100]//TD and [203]//TD. For Cu41Sn11, the preferred orientation of [111]//TD was found in the early nucleation stage, while the orientation of the formed full Cu41Sn11 solder joint was dispersed. Furthermore, α(Cu) grains exhibited {100}<100> preferred orientation. Originality/value Few researchers focused on the process of microstructure and grain orientation changes during high-temperature (> 300°C) aging of Cu3Sn solder joint. To bridge the research gap, a high-temperature aging experiment was conducted on Cu3Sn solder joints.