Effect of CoSn3 nanocrystals on Sn3Ag plating for electronic packaging

Jintao Wang; Luobin Zhang; ZiWen Lv; Jianqiang Wang; Weiwei Zhang; Xinjie Wang; Hongtao Chen; Mingyu Li

doi:10.1038/s41598-023-48159-5

Effect of CoSn₃ nanocrystals on Sn3Ag plating for electronic packaging

Sci Rep. 2023 Nov 24;13(1):20693. doi: 10.1038/s41598-023-48159-5.

Authors

Jintao Wang^{1

2

3}, Luobin Zhang^{4

5

6}, ZiWen Lv^{4

5

6}, Jianqiang Wang^{4

5

6}, Weiwei Zhang^{4

5

6}, Xinjie Wang^{4

5

6}, Hongtao Chen^{7

8

9}, Mingyu Li^{10

11

12}

Affiliations

¹ Department of Materials Science and Engineering, Harbin Institute of Technology (Shenzhen), Shenzhen, 518055, China. jintaowcqu@foxmail.com.
² State Key Lab of Advanced Brazing and Joining, Harbin Institute of Technology, Harbin, 150001, China. jintaowcqu@foxmail.com.
³ Sauvage Laboratory for Smart Materials, Harbin Institute of Technology (Shenzhen), Shenzhen, 518055, China. jintaowcqu@foxmail.com.
⁴ Department of Materials Science and Engineering, Harbin Institute of Technology (Shenzhen), Shenzhen, 518055, China.
⁵ State Key Lab of Advanced Brazing and Joining, Harbin Institute of Technology, Harbin, 150001, China.
⁶ Sauvage Laboratory for Smart Materials, Harbin Institute of Technology (Shenzhen), Shenzhen, 518055, China.
⁷ Department of Materials Science and Engineering, Harbin Institute of Technology (Shenzhen), Shenzhen, 518055, China. chenht@hit.edu.cn.
⁸ State Key Lab of Advanced Brazing and Joining, Harbin Institute of Technology, Harbin, 150001, China. chenht@hit.edu.cn.
⁹ Sauvage Laboratory for Smart Materials, Harbin Institute of Technology (Shenzhen), Shenzhen, 518055, China. chenht@hit.edu.cn.
¹⁰ Department of Materials Science and Engineering, Harbin Institute of Technology (Shenzhen), Shenzhen, 518055, China. myli@hit.edu.cn.
¹¹ State Key Lab of Advanced Brazing and Joining, Harbin Institute of Technology, Harbin, 150001, China. myli@hit.edu.cn.
¹² Sauvage Laboratory for Smart Materials, Harbin Institute of Technology (Shenzhen), Shenzhen, 518055, China. myli@hit.edu.cn.

Abstract

Plating Sn3Ag on copper substrates represents a crucial electronic packaging technique. In this study, we propose a novel composite plating approach, wherein CoSn₃ nanocrystals are deposited within the Sn3Ag coating. The resulting reflowed Sn3Ag joints exhibit a range of distinctive properties. Notably, CoSn₃ nanocrystals dissolve in Sn during the reflow process, thereby lowering the supercooling required for Sn nucleation. Consequently, Sn crystals grow in six-fold cyclic twins. Additionally, the dissolution of Co atoms in Sn leads to a reduced solubility of Cu atoms in Sn, consequently lowering the supercooling required for the nucleation of Cu₆Sn₅. Simultaneously, this phenomenon promotes the nucleation of Cu₆Sn₅, resulting in a considerable precipitation of Cu₆Sn₅ nanoparticles within the joints. Therefore, the mechanical properties of the joints are significantly enhanced, leading to a notable 20% increase in shear strength. Furthermore, the presence and distribution of Co elements within Sn induce changes in the growth pattern of interfacial Cu₆Sn₅. The growth process of Cu₆Sn₅ is dominated by the interfacial reaction, leading to its growth in a faceted shape. During the aging process, the dissolution of Co elements in Sn impedes the continuous growth of Cu₆Sn₅ at the interface, causing Cu₆Sn₅ to be distributed in the form of islands inside the joint. Remarkably, elemental Co acts as an inhibitor for the development of Cu₃Sn and reduces the occurrence of Kirkendall voids.