Ion implantation and subsequent annealing reshape the defect landscape and stress state of compound semiconductors, yet the temperature-dependent mechanisms in SiC remain incompletely understood. Here, we utilize molecular dynamics (MD) simulations and confocal micro-Raman measurements to resolve how implantation temperature and post-annealing regulate lattice disorder, amorphization kinetics, and residual-stress evolution in chemical vapor deposited (CVD) 4H-SiC. MD reveals surface-nucleated amorphization that propagates inward, whereas elevated implantation temperatures activate defect recombination pathways that suppress amorphous-layer formation. Raman signatures of optical-phonon shifts, linewidth broadening, and amorphization bands track the coupled evolution of lattice disorder and stress. Experimentally, increasing implantation temperature smooths the surface (S_a 0.133 → 0.101 nm) and reduces the amorphous-layer thickness (from ∼700 nm at 25°C to undetectable at 500°C), while driving more compressive residual stress (−57 → −132 MPa). Post-annealing largely restores phonon lifetimes and eliminates amorphization signatures, consistent with the recovery trends predicted by MD. These results delineate a thermal-treatment window that controls amorphization and residual stress in 4H-SiC, providing a transferable Raman-based methodology for nondestructive assessment of implantation-induced damage in compound semiconductors.

Fluxless tin soldering eliminates flux residues but introduces tin fog, which affects the reliability of electronic packaging. The influence of tin fog was first analyzed through the shear strength of the Al wires bonded on DBC substrates. After aging at 300 °C for 4 h, shear strength increased by 4.5 % on pure copper surfaces but decreased by 22.6 % on tin fog-covered surfaces. Further SEM revealed tin fog created interfacial porosity, reducing strength. Secondly, the impact of tin fog formation during the formic acid reflow process was studied under different formic acid concentrations and different vacuum frequencies during the reflow's preheating stage. Through SEM, EDS, Micro-IR, and XPS tests, the principal components of tin fog were identified as elemental tin, tin dioxide, and organic compounds such as amides and esters. It is found that tin fog forms through a process wherein tin formate produced during formic acid reflow adheres to the substrate surface, which is already adsorbed with organic substances such as esters and amides, and subsequently decomposes at high temperatures to generate derivative products creating the fog. Therefore, to mitigate tin fog formation, tin fog was effectively controlled under a tripled vacuum frequency, resulting in reduced organic residues on substrates. Under such a mitigation strategy, further reliability tests showed that the shear strength of Al wire bonding after aging at 300 °C was comparable to that on clean DBC substrates. This research provides a valuable reference for enhancing the reliability of fluxless soldering in electronic packaging.

The mechanical reliability of sintered silver joints, widely used in power electronics packaging, is critical for long-term applications such as electric vehicle converters. However, conventional homogeneous modeling often oversimplifies internal microstructural variations and limits the accuracy of stress prediction, especially under thermal cycling. In this study, a region-refined modeling framework is proposed to account for epoxy-regulated porosity and mechanical inhomogeneity across the joint. Pressureless die-attach joints were prepared using submicron silver pastes with varying epoxy contents (0∼4 wt%). The joint was divided into five sub-regions from the center to the fillet for localized characterization. Nanoindentation, SEM, and EDS analyses were conducted to assess region-specific mechanical properties and microstructure. Power-law constitutive models were extracted for each region and implemented into finite element simulations of thermal cycling (−55 ∼ 150 °C, 2 cycles/h, 250 h). The sub-region FEM model more accurately captured local stress concentrations and identified failure-prone areas, particularly near the fillet, compared to conventional homogeneous models. Experimental validation confirmed a good correlation between simulated stress zones and observed degradation. This sub-region strategy provides a robust framework for reliability prediction and design optimization of sintered silver joints in high-performance, large-area packaging applications.

This work investigated the impact of die-attach fillet geometry on the reliability of epoxy-based pressure-less sintered silver joints. Three types of sintered silver samples (Ag-0, Ag-1, and Ag-2) with 0%, 1%, and 2% epoxy content were prepared and characterized. Nanoindentation tests combined with inverse calculations were used to determine their elasto-plastic behavior. Fillet formation was influenced by organic solvent composition, dispense volume, and placement pressure, resulting in three geometries: rounded, triangular, and rounded rectangular. Finite element analysis was employed to simulate stress distribution and equivalent thermal strain under thermal cycling conditions (−55°C to 150°C). The simulation results were validated experimentally through shear strength testing and microstructural characterization using scanning electron microscopy (SEM). The findings highlight the significant role of fillet geometry, climbing height, and die-attach thickness in stress distribution and failure mechanisms, providing valuable insights into optimizing the die-attach process to enhance joint reliability in power electronics applications.

Pressureless sintered silver pastes composed of submicron particles represent a promising, cost-effective interconnect solution for power electronics. While epoxy additives are often introduced to modify solvent behavior and enhance mechanical integrity, they can simultaneously degrade electrical and thermal performance, leading to critical trade-offs. In this work, five custom-formulated pastes with varying epoxy contents (0–4 wt%) and two commercial benchmarks were systematically evaluated in terms of shear strength, resistivity, thermal conductivity, and coefficient of thermal expansion (CTE). To optimize across multiple criteria, the Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) was employed. The paste containing 2 wt% epoxy achieved the highest composite score, offering a favorable combination of mechanical, thermal, and electrical properties. Long-term reliability was further validated through high-temperature storage and thermal cycling tests. These results highlight that epoxy modulation, when integrated with an optimization framework, offers a viable strategy for tailoring high-performance, reliable sintered silver joints for next-generation power electronic packaging.