Sintered materials have been widely applied, as an alternative to soldering, for power electronics packaging. One key issue for such die-attach material is to characterize the actual porosity, which is difficult to obtain through SEM cross-section analysis. Therefore, in this work, the optimized Quartet Structure Generation Set (QSGS) algorithm was applied to sintered copper joints under various porosity levels to reconstruct 3D porous structures based on 2D SEM images. Firstly, copper joints with varying porosities were fabricated under different sintering conditions. Reconstructed 3D porous copper models were then generated through the QSGS algorithm to match experimental observations, including porosity and pore size. Finite element analysis (FEA) simulations were further conducted to explore the effects of pores on thermal and electrical performance. This work provides a method for accurately predicting the thermoelectric properties of sintered copper joints and insights for optimizing copper sintering in power electronics applications.

The 1.2 kV SiC VDMOSFETs with varied JFET width (LJFET) are designed and fabricated in this study. The static and dynamic characteristics of each design are measured and compared. There is the best trade-off performance in the design of LJFET = 1.8 μm according to FOM (BV2/Ron) and FOM (Ciss/Crss). Besides, the surge capacity and evaluation for series designs are investigated under conditions of Vgs = 0 V and Vgs = −5 V. There is a best surge capacity in design of LJFET=1.2 μm, and the largest surge energy is the design of LJFET=2.0 μm. Further, the surge failure mechanisms of LJFET = 1.2 μm, 1.8 μm, and 2.0 μm under condition of Vgs = −5 V are investigated by decapsulated and FIB. Besides, the TCAD simulation was employed to theoretical analysis. The results show that the extremely high temperature was generated instantaneously under surge condition, resulting in epoxy carbonization, polysilicon melting and ILD oxide crack in failed position. Besides, the surge dissipating energy causes an instantaneous high temperature on the entire chip, resulting in aluminum remetallization. This paper would provide suggestions for device design and surge study.

Power electronics devices, pivotal in advancing electronic system technology, are essential for energy saving, enhancing power control efficiency, reducing noise, and minimizing size and volume. The evolution of power modules is based on innovative packaging structures, technologies, and materials. This article provides a comprehensive review of inorganic nonmetallic packaging materials and technologies in power electronics packaging. It first analyzes the packaging structures and trends of power electronics. The article then discusses inorganic nonmetallic encapsulants such as cement and glass in detail. It also reviews traditional ceramic substrates and elaborates on the advantages of multilayer ceramic technologies, including low-temperature co-fired ceramics, as substrates, while looking forward to the commercialization of inorganic composite substrates such as SiCp/Al matrix composites and diamond. Subsequently, the article overviews inorganic nonmetallic fillers for thermal interface materials, emphasizing the application of two-dimensional materials such as graphene and boron nitride, and introduces inorganic nonmetallic phase change materials. Finally, it explores the application and future development trends of inorganic nonmetallic materials in embedded packaging technologies.

The study focuses on the optical and electrical properties of Tungsten Ditelluride (WTe2), a type II Weyl semimetal, as well as the influence of its self-limiting oxide (SLO) layer that forms during natural oxidation. WTe2 exhibits promising applications in photodetection and energy harvesting due to its unique gapless linear dispersion and Berry-field-enhanced nonlinear optical effects. However, surface oxidation poses a challenge as it degrades the performance of WTe2. By employing spectroscopic ellipsometry and Raman spectroscopy, the progression of the oxide layer’s thickness and its impact on the optical constants of WTe2 were examined. The results revealed a rapid increase in oxide thickness within the first 24 h, and it reached saturation at ∼10 nm after 45 h of atmospheric exposure. Electrical properties were explored using Kelvin Probe Force Microscopy, uncovering a modification in surface potential and Fermi level following oxidation. Additionally, a SLO/WTe2 heterojunction device exhibited a wide region of positive and negative coexisting photocurrent, highlighting the potential for logical operations in ambient air. Finally, the mechanism of operation of the device is discussed. The electrical and optical properties of the pristine, partially oxidized and fully oxidized WTe2 are analyzed using density functional theory calculations. It shows that the SLO layer has a significant effect on the optical and electronic properties, which is instructive for future wavelength-modulated device optoelectronic logic operations.

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.

Graphdiyne (GDY)/two-dimensional materials (2DMs) heterostructures present unique opportunities for advanced optoelectronic and neuromorphic devices because of their exceptional electrical, optical, and structural properties. However, the traditional methods for construction of GDY/2DMs heterostructures usually lead to inferior interfaces, which seriously affects the charge separation and transport. Herein, an in situ approach for growing GDY nanowalls (NWs) on WSe2 is employed in this work. The as-prepared GDY NWs/WSe2 heterostructure exhibits self-powered broadband photodetection across 405–980 nm with a high responsivity of 2176 A/W and detectivity of 3.6 × 1012 Jones at 532 nm under 0.02 mW/cm2 illumination, significantly outperforming previously reported GDY-based devices. The efficient charge separation and strong photocarrier trapping in the GDY NWs/WSe2 heterostructure result in pronounced short-term and long-term synaptic plasticity. The nonlinear, wavelength-dependent reservoir state separation enables clear distinction of multiple pulse sequences, which shows great potential for logic processing. The successfully resolved red, green, and violet patterns, and one-shot color image recognition of a 5-letter image highlight transformative potential of GDY NWs/WSe2 device for future adaptive imaging and neuromorphic computing technologies.

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%.

This article compares and evaluates the single pulse short-circuit robustness of silicon carbide (SiC) MOSFETs with linear and hexagonal cell topologies under different gate voltages, bus voltages, and case temperatures. The short-circuit failure mechanisms of the linear and hexagonal cell topologies are studied. A new switching model for gate failure and thermal runaway short-circuit failure modes is proposed and analyzed. The robustness performance of the linear and hexagonal cell topologies is compared and evaluated under the same short-circuit power for the first time, fully revealing the comprehensive impact mechanism of cell topologies on the short-circuit robustness for SiC MOSFETs.

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.

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 paper investigates the effects of three ageing factors (chemical, humidity, and temperature) and their interactions on the physical properties and degradation of silicone sealant used in microelectronic applications. The thermal degradation of silicone sealants was investigated by exposing samples to temperatures in the range of 150 up to 175 °C. Also, a set of samples were aged at 40 °C in a salt spray set-up with 100 % humidity in a salty atmosphere. Results showed detectable changes in the FTIR spectra of aged specimen as compared with the as-received sample. In all accelerated testing conditions, peak intensities decreased with ageing time, inferring that that the surface characteristics of the sealant is affected by ageing. Shear test results showed that with increasing the ageing time, the maximum shear stress in most cases has decreased in all ageing conditions. Also, it appears that samples with longer ageing times have experienced more elongation before failure. Results also show that salt spraying of specimens is associated with a decrease in the mechanical properties of the sealant, indicating the deleterious implications of ionic contaminations for the mechanical properties of samples.

The primary challenges posed by oral mucosal diseases are their high incidence and the difficulty in managing symptoms. Inspired by the ability of bioelectricity to activate cells, accelerate metabolism, and enhance immunity, a conductive polyacrylamide/sodium alginate crosslinked hydrogel composite containing reduced graphene oxide (PAA-SA@rGO) is developed. This composite possesses antibacterial, anti-inflammatory, and antioxidant properties, serving as a bridge to turn the “short circuit” of the injured site into a “completed circuit,” thereby prompting fibroblasts in proximity to the wound site to secrete growth factors and expedite tissue regeneration. Simultaneously, the PAA-SA@rGO hydrogel effectively seals wounds to form a barrier, exhibits antibacterial and anti-inflammatory properties, and prevents foreign bacterial invasion. As the electric field of the wound is rebuilt and repaired by the PAA-SA@rGO hydrogel, a 5 × 5 mm² wound in the full-thickness buccal mucosa of rats can be expeditiously mended within mere 7 days. The theoretical calculations indicate that the PAA-SA@rGO hydrogel can aggregate and express SOX2, PITX1, and PITX2 at the wound site, which has a promoting effect on rapid wound healing. Importantly, this PAA-SA@rGO hydrogel has a fast curative effect and only needs to be applied for the first three days, which significantly improves patient satisfaction during treatment.

Copper sintering has gained great attention as a die-attach technology for power electronics because of its potential cost effectiveness and high reliability under harsh working conditions. However, the mechanism of how the intrinsic pores within such sintered joints influence the thermal and electrical properties still needs further investigation. The evolution of pores within such sintered joints is difficult for in-situ observation during the sintering process and reliability tests, while the porosity level greatly affects the thermal and electrical properties. In this work, four two-dimensional (2D) models with various random pore structures were established based on the Quartet Structure Generation Set (QSGS) algorithm. Then, finite element method (FEM) simulations were conducted to simulate the heat and current conduction in the sintered materials. Subsequently, the distribution of temperature as well as the electric potential in the porous sintered materials were further discussed. Lastly, both the thermal and the electrical conductivities were calculated, followed by a concluded parabolic relationship of thermal and electrical conductivities with the porosity. These findings offer insights into optimizing and predicting copper sintered joint performance and accelerate the wide application of copper sintering.

Driven by the need for improved quality, energy efficiency, and visual innovation, display technology has evolved from CRT to Mini LED. However, the transfer process in Mini LED assembly poses challenges in precision. This study addressed the displacement issue during the transfer process by investigating the synergistic effects of solder and functional organic chemicals. Through the Mini LED assembly process, with the Mini LED size measuring 150 μm (length) ∗ 100 μm (width) ∗ 70 μm (thickness), polyamide was identified as a facilitator for precise alignment, which enhanced self-alignment capabilities by 68.8 % and improved the accuracy on self-aligned distance from 12.5 μm to 21.1 μm in Mini LED packaging. Through the powder coalescence approach, further extensive analysis using XPS, SEM, FTIR, and DSC reveals the synergistic effects. It supports the proposed three-dimensional polyamide-tin ion coordination interfacial network construction mechanism that facilitates solder-to-solder self-alignment and coalescence. This study provides insight into such a polymer-metal ion 3D coordination network for Mini LED precise alignment, which is promising for mass production.

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.

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.

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.

Synchronized rectifiers offer promising solutions for piezoelectric energy harvesting; however, achieving the promised energy extraction performance necessitates using either a bulky inductor or multiple large capacitors, which cannot be on-chip integrated and increase the system form factor. This article introduces a fully integrated sequenced synchronized switch harvesting on capacitors (3SHC) rectifier. The input piezoelectric transducer (PT) uses microelectromechanical system technology. The cantilever is equally split into multiple strongly coupled subcantilevers, with each cantilever treated as an individual PT connected to the proposed rectifier. The 3SHC rectifier cyclically operates multiple times to synchronously flip the voltage of each cantilever sequentially. With the proposed design, all the flying capacitors only need to match the capacitance of each subcantilever; hence, they can be fully integrated on-chip. The design is fabricated using standard 0.18 μ m CMOS technology. Measurement results show that the proposed 3SHC rectifier attains an 80% voltage flip efficiency and achieves a 730% power enhancement compared to a full-bridge rectifier.

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.

Silicon carbide (SiC) devices have shown definite advantages over Si counterparts in high-temperature, high-voltage, and high-frequency applications. To fully exploit the potentiality of SiC devices in high temperatures, die-attach materials that can withstand high temperatures for a long time are required in the power electronics packaging. In this article, the high-temperature die-attach materials, such as high-temperature solders and transient liquid-phase bonding materials, were reviewed first. Then, metallic (mainly Ag and Cu) nanoparticles (NPs) sintering technologies were thoroughly overviewed. The metallic NPs sintering materials, metallic NPs sintering process, and interface and reliability were analyzed, respectively. Finally, the challenges and outlook of promising Cu NPs sintering technology were discussed.