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.

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.

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.

While silver-based sintered materials are limited by cost and electromigration, and copper faces challenges with oxidation at high temperatures, Cu-based composite sintering materials offer promising alternative solutions. This review examines recent advances in Cu-based composite sintered materials for die-attach in power electronics packaging, focusing on their mechanical, thermal, electrical properties, and reliability. This review systematically categorizes such compounding strategies, including direct mixing, core-shell structures, and alloying, analyzing the impact on composite properties. Furthermore, the reliability of Cu-based composite sintered joints is evaluated, addressing high-temperature storage, thermal cycling, corrosion, and electrochemical migration. Challenges such as oxidation resistance, process optimization, and cost-effectiveness are discussed, together with future research directions. This work aims to support researchers in advancing Cu-based composite sintering materials research and development, broadening material options for high-temperature power electronics packaging applications.

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.

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.

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.

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.

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.

With the increased deployment of power modules in demanding conditions, sintering materials, especially composite sintering materials, have raised growing interest due to their cost-effectiveness and suitability. Therefore, this study explores the viability of Cu–Ag composite sintering material, focusing on solvent influence through microstructure and mechanical behavior analysis. Micron-sized particle-based Cu–Ag composite pastes were designed and compared using eight solvents (four epoxy-free and four epoxy-added) based on fluidity and thermal stability. The sintered joints' performance, assessed through shear strength analysis, showed comparable values to pure silver sintering for both epoxy-free and epoxy-added samples. Optimized samples from each solvent system underwent reliability analysis, demonstrating that Cu–Ag joints with epoxy resin exhibited significantly higher shear strength after high-temperature storage and thermal cycling tests. Micromorphology and elemental composition analysis revealed differences in aging mechanisms, primarily attributed to variations in porosity due to oxide formation and pore filling by epoxy resin under different solvent systems. Further nanoindentation characterization of micromechanical properties, including hardness, modulus, and creep properties, during high-temperature aging, established constitutive models for insights into reliability evolution. In conclusion, the optimized epoxy-added Cu–Ag sintered joints proposed in this study demonstrated exceptional reliability and acceptable micromechanical properties, presenting a promising option for high-temperature power packaging.

In the rapidly evolving era of information and intelligence,microelectronic devices are pivotal across various fields, such as mobile devices, big data computing, electric vehicles, and aerospace. However, the electrical performance of these devices often suffers due to residual stress from microelectronic manufacturing. This issue is compounded by the additional thermal stress that accumulates during device operation. Therefore, it is essential to understand, characterize, and control this residual stress to ensure the reliability and efficiency of microelectronic devices. Raman spectroscopy emerges as an invaluable tool for nondestructive, fast, noncontact, and precise testing of micro-scale mechanics, significantly aiding in stress and strain analysis within microelectronic manufacturing. This article aims to provide a thorough overview of the theory and application beyond a mere compilation of recent advances. Theoretically, it critically evaluates existing models that describe the Raman-stress relation. Practically, it explores the application of Raman spectroscopy in researching residual stress in various components, including substrate materials, epitaxial films, and packaging. Through a detailed examination of current applications, it highlights the significance of Raman spectroscopy in understanding micro-scale mechanics. Finally, it offers both theoretical and practical insights into the future developments of Raman-stress detection technology.

4H-SiC is widely used in power electronics owing to its superior physical properties. However, temperature-induced stresses compromise the reliability of 4H-SiC power devices in high-temperature applications, warranting precise, and nondestructive stress characterization responsive to temperature variations. Herein, a temperature-dependent predictive model is proposed for analyzing the Raman shift–stress in 4H-SiC. The 4H-SiC epitaxial samples prepared via chemical vapor deposition are characterized using in situ variable-temperature Raman spectroscopy, resulting in a temperature correction factor of approximately −0.021 cm−1 K−1, which is integrated into the conventional Raman shift–stress relationship to assess stress variations induced by temperature variations. The elastic modulus tensor of 4H-SiC at various temperatures determined using molecular dynamics simulations indicates a linear reduction in modulus with increasing temperature. This variable temperature modulus is incorporated into the Raman shift–stress relationship. Furthermore, a finite element method is used for model simplification to perform stress calculations in three axial directions. The experimental results confirm the consistency between calculated and experimental values with a 10% error range under the uniaxial stress condition. The study findings provide valuable insights into assessing stress evolution in 4H-SiC under temperature variations based on Raman spectroscopy, thereby advancing the application of spectroscopic techniques in material stress detection.

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.

With the popularization of wide band-gap power modules in offshore wind power systems and water surface photovoltaic power stations, packaging materials face challenges of corrosion by salt, blended with high humidity. Copper-silver (Cu-Ag) composite sintered paste was proposed by researchers as a novel die-attach material for a lower cost and anti-electro migration ability. However, the potential difference between copper and silver forms galvanic corrosion in a high-humidity environment, resulting in accelerated failure combined with salt mist. To further promote the application of composite sintered materials, a copper-silver double-sphere galvanic corrosion model based on finite element simulation was proposed in this paper. The relationship between corrosion rate and time of different Cu-Ag particle size combinations under different sintering degrees was predicted by initial exchange current density. Through the electrochemical characterization of the sintered samples, the optimal combination of materials was further discussed. The accuracy of the model was also verified. The conclusions obtained from both the experiments and simulation work provide guidance for future anti-corrosion analysis, as well as the reliability improvement of novel composite sintered materials.

Power modules applied in offshore applications are facing risks of corrosion failures on die-attach materials due to high humidity and H₂S exposure. To investigate such corrosion behavior for sintered die-attach materials, we conducted a study with four groups of samples fabricated using copper and silver metal particles under different solvent systems. Such samples were firstly subjected to high-humidity-H₂S conditions for 168 h to simulate the harsh offshore environment. After undergoing corrosion, the primary compounds formed were CuO/Cu₂O and Ag₂S through SEM, XRD, and XPS analysis. Notably, the incorporation of epoxy resin into sintered copper joints resulted in a remarkable reduction in corrosion and a substantial improvement in electrical conductivity after the reaction. In contrast, while the addition of epoxy did not evidently reduce corrosion in silver joints, it did lead to a significant increase in shear strength. Furthermore, to gain further insights into the effect of epoxy resin on corrosion behavior, electrochemical analysis, and molecular dynamics simulations were conducted. Finally, the mechanical reliability of the corroded copper and silver joints was evaluated through thermal shock tests. In summary, sintered copper joints exhibited better anti-corrosion behaviors than sintered silver under high humidity and H₂S exposure, especially with the addition of epoxy resin. However, the corrosion products of sintered copper suffered from a sharp decrease in shear strength after thermal shock tests than sintered silver, which is probably due to the coefficient of thermal expansion mismatch.