Wang Jintao, Wang Jianqiang, Zhang Luobin, Lv Ziwen, Chen Hongtao, Li Mingyu
Department of Materials Science and Engineering, Harbin Institute of Technology (Shenzhen), Shenzhen 518055, China.
State Key Lab of Advanced Solder and Joining, Harbin Institute of Technology, Harbin 150001, China.
ACS Omega. 2023 Aug 24;8(35):32176-32184. doi: 10.1021/acsomega.3c04762. eCollection 2023 Sep 5.
In order to optimize the interfacial properties by adding Co to the bumps of copper pillars and to overcome the strong tendency of Co to oxidize, an intermetallic compound (IMC) "capsule" was developed for the purpose of transporting elements through the intermetallic compound. In this study, we present a comprehensive analysis of the transformation process of CoSn nanoparticles into CoSn at the nanoscale using in situ heating transmission electron microscopy (TEM). The experimental results reveal that CoSn nanoparticle growth occurs through polymerization, whereas CoSn nanoparticle formation relies on the reaction between CoSn and Sn. During the initial stages of the reaction, Co dissolves and diffuses into Sn, leading to the nucleation and growth of CoSn in Sn via Ostwald ripening. As the input energy increases, vacancies in CoSn drive a reaction at the Sn/CoSn interface, resulting in the generation of CoSn. In this process, Sn nanoparticles enter the CoSn structure through the "Anti Structure Bridge (ASB) mechanism" to fill vacancies. Following the codeposition process, CoSn nanoparticles were successfully plated within the Sn layer of the Cu-pillar bumps. Upon reflow heating, the CoSn nanoparticles exhibited a preference for precipitating the vacant sites within the Sn layer. This process facilitated the release of Co atoms from CoSn, enabling their diffusion throughout the entire Sn layer.
为了通过在铜柱凸块中添加钴来优化界面性能，并克服钴强烈的氧化倾向，开发了一种金属间化合物（IMC）“胶囊”，用于通过金属间化合物传输元素。在本研究中，我们使用原位加热透射电子显微镜（TEM）对纳米尺度下CoSn纳米颗粒向CoSn的转变过程进行了全面分析。实验结果表明，CoSn纳米颗粒的生长通过聚合发生，而CoSn纳米颗粒的形成依赖于CoSn与Sn之间的反应。在反应的初始阶段，Co溶解并扩散到Sn中，通过奥斯特瓦尔德熟化导致CoSn在Sn中形核和生长。随着输入能量的增加，CoSn中的空位驱动Sn/CoSn界面处的反应，从而生成CoSn。在此过程中，Sn纳米颗粒通过“反结构桥（ASB）机制”进入CoSn结构以填充空位。在共沉积过程之后，CoSn纳米颗粒成功地镀覆在铜柱凸块的Sn层内。回流加热时，CoSn纳米颗粒倾向于在Sn层内的空位处析出。这一过程促进了Co原子从CoSn中释放，使其能够在整个Sn层中扩散。
