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.

Citation

Yang, G., Li, X., Han, X. and Li, S. (2023), "Effect of isothermal storage on the microstructure and grain orientation of Cu/Cu₃Sn/Cu solder joint", Soldering & Surface Mount Technology, Vol. 35 No. 1, pp. 44-50. https://doi.org/10.1108/SSMT-04-2022-0034