Active element Ti plays a crucial role in the graphite soldering process. However, the atomic interaction mechanism between the active element Ti and graphite remains unclear. In this study, the enhancement effect of the active element Ti on the Sn-based alloy filler/graphite soldering interface was investigated by employing first-principles calculations combined with experimental methods. Based on the first-principles calculations, the adhesion work of the Sn/graphite interface models doped with two and four Ti atoms is 0.884 J/m and 1.896 J/m, respectively, while that of the clean model is negative. Moreover, the segregation heat of the Sn/graphite interface model doped with more Ti atoms is more negative. All of these results indicate that Ti atoms doped at the Sn/graphite interface play a significant role in enhancing the interface. The electronic structures of the interface models with different numbers of titanium atoms were analyzed. The results revealed that the enhancement of the Sn/graphite interface was attributed to the transfer of electrons from the Ti-3d orbitals to the C-2p orbitals, leading to a strong interaction between the Ti and C atoms. The segregation of Ti was clearly observed at the Sn3·5Ag4Ti (Ce,Ga)/graphite soldering interface in the experiments, which was consistent with the results from the first-principles calculations. The shear strength of the Sn3·5Ag4Ti (Ce,Ga)/graphite soldered joint was tested, and an enriched region of titanium was found in the fracture surface on the graphite side. In addition, a tensile simulation was performed on the clean and Ti-doped Sn/graphite interfaces, and the results indicated that the Sn/graphite interface model enriched with Ti atoms had greater tensile simulation strength than that of the clean Sn/graphite interface model. These results further showed that Ti played a reinforcing role at the Sn/graphite interface. The results from our study provide a theoretical basis for exploring low-temperature active bonding methods in the packaging process of graphite connected to the heat dissipation surface of electronic devices.

中文翻译：

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活性元素Ti改善锡基合金填料/石墨焊接界面：第一原理与实验研究相结合

活性元素Ti在石墨焊接过程中起着至关重要的作用。然而，活性元素Ti与石墨之间的原子相互作用机制仍不清楚。本研究采用第一性原理计算结合实验方法，研究了活性元素Ti对Sn基合金填料/石墨焊接界面的增强作用。根据第一性原理计算，掺杂2个和4个Ti原子的Sn/石墨界面模型的粘附功分别为0.884 J/m和1.896 J/m，而清洁模型的粘附功为负。此外，掺杂较多Ti原子的Sn/石墨界面模型的偏析热更负。所有这些结果表明，在Sn/石墨界面掺杂Ti原子对增强界面起到了重要作用。分析了不同钛原子数量界面模型的电子结构。结果表明，Sn/石墨界面的增强归因于电子从Ti-3d轨道转移到C-2p轨道，导致Ti和C原子之间的强相互作用。实验中在Sn3·5Ag4Ti(Ce,Ga)/石墨焊接界面处明显观察到Ti的偏析，这与第一性原理计算的结果一致。测试了Sn3·5Ag4Ti(Ce,Ga)/石墨焊点的剪切强度，在石墨侧断口处发现了钛富集区。此外，对干净和Ti掺杂的Sn/石墨界面进行了拉伸模拟，结果表明，富含Ti原子的Sn/石墨界面模型比干净的Sn/石墨界面模型具有更大的拉伸模拟强度。这些结果进一步表明Ti在Sn/石墨界面上起到了增强作用。研究结果为探索电子器件散热表面石墨封装过程中的低温活性键合方法提供了理论依据。