Bi对Sn-0.3Ag-0.7Cu-xBi/Ni焊点IMC的影响

Influence of Bi on IMC of Sn-0.3Ag-0.7Cu-xBi/Ni Solder

无铅钎料和基板间金属间化合物(IMC)的生长对元器件的可靠性有重要影响。使用Sn-0.3Ag-0.7Cu-xBi无铅钎料与Ni盘进行焊接,并对焊点进行了180℃时效试验,时效时间分别为0、24、96、216和384h。采用金相显微镜、扫描电镜和能谱仪观察分析了钎料与Ni界面IMC的生长及形貌变化,并对其焊点IMC层Ni的分布进行了分析,同时对其界面生长速率进行了拟合。结果表明:Sn-0.3Ag-0.7Cu焊料与Ni焊盘之间的IMC是棒状的(CuxNi1-x)6Sn5,Bi的加入并没有起到很好的抑制作用,而是随着Bi含量的增加IMC先增加后减少。Sn-0.3Ag-0.7Cu/Ni焊点IMC中Ni的平均含量(wNi)分为15%、5%两区域,由近Ni向钎料基体方向呈下降趋势。但是Sn-0.3Ag-0.7Cu-3.0Bi/Ni焊点IMC中Ni的平均含量在7%左右。时效后IMC层的厚度会随着老化时间的延长而增加,但是Sn-0.3Ag-0.7Cu-xBi/Ni焊点由于Bi的析出IMC增长得缓慢;Sn-0.3Ag-0.7Cu/Ni焊点(CuxNi1-x)6Sn5中15%Ni的含量区域逐渐过渡到5%区域,但是Sn-0.3Ag-0.7Cu-xBi/Ni焊点IMC中Ni的平均含量维持9%较时效前有所增加。通过生长速率计算,Sn-0.3Ag-0.7Cu-xBi/Ni焊点IMC的生长速率随着Bi含量的增加而减少。

The growth of intermetallic compounds（IMC） between lead-free solder and pad has an important influence on the reliability of primary device.Ni substrate was welded by Sn-0.3Ag-0.7Cu-xBi lead-free solder,and the joints were aging-treated at 180℃,aging time was 0,24,95,216 and 384 h respectively,The growth and morphology characteristics of the IMCs were investigated by metallographic microscope,SEM and EDX.The content change of Ni in the IMC was also analysed,meanwhile,the IMC growth rates were fitted by experimental data.The results show that the IMC between Sn-0.3Ag-0.7Cu-xBi and Ni substrate is（CuxNi1-x）6Sn5.The effect of controlling the thickness of IMC is not very good after the addition of Bi,with the increase of Bi content,the thickness of IMC firstly increases,then decreases,when the content of Bi is more than 1.0%.And there are two regions whose average content of Ni in the Sn-0.3Ag-0.7Cu/Ni solder IMC is respectively 15wt% and 5wt%,which show a descending tend from the near Ni substrate side to the bulk solder side.But the average content of Ni in Sn-0.3Ag-0.7Cu-3.0Bi/Ni solder IMC is 7%.After aging,the thickness of IMC increases as aging time prolonging.But the growth speed of Sn-0.3Ag-0.7Cu-3.0Bi/Ni IMC is slower than Sn-0.3Ag-0.7Cu/Ni IMC,because of the precipitation of Bi.Besides,the content of Ni in the（CuxNi1-x）6Sn5 decreases from 15% to 5%,but the average content of Ni in Sn-0.3Ag-0.7Cu-xBi/Ni IMC increases from 7% to 9%.According to the calculation,the growth rate of Sn-0.3Ag-0.7Cu-xBi/Ni IMC decreases as Bi content increasing.