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

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 degrees C. Design/methodology/approach The Cu3Sn solder joint was fabricated through soldering Cu/Sn/Cu structure and then aged at 420 degrees 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 Cu(41)Sn(11)solder joint (Cu/Cu41Sn11/Cu) at 10 h and finally into the full alpha(Cu) solder joint (Cu/alpha(Cu)/Cu) at 150 h during aging. Micro-voids formed in the center of the solder joint interface during the conversion of Cu(41)Sn(11)to alpha(Cu), resulting in lower reliability of the solder joint. Cu3Sn and Cu41Sn11 grains presented a column-like shape, while alpha(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, alpha(Cu) grains exhibited {100} preferred orientation. Originality/value Few researchers focused on the process of microstructure and grain orientation changes during high-temperature (> 300 degrees C) aging of Cu3Sn solder joint. To bridge the research gap, a high-temperature aging experiment was conducted on Cu3Sn solder joints.

Automated summary

This study investigated the changes in microstructure and grain orientation of the Cu3Sn solder joint during isothermal aging at 420 degrees C. It was found that the original Cu3Sn solder joint transformed into full Cu(41)Sn(11) solder joint and eventually into full alpha(Cu) solder joint during aging. The formation of micro-voids during the conversion process resulted in lower reliability of the solder joint. The average grain sizes of interfacial phases exhibited an initial increase followed by a decrease during aging. The preferred orientations of the different phases were also examined.