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The effect of ZnO nanoparticles on intermetallic compound (IMC) layer in solder joints was investigated by comparing plain Sn-3.0Ag-0.5Cu (SAC305) and Sn-3.0Ag-0.5Cu + 0.5ZnO composite solder during isothermal aging. It was shown that the morphology of the IMC layer in composite solder is flatter and the thickness of the IMC layer solder was thinner than the composite solder. The wettability was better and the melting point was not changed distinctly by adding ZnO nanoparticles into the SAC305 solder. The diffusion coefficients of plain SAC305 and composite solder were calculated and were 0.28 and 0.151 μm 2 h −1 , respectively. Furthermore, the activation energy of composite solder is higher, and it was indicated that the activation energy dominated the growth of the IMC layer in solder during aging. The emphasis was placed on the mechanism of ZnO nanoparticles, and it was clarified that the ZnO nanoparticles acted as an adsorbate and diffusion obstacle that restrained the diffusion of Sn and Cu atoms. Consequently, the growth of the IMC layer was suppressed on account of insufficient activation energy.

The interfacial intermetallic compound growth behavior of Sn-3.0Ag-0.5Cu lead free solder joints with 2.0wt.% ZnO of micrometer was investigated in this study. Solder joints were fabricated in F4N reflow furnace at 255°Cfor less than 5min and thereafter aged at 150°C up to 240h. Results showed that the IMCs layer were almost layer type and grew thicker with extended aging time. The IMCs of Sn-3.0Ag-0.5Cu-2.0ZnO composite solder was diffusion controlled mechanism by diffusion growth kinetics analysis, moreover, the diffusion coefficient of Sn-3.0Ag-0.5Cu-2.0Zn0 composite solder was 0.31 μm2/h and smaller than that of Sn-3.0Ag-0.5Cu plain solder, it revealed that ZnO powder can reduced the diffusion coefficient of interfacial intermetallic compound.

Abstract. Two different aging modes of continuous aging and interval aging were adopted to investigate the intermetallic compound (IMC) growth between Sn-3.0Ag-0.5Cu (SAC(305) )solder and Cu substrate. The morphologies of IMC layer are different during two different aging modes, and there is only one phase(Cu 6 Sn 5 phase) form during interval aging. Despite the different morphologies, the growth of IMC layers both follow diffusion control mode during two different aging styles, and the growth rate of IMC layer is slowlier over interval aging than that over continuous aging. In addition, it is illuminated the phenomenon of no Cu 3 Sn form during interval aging, this can be mainly explained by interval aging mode and diffusion growth mode, the free energy of system is not high enough to overcome the kinetic energy barrier and make the Cu 6 Sn 5 phase change into Cu 3 Sn. In a word, the reliability of SAC(305)/Cu solder joints can be improved during interval aging.

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