回流次数对In3Ag焊料微观组织和剪切性能的影响

用扫描电镜和能量色散仪分别对In3Ag焊料焊点基体及其与铜基板界面IMC（Intermetallic compound）层的组织结构进行观察和分析,用力学试验机测试焊点的剪切强度,研究了电子封装中回流次数对In3Ag焊料微观组织和剪切性能的影响。结果表明:随着回流次数的增加,基体中二次相AgIn2显著长大,由颗粒状变为长条状,界面IMC层（成分为（Ag,Cu）In₂）的厚度线性增加,其生长由界面反应速率和组元扩散速率混合控制,焊点剪切强度呈下降趋势,由1次回流的5.03 MPa降到5次回流的2.58 MPa;回流1、2、3次后焊点剪切断裂方式均为焊料内部韧性断裂,回流5次后断裂机制转变为韧脆混合断裂。

Effects of Multiple Reflows on Microstructure and Shear Properties of In3Ag Solder

The IMC layer microstructure and the composition of ln3Ag solder joint were observed and analyzed using SEM and EDS,and the shear strength of solder joint was measured using mechanical testing machine.The effects of reflow soldering cycles on microstructure and shear property of ln3Ag solder were investigated.The results show that with increase of the reflow soldering cycles,the quadratic phase Agln₂ in solder matrix grows prominently,and the shape changes from grain to long strip.The thickness of（Ag,Cu）In₂ layer increases linearly,which is controlled by interfacial reaction rate and component diffusion rate.The shear strength of solder joints decreases with reflow soldering cycles increasing,and those decrease from 5.03MPa after one cycle to 2.58MPa after five cycles.The fracture type is ductile fracture in solder matrix after 1,2 and 3 cycles.After five reflow soldering cycles,the fracture type belongs to the mixed fracture of toughness and brittleness.