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# Loughborough University Institutional Repository

 Please use this identifier to cite or link to this item: https://dspace.lboro.ac.uk/2134/19455

 Title: Perpendicular growth characteristics of Cu-Sn intermetallic compounds at the surface of Sn99Cu1/Cu solder interconnects Authors: Chen, ZhiwenLiu, ChangqingWu, YipingAn, Bing Keywords: Solder jointPlanar growth of IMCsPerpendicular growth of 31 IMCsInterdiffusionGrowth rateFormation sequence of IMCs Issue Date: 2015 Publisher: © The Minerals, Metals & Materials Society. Published by Springer. Citation: CHEN, Z. ...et al., 2015. Perpendicular growth characteristics of Cu-Sn intermetallic compounds at the surface of Sn99Cu1/Cu solder interconnects. Journal of Electronic Materials, 44(12), pp. 4836-4845. Abstract: The growth of intermetallic compounds (IMCs) on the free surface of 99Sn-1Cu solder joints perpendicular to the interdiffusion direction has been investigated in this work. The specimens were specifically designed and polished to reveal a flat free surface at the solder/Cu interface for investigation. After aging at 175°C for progressively increased durations, the height of the perpendicular IMCs was examined and found to follow a parabolic law with aging duration that could be expressed as $$y = 0.11\sqrt t$$, where t is the aging duration in hours and y is the height of the perpendicular IMCs in μm. For comparison, the planar growth of IMCs along the interdiffusion direction was also investigated in 99Sn-1Cu/Cu solder joints. After prolonged aging at 175°C, the thickness of the planar interfacial IMC layers also increased parabolically with aging duration and could be expressed as $$h_{\rm{IMC}} = 0.27\sqrt t + 4.6$$, where h is the thickness in μm and t is the time in hours. It was found that both the planar and perpendicular growth of the IMCs were diffusion-controlled processes, but the perpendicular growth of the IMCs was much slower than their planar growth due to the longer diffusion distance. It is proposed that Cu3Sn forms prior to the formation of Cu6Sn5 in the perpendicular IMCs, being the reverse order compared with the planar IMC growth. Description: The final publication is available at Springer via http://dx.doi.org/10.1007/s11664-015-4043-7 Version: Accepted for publication DOI: 10.1007/s11664-015-4043-7 URI: https://dspace.lboro.ac.uk/2134/19455 Publisher Link: http://dx.doi.org/10.1007/s11664-015-4043-7 ISSN: 0361-5235 Appears in Collections: Published Articles (Mechanical, Electrical and Manufacturing Engineering)

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