热老化与热循环条件下Bi对Sn-1.0Ag-0.5Cu无铅焊点界面组织与性能的影响

研究了在热老化和热循环过程中Bi的添加对低银无铅钎料Sn-1.0Ag-0.5Cu (SAC105)的BGA焊点界面微观组织演变的影响，分析了Bi的添加对SAC105微焊点热老化与热循环剪切性能的影响. 结果表明，Bi元素添加量为2%(质量分数)时，对热循环过程中微焊点界面处金属间化合物(IMC)层整体厚度的增加起到抑制作用，同时阻碍了热循环过程中因焊点热失配导致的IMC层破碎. 但是Bi的添加促进了界面IMC层中Cu₃Sn层的生长，因此在经过20天以上热老化处理后SAC105-2Bi微焊点界面IMC层厚度与SAC105微焊点接近. 此外，Bi的添加可以显著提升热循环处理后SAC105微焊点的抗剪切能力. SAC105-2Bi微焊点的剪切力学性能受到热循环处理的影响较小. 与SAC105微焊点相比，SAC105-2Bi微焊点的断裂模式更早地从韧性断裂向脆性断裂转变，因此Bi的添加降低了SAC105微焊点的热循环可靠性.

Effect of Bi addition on interfacial microstructures and properties of Sn-1.0Ag-0.5Cu Pb-free solder joints during isothermal aging and thermal cycling

Effect of Bi addition into Sn-1.0Ag-0.5Cu (SAC105) Pb-free solder on the interfacial microstructural evolution in BGA solder joints was studied, and the shear properties of solder joints during isothermal aging and thermal cycling were analyzed The results showed that 2wt.% Bi addition into SAC105 depressed the growth intermetallic compound (IMC) thickness at the interface of solder joints during thermal cycling, and also depressed the breaking of interfacial IMC layer caused by thermal mismatch of solder joints during the thermal cycle. However, Bi addition can also increase the shear strength of SAC105 solder joints during thermal cycling or isothermal aging, while the effect of thermal cycling treatment on shear properties on SAC105-2Bi solder joints is little. Compared with SAC105 solder joints, Bi addition changed the failure mode from ductile to brittle mode of SAC105-2Bi solder joints during thermal conditions. Therefore, Bi addition decreased the thermal cycling reliability of SAC105 solder joints.