Cu6Sn5和Ni3Sn4结构性能的第一原理计算

基于密度泛函理论的第一原理,计算了锡基无铅焊点界面常见的金属间化合物Cu6Sn5和Ni3Sn4的平衡晶格常数、合金形成焓以及弹性常数,分析了结构稳定的电子机制.结果表明,Cu6Sn5较Ni3Sn4合金形成能负,因此Cu6Sn5在热力学上更稳定,其合金化能力也较强.在力学性能方面,两相均属脆性相,表现出弹性各向异性,而Ni3Sn4的键合作用较强,弹性模量、剪切模量均大于Cu6Sn5,但Cu6Sn5表现出更好的塑性.从电子结构的角度,Cu6Sn5的成键主要来自于Cu原子d,p轨道与Sn原子p杂化,而Ni原子d轨道与Sn原子p轨道的强烈杂化作用是Ni3Sn4成键的主要原因.

First-principles investigation on structure and properties of Cu6Sn5 and Ni3Sn4 intermetallic compounds

Cu6Sn and Ni₃Sn₄ are important intermetallic compounds(IMCs), which were known to greatly improve the reliability of the soldered joints.In this paper, the first-principles calculations were performed to determine the stable structure of Cu₆Sn₅ and Ni₃Sn₄ IMCs.The structural and electronic properties of Cu₆Sn₅ and Ni₃Sn₄ IMCs were calculated.The results of energy calculation and density of states demonstrate that Cu₆Sn₅ IMCs have a more stable structure than Ni₃Sn₄.The results also show that they are exhibit anisotropy in elastic modulus.Moreover, the Ni₃Sn₄ shows more strong bonding effect and exhibits greater elastic modulus.However, Cu₆Sn₅ performs better in plastic, which is expected to account for the improvement in the reliability of the soldered joint.