The Research on Characteristics of SAC305/Sn-37Pb/ENIG Solder Joint

Abstract

The reliability of the mix alloy of lead and lead-free components with SnPb paste is an important issue for military electronics. With the increase of density in PCB assembly, the traditional HASL pad has been gradually replaced by the ENIG pad for its better flatness and solderability. But the relationship between the interfacial morphology, microstructure and reliability of the alloy of lead and lead-free components still needs to be further studied. In this paper, the microstructure on the interface of SAC305/ Sn-37Pb/ ENIG solder joint is compared with that of typical SAC305/ Sn-37Pb3/ Cu solder joint, Sn63Pb37 / ENIG solder joint. It is found that the IMC layer on the interface of SAC305/Sn-37Pb/ENIG solder joint is more closer to compound (Cu, Ni) 6Sn5, and limited reflow soldering times has little effect on the strength of SAC305/Sn-37Pb/ENIG solder joint. Based on the case study, the thickness of gold layers has a significant effect on black pad problem in ENIG pad.