Sintered nanocopper (nanoCu) paste, exhibiting excellent electrical, thermal, and mechanical performances, offers promise for interconnections in wide bandgap (WBG) semiconductors operating at higher temperatures. However, sintered nanoCu is prone to severe corrosion in environments containing H2S, with on-site characterization methods for the composition of corrosion products currently lacking. In this study, a novel method was proposed for the rapid characterization of corrosion products during the corrosion process based on hyperspectral imaging (HSI) technology. Sintered nanoCu samples were subjected to 336 h H2S gas corrosion tests with bulk Cu as the reference, followed by correlating the corrosion element content with hyperspectral characteristic parameters. Then, the morphology and composition of corrosion products were researched using focused ion beam scanning electron microscope (FIB-SEM) and transmission electron microscope (TEM) analysis. The results showed that (1) during the corrosion process, a linear relationship was established between the Cu, O elemental atomic contents on the sample surfaces and their hyperspectral characteristic parameters. (2) The elemental atomic content of S exhibited an exponential relationship with the characteristic parameter. (3) The change rate in the spectral characteristic parameters during the corrosion process reflected the severity of corrosion, which was confirmed by comparing the thickness of the corrosion products of the sintered nanoCu and bulk Cu. This study offers a foundation for the further investigation of rapid on-site characterization of sintered nanoCu corrosion involving H2S.@en

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

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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.@en

Electromigration (EM) is a crucial failure mode in Aluminum (Al) interconnection wires those are widely used in high density semiconductor packaging. This study systematically investigated the influence of EM on the mechanical properties of Al interconnects via nanoindentation experiments and molecular dynamics (MD) simulations. The results are list as follows. (1) The indentation depth gradually increases with the increase in indentation load, resulting in a gradual increase and stabilization of the Young’s modulus and hardness of the structure. Within a specific range, the influence of the loading rate on the indentation depth and mechanical properties is relatively small. (2) The region where Young’s modulus of the interconnect decreases correlates with the location where EM-induced voids initiate. EM-induced voids have a direct impact on the material’s mechanical properties, particularly the decrease in Young’s modulus. (3) These EM-induced voids affect the nucleation and formation of dislocations. With the increase in void concentration and indentation depth, The generation and slip of dislocations increase as the void concentration and indentation depth increase, leading to a decrease in the material’s mechanical properties over time. This comprehensive findings expand the knowledge on mechanical behavior degradation of Al interconnects when EM failure occurs, providing a scientific basis for designing and optimizing high density semiconductor packaging.@en

Silicon carbide (SiC) MOSFETs, as leading wide bandgap semiconductor devices, exhibit superior stability and reliability under high-temperature, high-switching frequencies, and high-power density operational conditions. SiC MOSFET with fan-out panel-level packaging (FOPLP) utilizes a redistribution layer (RDL) to substitute bonding wires, achieving low thermal resistance, electrical resistance, and parasitic inductance. This study proposes an optimal design strategy for SiC MOSFET FOPLP, considering parasitic inductance suppression, heat dissipation, thermal-mechanical reliability, and insulation enhancements. First, we establish the parasitic inductance, heat transfer network, and thermomechanical stress physical analytical models of SiC MOSFET FOPLP. Subsequently, the non-dominated sorting genetic algorithm (NSGA-II) and the improved multi-objective particle swarm optimization algorithm (MOPSO) are integrated to realize the co-optimization of parasitic inductance, thermal resistance, thermal stress, and electric field intensity distribution. Finally, we attain the optimal parameters of the SiC MOSFET FOPLP, i.e. chip thickness (x₁), solder thickness (x₂), RDL thickness (x₃), and chip side length (x₄) as 0.25 mm, 0.05 mm, 0.35 mm, and 6.00 mm, respectively. Additionally, according to comparison the MOPSO algorithm exhibits faster convergence and superior diversity than NAGA-II in the electrical-thermal-mechanical multiphysics co-optimization. Generally, the proposed physical analytical models combined with a multi-objective optimization method have a substantial guidance and forward-looking prospect on the design of SiC MOSFET FOPLP.

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This paper studied the behaviors of sintering between Ag nanoparticle (NP) and nanoflake (NF) in the same size by molecular dynamics simulation. Before the sintering simulation, the melting simulation of NF was carried out to calculate the melting points of NFs and investigate the thermostability of NF. The Lindemann index and potential energy showed that the melting points of NF were significantly size-dependent. During the heating process, the sharp corner of NF transformed to the round corner and could bend spontaneously lower than melting points. In sintering simulation, the sintering process of NF-NP showed a metastable stage before equilibrium. Under low sintering temperature (500 K), the degree of plasticity sintering mechanism of NF-NP was more prominent, which generated more defects, such as amorphous atoms, dislocations, and stacking faults, than NP-NP. The sintered products of NF-NP also presented a better neck size and shrinkage than NP-NP in the same size. A new sintering behavior was observed: NF was bent toward the NP during the sintering. The bending curvature of NF increased as the thickness or the length/width decreased. For the NF with the ratio of length/width to thickness of 5:1, bending could further significantly facilitate neck growth. At 700 K, the plasticity mechanism dominated both the sintering processes of NF-NP and NP-NP. And NF-NP showed a larger diffusivity than NP-NP. At last, we investigated the effects of crystal misorientation, and found that a tilted grain boundary generated in the neck. The NF had the trend of rotation to decrease the crystal misorientation.

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Nano-copper sintering is one of new die-attachment and interconnection solutions to realize the wide bandgap semiconductor power electronics packaging with benefits on high temperature, low inductance, low thermal resistance and low cost. Aiming to assess the high-temperature reliability of sintered nano-copper die-attachment and interconnection, this study characterized the mechanical properties of sintered nano-copper particles using the high-temperature nanoindentation tests. The results showed that: firstly, the hardness and indentation modulus of the sintered nano-copper particles increased rapidly when the loading rate increased below 0.2 mN·s⁻¹ and then stabilized, and decreased with increased applied load up to 30 mN. Next, by extracting the yield stress and strain hardening index, a plastic stress–strain constitutive model at room temperature for sintered nano-copper particles was obtained. Finally, the high temperature nanoindentation tests were performed at 140 ˚C–200 ˚C on the sintered nano-copper particles prepared under different assisted pressures, which showed that a high assisted pressure resulted in the reduced temperature sensitivity of hardness and indentation modulus. The creep tests indicated that high operation temperature resulted in a high steady-state creep rate, which negatively impacted the creep resistance of sintered nano-copper particles, while the higher assisted pressure could improve the creep resistance.

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This study selects yellow, red and orange phosphors used in high color rendering white packages, analyzes their luminescence and thermal properties, crystal structures and micro morphologies during both the high temperature and high moisture ageing test and the water immersion test, and finally figures out the degradation mechanisms of different phosphors. The results show that: 1) the hydrolysis reaction of phosphors under hygrothermal environment produces OH^- and increases the environment's pH value, which can lower the crystallinity of phosphor hosts, increase the lattice vibration and light-induced heat, and enhance the thermal quenching effect of phosphors. Meanwhile, the surface roughening of phosphor particles can increase the blue light scattering and lower its absorption and conversion efficiency; 2) the degradation trends of both luminescence and thermal properties of phosphors under the water immersion test are similar to those under high temperature and high moisture ageing test. So it is an effective method to assess the reliability of LED phosphors under hygrothermal environment.

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In this paper, moisture absorption/desorption and hygroscopic swelling of silicone/phosphor composite film and epoxy mold compound (EMC) used in chip-on-board (COB) LED packaging is studied with in-situ characterization. Material properties, including diffusivity, activation energy, saturated moisture concentration and the coefficient of hygroscopic swelling, are extracted from the experimental data. For silicone/phosphor film, the moisture diffusion can be described by the conventional Fickian diffusion model. However, the saturated moisture concentration increases with temperatures under the same relative humidity condition. The dependence of saturated moisture concentration on temperature is characterized by an Arrhenius-like equation, and the net absorption heat is found to be 8–11 kJ/mol. Furthermore, the silicone/phosphor composite film shows reversible diffusion process during absorption and desorption cycle, which confirms the Fickian behavior of moisture absorption. Moisture diffusion in EMC, on the other hand, exhibits non-Fickian diffusion, and thus, a dual stage diffusion model is adopted to fit experimental data. Moreover, EMC shows partially non-reversible moisture absorption during absorption and desorption cycle, which is consistent with the dual-stage model description. In hygroscopic swelling testing, silicone/phosphor film shows a permanent swelling during moisture absorption despite that the moisture absorption is completely reversible. EMC shows partially reversible swelling after moisture is removed, which indicates the residual moisture in material. Further study is needed to understand the mechanism of permanent hygroscopic swelling for silicone/phosphor composite during moisture absorption and desorption.

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