Effects of location and size of Kirkendall voids on mechanical response of Cu/Sn solder joint under tension

• Published in: Molecular simulation Vol. 49; no. 9; pp. 885 - 892
• Main Authors: Wu, Cheng-Da, Liu, Kai-Wei
• Format: Journal Article
• Language: English
• Published: Abingdon Taylor & Francis 13.06.2023; Taylor & Francis Ltd
• Subjects: Copper; Elastic deformation; intermetallic compound; Mechanical analysis; Molecular dynamics; Solder joint; Soldered joints; Solders; stress; Tensile stress; Tensile tests; Tension tests; Tin; void; Voids
• ISSN: 0892-7022; 1029-0435
• DOI: 10.1080/08927022.2023.2202754

The effects of the location and size of Kirkendall voids at the nanoscale on the mechanical response of a Cu/Sn solder joint under a tension test are studied using molecular dynamics simulations. The simulation results show that the ultimate stress and ultimate strain of a solder joint with two pre-existing voids decrease with increasing void radius regardless of the distance (L 2 ) between the centre of void 2 and the interface when the distance (L 1 ) for void 1 is 4 nm. The elastic deformation period of the solder joint shortens with increasing void radius for void radii ≥3 nm. At the end of the tensile test, a collapse occurs at the layer interface when the two pre-existing voids are very small (e.g. void radius = 1 nm) regardless of the L 2 value. For two pre-existing voids with different radii, cracks at the interface grow toward the larger void and then merge with it when the two voids are close to the interface (e.g. L 1  = L 2  = 4 nm). Fracture occurs at the pre-existing voids when the two voids have large radii (e.g. 4 nm) and are very close to each other.