Selective electrochemical etching of the Sn-3Ag-0.5Cu/0.07 wt% graphene nanoparticle composite solder

Abstract

The morphological changes of SAC305 solder alloy with the addition of 0.07 wt% graphene was investigated using selective electrochemical etching. To evaluate the effect of graphene inclusion, selective electrochemical removal of the β-Sn phase from SAC305 and SAC305/0.07GNP was performed using a standard three-electrode cell approach at specific potentials determined by cyclic voltammetry. The phase, chemical structure and microstructural changes were observed. The texture and the phases of SAC305 solder paste were retained, while the microstructure of β-Sn and Ag3Sn was refined owning to graphene addition. Sufficient removal of β-Sn without affecting other phases was obtained by using etching potential below −350 mV. Due to Van der Waals force attraction, two types of agglomeration of graphene were observed from cross-sectional observation. Large agglomerations seen at the vicinity of solder/substrate interface were found to help in forming diffusion barrier. This contributes to the refinement of microstructure with the presence of graphene. Accurate observation regarding the shape and texture of the intermetallic compound (IMC) phases affected by the addition of graphene provided by selective electrochemical removal helps better insight into understanding the electrochemical dissolution mechanism of SAC alloys.

Keywords

• Lead-free solders
• Sn-3.0Ag-0.5Cu
• Selective electrochemical etching
• Microstructure
• Graphene
• Composite solder