Nano-metal materials have received considerable attention because of their promising performance in wide bandgap semiconductor packaging. In this study, molecular dynamics (MD) simulation was performed to simulate the nano-Cu sintering mechanism and the subsequent mechanical behaviors. Hybrid sintering, comprising nanosphere (NS) and nanoflake (NF), was performed at temperatures from 500 to 650 K. Furthermore, shear and tensile simulations were conducted with constant strain rates on the sintered structure at multiple temperatures. Subsequently, the extracted mechanical properties were correlated with the sintering behavior. The results revealed that the mechanical properties of the nano-Cu sintered structure could be improved by tuning material composition and increasing the sintering temperature. We established a relationship between the sintered microstructure and mechanical response. The shear modulus and shear strength of the sintered structure with NF particles increased to 41.20 and 3.51 GPa respectively. Furthermore, the elastic modulus increased to 55.60, and the tensile strength increased to 4.88 GPa. This result provides insights into the preparation phase of nano-Cu paste for sintering technology.

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During operation in environments containing hydrogen sulfide (H₂S), such as in offshore and coastal environments, sintered nanoCu in power electronics is susceptible to degradation caused by corrosion. In this study, experimental and molecular dynamics (MD) simulation analyses were conducted to investigate the evolution and mechanism of H₂S-induced corrosion of sintered nanoCu, and bulk Cu was used as the reference. The following results are obtained: (1) Both sintered nanoCu and bulk Cu reacted with O₂ prior to reacting with H₂S, forming Cu₂O, Cu₂S, CuO, and CuS. In addition, sintered nanoCu exhibited more severe corrosion. (2) For both sintered nanoCu and bulk Cu, H₂S-induced corrosion resulted in the deterioration of electrical, thermal, and mechanical properties, and sintered nanoCu experienced a greater extent of deterioration. (3) As was ascertained through Reactive Force Field (ReaxFF) MD simulations, the penetration of H₂S and O₂ combined with the upward migration of Cu resulted in the formation of a corrosion film. In addition, compared to bulk Cu, the H₂S and O₂ penetration in the sintered nanoCu structure was observed to occur to a greater depth, accounting for the more pronounced performance degradation.

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The power semiconductor joining technology through sintering of copper nanoparticles is well-suited for die attachment in wide bandgap (WBG) semiconductors, offering high electrical, thermal, and mechanical performances. However, sintered nanocopper will be prone to degradation resulting from corrosion in sulfur-containing corrosive environments such as offshore areas. In this study, experiments, including aging test and corrosion characterization, and simulations based on density functional theory (DFT) studies were conducted to explore the corrosion behavior and mechanism of elemental sulfur (S₈) and hydrogen sulfide (H₂S) on sintered nanocopper. The experimental results indicated that loose corrosion products were observed on the sintered nanocopper during the ageing process involving S₈, and compact layered corrosion products formed during the ageing process involving H₂S. Furthermore, similar corrosion product compositions (Cu₂O, Cu₂S, CuO, CuS, and potentially Cu₂SO₄ or CuSO₄) were observed in both the S₈- and H₂S-ageing processes. However, the S₈-ageing process exhibited more noticeable corrosion penetration. This was explained in simulations results: the unsaturated Cu sites on the oxide layer [Cu₂O(1 1 1)] of the sintered nanocopper could adsorb both H₂S and S₈, while the saturated Cu sites only exhibited the potential to adsorb S₈.

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The nano-copper particles are widely used in the sintering processes of packaging wide bandgap semiconductors. Despite the significant success in the industry, the mechanism bridging the sintering process to the mechanical properties of sintered nano-copper is not yet well-modeled. In this paper, the impacts of different sintering temperatures and initial porosities caused by different stacking patterns on the uniaxial tensile performance of the sintered layer were studied via a molecular dynamics approach. Two stacking patterns, simple cubic and face-centered cubic, were simulated, respectively. Evolution of their structure at temperatures of 300, 400, 500, and 600 K were simulated as the sintering process. Afterward, the sintered structures were subjected to uniaxial tensile with rates of 0.01 and 0.04 Å/ps at different temperatures to compare the mechanical properties. The results show that the sintering rate and density of the sintered structure increase with a higher temperature. However, the tensile strength of the sintered structure is less relevant to the difference in stacking pattern. This study proves that porosity has a greater effect on sintering quality.@en

In this article, the avalanche withstand capability and transient failure model of commercial 1200 V asymmetric trench gate SiC MOSFETs are investigated by experiment and simulation under single-pulse unclamped inductive switching (UIS) conditions. The limiting avalanche current and limiting avalanche energy of the device are determined by evaluating the voltage and current waveforms, the power dissipation, and the avalanche energy curves before and during avalanche failure. Then, by using the calibrated simulation model, the sequence between the critical electric field stress and critical thermal stress suffered by the device is revealed, and the transient failure mode of the device is proved to be the thermal runaway. Moreover, after decapping the failed device, the failure mode of the device is further confirmed by analyzing the failure point. Finally, by using the focused ion beam (FIB) technology, the failure mechanism of the device is confirmed as a structural rupture caused by avalanche thermal stress.@en

Nano-metal materials sintering has received increasing attention in recent years for its promising performance in the wide bandgap semiconductor packaging. In this paper, molecular dynamics (MD) simulation method were applied to simulate the nano-Cu sintering mechanism and the subsequent mechanical behavior. Hybrid sintering, comprising nanosphere (NS) and nanoflake (NF), was carried out at temperatures ranging from 500K to 650K. Furthermore, shearing simulations were conducted with constant strain rates on the sintered structure at multiple temperatures, and subsequently correlated the extracted mechanical properties with the sintering behavior. The results indicated that the mechanical properties of nano-Cu sintered structure were improved by tuning material composition and increasing the sintering temperature. We established a relationship between the sintered microstructure and mechanical response, the shear modulus and shear strength of the sintered structure with NF particles increased to 41.2GPa and 3.51GPa respectively. It offers valuable insights into the preparation phase of nano Cu paste for sintering technology.@en

The interactions of external disruptions and technical-human-organizational factors in emergency operations are usually observed. Resilience assessment of emergency systems can improve emergency response capability and system functional recovery. The increasing complexity and coupling of factors in emergency response systems need to be investigated from a system resilience perspective. In this paper, we propose to integrate a multi-stage System-Theoretic Accident Model and Processes (STAMP) with a dynamic Bayesian network (DBN) for the resilience assessment of emergency response systems. In the proposed methodology, emergency response systems are viewed as multi-step emergency operations for STAMP to analyze the hierarchical control and feedback structures. The output of multi-stage STAMP in controllers, actuators, sensors, and controlled processes is applied to develop a DBN for resilience assessment. For known external shocks (e.g., natural disasters), the effects of external shocks on the system are decomposed into subsystems or components. System degradation and recovery models are established. Regarding unknown external disruption (e.g., unforeseen failure modes), degeneration and recovery are temporally integrated into the analysis of system functionality. System performance is evaluated through the combination of socio-technical factors and external disasters. Eventually, the resilience of emergency response systems is obtained from the performance curves. The results demonstrate that the proposed model can evaluate system resilience after the system suffers from external disasters.@en