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Formation Mechanism of Novel Sidewall Intermetallic Compounds in Micron Level Sn/Ni/Cu Bumps

  • Original Article - Electronics, Magnetics and Photonics
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Abstract

A new kind of intermetallic compounds (IMC) were found around copper pillar in micron level bumps. To investigate the formation mechanism, three different sized Sn/Ni/Cu bumps (10 μm, 20 μm, 50 μm) were electroplated then reflowed at 230 °C for 100 s. After reflow process, a thin layer of IMC was formed around copper pillar, which is attributed to surface wetting behavior. After aging at 170 °C and 200 °C for different times, the growth mechanism of sidewall IMC was observed by scanning electron microscopy combined with electron backscatter diffraction (EBSD) technology. Surface diffusion was considered to be the main driving force for sidewall IMC growth for the activation energy of them was found to be much smaller than that in previous studies. The EBSD results showed a preferred orientation of sidewall Cu3Sn grains <100> being perpendicular to copper periphery, which indicated direction of Cu atoms flux during Cu3Sn growth. Formation mechanism of this novel sidewall IMC was proposed based on surface wetting and surface diffusion. The findings contribute to the failure mechanism study in small size bumps and provide insights into the reliability of 3D electronic packaging.

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Funding

This work is sponsored by the National Basic Research Program of China (973 Program, 2015CB057200) and the National Natural Science Foundation of China (61376107). We also thank the Instrumental Analysis Center of Shanghai Jiao Tong University, for the use of the SEM equipment.

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Authors and Affiliations

  1. State Key Laboratory of Metal Matrix Composites, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China

    Siru Ren, Menglong Sun, Zebin Jin, Yukun Guo, Huiqin Ling, An-min Hu & Ming Li

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  1. Siru Ren
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Correspondence to An-min Hu.

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Ren, S., Sun, M., Jin, Z. et al. Formation Mechanism of Novel Sidewall Intermetallic Compounds in Micron Level Sn/Ni/Cu Bumps. Electron. Mater. Lett. 15, 562–571 (2019). https://doi.org/10.1007/s13391-019-00154-7

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