Erosion Resistance Properties of Iron–Carbon Composite Plating to Molten Lead-Free Solder

Abstract

The use of Sn-3mass%Ag-0.5mass%Cu lead-free solder (SAC305) has become common. Since SAC305 has a higher content of tin than conventional tin–lead eutectic solder, erosion of the Fe plating layer used in the solder iron tip and the point soldering machine nozzle frequently occurs. In this study, to prolong the life of the Fe plating layer, the applicability of composite plating in which a carbon-type filler is compounded with Fe was studied. Graphite and a multi-walled carbon nanotube (MWCNT) were used as filler materials in the composite plating layer. For both Fe-graphite and Fe-MWCNT composite plating layers, solderability testing and erosion-resistance testing were carried out. In the solderability test, although the spread rates of SAC305 to both Fe-graphite and Fe-MWCNT plating layers slightly decreased compared to the Fe plating layer, SAC305 solder was not repelled against both plating layers. In the erosion-resistance test, the Fe-MWCNT composite plating layer performed the best with the least erosion depth. The erosion depth of the Fe-graphite composite plating layer and the Fe plating layer were 10 and 100 times larger than that of the Fe-MWCNT composite plating layer, respectively. It was confirmed that the diffusion of Fe into molten SAC305 could be greatly reduced due to the composing carbon filler in Fe.