First-principles investigation of the structural and electronic properties of Cu 6− xNi xSn 5 ( x = 0, 1, 2) intermetallic compounds

Abstract

Cu 6− x Ni x Sn 5 is an important intermetallic compound (IMC), which was known to greatly improve the reliability of the solder joints in integrated circuits. However, the improvement mechanisms and even the crystal structure of the IMC were not fully understood. In this paper, the first-principles calculations were performed to determine the stable structure of Cu 6− x Ni x Sn 5 IMC. The structural and electronic properties of Cu 6− x Ni x Sn 5 ( x = 0, 1, 2) IMCs have been calculated. The results show that Ni atoms preferentially occupied 8f sites (Cu2) and formed Cu 4Ni 2Sn 5. The results of energy calculation and density of states demonstrate that this Cu 4Ni 2Sn 5 IMC had a more stable structure than Cu 6Sn 5. These results are also expected to account for the improvement in the reliability of the solder joint.