纳米压痕研究石墨烯增强Sn-Ag-Cu钎料焊点的高温蠕变行为

High Temperature Creep Behavior of Sn-Ag-Cu Solder Joints Reinforced by Graphene via Nanoindentation

当前,为应对电子封装产业微型化、高密度化的发展趋势,提高钎料焊点的可靠性,石墨烯增强锡基复合钎料成为研究热点。但相关研究多集中于石墨烯对界面反应及剪切强度的影响,对焊点高温蠕变行为及本构方程的研究较少。为强化传统的Sn基钎料,首先通过机械混合的方法制备了石墨烯增强Sn-Ag-Cu复合钎料。然后利用纳米压痕技术对复合钎料焊点在高温下的蠕变行为进行研究,并与Sn-Ag-Cu焊点进行了对比。试验结果表明,保载阶段,蠕变应力会发生松弛(Δσ),同时石墨烯可有效减慢焊点的蠕变应变速率,抑制晶界滑移,提高激活能。修正的Dorn模型考虑了位错强化、细晶强化、奥罗万强化、载荷传递强化等强化机制以及温度的影响,与纳米压痕得到的蠕变数据较好的吻合,验证了修正模型的有效性。

Currently,in order to cope with the development trend of miniaturization and high density of electronic packaging industry and improve the reliability of solder joints,graphene reinforced Sn-based composite solder has become a research focus.However,most of the related studies focus on the effects of graphene on interfacial reaction and shear strength,and there are few studies on the high temperature creep behavior and constitutive equation of solder joints.In order to strengthen the conventional Sn-based solder,graphene reinforced Sn-Ag-Cu composite solder was prepared by mechanical mixing method.Then,the creep behavior of composite solder joints at high temperature is studied by nanoindentation technology,and compared with Sn-Ag-Cu joints.The experimental results showed that the creep stress relaxation occurs during the holding stage.At the same time,graphene can effectively slow down the creep strain rate of joints,inhibit grain boundary sliding,and improve the activation energy.The modified Dorn model considers the strengthening mechanisms such as dislocation strengthening,fine grain strengthening,Orowan strengthening,load transfer strengthening and the influence of temperature,which was in good agreement with the creep data obtained by nanoindentation,and verified the effectiveness of the modified model.