Nano-copper (nano-Cu) sintering is a promising lead-free interconnection technology for advanced electronic packaging due to its high electrical conductivity. However, practical applications are hindered by oxidation and limited sintering efficiency. Carbon nanotube (CNT) doping has been proposed to modify sintering behavior by influencing diffusion and interfacial interactions. In this study, molecular dynamics (MD) simulations and experiments were combined to investigate the effects of CNT doping on nano-Cu sintering and interconnection performance.Two MD models were constructed: a Cu NP–CNT dual-particle model to examine interfacial interactions, and a multi-particle model to evaluate overall sintering dynamics. Results show that Cu nanoparticle size significantly affects sintering, with 4 nm particles exhibiting optimal energy reduction at 500 K, while 2 nm particles show stronger bonding at 700 K due to partial melting. CNT doping in the multi-particle system increased defect density, improving bonding strength but compromising electrical and thermal conductivity.Experimentally, nano-Cu pastes doped with various CNT types and contents were tested. A 1 wt% CNT addition enhanced shear strength, while higher contents led to agglomeration, reduced uniformity, and degraded electrical performance. SEM revealed CNT accumulation at sintering necks, and XPS indicated potential interfacial reactions involving functional groups on CNTs.Overall, CNTs play a dual role in nano-Cu sintering—enhancing mechanical performance via defect formation but reducing conductivity due to interfacial resistance. Optimizing CNT surface chemistry and dispersion is essential to balance mechanical and electrical properties in future interconnect applications.

Graphene is widely used to reinforce metal matrix composites due to its excellent physical and mechanical properties. However, its poor interfacial wettability and dispersion problems in copper-based brazing filler metals still limit its application effect.This study explored the influence of graphene on the sintering behavior and structural properties of copper nanoparticles under different doping conditions through molecular dynamics simulation combined with experimental methods. The results show that an appropriate amount of well-dispersed graphene helps promote the densification process and improve the structural stability, while graphene in the agglomerated state may have an adverse effect on the mechanical properties. This work provides theoretical support and experimental basis for optimizing the application of graphene in copper-based brazing metals.

With the rapid advancement of power semiconductor packaging technologies, Smart P2 Packagingaging has emerged as a pivotal innovation for enhancing system performance and miniaturization. This study systematically investigates the thermal conduction characteristics and stress distributions of copper-filled vias (CFVs) in Smart P2Pack frontal interconnects through coupled thermal-mechanical finite element analysis. Results indicate that increasing CFV diameter enhances vertical heat conduction but causes localized heat accumulation and stress concentration due to the low thermal conductivity of encapsulation materials, elevating interfacial failure risks. Conversely, expanding CFV pitch promotes dispersed heat flow and reduces chip temperature but concurrently lowers local structural stiffness and exacerbates stress concentration. Optimal CFV design thus requires balancing thermal diffusion performance and mechanical constraints to ensure structural reliability and thermal stability.

The significance of wafer bonding is fundamental to the progression of electronic systems. Common fabrication techniques for Cu pillars play a crucial role in establishing resilient and efficient interconnects within semiconductor devices. It is imperative to explore the potential of nano-copper as an alternative material to overcome limitations associated with conventional copper. The use of nano copper paste in manufacturing has the potential to simplify the process, potentially reducing the number of steps compared to conventional methods. This study delves into the intricacies of wafer-level packaging (WLP), with a particular focus on hybrid bonding processes utilizing nanocopper sintering. Through the application of Finite Element Method (FEM) simulations, we investigate the stress distribution and thermal dynamics inherent in the sintering and hybrid bonding of both bulk copper and nanocopper materials. Our findings illuminate the superior mechanical and thermal properties of nanocopper, which contribute to reduced stress concentrations and enhanced mechanical integrity in semiconductor packaging. The research highlights the pivotal role of nanocopper sintering in advancing WLP technologies, offering insights into optimizing sintering and bonding parameters for improved device reliability and performance.

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.

Prognostic monitoring of power quad flat no-lead (PQFN) packages with four distinct silver pastes, each varying in material composition (pure-Ag and resin-reinforced hybridAg) and sintering processes (pressure-assisted and pressureless), was investigated in this study. The PQFN packages with silver sintered die-attach materials were subjected to thermal cycling tests (?55 ° C to 150 ° C), and the performance degradation was evaluated based on the following metrics: 1) electrical ON-state resistance RDSon monitored periodically at specific thermal cycling intervals and 2) transient thermal impedance Zth(t = 0.1 s) monitored online during thermal cycling. These measurements were further validated using acoustic microscopy imaging and cross-sectional inspection. The pressureless Ag-sintering material demonstrated comparable performance to pressure-assisted Agsintering, with a dense microstructure, and consistent electrical and stable thermal performance. Whereas the pressureless resinreinforced hybrid-Ag material exhibited degradation with a relative increase of 33% in RDSon, 38% in Zth(t = 0.1 s), and 67% delamination of the die-attach interface over 1000 cycles. These findings suggest that pressureless Ag-sintering may offer a viable alternative to pressure-assisted methods for lead (Pb)- free die-attachments, while resin-reinforced hybrid-Ag requires further development for improved thermomechanical reliability..

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.

In this study, a convenient chitosan oligosaccharide laser lithograph (COSLL) technology was developed to fabricate laser-induced graphene (LIG) electrodes and flexible on-chip microsupercapacitors (MSCs). With a simple one-step CO₂ laser, the pyrolysis of a chitosan oligosaccharide (COS) and in situ welding of the generated LIGs to engineering plastic substrates are achieved simultaneously. The resulting LIG products display a hierarchical porous architecture, excellent electrical conductivity (6.3 Ω sq^-1), and superhydrophilic properties, making them ideal electrode materials for MSCs. The pyrolysis-welding coupled mechanism is deeply discussed through cross-sectional analyses and finite element simulations. The MSCs prepared by COSLL exhibit considerable areal capacitance of over 4 mF cm^-2, which is comparable to that of the polyimide-LIG-based counterpart. COSLL is also compatible with complementary metal-oxide-semiconductor (CMOS) and micro-electro-mechanical system (MEMS) processes, enabling the fabrication of LIG/Au MSCs with comparable areal capacitance and lower internal resistance. Furthermore, the as-prepared MSCs demonstrate excellent mechanical robustness, long-cycle capability, and ease of series-parallel integration, benefiting their practical application in various scenarios. With the use of eco-friendly biomass carbon source and convenient process flowchart, the COSLL emerges as an attractive method for the fabrication of flexible LIG on-chip MSCs and various other advanced LIG devices.

Laser-induced graphene (LIG) has aroused a wide range of research interests ranging from micro-nano energy devices to the Internet of Things (IoT). Nevertheless, the non-degradability of most-used synthetic polymer carbon sources poses a serious threat to the environment. In this work, ecofriendly chitosan-based derivatives, including carboxymethyl chitosan (CMCS), chitosan oligosaccharide, and chitosan hydrochloride, are successfully converted into LIGs for the first time via a convenient one-step CO₂ laser engraving at ambient air. The obtained LIGs are characterized by a three-dimensional hierarchical porous structure and exhibit good sheet conductivity. The consecutive carbonization and graphitization mechanism of target precursors induced by laser heat accumulation is also deeply discussed. Besides, based on a mechanically reliable LIG/CMCS composite film and tribo-negative acrylic/polyimide anti-layers, two contact-separation mode triboelectric nanogenerators are built and their power densities range from 1.44 to 2.48 mW cm^-2. These devices with long cycle life can be used for low-frequency mechanical energy harvesting and commercial capacitance charging, which could be potentially applied in the wireless sensor network nodes. Such a family of chitosan derivatives paves a new route for LIG synthesis and provides new ideas for ecofriendly LIG electronics.

Substrate metallization is a crucial factor affecting the mechanical properties of sintered nanoparticles in microelectronics applications, as it is essential for ensuring good adhesion between the substrate and the sintered material. In this study, we investigated the influence of metallization on pressure-assisted nanocopper sintering and analyzed the related mechanism of interaction using experiments and molecular dynamics simulation. In the first session, we bonded dummy dies on various substrates, including bare Cu, and substrates with Ag or Au metallization by nanocopper pressure-assisted sintering. The mechanical properties of the bonding layers were estimated using shear strength and SEM image analysis of fracture and cross-section morphologies under different sintering conditions. We found that the group of Cu-bare Cu have better bonding strength as the sintering temperature or assisted pressure is not high enough. However, as more energy input to the bonding layer, such as higher temperature or larger sintering pressure, the mechanical performance showed a significant increase. In the second session, a sintering model, which contained a single nanoparticle and substrate, was built to illustrate the effects of metallization from the perspective of solid-state wetting. The contact angle was estimated using a creative method, and the crystallization structure evolutions under different sintering conditions were analyzed. We found that the lattice boundary generated as the Cu nanoparticle coalescence with Ag or Au substrate, which may decrease the bonding strength. However, for Ag and Au metallization, limited interface diffusion can be observed at the neck region, where a few numbers of substrate atoms transmitted toward Cu nanoparticle, and the contact area was larger than that of bare Cu substrate. Finally, a simple uniaxial stretching simulation was conducted to prove the results of sintering simulation. This study provides valuable insights into the effects of metallization on pressure-assisted nanocopper sintering, which can contribute to the optimization of mechanical properties of sintered nanoparticles in microelectronics applications.

The fabrication of flexible pressure sensors with low cost, high scalability, and easy fabrication is an essential driving force in developing flexible electronics, especially for high-performance sensors that require precise surface microstructures. However, optimizing complex fabrication processes and expensive microfabrication methods remains a significant challenge. In this study, we introduce a laser pyrolysis direct writing technology that enables rapid and efficient fabrication of high-performance flexible pressure sensors with a micro-truncated pyramid array. The pressure sensor demonstrates exceptional sensitivities, with the values of 3132.0, 322.5, and 27.8 kPa^-1 in the pressure ranges of 0-0.5, 0.5-3.5, and 3.5-10 kPa, respectively. Furthermore, the sensor exhibits rapid response times (loading: 22 ms, unloading: 18 ms) and exceptional reliability, enduring over 3000 pressure loading and unloading cycles. Moreover, the pressure sensor can be easily integrated into a sensor array for spatial pressure distribution detection. The laser pyrolysis direct writing technology introduced in this study presents a highly efficient and promising approach to designing and fabricating high-performance flexible pressure sensors utilizing micro-structured polymer substrates.

The rapid development of power electronics has challenged the thermal integrity of semiconductor packaging. Further developments in this domain can be supported significantly by utilizing fast and flexible thermal characteristic evaluation. This study employs the transient dual interface method (TDIM) to characterize and compare the thermal resistance of Ag- and Cu-sintered die-attach joints using an in-house developed thermal test chip (TTC). The proposed TTC with 82.5% active area achieves a temperature sensitivity of 12 Ω/K and maximum power of 360 W per cell, which are 50% and 44% higher than the state-of-the-art, respectively. The uniformity of the temperature distribution (1 °C at 68 W) is verified by infrared thermography. The cost-effective manufacturing process allows the design to be applied to any substrate, such as SiC or GaN. Ag and Cu sintering is performed to bond the TTC on a Cu substrate, and the junction-to-case thermal resistance of the sintered structures is extracted. The lowest junction-to-case thermal resistance of 0.144 K/W is measured for the device sintered using Ag paste. Meanwhile, the Cu sintered structure exhibits a comparable value of 0.158 K/W. The proposed TTC in combination with TDIM accelerates the introduction of novel and cost-effective materials such as Cu.

Short-wave ultraviolet (also called UVC) irradiation is a well-adopted method of viral inactivation due to its ability to damage genetic material. A fundamental problem with the UVC inactivation method is that its mechanism of action on viruses is still unknown at the molecular level. To address this problem, herein we investigate the response mechanism of genome materials to UVC light by means of quantum chemical calculations. The spectral properties of four nucleotides, namely, adenine, cytosine, guanine, and uracil, are mainly focused on. Meanwhile, the transition state and reaction rate constant of uracil molecules are also considered to demonstrate the difficulty level of adjacent nucleotide reaction without and with UVC irradiation. The results show that the peak wavelengths are 248.7 nm, 226.1 nm (252.7 nm), 248.3 nm, and 205.8 nm (249.2 nm) for adenine, cytosine, guanine, and uracil nucleotides, respectively. Besides, the reaction rate constants of uracil molecules are 6.419 × 10⁻⁴⁹ s⁻¹ M⁻¹ and 5.436 × 10¹¹ s⁻¹ M⁻¹ for the ground state and excited state, respectively. Their corresponding half-life values are 1.56 × 10⁴⁸ s and 1.84 × 10⁻¹² s. This directly suggests that the molecular reaction between nucleotides is a photochemical process and the reaction without UVC irradiation almost cannot occur.

This paper proposes and simulates research on the reverse recovery characteristics of two novel superjunction (SJ) MOSFETs by adjusting the doping profile. In the manufacturing process of the SJ MOSFET using multilayer epitaxial deposition (MED), the position and concentration of each Boron bubble can be adjusted by designing different doping profiles to adjust the resistance of the upper half P-pillar. A higher P-pillar resistance can slow down the sweep out speed of hole carriers when the body diode is turned off, thus resulting in a smoother reverse recovery current and reducing the current recovery rate (d (Formula presented.) /d (Formula presented.)) from a peak to zero. The simulation results show that the reverse recovery peak current (I (Formula presented.)) of the two proposed devices decreased by 5% and 3%, respectively, compared to the conventional SJ. Additionally, the softness factor (S) increased by 64% and 55%, respectively. Furthermore, this study also demonstrates a trade-off relationship between static and reverse recovery characteristics with the adjustable doping profile, thus providing a guideline for actual application scenarios.

As a promising technology for high-power and high-temperature power electronics packaging, nanocopper (nanoCu) paste sintering has recently received increasing attention as a die-attachment. The high-temperature deformation of sintered nanoCu paste and its underlying mechanisms challenge the reliability of high-power electronics packaging. In this study, the tensile deformation behaviors of sintered nanoCu paste were firstly characterized by high-temperature tensile tests performed at various temperatures and strain rates ranging from 180 °C to 360 °C, 1 × 10⁻⁴ s⁻¹ to 1 × 10⁻³ s⁻¹ respectively. It was found that the elastic modulus and tensile strength decreased at the higher tensile temperature while the ductility increased accordingly. The highest elastic modulus and tensile strength results were 12.15 GPa and 46.97 MPa, respectively. Second, failure analysis was conducted based on the fracture surface after tensile testing. Recrystallization was revealed as the main factor for ductility improvement. Subsequently, an Anand model was fitted by stress-strain curves to describe the tensile constitutive behavior of the sintered nanoCu paste. Multi-scale modelling techniques also investigated the impact of tensile temperature and strain rate on the tensile response. Molecular dynamics simulation was implemented using a hemispherical Cu nanoparticle model to reveal the properties from an atomistic perspective. In addition, a two-dimensional equivalent model was further established by using a stochastically distributed void morphology. The multi-scale modelling techniques successfully describe the evolution of tensile response to the different tensile temperatures and strain rates. Besides, the equivalent model with random void morphology was demonstrated as the finite element simulation results were highly consistent with the high-temperature tensile experiments.

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.

Robust bonding of Cu quasi-nanoparticles sintering for Ag coated chip and bare copper substrate was achieved. The effect of temperature, pressure and time on the sintering bonding strength and microstructural evolution was deeply studied. 36.5 MPa shear strength was achieved when applied 5 MPa pressure. By increasing to 30 MPa, it shows the best die shear strength of 116 MPa, accomplished with a sintering temperature of 250 °C for 3 min. Temperature also influenced the shear strength a lot. Between 210 °C and 230 °C can already provide strength over 30 MPa. When increased to 270 °C, the strength was extremely enhanced to over 120 MPa. Inspection on the fracture behaviors and cross-section of sheared off samples was conducted by SEM, EDS, and XRD. It is found that low bonding performance is due to both of the incomplete burnt out of organics and incomplete Cu QNPs sintering. In addition, high bonding is account for the positive effect of pressure and temperature on promoting the necking growth, sintering networking formation, pores isolation and brittle-ductile fracture transformation. The recommended sintering profile is 250 °C, 3 min, 20 MPa. Finally, the feasibility for SiC MOSFET power electronics DA was verified by testing its static characteristics at both room temperature and 150 °C.

Nano copper sintering technology has great potential to be widely applied in the wide-bandgap semiconductor packaging. In order to investigate the coalescence kinetics of copper nano particles for this application, a molecular dynamic (MD) simulation was carried out at low temperature on a special model containing two substrate and multiple particles in between. Accordingly, thorough microstructure and dislocation investigation was conducted to identify the atomic-scale evolution in the system. The corresponding findings could provide evidence on the new particle-substrate sintering mechanism. Furthermore, atomic trajectories tracking method was applied to study the rotation behavior of different sized nano particles. New rotation behavior and mechanism were described. Additionally, the study on the size effect of copper particles on the sintering process and coalescence mechanism was conducted via comparing the microstructural and dislocation distribution of 3 nm, 4 nm and 5 nm models. Finally, by comparing the MSD results at low and high temperature for each model, the dominant coalescence dynamics changes were obtained.

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.