回流焊对SnAgCuBi/Cu焊点IMC及剪切强度的影响

Effect of reflow soldering on the IMC and shear strength of Sn-0.3Ag-0.7Cu-xBi/Cu solder joints

利用金相显微镜和扫描电镜对多次回流焊后的Sn-0.3Ag-0.7Cu-xBi/Cu焊点IMC和剪切断口形貌进行了观察和分析。结果表明:Bi的加入提高了接头剪切强度,且随着Bi含量的增加而增加,当w(Bi)为4.5%时达最大值45.07MPa,同时Bi的加入有效抑制了焊点IMC的增长。经过5次回流焊后,未加入Bi的焊点剪切强度由24.55MPa下降到20.82MPa,而加入w(Bi)为3.0%的焊点剪切强度由35.95MPa下降到32.46MPa。

The morphology of the intermetallic compound （IMC） and the shear fracture surface of Sn-0.3Ag-0.7Cu-xBi/Cu solder joints, which have experienced several cycles of reflow soldering, were observed by scanning electron microscope （SEM） and metallurgical microscope. The results show that the shear strength of Sn-0.3Ag-0.7Cu/Cu solder joints is enhanced by the introduction of Bi and increases with increasing Bi content, with the largest shear strength of 45.07 MPa being reached at a Bi content of 4.5% （mass fraction）. Moreover, the incorporation of Bi effectively inhibits the increase of the thickness of IMC. After five reflow cycles, the shear strengths of solder joints without Bi and with 3.0% （mass fraction） of Bi decreases from 24.55 MPa to 20.82 MPa and from 35.95 MPa to 32.46 MPa respectively.