With the miniaturization and high-power requirements of microelectronic devices, the current density carried by interconnects in packaging structures continually increases and reaches the threshold of electromigration (EM) failure. In this study, we investigated the microstructure evolution and void formation in aluminum (Al) interconnects during EM at three different current densities (1/3/5 MA/cm ²) and proposed a method coupling the fully coupled theory with an optimized atomic flux divergence method. The results show as follows. First, for the interconnects in integrated circuits, current density is the main factor affecting the EM lifetime of the interconnects in a certain temperature range. With the gradual increase of current density, the contribution of thermal transfer on EM cannot be ignored. The atomic concentration gradient and stress gradient can inhibit EM failure. Second, the increase of length and the decrease of width of interconnect will lead to the increase of atomic flux inside the structure, resulting in the accumulation of voids and atoms. Third, the structure is dynamically reconstructed after deleting the atoms below the failure threshold and the simulation results agree well with the experimental results. Compared with the traditional atomic flux divergence method, the improved atomic flux divergence method based on the fully coupled theory can better fit the change trend of atomic concentration after interconnect failure, and the failure time error is reduced by about 10%.

Optical micro-electromechanical systems (MEMS) demand exceptional precision, yet warpage during the die attach process on printed circuit boards can compromise performance. Here, a three-dimensional thermoelastic analytical model has been developed based on Fourier heat conduction and supported beam theory. This model facilitates the in-situ calibration of solder parameters via confocal micro-Raman spectroscopy, ensuring that the simulated dynamic evolution of warpage during soldering aligns closely with digital image correlation experiments. The results show consistence with Finite Element Method with error less than 1 % and time saving more than 60 %. Orthogonal experimental analysis further reveals that substrate thickness and thermal expansion coefficient variations are the primary factors affecting warpage, while chip area has a negligible role. Given the practical challenges in reducing substrate thickness, a stress-balancing strategy incorporating an additional transition layer is proposed, which is effectively validated with a high-resolution three-dimensional profilometer. This work provides valuable insights into the predictive modeling and warpage behavior characterization, directly supporting improved mitigation strategies in the die attach process.

Pressureless sintered silver paste is widely used in SiC power electronic packaging for its superior thermal and electrical properties, enabling efficient heat dissipation and improved device reliability. Current thermal conductivity models frequently assume isotropic thermal behavior to simplify heat transfer calculations, yet these models neglect the inherent anisotropic porosity of sintered silver materials. This omission introduces errors in the characterization of these materials' thermal performance. This research investigates how the spatial anisotropic distribution of pressureless sintered silver's microstructure impacts QFN packaging's overall thermal conduction performance. This investigation is achieved by comparing lateral/vertical porosity differences between two materials and applying multidimensional thermal conductivity modeling. Two types of pressureless sintered silver were employed as die-attach materials to fabricate SiC MOSFET-based QFN packaging. The sintered microstructures' lateral and vertical cross-sections were characterized using scanning electron microscopy (SEM), enabling quantitative extraction of anisotropic porosity distributions. Subsequently, a numerical model was developed using the extracted porosity data to enhance the accuracy of heat transfer predictions in sintered silver layers while considering anisotropic thermal conductivity. Thermal resistance characterization was conducted on two QFN packages, and the accuracy of the proposed modeling methodology was validated by establishing the interrelation between experimental thermal resistance measurements and theoretical thermal conductivity predictions. This study demonstrates a refined approach to evaluating and optimizing sintered silver materials, providing a more accurate and application-driven thermal management strategy for SiC MOSFET power packaging.