Cu基板表面镀镍浸金保护层对无铅焊点可靠性的影响

Effects of Electroless Nickle Immersion Gold Protective Finish of Cu on the Reliability of the Lead-free Solder Joint

结合Sn-3.5Ag和Sn-3.0Ag-0.5Cu两种无铅钎料研究了镀镍浸金层(Electroless Nickel Immersion Gold,ENIG)表面层对焊点界面反应以及力学性能的影响。结果表明,钎焊后在Sn-3.5Ag/ENIG/Cu界面主要生成(Ni_yCu_(1-y))_3Sn_4,在Sn-3.0Ag-0.5Cu/ENIG/Cu界面主要生成(Cu_xNi_(1-x))_6Sn_5。在Sn基钎料/ENIG(Ni)/Cu界面处生成金属间化合物的种类及形貌由焊点中Cu原子含量决定。在时效过程中,ENIG表面层中Ni层有效抑制了焊点界面处金属间化合物的生长,减缓了焊点剪切性能的下降。在钎焊过程中ENIG表面层中的Au层不参与界面反应而是进入钎料基体与Sn反应,但是在时效过程中Au原子向界面迁移并造成焊点界面金属间化合物成分和焊点剪切强度的明显变化。

The effects of Electroless nickel immersion gold（ENIG） on the interfacial reaction and solder joints＇ reliability was investigated in this paper.The results show that（Ni_yCu_（1-y））_3Sn_4 forms at the Sn-3.5Ag/ENIG（Ni）/Cu,while（Cu_xNi_（1-x））_6Sn_5 forms at the Sn-3.0Ag-0.5Cu/ENIG/Cu during the reflow.The composition and morphology of the interfacial intermetallic compounds（IMCs） show strong dependency on the Cu concentration in the solder joint.The Ni layer in the ENIG can retard the excessive growth of interfacial IMCs which is the culprit of the solder joints＇ failure during aging.The Au layer in ENIG exerts little influence on the interfacial reaction but reacts with Sn in the solder matrix during the reflow.In the stage of aging the Au migrates towards the interface and in turn changes the composition of the interfacial IMCs as well as the shear strength of the solder joint.