Search Results (79)

The high-temperature operating requirements and the issues in the packaging process of wide-bandgap power semiconductors have positioned pressureless sinter-bonding using Ag nanoparticle paste as the most promising die-attach technology. However, under pressureless conditions, where externally applied pressure-driven particle rearrangement is absent, achieving sufficient densification and suppressing residual porosity during short-duration annealing at 250 °C remain significant challenges for conventional single-composition Ag pastes. In this study, a hybrid filler paste composed of Ag nanoparticles and a Ag complex solution was developed to implement an active mass supply strategy, in which additional Ag atoms were directly introduced into interparticle voids through in situ reduction during sinter-bonding. Mono-dispersed Ag nanoparticles with a mean diameter of 75.26 nm were synthesized via H₂O₂-mediated wet-chemical reduction, and the Ag complex solution was prepared using a Ag salt–complexing agent–formic acid system dispersed in an ethylene glycol medium. TG-DTA analysis of the hybrid paste revealed four sequential thermal stages, consisting of solvent evaporation, Ag ion reduction, organic decomposition, and interparticle sintering, accompanied by approximately 16 wt% out-gassing. Based on these results, a three-step temperature profile was designed to initiate sintering after complete out-gassing. When chip/paste/substrate assemblies, pre-dried at 50 °C for 90 s and pre-compressed at 5 MPa for 60 s, were subjected to the three-step profile with a peak temperature of 250 °C, the in situ reduced Ag effectively bridged adjacent nanoparticles and filled fine interparticle voids, leading to pronounced densification of the bond line. As a result, the hybrid paste achieved an average shear strength of 19.1 MPa, exceeding the minimum requirement for sinter-bonding applications. These findings demonstrate that the proposed hybrid filler approach provides an effective pathway for enhancing pressureless Ag sinter-bonding performance. Full article

Sintered nano-silver is widely investigated as a die-attach material for next-generation power electronic modules due to its high thermal conductivity, favorable electrical performance, and stability at elevated temperatures. However, how bonding pressure and joint thickness jointly affect densification, interfacial diffusion, and mechanical reliability has not been systematically clarified, especially under the low-pressure conditions required for large-area SiC and GaN devices. In this work, nano-silver lap-shear joints with three bond-line thicknesses (50, 70, and 100 μm) were fabricated under two applied pressures (1.0 and 1.5 MPa) using a controlled sintering fixture. Shear testing and cross-sectional SEM were employed to evaluate the relationships between microstructural evolution and joint integrity. When the bonding pressure was increased from 1.0 to 1.5 MPa, more effective particle rearrangement and reduced pore connectivity were observed, together with improved metallurgical bonding at the Ag–Au interface, leading to a strength increase from 15.3 to 28.2 MPa. Although thicker joints exhibited slightly higher bulk relative density due to greater heat retention and accelerated local sintering, this densification advantage did not lead to improved mechanical performance. Instead, the lower strength of thicker joints is attributed to a narrower Ag–Au interdiffusion region, which limited the formation of continuous load-bearing paths at the interface. Fractographic analyses confirmed that failure occurred predominantly by interfacial delamination rather than cohesive fracture, indicating that the reliability of the joints under low-pressure sintering is governed by the quality of interfacial bonding rather than by overall densification. The experimental results show that, under low-pressure sintering conditions (1.0–1.5 MPa), variations in bonding pressure and bond-line thickness lead to distinct effects on joint performance, with the extent of Ag–Au interfacial interaction playing a key role in determining the mechanical robustness of the joints. Full article

Epithelial, endothelial, and many connective tissue cells are normally attached to the extracellular matrix (ECM). These cells rely on the ECM for structural support, signaling, and regulation of their behavior. When these cells lose this attachment or are in an inappropriate location, these cells soon die by a mechanism called anoikis (homelessness). Anoikis is a programmed cell death of an apoptotic nature; however, it can, in certain cases, be overcome, and detached cells can survive in the absence of the correct signals from the ECM. This is the case of malignant cells, where anoikis resistance is a prerequisite for invasion and metastasis. Without anoikis resistance (anchorage-independency), tumors would be unable to abandon their normal sites and would invade neighboring tissues and metastasize at distant locations. Anoikis is the natural barrier against cancer progression. Therefore, overcoming anoikis is a major step in cellular transformation. Cancer cells have developed many successful strategies to bypass anoikis. The main mechanism, albeit not the only one, involves hyper-activating survival pathways and over-expressing anti-apoptotic molecules. There is a strong and intertwining association between epithelial–mesenchymal transition and anoikis resistance that is discussed in depth. A better understanding of these anoikis resistance mechanisms has led to the research and development of pharmaceuticals that can counteract them. Full article

A sheet-type sinter-bonding material was developed to form thermally stable and highly heat-conductive joints suitable for wide-bandgap (WBG) semiconductor dies and high-heat-flux devices, and its bonding characteristics were investigated. To enhance the cost-competitiveness of the bonding material, Ag-coated Cu (Cu@Ag) particles were employed as fillers instead of conventional Ag particles. To facilitate accelerated sintering, a bimodal particle size distribution comprising several micron- and submicron-sized particles was adopted by synthesizing and mixing both size ranges. For sheet fabrication, a decomposable resin was used as the essential binder component, which could be removed during the bonding process via thermal decomposition. This approach enabled the formation of a sintered bond line composed entirely of Cu@Ag particles. Thermogravimetric and differential thermal analyses revealed that the decomposition of the resin in the sheet occurred within the temperature range of 290–340 °C. Consequently, sinter-bonding conducted at 350 °C and 370 °C exhibited significantly superior bondability compared to bonding at 330 °C. In particular, sinter-bonding at 350 °C for just 60 s resulted in a highly densified joint microstructure with a low porosity of 7.6% and high shear strength exceeding 25 MPa. The formation of the bond line was initiated by sintering between the outer Ag shells of the adjacent particles. However, with increasing bonding time or temperature, sintering driven by Cu diffusion from the particle cores to the outer Ag shells, particularly in the submicron-sized particles, was progressively enhanced. These results obtained from the fabricated sheet-type materials demonstrate that, even with the use of resin, rapid solid-state sintering between filler particles combined with the removal of resin through decomposition enables the formation of a metallic bond line with excellent thermal conductivity. Full article

Third-generation wide-bandgap (WBG) semiconductor power electronics exhibit excellent workability, but high-temperature packaging technology limits their applications. TLP, TLPS, and nanoparticle sintering have the potential to achieve a high-temperature-resistant joint at a lower bonding temperature. However, a long bonding time, voids in the joint, powder oxidation, and organic solvent residues impede their application. A novel interlayer and other approaches have been proposed, such as preformed Sn-coated Cu foam (CF@Sn), a Cu-Sn nanocomposite interlayer, self-reducible Cu nanoparticle paste, bimodal-sized Cu nanoparticle pastes, organic-free nanoparticle films, and high-thermal-conductivity and low-CTE composite paste. Their preparation, bonding processes, and joint properties are compared in this paper. Full article

This paper investigates the suppression of the cohesive cracking mode (CCM) in the sintered silver (s-Ag) die layer by intentionally introducing anisotropic porosity through two press sintering methods. Full press (FP) and local press (LP) bonding represent the s-Ag formed by pressing the die-attached assemblies (DAAs) on either the entire top surface or only on the silicon carbide (SiC) top surface, respectively. The fabricated DAAs were encapsulated with epoxy molding compounds. Degradation was evaluated using a nine-point bending test (NBT) under cyclic force between 0 and 270 N with a triangle waveform for 3 min per cycle at 150 °C. Scanning tomography images after 500 NBT cycles showed that the LP reduced the inner degradation ratio by up to 21.1% compared to the FP. Cross-sectional scanning electron microscopy revealed that the FP progressed cracking in the s-Ag die layer, whereas the LP showed no evidence of cracking. A finite element analysis revealed that in the FP, the accumulated plastic strain (APS) was concentrated in the s-Ag layer within the inner SiC chip. In contrast, the APS of the LP was preferentially concentrated outside the SiC chip. This preferential localization of damage outside the chip presents a promising approach for enhancing the reliability of packaging products. Full article

Changes in the refractive indices of a GaAs laser chip owing to bonding strain are investigated by two-dimensional (2D) and three-dimensional (3D) finite element method (FEM) simulations. The strain induced by die attach (i.e., the bonding strain) was estimated by fitting simulations to the measured degree of polarisation (DOP) of photoluminescence from the facet of the bonded chip. Changes in the refractive indices were estimated using the strains obtained from fits to DOP data. Differences between the 2D and 3D FEM estimations of the deformation and of the photo-elastic effect are noted. It is recommended that 2D FEM simulations be used as starting points for 3D FEM simulations. Elastic constants for GaAs in plane-of-the-facet coordinate systems for 2D (plane stress and plane strain) and 3D FEM simulations are given. Full article

To address solder paste drawbacks, such as die contamination and flux residue, a polymer-based sheet containing Sn-3.0 (wt%) Ag-0.5Cu solder particles as fillers was fabricated, and its bonding characteristics were analyzed. The reductant in the manufactured sheet evaporated while removing the oxide layers on the solder and copper finish surfaces during heating. Subsequently, the resin component (polymethyl methacrylate) began to decompose thermally and gradually dissipated. Ultimately, the resulting joint formed a solder interconnection with a small amount of residual resin. This joint is expected to exhibit superior thermal conductivity compared with composite joints with a polymer matrix structure. Die-attach tests were conducted in air using the fabricated sheet between Cu finishes. Results showed that joints formed at 300 °C for 30 s and 350 °C for 10 s provided excellent shear strength values of 48.0 and 44.3 MPa, respectively, along with appropriately developed intermetallic compound (IMC) layers at the bonding interface. In contrast, bonding at 350 °C for 60 s resulted in excessive growth of IMC layers at the interface. When comparing size effects of solder particles, type 6 particles exhibited superior shear strength along with a relatively thinner total IMC layer thickness compared to when type 7 particles were used. Full article

Electronic packaging can transform the chip to a device for assembly. Soldering and bonding are important procedures in the process of electronic packaging. The continuous development of packaging architecture has driven the emergence of improved soldering and bonding processes. At the same time, conventional soldering and bonding processes are still widely used in device packaging. This paper introduces two kinds of technologies in wafer bonding, direct and indirect, expounds on five kinds of die attachment processes, and also describes the process of ball bonding and wedge bonding in wire bonding in detail. Flip chip bonding and methods for making bumps are also described in depth. Bump bonding processes are vital for 3D-SiP packages, and the bonding technology of copper bumps is a research hotspot in the field of advanced packaging. The surface mount technology and sealing technology used in some electronic devices are also briefly introduced. This paper provides insights for researchers studying soldering and bonding in contemporary electronic device packaging. Full article

In this paper, the concept of symmetry is utilized to design the composite controller for the die attach machine’s motion platform—that is, the construction and the solution of the nominal model-based composite controller design approach are symmetrical. With escalating demands for ultra-high-speed operations and microscale positioning accuracy (<5 μm) in semiconductor manufacturing, motion platforms face critical challenges, including high-speed instability, positioning jitter, and insufficient disturbance rejection. To address these limitations, a composite control strategy integrating nominal model-based linear active disturbance rejection control (NMLADRC) with sliding mode control (SMC) is developed. The synergistic interaction ensures the concurrent realization of robust tracking accuracy and rapid transient convergence. Simulation results demonstrate significant improvements over conventional PI control, LADRC, and NMLADRC. The phase lag is reduced by 50.04%, 36.34%, and 23.07%, respectively, while positioning time within ±5 μm accuracy threshold is shortened by 44.00%, 56.31%, and 31.51% when tracking the executed motion profile. The composite controller substantially enhances motion control precision, strengthens disturbance rejection capability, and improves system stability during high-speed operations. These advancements highlight the method’s strong practical applicability in precision motion control systems requiring both rapid response and microscale positioning accuracy. Full article

This paper presents the design and characterisation of a novel double-sided cooling, wire-bondless half-bridge power module incorporating silver sintering technology and silicon carbide MOSFETs. Initially, the module was meticulously designed, optimised, and simulated using Ansys (Electronics Desktop 2021 R1) Q3D and Icepak to assess its stray parameters and thermal performance, respectively. The module has a low simulated stray inductance of 4.7 nH, which would be even lower in a multi-chip version of the design. Additionally, the thermal performance of the double-sided power module is compared with the single-sided version, showing a 30 °C reduction in junction temperature. Following the design work, a double-sided cooled half-bridge module was successfully fabricated, which underwent double pulse analysis and single-phase inductive load testing. Die attachment within the module employs nanosilver paste, with the flexibility to adjust the length of the copper connector to meet diverse requirements. The design exhibits remarkable compactness, and comprehensive electrical testing affirms its suitability for practical applications. Full article

The application of wide-bandgap semiconductors in next-generation power modules requires cost-effective Cu particles and a reduced bonding time in the die attachment process to enable efficient industrial-scale manufacturing. Therefore, this study aimed to analyze the effect of Cu particle size variation on pressure-assisted sinter-bondability and bond line shear strength. Cu particles were synthesized through a simple wet-chemical process, in which pH variation was employed to obtain submicrometer-sized Cu particles with average diameters of 500, 300, and 150 nm. The synthesized particles exhibited pure Cu composition, forming only a native oxide layer on their surfaces. In pastes containing these Cu particles, smaller particle sizes led to the delayed evaporation of the reducing solvent, which in turn delayed the exothermic reactions associated with particle sintering and oxidation. However, the sintering-induced exothermic peak became more pronounced as the particle size decreased, confirming that smaller particles improved sinterability. Pressure-assisted sinter bonding performed in air at 300 °C indicated that a decreased particle size contributed to the densification of the bond line structure and an increase in shear strength. Specifically, the paste containing 150 nm Cu particles achieved a highly dense microstructure and an exceptional shear strength of 36.7 MPa within just 30 s of sinter bonding. These findings demonstrate that reducing the particle size is essential for enhancing the sinter-bondability of cost-effective Cu particle-based sinter-bonding pastes. Full article

Pastes were prepared using dendritic Cu particles as fillers, and a compression die attachment process was implemented to establish a pure Cu joint using low-cost materials and high-speed sinter bonding. We aimed to grow an oxidation layer on the particle surface to improve sinter-bondability. Because the growth of the oxidation layer by general thermal oxidation methods makes it difficult to use as a filler owing to agglomeration between particles, we induced oxidation growth by wet surface treatment. Consequently, when the oxidation layer was appropriately grown by surface treatment using an acetic acid–ethanol solution, we obtained an improved joint strength, approximately 2.8 times higher than the existing excellent result based on a bonding time of 10 s. The joint formed in just 10 s at 300 °C in the air under 10 MPa compression showed a shear strength of 28.4 MPa. When the bonding time was increased to 60 s, the joint exhibited a higher strength (35.1 MPa) and a very dense microstructure without voids. These results were attributed to the acceleration of sintering by the in situ formation of more Cu nanoparticles, which effectively reduced the increased oxide layers in the particles using a reducing solvent. Full article

Aluminum alloy die casting has achieved rapid development in recent years and has been widely used in all walks of life. However, due to its high pressure and high-speed technological characteristics, avoiding hole defects has become a problem of great significance in aluminum alloy die casting production. In this paper, the filling visualization dynamic characterization experiment was innovatively developed, which can directly study and analyze the influence of different injection rates on the formation and evolution of alloy flow patterns and gas-induced defects. As the injection speed increased from 1.0 m/s to 1.5 m/s, the average porosity increased from 7.49% to 9.57%, marking an increase in the number and size of the pores. According to the comparison with Anycasting, simulation results show that a liquid metal injection speed of 1.5 m/s when filling the flow front vs. the previous injection rate of 1.0 m/s caused fractures when filling at the same filling distance. Therefore, the degree of the broken splash at the flow front is more serious. Combined with the analysis of transport mechanics, the fracturing is due to the wall-attached jet effect of the liquid metal in the filling process. It is difficult for the liquid metal to adhere to the type wall in order to fuse with subsequent liquid metal to form cavity defects. With an increase in injection velocity, the microgroup volume formed via liquid breakage decreases; thus the volume of air entrapment increases, finally leading to an increase in cavity defects. Full article

Fusarium spp. can cause root rot in alfalfa, leading to the death of the whole plant, which seriously affects the yield and quality of alfalfa. This study used a Fusarium acuminatum strain labeled with green fluorescent protein (GFP) to observe the infection process of F. acuminatum on alfalfa by confocal fluorescence microscopy. The aim of this study was to reveal the infection mechanism of alfalfa Fusarium root rot at the cellular histological level. The results showed that conidia of F. acuminatum attached to the surface of the root and germinated at one day post-inoculation, the mycelium then entered the vascular bundle tissue of the alfalfa root at 5 days post-inoculation, reached the base of the plant stem at 14 days post-inoculation, and colonized the stem of the first and second compound leaf at 28 and 49 days post-inoculation, respectively. Moreover, the experiment, which sprayed a spore suspension, showed that the conidia of F. acuminatum could spread through the air to infect the pericarp and seed coat tissue of the pod. For the first time, we report the infection process of alfalfa Fusarium root rot caused by F. acuminatum and clarify that F. acuminatum can initially infect the root tissue of alfalfa, colonize the bottom stem of the plant through systematic infection, and eventually cause the plant to wilt and die. The results reveal the infection mechanism of F. acuminatum at the cell level via histology and provide theoretical support for the development of control strategies and key control technologies for alfalfa root rot. Full article