Although silver sintering is widely used in die attach, its reliability under low-pressure and pressureless sintering conditions remains a challenge, and the degradation mechanism needs to be addressed urgently. This study investigates the degradation mechanisms of silver sintered die attach subjected to thermal shock (TS) (−45 °C to 125 °C), revealing its microstructural evolution, degradation of mechanical properties, and pore dynamics. After 1500 cycles, the average porosity did not decrease and remained at approximately 10%, but the porosity distribution exhibited significant heterogeneity, forming three characteristic regions of high porosity, low porosity, and crack regions. With the porosity evolution, the grain size increased by a factor of 2.1–2.8, with the largest grain sizes in the crack region, and the recrystallization fraction decreased significantly, from 89.6 % to a range of 37.3 %–72.1 %. Additionally, the combination with the decrease in both statistically stored dislocation density and total dislocation density reveals a decline in hardness and yield strength of silver sintered layer from 1.05 GPa and 326 MPa to 0.92 GPa and 231 MPa, respectively, gradually diminishing their ability to impede pore migration and merging. Thermal-mechanical coupling simulations based on the actual porous structure images show that the mismatch in the coefficient of thermal expansion induces alternating tensile and compressive thermal stresses, driving pore evolution and crack propagation. The kinetic Monte Carlo (KMC) Potts model based on Kawasaki dynamics combined with pore conservation can effectively predict the long-term pore evolution in this case. These findings provide important guidance for optimizing the sintering process and improving the application of silver sintering materials in high-reliability electronic packaging.

Residual stress and thermally induced warpage are critical reliability concerns in power electronic packaging, particularly when employing sintered copper nanoparticle (Cu NP) interconnects. While these interconnects provide high thermal and electrical performance, they also introduce significant interfacial stresses during bonding that alter mechanical behavior during service. This study develops an integrated confocal Raman–analytical modeling framework to directly quantify and mechanistically interpret these stresses in a representative SiC/Sintered Cu NPs/Active Metal Brazing ceramic substrate (AMB) stack. Raman spectroscopy reveals a compressive interfacial stress field peaking at −334 MPa near the chip center with localized hotspots linked to microporosity. Complementary in-situ Moiré interferometry tracked warpage evolution during thermal cycle (30–310°C). Coupling this stress measurement with a three-dimensional thermoelastic model, and explicitly assigning the bonding temperature as the stress-free reference, enables accurate reproduction of the temperature-dependent warpage trajectory. The model predictions align with experimental interferometry within < 5% deviation. These results demonstrate that incorporating residual stress is essential to realistically capture thermo-mechanical evolution. The proposed Raman–model paradigm advances beyond prior purely numerical or purely experimental efforts by bridging quantitative stress mapping with predictive warpage modeling. This methodology provides essential insights for thermal-induced residual stress and warpage managements in high-temperature power electronics packaging, providing a stress-informed foundation for reliability assessment and design optimization.

This study investigates the interface strength and fracture behavior of sintered copper (Cu) nanoparticles (NPs) for all-Cu integration in advanced microelectronics packaging. Micro-cantilever bending tests on three configurations (Cu NP-notched, interface-notched and un-notched micro-cantilevers) were analyzed using scanning electron microscopy (SEM), transmission electron microscopy (TEM), transmission Kikuchi diffraction (TKD) and cohesive zone model (CZM). The interface-notched micro-cantilevers demonstrate superior fracture resistance, with a stress intensity factor (K_Q) of 2.88±0.10 MPa m^1/2, compared to 2.12±0.11 MPa m^1/2 for Cu NP-notched micro-cantilevers. Simulation results, consistent with experimental results, reveal that Cu NP-notched micro-cantilevers exhibit lower fracture resistance due to porosity and stress concentrations, while interface-notched micro-cantilevers show enhanced strength, attributed to robust bonding and reduced void distribution. Un-notched micro-cantilevers display superior load-bearing capacity, with cracks bypassing the interface and propagating through porous regions. Moreover, in un-notched micro-cantilevers, a synergistic deformation mechanism is observed, where crack propagation through the sintered Cu NPs coexists with plastic slip deformation in the Cu substrate. These findings highlight the strong interfacial bonding and effective stress transfer at the Cu substrate-sintered Cu NP interface, validating the feasibility of direct sintering using Cu NPs without additional coatings.

Accurate characterization and calculation of the interfacial stresses are of key importance for the optimization of the chip sintering process and the evaluation of the long-term reliability of the chip interconnect. In this study, the pioneering application of confocal Raman spectroscopy for the accurate, rapid, and nondestructive characterization of interfacial stresses at the interconnections of silicon carbide chips was undertaken. Silicon carbide chips (5 mm ∗ 5 mm) were mounted to active metal brazing substrates by pressure-assisted sintering using copper nanoparticles. Subsequently, finite element simulations were used to model the thermally induced deformation and stress in the SiC chip. The thermally induced warpage of the SiC chip was then measured using interferometry. Finally, confocal Raman spectroscopy was employed to measure the interface stress distribution at the SiC sintered copper interface. The results showed that finite element simulations could not accurately assess the thermally induced deformation and stress in the SiC chip. The proposed method based on confocal Raman spectroscopy for testing chip interconnection interface stresses achieved an excellent balance between accuracy, non-contact measurement, and non-destructive testing. The residual stress at the backside interface of the SiC chip was concentrated in the central region of the chip, with compressive stress values ranging from -139 MPa to -165 MPa. Theoretically, this study provides a new framework for modeling and researching the reliability of electronic packaging interfaces.

With the rapid development of new energy vehicles and offshore wind power systems in coastal cities, the application scale of power devices is constantly increasing. However, the corrosion problem of power packaging interconnection materials caused by the humid air and chlorine-rich environment near the sea is gradually emerging. This study addresses the corrosion protection of sintered nano-copper by innovatively employing atmospheric pressure plasma jet (APPJ) technology with hexamethyldisiloxane (HMDSO) as precursor to construct organic-inorganic hybrid hydrophobic coatings on copper surfaces. Experimental results demonstrate that the coating exhibits a three-dimensional crosslinked Si-O network structure. The synergistic effect between surface micron-scale spherical clusters and methyl groups elevates the contact angle by 50 % to 153.1° Electrochemical characterization reveals that the coating positively shifts corrosion potential by 0.035 V and reduces corrosion current density from 6.008×10−7 A/cm2 to 5.542×10−7 A/cm2, while maintaining higher activation energy across the experimental temperature range (30–60℃). EIS tests show that the coating effectively increases the charge transfer impedance of the sample, indicating an improvement in corrosion resistance. The 168-hour immersion test confirms effective barrier against Cl−corrosive attack with preserved substrate integrity. Density functional theory (DFT) simulations elucidate that unsaturated methylated fragments in HMDSO preferentially graft onto copper surface via chemisorption, where strong interfacial bonding energies (-2.26 ∼ -4.38 eV) facilitate cleavage and crosslinking to form stable siloxane networks. This work proposes a novel anti-corrosion surface engineering strategy for copper interconnects, while revealing the plasma-induced interfacial bonding mechanisms of hybrid coatings, providing both theoretical and experimental foundations for developing durable electronic packaging materials.

Van der Waals heterojunctions (vdWHs) have garnered significant attention for their promising applications in optoelectronics, attributed to their exceptional physical attributes. In this study, we present a straightforward approach to fabricating high-performance vdWHs photodetectors. Specifically, we prepared WSO_x/WS₂ vdWH photodetectors through the ozone oxidation of a WS₂ thin films at 100 °C. To characterize the morphology and optical properties of both the WS₂ and WSO_x/WS₂ thin films, we utilized atomic force microscopy (AFM) and Raman spectroscopy. Additionally, X-ray photoelectron spectroscopy (XPS) was employed to delve into the structural evolution by scrutinizing the bonding states of W, O, and S in the WS₂ before and after the ozone oxidation process. The resultant WSO_x/WS₂ vdWH photodetectors exhibited impressive photoelectric performance at wavelengths of 475 nm and 532 nm. It demonstrated a high responsivity of 230.7 A/W, a remarkable specific detectivity of 1.794 × 10¹¹ Jones, and a swift response speed of 60 ms at 475 nm. Furthermore, first-principles calculations based on density functional theory (DFT) were conducted to validate the oxidation kinetics of monolayer WS₂, the type II energy band alignment, and the interlayer charge transfer within the WSO_x/WS₂ vdWH. This research contributes novel insights into the synthesis of two-dimensional transition metal oxides (TMOs)-transition metal dichalcogenides (TMDCs) heterostructures for photodetector applications.

This study investigates the size-dependent mechanical behavior and deformation mechanisms of sintered copper (Cu) nanoparticles (NPs) through micro-pillar (2–6 μm diameter) compression tests, scanning electron microscopy (SEM), transmission electron microscopy (TEM), transmission Kikuchi diffraction (TKD) analysis and molecular dynamics (MD) simulations. In-situ micro-pillar compression tests reveal a 25.9% reduction in yield strength (812 ± 64 MPa to 643 ± 47 MPa) with increasing pillar size, attributed to dislocation starvation in smaller pillars and porosity-driven strain localization in larger ones. TKD quantifies dynamic grain refinement (24.9% reduction in grain size) and geometrically necessary dislocation (GND) density escalation (74.8%), driven by stress gradients and grain boundary-mediated plasticity. Nanoindentation-derived elastic modulus (48.3 ± 11.1 GPa) exceeds micropillar values (29.5–33.9 GPa), reflecting substrate constraints in bulk testing. Microstructural analysis identifies a transition from shear banding in high-porosity pillars to uniform plasticity in denser systems, mediated by texture evolution (Brass/S components) and Schmid factor redistribution (62% increase in high-slip-activity grains). MD simulations of pressure-sintered Cu NPs elucidate atomic-scale mechanisms: dislocation nucleation at sintering necks, pore collapse-induced strain localization, and grain boundary sliding. These findings establish a multiscale framework linking porosity, grain refinement, and dislocation dynamics to mechanical performance, emphasizing microstructural optimization for enhanced reliability in microelectronic applications. The integration of MD simulations bridges atomic-scale mechanisms to microscale deformation, providing actionable insights for tailoring sintered Cu NPs via reduced porosity and controlled grain boundary architectures.

In harsh offshore environments, large-area sintered nano-copper (Cu) interconnections, which serve as die attachment material or thermal interface material (TIM), are prone to degradation from hydrogen sulfide (H2S) corrosion. This study introduced a film-forming technique based on atmospheric pressure plasma jet (APPJ) to improve the corrosion resistance of large-area sintered nanoCu joint. The corrosion protection mechanism against H2S-containing atmospheric corrosion was investigated using both experimental methods and density functional theory (DFT) simulations. The key findings were as follows: (1) The deposition film, primarily composed of a Si-O3 network, effectively protected sintered Cu plate from corrosion by H2S gas, and maintaining the mechanical performance of sintered Cu joint after 384 h of H2S testing. (2) The dissociation products of the APPJ-treated precursor hexamethyldisiloxane (HMDSO), −OSiCH3 and −OSi(CH3)3, formed stable chemical bonds on the sintered nanoCu surface, resulting in the formation of −OSiCH3(O-CH3)2 fragments. (3) The −OSiCH3(O-CH3)2 fragments were unreactive toward to corrosion agents such as H2S, O2, and H2O, and also serving as a barrier to block their access to the sintered nanoCu surface. This study provided a comprehensive understanding of the corrosion protection mechanism of sintered nanoCu using APPJ-deposited films, offering valuable insights for improving the reliability of power electronics.

The mechanical strength of sintered nanoparticles (NPs) limits their application in advanced electronics packaging. In this study, we explore the anisotropy in the microstructure and mechanical properties of sintered copper (Cu) NPs by combining experimental techniques with molecular dynamics (MD) simulations. We establish a clear relationship between processing conditions, microstructural evolution, and resulting properties in pressure-assisted sintering of Cu NPs. Our findings reveal that pressure-assisted sintering induces significant anisotropy in the microstructure, as evidenced by variations in areal relative density and the orientation distribution of necks formed during sintering. Specifically, along the direction of applied pressure, the microstructure exhibits reduced variation in areal relative density and a higher prevalence of necks with favorable orientations. The resulting anisotropic mechanical properties, with significantly higher strength along the pressure direction compared to other directions, are demonstrated through micro-cantilever bending tests and tensile simulations. This anisotropy is further explained by the combined effects of strain localization (influenced by areal relative density) and the failure modes of necks (determined by their orientation relative to the loading direction). This work provides valuable insights into the analysis of sintered NPs microstructures and offers guidance for optimizing the sintering process.

High-energy Al ion implantation is an indispensable technique for achieving precise doping in fabricating 4H‑SiC devices. However, it inevitably introduces interfacial damage and residual stress that can compromise subsequent manufacturing processes and device reliability. Conventional destructive characterization techniques cannot provide real-time, in‑situ, nondestructive monitoring under process conditions, creating a major bottleneck in quality control. Here, we establish a predictive modeling framework that integrates multiscale simulations with advanced, non‑destructive micro‑Raman spectroscopy to systematically investigate the evolution of high-energy Al ion implantation–induced interface defects and residual stress in 4H-SiC. Simulation results reveal a linear relationship between the implantation dose and the formation of vacancies and interstitial defects, while the stress accumulation tends to saturate at higher doses due to a dynamic equilibrium among defect interactions. Complementary micro‐Raman spectroscopy corroborates the simulations, showing that the damaged interface layer deepens from approximately 300 nm at a dose of 1014 ions cm−2 to nearly 500 nm at 1016 ions cm−2, consistent with Monte Carlo predictions. Furthermore, the molecular dynamics simulations capture a trend of the implantation stress evolution with strong concurrence with the Raman-measured residual stress. This combined computational–experimental approach elucidates the fundamental mechanisms governing defect formation and residual stress in ion‑implanted 4H‑SiC, establishes implantation dose as the pivotal role of 4H-SiC in defect density and residual stress, and underscores the utility of optical‑based characterization in real‑time, non‑invasive quality control for advanced manufacturing.

4H-SiC is widely employed in power electronic devices operating under high frequencies, voltages, and temperatures due to its exceptional physical properties. However, its inherent high hardness and elastic modulus induce inevitable residual stress during device fabrication. Raman spectroscopy, which leverages lattice dynamics, offers an effective, non-destructive, rapid, and contactless method for measuring these stresses. Nevertheless, its accuracy critically depends on precisely determining the Raman phonon deformation potential constant. This work investigates mechanically induced Raman shifts in 4H-SiC via first-principles calculations and in-situ Raman spectroscopy under hydrostatic and non-hydrostatic stress conditions. The E2(TO) and A1(LO) phonon modes exhibit sensitivity to hydrostatic stress, whereas A1(LO) remains largely unaffected under shear, reflecting directional vibrational differences. Theoretical predictions and experimental measurements agree well within 16% error, highlighting the effectiveness of Raman-based stress detection for 4H-SiC. This integrated theoretical–experimental approach provides a robust framework for stress and strain analysis, facilitating the design and fabrication of next-generation 4H-SiC electronic devices.

The degradation mechanisms of silicon carbide (SiC) VDMOSFET and trench metal oxide semiconductor field effect transistor (MOSFET) in a 60Co gamma irradiation environment were investigated. The degradation of electrical characteristics of SiC MOSFET in different working states after irradiation with different total ionizing doses (TIDs) was explored. The defects induced during the irradiation process were studied in annealing experiments conducted after irradiation. The reasons for the degradation of SiC MOSFET caused by TID were revealed, and a prediction model of threshold voltage (Vth) shift was proposed and verified through TCAD simulation. The Vth, breakdown voltage (BV), on-resistance R, input capacitance (Ciss), output capacitance Coss, and reverse transfer capacitance C _rss were measured at different irradiation doses and annealing conditions. Experimental results indicated that the degradation of both Ron and Ciss was primarily caused by the Vth shift. As the doses increased, the shift in Vth gradually reached saturation. Similar trends to VDMOSFET were observed in trench MOSFET but with greater sensitivity to TID. In addition, MOSFETs biased at zero voltage exhibited lower shifts in Vth compared with those under high gate bias conditions. Furthermore, the increase in defects in the gate oxide during irradiation and annealing processes were calculated. Finally, a model predicting Vth shift path was established, and its accuracy and limitations were determined. This study provides valuable insights into the effect of TID on SiC MOSFETs.

Investigating the interconnection and strengthening mechanisms of die-attach layers is instrumental for advancing die attach process toward low-pressure and, ultimately, pressureless sintering while maintaining reliability. This study compares the microstructure and micromechanical heterogeneity of the pressure-assisted and pressureless regions in SiC die attach to elucidate the interconnection and strengthening mechanisms. Recrystallized grains make up 71.7 % of the pressureless region, markedly lower than the approximately 90 % observed in the pressure-assisted region, resulting in a higher porosity in the former. Evidence of both continuous dynamic recrystallization and discontinuous dynamic recrystallization is identified throughout the sintered layer. Microhardness reveals that the pressureless zone exhibits a hardness of 0.373 GPa, significantly lower than left (0.745 GPa) and right (1.832 GPa) of pressure-assisted region. All three regions share an average grain size of 400 ± 50 nm, and geometrically necessary dislocation density in pressureless zone exceeds that in pressure-assisted areas, neither of which can account for the difference in micromechanical performance. In contrast, the statistically stored dislocation (SSD) densities on the left and right of the pressure-assisted region are approximately 4.74 × 10¹⁴ m⁻² and 2.88 × 10¹⁵ m⁻², respectively—substantially higher than the 2.88 × 10¹⁴ m⁻² measured in the pressureless region. Collectively, these findings demonstrate that dislocation strengthening, and particularly SSD density, constitutes the dominant strengthening mechanism in silver sintered layers. This work not only provides new insights for enhancing reliability under low-pressure and pressureless sintering but also establishes a theoretical foundation for optimizing sintering material formulations.

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.

Sintered Cu nanoparticles (NPs) are promising for high-performance electronics due to their excellent thermal and electrical conductivity, as well as mechanical reliability. This study investigates the microscale mechanical behavior of sintered Cu NPs with a bimodal particle size distribution, focusing on strain rate and temperature effects. Micro-pillar compression tests were performed across strain rates of 0.0001 s⁻¹ to 0.01 s⁻¹ and temperatures from 25 °C to 350 °C. Results show that higher strain rates enhance yield strength through strain-rate hardening, while elevated temperatures lead to thermal softening and reduced mechanical stability. The Anand viscoplastic model accurately predicts these deformation behaviors. Microstructural analysis via scanning electron microscopy (SEM) and transmission electron microscopy (TEM) reveals localized deformation at 175 °C, with dislocations concentrated near the top surface and persistent porosity below, whereas at 350 °C, re-sintering and grain boundary diffusion create a denser microstructure. Phase-field fracture modeling further elucidates crack propagation, emphasizing the role of pore size and temperature. This combined experimental and modeling approach enhances understanding of viscoplastic deformation and fracture mechanisms in sintered Cu NPs, informing their use in interconnects, power electronics and thermal management systems.

This Letter presents a combined analytical and experimental method to effectively decouple the radial and tangential residual stress fields induced by Berkovich nanoindentation in single-crystalline 4H-SiC using micro-Raman spectroscopy. By integrating the Raman stress characterization model with Yoffe’s expanding cavity model, precise extraction of individual residual stress components around the indentation region is realized. Through the vertical backscattering micro-Raman mapping of the E2 phonon mode, we systematically investigate the residual stress distribution near the indentation. The results highlight significant anisotropy in nanoindentation-induced stress fields, strongly dependent on the crystal orientation of 4H-SiC, predominantly featuring radial tensile stress gradients. This comprehensive theoretical–experimental approach offers a robust optical framework for residual stress characterization in 4H-SiC and provides foundational insights for extending Raman spectroscopy-based stress characterization to other crystalline materials and related device structures.

This study investigates the microstructure evolution and mechanical behavior of bimodal-sized sintered copper (Cu) nanoparticles (NPs) under varying sintering pressures. Micro-pillar compression tests reveal a transition from collapse-dominated to compaction-driven deformation as sintering pressure increases. Transmission electron microscopy (TEM) and transmission Kikuchi diffraction (TKD) analyses identify a two-stage deformation mechanism—initial pore compaction followed by intragranular slip—fundamentally distinct from bulk Cu. Molecular dynamics (MD) simulations further reveal that large particles promote dislocation-mediated plasticity by accommodating intragranular slip, while small particles enhance load transfer through localized shear-compaction, together enabling uniform strain distribution and supporting the experimentally observed strain accommodation. The resulting microstructure achieves a combination of high yield strength (up to 320 MPa) and low elastic modulus (20 GPa), offering a compliant yet robust response. These findings elucidate a unique processing–structure–property relationship and provide a rational basis for designing porous metal interconnects capable of withstanding thermomechanical stresses in advanced electronic packaging.

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%.

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.

This study demonstrates a breakdown analysis of the dynamics of a liquid crystal elastomer (LCE) including quality check, geometric measurement, thermal characterization, and comparison of heat- and light-induced contractions. A blue light-responsive acrylate side chain LCE with 1% azobenzene dye was characterized. From a classical viewpoint, photo-thermal contraction is considered a dominating effect, while direct photo-mechanical deformation can be neglected due to a low dye percentage. However, the findings of this research suggest that a low percentage of azobenzene dye does not necessarily lead to heat-dominating dynamics of LCE. This phenomenon has not yet been quantitatively studied before. The approach reported in this Letter can potentially be used to extract the data to improve the dynamics models of light-driven LCEs.