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R.H. Poelma

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58 records found

Journal article (2026) - Fatin Battal, N. Gupta, Peter Mulder, Jeroen Maasen, René H. Poelma, Elias Vlieg, John J. Schermer
Porous copper films with nanoscale dendritic architectures are of growing interest in various advanced technology domains. These copper films form a three-dimensional porous network with internal surfaces that are covered with “Romanesco-like” dendritic features. This study investigates the influence of pulse-assisted electrodeposition and targeted additive chemistry on the dynamic hydrogen bubble templating process and the resulting film morphology. It is found that duty cycle modulation controls pore size and distribution. SEM analysis reveals that deposition with 25% duty cycle produces films with nearly 50% smaller pores and significantly thinner, shorter dendritic branches compared to continuous deposition. The addition of chloride ions induces a transition from multi-branched dendrites to elongated fractal structures, whereas citric acid promotes smaller, more uniformly distributed pores by modifying hydrogen bubble dynamics. When both additives are present, each retains its dominant influence, with chloride shaping branch structure and citric acid refining macro porosity, together producing a well-balanced porous network. The ability to selectively control both pore size and dendritic/fractal nanostructures provides a versatile pathway to engineer porous copper films with tailored architectures to achieve application-specific properties through a scalable electrodeposition process. ...
Due to the better performance of the Wide Band Gap (WBG) devices, there has been a paradigm shift toward WBG-based power modules for diverse applications like Electric Vehicles (EVs). However, the high parasitic inductance value of power modules hinders these devices from unlocking their full potential. Therefore, this paper comprehensively reviews SiC-based Single Side Cooling (SSC) power modules that benefit from low parasitic inductance. The paper also discusses the need to develop newer power modules using modern packaging methods. The surveyed power modules are categorized into three main groups, namely wire bonding, hybrid, and 3D packaging methods. This classification contains several vital parameters of the studied power modules, such as nominal and Double Pulse Tests (DPT) power ratings, parasitic inductance, size, etc. The main features and characteristics corresponding to the reviewed power modules' packaging methods and techniques are also briefly described. Finally, a thorough discussion about challenges and future trends is highlighted before concluding the paper. ...
Journal article (2026) - Henry A. Martin, Zihan Zhang, Mahad Saeed, Sander Dorrestein, Edsger C.P. Smits, René H. Poelma, Willem D. van Driel, Guo Qi Zhang
Power semiconductors operating under high heat fluxes and elevated temperatures rely on liquid-cooled heat sinks with substantial coolant volumes. Recent advancements in direct-to-chip (D2C) cooling techniques have shown enhanced thermal performance, reduced energy consumption, compact form factor, and minimized coolant usage. However, integrating microchannels onto semiconductor substrates poses significant fabrication challenges. Hence, we propose a direct-to-package (D2P) cooling approach that embeds microchannels within the package substrate, thereby bypassing the need for Thermal Interface Materials and complex fabrication processes. This D2P approach achieves high heat flux dissipation (up to ~ 625 W cm−2) tested in this study, while consuming a fraction of the coolant volume (~ 2 − 4 mL). The co-packaged architecture demonstrates ~ 6 − 7 × lower junction temperatures and thermal resistances than ambient-air cooling and ~ 2 − 3 × lower than heat sink cooling. A very high coefficient of performance is achieved, with an effective global Nusselt number > 10. This work establishes D2P liquid cooling integration as a scalable and energy-efficient approach for high-power systems. ...
Journal article (2026) - Shanliang Deng, Niels Harlaar, Juan Zhang, Sven O. Dekker, T. Jin, W.D. van Driel, René H. Poelma, Kouchi Zhang, D.A. Pijnappels, More authors...
Control theory underpins the stabilization of dynamic systems, including cardiac tissue, where disruptions in electrical conduction cause arrhythmias. Current treatments either act rapidly but without precision or deliver targeted interventions that cannot adapt in real time. We present an integrated platform combining optical voltage mapping (OVM), machine learning (ML), and optogenetics for autonomous, real-time detection and correction of cardiac rhythm disorders in vitro. OVM provides high-resolution membrane potential visualization; the ML module identifies arrhythmic events and drives microLED-based light patterns restoring normal conduction; and optogenetics enables light-based modulation of excitable cells. This integration of electrical, optical, and bioelectrical domains through a unified computational control layer enables adaptive, closed-loop rhythm stabilization, a significant advance in real-time electrophysiological interventions. Because inference and actuation run in real time on modest hardware, the same control loop could be embedded into miniaturized devices or microcontrollers, accelerating the transition from in-vitro to in-vivo automated rhythm management. ...
Conference paper (2025) - Nikhil Gupta, Guoqi Zhang, Sebastian Quednau, Sandy Klengel, Robert Klengel, Robin Simpson, Rene Poelma, Nick Liu, Sebastian Fritzsche, Frank Krueger
This study evaluates the reliability of die interconnect layers in a stacked die system fabricated using two different sintering agents: a microparticle-based silver paste and preform-based copper nanowires, intended for high-power packaging applications. Single-step sintering is performed to attach both dies at the same time, offering a faster and efficient assembly for improving scalability in manufacturing. The copper nanowires are sintered using KlettSintering method at 230° C for 5 minutes under a pressure of 20 MPa, while the silver paste was sintered pressure-free at 280 °C for 45 minutes in nitrogen. The assembled units were characterized using shear strength and microstructural analysis. Both sintering methods showed high porosity in the top die-attach layer compared to the bottom die-attach layer, which is reflected in lower shear values for top die (35 MPa) compared to bottom die (45 MPa) in the silver sintered unit. The long-term reliability of the die-stack systems was assessed through a 500 -hour high-temperature storage test and a 500-cycle temperature cycling test, revealing significant impacts of thermo-mechanical stresses on die attach layers of both sintered units. The KlettSintered system maintained consistent performance throughout the reliability tests but exhibited coarsening and oxidation during temperature cycling. Furthermore, the study identifies areas for potential improvement, particularly in improving multi-die sintering performance in a single-step process, which is crucial for ensuring durability in high-power applications. ...
Journal article (2025) - Leiming Du, Gerald Schaffar, René H. Poelma, Jiajie Fan, Willem D. van Driel, Xuejun Fan, Daniel Kiener, Guoqi Zhang, Verena Maier-Kiener
Sintered Cu nanoparticles (NPs) are promising for high-performance electronics due to their excellent thermal and electrical conductivity, as well as mechanical reliability. This study investigates the microscale mechanical behavior of sintered Cu NPs with a bimodal particle size distribution, focusing on strain rate and temperature effects. Micro-pillar compression tests were performed across strain rates of 0.0001 s−1 to 0.01 s−1 and temperatures from 25 °C to 350 °C. Results show that higher strain rates enhance yield strength through strain-rate hardening, while elevated temperatures lead to thermal softening and reduced mechanical stability. The Anand viscoplastic model accurately predicts these deformation behaviors. Microstructural analysis via scanning electron microscopy (SEM) and transmission electron microscopy (TEM) reveals localized deformation at 175 °C, with dislocations concentrated near the top surface and persistent porosity below, whereas at 350 °C, re-sintering and grain boundary diffusion create a denser microstructure. Phase-field fracture modeling further elucidates crack propagation, emphasizing the role of pore size and temperature. This combined experimental and modeling approach enhances understanding of viscoplastic deformation and fracture mechanisms in sintered Cu NPs, informing their use in interconnects, power electronics and thermal management systems. ...
Journal article (2025) - Leiming Du, Kai Liu, Dong Hu, Olof Bäcke, Xiao Hu, Xinrui Ji, Jiajie Fan, René H. Poelma, Magnus Hörnqvist Colliander, Guoqi Zhang
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. ...
Journal article (2025) - Leiming Du, Weiping Jiao, Olof Bäcke, Magnus Hörnqvist Colliander, René H. Poelma, Jiajie Fan, Willem D. van Driel, Xuejun Fan, Guoqi Zhang
This study investigates the interface strength and fracture behavior of sintered copper (Cu) nanoparticles (NPs) for all-Cu integration in advanced microelectronics packaging. Micro-cantilever bending tests on three configurations (Cu NP-notched, interface-notched and un-notched micro-cantilevers) were analyzed using scanning electron microscopy (SEM), transmission electron microscopy (TEM), transmission Kikuchi diffraction (TKD) and cohesive zone model (CZM). The interface-notched micro-cantilevers demonstrate superior fracture resistance, with a stress intensity factor (KQ) of 2.88±0.10 MPa m1/2, compared to 2.12±0.11 MPa m1/2 for Cu NP-notched micro-cantilevers. Simulation results, consistent with experimental results, reveal that Cu NP-notched micro-cantilevers exhibit lower fracture resistance due to porosity and stress concentrations, while interface-notched micro-cantilevers show enhanced strength, attributed to robust bonding and reduced void distribution. Un-notched micro-cantilevers display superior load-bearing capacity, with cracks bypassing the interface and propagating through porous regions. Moreover, in un-notched micro-cantilevers, a synergistic deformation mechanism is observed, where crack propagation through the sintered Cu NPs coexists with plastic slip deformation in the Cu substrate. These findings highlight the strong interfacial bonding and effective stress transfer at the Cu substrate-sintered Cu NP interface, validating the feasibility of direct sintering using Cu NPs without additional coatings. ...
Conference paper (2025) - Xiao Hu, Jianlin Huang, René Poelma, Hans van Rijckevorsel, Willem Dirk van Driel, Guoqi Zhang
In this study, we introduced a hybrid Potts-phase field model to simulate the co-evolution of grain growth and pores migration in sintered silver layers. The Potts model is good at capture the grain growth dynamics, while the phase field model describes the evolution of the porous network. These models are coupled via a hybrid free energy function to achieve a realistic representation of the microstructure evolution. This study further extends the hybrid model by incorporating (a) a flexible exchange interaction matrix to model the crystal anisotropy in grain growth, (b) Glauber or Kawasaki dynamics to describe different diffusion mechanisms, and (c) the effect of pinning sites, representing impurity-driven grain boundary stabilization. The computational framework is implemented using Taichi Lang, which allows for efficient parallel simulations. Results show that the model effectively captures the long-term evolution of the sintered silver microstructure in good agreement with experimental observations. This hybrid model is a powerful tool to predict microstructural reliability of sintered silver die attach layers, supporting material design and process optimization for high-power electronic applications. ...
Journal article (2025) - Leiming Du, Gerald Schaffar, Weiping Jiao, Kai Liu, René H. Poelma, Jiajie Fan, Willem D. van Driel, Xuejun Fan, Guoqi Zhang, More Authors...
This study investigates the microstructure evolution and mechanical behavior of bimodal-sized sintered copper (Cu) nanoparticles (NPs) under varying sintering pressures. Micro-pillar compression tests reveal a transition from collapse-dominated to compaction-driven deformation as sintering pressure increases. Transmission electron microscopy (TEM) and transmission Kikuchi diffraction (TKD) analyses identify a two-stage deformation mechanism—initial pore compaction followed by intragranular slip—fundamentally distinct from bulk Cu. Molecular dynamics (MD) simulations further reveal that large particles promote dislocation-mediated plasticity by accommodating intragranular slip, while small particles enhance load transfer through localized shear-compaction, together enabling uniform strain distribution and supporting the experimentally observed strain accommodation. The resulting microstructure achieves a combination of high yield strength (up to 320 MPa) and low elastic modulus (20 GPa), offering a compliant yet robust response. These findings elucidate a unique processing–structure–property relationship and provide a rational basis for designing porous metal interconnects capable of withstanding thermomechanical stresses in advanced electronic packaging. ...
Silicon-Carbide (SiC) MOSFETs are widely used in high-power and high-efficiency applications such as electric vehicles and power supplies. However, long-term reliability remains a critical concern, particularly under extreme operating conditions. This work aims to explain the health monitoring of SiC metal oxide-semiconductor field effect transistors (MOSFETs) through precise junction temperature (Tj) profiling based on performed measurements. The study focuses on the temperature-dependent behavior of the on-resistance (RDS(on)), a key parameter that varies with the aging, degradation, and temperature of the device. By systematically measuring RDS(on) at different temperatures and at various stages of the operating life of the device, we can establish a predictive model to assess the health of SiC MOSFETs. The importance of pulse duration of the drain current is stressed to avoid the self-heating effect with some device physics insights. The proposed methodology enables better understanding of the SiC MOSFET performance for future real-time condition monitoring, facilitating early failure detection and lifetime estimation. This approach provides valuable information for improving reliability and optimizing maintenance strategies in power electronics systems. Experimental results validate the effectiveness of the proposed method and give direction for future research opportunities. ...
Journal article (2024) - Xiao Hu, Henry Antony Martin, René Poelma, Jianlin Huang, Hans van Rijckevorsel, Huib Scholten, Edsger Smits, Willem D. van Driel, Guoqi Zhang
Resin-reinforced Ag sintering materials represent a promising solution for die-attach applications in high-power devices requiring enhanced reliability and heat dissipation. However, the presence of resin and intricate microstructure poses challenges to its thermal performance, and improvement strategies remain unclear. This work utilizes 3D FIB-SEM nanotomography to reconstruct the microstructure of this material under various process conditions. The analysis reveals that, even with an Ag volume fraction as low as 47.3%, Ag particles form a robust 3D network. Geometric tortuosity quantifies the effect of different sintering conditions on the Ag particle network in all spatial directions. Effective thermal conductivity is simulated based on realistic microstructure models. Results show a significant negative correlation between tortuosity and effective thermal conductivity. Increasing sintering temperature in Model B notably reduces tortuosity and enhances effective thermal conductivity. Sensitivity analysis underscores the dominant role of Ag volume fraction in regulating effective thermal conductivity. Finally, transient thermal impedance measurement of this material as a thin die-attach layer in actual high-power devices demonstrated its application potential. This article strives to explore the relationship between process, microstructure, and thermal properties of this material to provide a reference for further development. ...
Journal article (2024) - Henry A. Martin, Dong Hu, Xu Liu, Rene H. Poelma, Edsger C.P. Smits, Willem D. Van Driel, Guo Qi Zhang
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.. ...
Book chapter (2024) - L. Du, X. Zhao, R. H. Poelma, W. D. van Driel, G. Q. Zhang
Solder fatigue is a key failure mode in the electronic industry. Monitoring the actual degradation of the solder under real-time conditions in any application would be extremely beneficial. In this chapter, we describe the combination of experimental material characterization with numerical finite element (FE) simulations to obtain a prognostics and health monitoring (PHM) methodology for LED drivers used in outdoor lighting applications. Experimental characterization of a new type of solder is described. A FE model is created of a typical component in electronic drivers. The calculated damage level and the collected life data correlate together and form a model for predicting the lifetime of the drivers at certain user condition. The developed PHM methodology helps in identifying and reporting the failure of the driver in real time or can be used for predicting the actual remaining useful life (RUL). ...
Book chapter (2024) - Henry A. Martin, Edsger C.P. Smits, R. H. Poelma, Willem D. van Driel, G. Q. Zhang
The increasing awareness of environmental concerns and sustainability underlines the importance of energy-efficient systems, renewable energy technologies, electric vehicles, and smart grids. Hence, stringent constraints and safety regulations have been prompted to meet reliability standards in power electronics. This chapter provides a comprehensive outlook on the current state of power semiconductor devices, field-critical applications, dominant degradation mechanism (chip-related and package-related), and the emerging measurement techniques for reliability/condition monitoring. This chapter delves into the underlying physics behind each reliability measurement method reviewed. A comparative summary of cost, complexity, online monitoring capability, accuracy, and intrusiveness is provided to enable readers to make informed decisions about the measurement methods. This chapter emphasizes the significance of early fault detection through online monitoring, as it can effectively reduce system downtime for seamless non-interruptive operation. ...
Journal article (2024) - Shanliang Deng, B.L. den Ouden, Tim De Coster, Cindy I. Bart, Wilhelmina H. Bax, René H. Poelma, Antoine A.F. de Vries, Kouchi Zhang, Vincent Portero, D.A. Pijnappels
The heart produces bioelectrical signals, which can be measured as an electrocardiogram (ECG) for the detection of rhythm disturbances. Rapid and precise detection of these arrhythmias is crucial for their termination by closed-looped therapeutic interventions to counteract detrimental effects. However, there is a current lack of such systems tailored for experimental cardiovascular applications. This hampers not only in-depth mechanistic studies but also translational testing of new therapeutic strategies, especially in an untethered manner in awake animal models. To break new ground, recent advances to develop a non-invasive AI-supported heart rhythm monitoring system for untethered automated arrhythmia detection in a continuous manner is combined. This system is housed in a lightweight jacket for mobile use and includes an on-skin ECG sensor, a low-power microprocessor unit, a massive data storage unit, and a power-management system. By implementing a novel hybrid algorithm based on so-called heart rate (R-R) variability and a case-specific AI model, 100% sensitivity and 95% specificity is achieved in detecting atrial arrhythmias within 2 s upon initiation in adult rats. Thereby, the novel system sets the stage for advanced mechanistic studies and therapeutic testing, including closed-loop applications aiming for the termination of a broad range of atrial arrhythmias. ...
Journal article (2024) - Henry A. Martin, Sébastien Libon, Edsger C.P. Smits, René H. Poelma, Willem D. van Driel, Guo Qi Zhang
Silver sintering offers a promising landscape for Pb-free die attachment in electronics packaging. However, the sintered interface properties are highly process-dependent and deviate from bulk silver properties. Conventional measurement methods do not adequately capture the die-attach application geometry. Hence, this study introduces a novel methodology for characterizing thin bond-line interfaces with high-conductive materials. The transient heat flux impedance ΔZth(t, Δx) was measured between two thermally sensitive devices interconnected using pressureless Ag-sintering material. A correction factor was derived, based on thermal half-space principles, to account for non-uniform heat spreading over the die-attach interface. Experimental findings estimate an effective conductivity of ∼115W/mk for the pressureless Ag-sintered interface. The measurement results were validated by measuring a SAC305 soldered interface, which exhibited ∼55 W/mK, and a non-conductive epoxy interface of ∼2.5 W/mK. Voids on the die-attach layer, resulting from material processing, were identified to influence the interface thermal behavior. An uncertainty analysis was further discussed, emphasizing equipment tolerances, measurement sensitivity, and geometrical and thermal anisotropies. The article concludes with a comparative summary of the proposed methodology against conventional methods, highlighting differences in working principle, thickness range, measurement parameters, and their advantages and limitations. ...
Conference paper (2024) - Xiao Hu, Jianlin Huang, René H. Poelma, Willem Dirk van Driel, Guoqi Zhang
Low-temperature sintering technology of Ag nanoparticles is widely used in high-power electronic device packaging. Utilizing simulation methods to comprehend and control the microstructure and properties of Ag sintering materials has emerged as a prominent research area. This work uses the General Form PDE module in COMSOL to simplify the implementation of the phase field method. A two-particle model was established to explore the effects of different particle sizes and temperatures on the sintering neck of Ag nanoparticles. The two-particle model was expanded to multi-particle models and 3D models flexibly. This work presents the potential and limitations of these phase-field models, preparing for further multiphysics analysis and optimization of Ag sintering materials. ...
The introduction of silicon carbide(SiC) has reduced the superiority of traditional silicon-based power module pack-aging strategies. As packaging strategies become increasingly complex, classical thermal modelling tools often prove inadequate in balancing efficiency with accuracy. Integrating these tools with machine learning (ML) can significantly enhance their application potential. This discussion commences by addressing the pressing issues in thermal modelling of SiC modules, specifically the challenges associated with multiple heat sources and heat spreading. During the design stage, ML models can swiftly simulate the thermal response of various packaging strategies, aiding engineers in eliminating ineffective options. In the monitoring phase, the employment of a digital twin enables a deeper investigation into degradation phenomena. This article reviews the current status and explores the potential applications of ML in thermal modelling of SiC power modules. ...
Conference paper (2024) - Leiming Du, Shanliang Deng, Zhen Cui, René Poelma, Caroline Beelen-Hendrikx, Kouchi Zhang
In this study, we combined finite element method (FEM) based on Ansys and Noesis Optimus software to investigate the effect of bump structures and loading conditions on the electromigration properties of solder bumps in WLCSP. A numerical model considering current density, vacancy concentration, stress and temperature was utilized to calculate the vacancy concentration in solder bumps. The Optimus is an optimization software which can be used to perform the design of experiment (DOE) and sensitivity analysis. To optimize the bump structure, the DOE and response surface modeling (RSM) analysis were performed by using Noesis Optimus. The design optimization based on Noesis Optimus has three main advantages. First, the sensitivity analysis based on DOE results helps to find the most contributing factors. Second, it saves huge time because hundreds of experiments can be executed automatically. Third, it is able to perform evolutionary design optimization directly on RSM to identify the design’s optimal performance point. The maximum and concentration around solder were selected as the index to evaluate the effect of parameter combination on electromigration properties. ...