Effect of trace diamond nanoparticle addition on the interfacial, mechanical, and damping properties of Sn-3.0Ag-0.5Cu solder alloy

In the present study, small amounts of nanodiamond particles were added to Sn-3.0Ag-0.5Cu eutectic solder to investigate the growth kinetics of the intermetallic compound (IMC) layer at ball grid array pad/solder interfaces. The IMC growth behavior was found to be comparatively slower than that of plain solder joints due to a change in the diffusivity of the constituent atoms and the thermodynamic parameters of elemental affinity. The solder joints containing nanodiamond particles consistently showed higher hardness and strength than plain Sn-3.0Ag-0.5Cu solder joints, after a number of reflow cycles. The hardness of the doped solder was enhanced due to the homogeneous dispersion of nanoparticles, refining IMC phases which act as reinforcements in the solder matrix and as barriers to movement of dislocations. The fracture surface after shear testing of plain solder exhibited a relatively smooth fracture surface, while doped solder joints showed ductile failures with very rough dimpled surfaces. The damping capacity of the doped solder was better than the plain solder at a wide range of temperatures, and the solder with nanoparticle diamond exhibited lower internal friction. © 2013 TMS.