First-principles investigation of the structural and electronic properties of Cu6-xNixSn5 (x=0, 1, 2) intermetallic compounds

Cu6-xNixSn5 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 Cu6-xNixSn5 IMC. The structural and electronic properties of Cu6-xNixSn5 (x = 0, 1, 2) IMCs have been calculated. The results show that Ni atoms preferentially occupied 8f sites (Cu2) and formed Cu4NixSn5. The results of energy calculation and density of states demonstrate that this Cu4NixSn5 IMC had a more stable structure than Cu6Sn5. These results are also expected to account for the improvement in the reliability of the solder joint. (c) 2007 Elsevier Ltd. All rights reserved.