基于纳米压入法Sn-Ag-Cu无铅焊料高温力学性能的研究

On the Mechanical Properties of Sn-Ag-Cu Lead-free Solder at High Temperature Based on Nanoindentation

无铅化和微型化已经成为电子封装的发展趋势,温度对无铅焊点的可靠性产生了不可忽视的影响。本文对Sn96.5Ag3Cu0.5无铅焊料进行回流处理,采用纳米压入法研究其在实际工况下的高温力学性能。结果表明,温度对焊料试样的力学性能影响显著。随着温度的升高,弹性模量和硬度逐渐降低,焊料发生软化;较高温度下的蠕变应力指数较小,焊料的蠕变抗力降低,其相应的蠕变激活能为76kJ/mol。由此可知,随温度的升高,焊料的蠕变机制由位错攀移逐渐转变为晶界滑移。

Lead-free and miniaturization have become the development trend of electronic packaging,so the effect of temperature on lead-free solder joint reliability is negligible.In this paper,mechanical properties at high temperature of Sn96.5Ag3Cu0.5lead-free solder subjected reflux treatment were investigated by using nanoindentation.Results show that temperature has a great effect on mechanical properties of lead-free solder samples.Along with the increase of temperature,both elastic modulus and hardness decrease gradually and solder is softening.The creep stress exponent is smaller at higher temperature,indicating the lower creep resistance.The creep activation energy of Sn96.5Ag3Cu0.5lead-free solder subjected reflux treatment is 75.5KJ/mol.From above results,it is known that along with the increase of temperature,the creep mechanism of Sn96.5Ag3Cu0.5lead-free solder is gradually transformed from dislocation climb into grain boundary sliding.