Development and Analysis of New Conductor Materials for Electronic Industry

以纯锡和不同银含量的二元Au-Ag合金为原料，采用扩散连接技术制备了夹心式锡/(金-银)/锡扩散偶。扩散偶在433~473K的温度下，在硅油油浴中进行不同时间的等温退火热处理。用扫描电子显微镜观察了扩散偶的显微组织，用电子探针分析了各相的化学成分。观察到，由于二元Au-Ag合金与纯锡之间的反应扩散，在扩散偶界面上形成了由Au-Sn二元化合物和Ag-Sn化合物组成的金属间化合物层。金属间化合物层的总厚度与退火时间的幂函数成正比。根据Au-Ag合金的成分不同，幂函数的指数取值在0.3到0.5之间。当指数等于0.5时，金属间化合物层的生长受体扩散控制。另一方面，当指数小于0.5时，晶界扩散和体积扩散共同作用于速率控制过程。因此，速率控制过程因Au-Ag合金的成分而异。幂函数的比例系数也随Au-Ag合金成分的不同而变化。当银的浓度为87at%时，比例系数达到最小值。这意味着Au-87Ag合金的金属间化合物层生长速度最慢。金属间化合物层是脆性的，具有很高的电阻率。结果表明，在通常的通电加热条件下，Au-87Ag合金是一种优良的抗反应扩散导体材料。

Sandwich Sn/(Au-Ag)/Sn diffusion couples were prepared from pure Sn and binary Au-Ag alloys with different Ag concentrations by a diffusion bonding technique. The diffusion couples were isothermally annealed at temperatures between 433 and 473 K for various times in an oil bath with silicone oil. For the cross-section of the annealed diffusion couple, the microstructure was observed by scanning electron microscopy and the chemical composition of each phase was determined by electron probe microanalysis. According to the observation, intermetallic layers consisting of binary Au-Sn and Ag-Sn compounds are formed at the interface of the diffusion couple due to the reactive diffusion between the binary Au-Ag alloy and pure Sn. The total thickness of the intermetallic layers is proportional to a power function of the annealing time. The exponent of the power function takes values between 0.3 and 0.5 depending on the composition of the Au-Ag alloy. When the exponent is equal to 0.5, the growth of the intermetallic layer is controlled by volume diffusion. On the other hand, grain boundary diffusion as well as volume diffusion contributes to the rate-controlling process, if the exponent is smaller than 0.5. Thus, the rate-controlling process varies depending on the composition of the Au-Ag alloy. The proportionality coefficient of the power function also changes depending on the composition of the Au-Ag alloy. The minimum value of the proportionality coefficient is realized for the concentration of 87 at% Ag. This means that the growth rate of the intermetallic layer is most sluggish for the Au-87Ag alloy. The intermetallic layer is brittle and possesses high electrical resistivity. As a result, it is concluded that the Au-87Ag alloy is an excellent conductor material with resistance against the reactive diffusion under usual energization heating conditions.