Wang Fengyi,Ma Jingyuan,Liu Jiahao,Ji Hongjun,Chen Hongtao
This study investigates using an antioxidation copper particle-free paste, formulated with self-reducing copper formate, for Cu-Cu bonding in electronic packaging applications. The research highlights the oxidation resistance of copper formate compared to traditional copper nanoparticles (CuNPs) and its ability to generate CuNPs through thermal decomposition. Experimental results demonstrate that the sintering process benefits from releasing reductive gases during decomposition, improving joint quality with reduced porosity and enhanced mechanical strength at elevated temperatures. Molecular dynamics simulations further elucidate the sintering behavior of CuNPs, providing significant insights into pore collapse, atomic mobility, and neck formation. The findings indicate that increased temperatures enhance surface and bulk diffusion, facilitating robust particle connections. Overall, this work establishes the potential of copper formate for achieving reliable interconnects in semiconductor devices, paving the way for advancements in material formulations for direct copper–copper bonding.
The third-generation wide-bandgap semiconductor devices are supposed to be operated in a severe condition of high temperature. Die-attach bonding is also critical to realizing such high temperature operation. Cu particles paste has attracted considerable interest recently due to the superior conductivity and mechanical properties of copper. This work developed a long-time stable Cu paste with self-reducibility. The long-time stability can be attributed to the oxide passivation layer, the construction of physical barrier of polyethylene glycol 400 (PEG400) and the acid protection of ascorbic acid (AA). Additionally, both AA and PEG400 serve as reductants during the sintering process. AA initially reduces the oxides, while the reducing gases decomposed from PEG400 further enhance the reduction. Through combining the reduction process with the sintering process, in-situ generated fresh Cu nanoparticles with high surface energy can promote the necking growth of Cu grains, and lead to a stronger strength. In addition, it is revealed that the AA content, sintering temperature and sintering time play important roles in the sintering behaviors of Cu paste, thus affecting the mechanical and electrical properties of copper joints. The 2 wt.% AA joints that sintered for 5 min at 300 ℃ had an average shear strength of 43.91 MPa, which is 2.6 times higher than that of the bonding joints without AA. The utmost shear strength of 51.30 MPa and a low electrical resistivity of 8.85 × 10 –8 Ω m were achieved by sintering for 30 min. This long-term stable Cu paste paves the way for the wide application of Cu paste in power electronics.
危险品化学品经营许可证（带存储）