Fengjiang Wang

This study formulates an organic vehicle system using triethylene glycol monobutyl ether as the solvent, ethyl cellulose as the binder, and oleic acid as the dispersant to investigate the low‐temperature pressureless sintering of silver paste. The effects of sintering temperature and the composite ratios of silver powders with different sizes and morphologies (400 nm spherical silver powder, 2 μm flake silver powder, and 300 nm flake silver powder) on the electrical and mechanical properties of the sintered bodies were systematically studied. Results indicate that increasing the sintering temperature reduced the number of pores while increasing their size, leading to improved densification that approached the compact structure of bulk silver, thereby optimizing performance. The morphology and size of the silver powders significantly influenced the sintering behavior. Flake powders reduced interfacial resistance through two‐dimensional planar contacts, whereas spherical powders enhanced electrical performance and shear strength by forming more sintering necks. A synergistic effect was achieved by combining spherical and flake powders. Notably, when spherical silver powder was blended with 300 nm flake silver powder at a ratio of 1:3, a minimum porosity of 1.658% was achieved, along with a shear strength of 63.34 MPa and a volume resistivity of 4.85 × 10 ⁻⁶ Ω cm. Furthermore, comparative analysis revealed the distinct advantages of the smaller flake powder over its larger counterpart (2 μm) in enhancing sintered quality, providing experimental basis for the material selection of silver paste.

This study systematically investigated the thermomigration behavior of Sn–35Bi solder joints under both temperature gradient and isothermal aging conditions, with particular emphasis on the comparative effects of Cu and Ni substrates as hot‐end materials on microstructural evolution. Through comprehensive finite element modeling (FEM) and detailed microstructural characterization, the results revealed that replacing Cu with Ni as the hot‐end substrate significantly influenced the thermomigration phenomena. During solid‐state thermomigration, the Ni substrate effectively reduced the temperature gradient from 914 to 794°C/cm, thereby suppressing the asymmetric growth of interfacial intermetallic compounds (IMCs) and retarding Bi segregation. In liquid‐state thermomigration, the Ni substrate demonstrated a similar beneficial effect, decreasing the temperature gradient from 159 to 143°C/cm and reducing the IMC growth rate at the cold end. Furthermore, under isothermal aging conditions, the Ni substrate maintained excellent phase stability by preserving the uniform distribution of the Bi phase throughout the solder joint. These findings underscore the superior performance of Ni substrates in mitigating thermomigration‐induced microstructural degradation, offering valuable insights for enhancing the reliability of Sn–35Bi solder joints in advanced electronic packaging applications.

In this work, we proposed a fully carbon-based p-electron altermagnetic semiconductor, denoted as AM-C33, featuring a bandgap of 0.52 eV, spin-splitting energy of 0.31 eV, and transition temperature of 121.5 K.

Due to their long-distance spin transport and long spin lifetime, p-electron-induced spintronic materials have been attracting increasing attention. As the most common d-electron-free elements, carbon allotropes present many excellent properties. However, pure three-dimensional carbon spintronics material has not been reported so far. Here, we proposed a superhard (HV = 60 GPa) carbon material named half-metal (HM)-C21, which presents multi-stable magnetic states and unexpected properties, such as those of half-metal, half-semiconductor, bipolar magnetic semiconductor, and asymmetric antiferromagnetic semiconductors. The mechanical, dynamical, and thermodynamical stabilities of HM-C21 are confirmed. Moreover, HM-C21 is considered to be a promising candidate for an unidentified cubic-form carbon reported in previous experiments. Hence, the present work holds great promise for discovering spintronic materials in pure three-dimensional carbon.