This article introduces an online condition monitoring strategy that utilizes a transient heat pulse to detect package thermal performance degradation. The metric employed is the temperature-dependent transient thermal impedance "Zth(t, Tamb)."The proposed methodology offers quantitative insights into package thermal performance degradation and effectively pinpoints the presence of multiple failure mechanisms. A thermal test chip assembled in a power quad flat no-lead package is used in this study to demonstrate the methodology. The packaged devices are first characterized to determine the transient pulse duration, a critical parameter to monitor a specific region of interest. Subsequently, package thermal performance degradation is continuously monitored online during thermomechanical cycling lifetime experiments. The validity of the measurement results is later confirmed through acoustic imaging and cross-sectional analysis. The changes observed in Zth(t, Tamb) over thermal cycling correspond to the delamination of the active metal layers on the die and cohesive failure on the die attach. This article further includes a comparative summary, highlighting the distinctions between the proposed and industry-standard test methods. In conclusion, the importance of online condition monitoring to detect early signs of failure is emphasized, and the proposed methodology s practical applicability in real-life scenarios is briefly discussed.

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Driven by the increasing demand for high-power systems, ceramic substrates have received more attention for handling higher power density. Warpage in active metal brazed (AMB) ceramic substrate becomes a critical issue as it can deteriorate the reliability performance. This study comprises three phases, including investigation of the cause of the warpage, validation of the proposed model, and optimization for effective warpage management. At first, the coefficient of thermal expansion (CTE) and yield strength of the copper (Cu) layer in AMB were characterized and adopted in a two-dimensional (2D) finite element model. The evolution of simulated strain and moments revealed the cause of the warpage during the manufacturing processes. Furthermore, the 2D model was extended to a three-dimensional (3D) model. The finite element method (FEM) and experiments were conducted on different heat treatment conditions for 3D model validation. The validated 3D model was applied to carry out a design of experiments (DoEs) for design optimization to reduce the warpage. Consequently, the factor analysis in DoEs was demonstrated by different pattern designs using subtractive milling techniques.@en

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.

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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.@en

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.@en

A significant challenge in the implementation of health monitoring systems for estimating the health state of devices is the lack of accurate information about design details. This challenge is particularly prominent in the field of power electronics, where both IC designers and converter designers are often hesitant to share information about their designs. Addressing this issue, this paper introduces a novel AI-driven digital twin modeling methodology that enables the detection and classification of failures in power semiconductors, particularly Wide Band Gap semiconductors. By employing AI-based system identification techniques, this method offers a noninvasive approach to health monitoring of power switches with high resolution, even while operating under real conditions. The proposed method has been validated by simulating wire bond failure in a SiC power MOSFET using MATLAB SIMULINK, and the results demonstrate its accuracy.

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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.@en

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.

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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.

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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).

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Abstract-Prognostic monitoring of Power QFN packages with four distinct silver pastes, each varying in material composition (pure-Ag and resin-reinforced hybrid-Ag) 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 to 150°C), and the performance degradation was evaluated based on the following metrics: (i.) Electrical on-state resistance R_DS monitored periodically at specific thermal cycling intervals, and (ii.) Transient thermal impedance Z_th(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 Ag-sintering, with a dense microstructure, and consistent electrical and stable thermal performance. Whereas the pressureless resin-reinforced hybrid-Ag material exhibited degradation with a relative increase of ~33% in R_DSon, ~38% in Z_th(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 Pb-free die-attachments, while resin-reinforced hybrid-Ag requires further development for improved thermo-mechanical reliability.

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Power MOSFET dies in the automotive industry are becoming larger (>5 × 5 mm) and thinner (<50 µm) to meet high-performance and lifetime requirements. Ensuring the mechanical robustness of these large ultrathin chips is crucial for reliable electronic devices and high-throughput packaging processes. The high aspect ratio and advanced chip designs incorporating trench technology present significant challenges in semiconductor assembly, packaging, and testing. This paper introduces an experimental front-end strategy aimed at strengthening the front side (FS) of large ultrathin dies using various die-top systems. Industry-equivalent 50 µm thick dummy power MOSFET dies were fabricated to evaluate the efficacy of different chip designs and materials, such as polyimide (PI), in mitigating fracture risks. Fabrication-induced stresses and warpage in the device layers were measured using a thin-film stress measurement tool. Additionally, the FS strength of the ultrathin dies was assessed using the three-point bending method, with the resulting data analyzed via two-parameter Weibull distribution plots. Results demonstrated that the deposition of 5 µm PI on the nitride die topside significantly increased die strength from 339 MPa to 760 MPa, with 5 µm PI proving more effective for die strengthening than 10 µm. The interaction between the metal-trench layer and the die was found to be critical to the robustness of ultrathin dies, influenced by the pattern and layout of the trenches. Die-top metallization designs, such as meandering patterns, showed promising improvements in die strength compared to standard designs. A proposed chip layout aims to maximize PI coverage for clip-bonded products on the die topside, leveraging its strengthening effect. The study also demonstrated that dummy reference chips can facilitate rapid and straightforward evaluation of extensive design experiments to identify robust chip designs.

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Resin-reinforced silver (Ag) sintering material is an effective and highly reliable solution for power electronics packaging. The hybrid material’s process parameters strongly influence its microstructure and pose a significant challenge in estimating its effective properties as a thin interconnect layer. This research demonstrates a novel 3D reconstruction methodology for the microstructural investigation of the resin-reinforced Ag sintering material from OverMolded Plastic (OMP) packages. Based on the reconstructed models with different sintering parameters (temperature and time), the fraction of Ag and Resin volume distribution, the connectivity of silver particles, and the tortuosity factors were estimated. A 99% connectivity of sintered Ag particles was achieved with various sintering conditions, such as 200°C for 2 hours, 200°C for 4 hours, and 250°C for 2 hours. However, coarsening of Ag particles was promoted when sintered at 250°C. Increasing the sintering time at 200°C had insignificant changes. The estimated tortuosity factor also indicated that sintering at 250°C provides the shortest heat transport path between the semiconductor die and the package substrate. In order to quantify the microstructural findings, the OMP packages’ thermal performance with different sintering conditions (temperature, time, and interconnect thickness) was experimentally assessed. Although the experimental measurements were less sensitive to the effective interface thermal resistances’, the measurement results show a good correlation with the microstructural analysis. Sintering the Resin-reinforced Ag sintering material at higher temperatures (250°C) seems to improve the package thermal performance, and increasing the sintering time at 200°C has a negligible effect.@en

Background: Optogenetics could offer a solution to the current lack of an ambulatory method for the rapid automated cardioversion of atrial fibrillation (AF), but key translational aspects remain to be studied. Objective: To investigate whether optogenetic cardioversion of AF is effective in the aged heart and whether sufficient light penetrates the human atrial wall. Methods: Atria of adult and aged rats were optogenetically modified to express light-gated ion channels (i.e., red-activatable channelrhodopsin), followed by AF induction and atrial illumination to determine the effectivity of optogenetic cardioversion. The irradiance level was determined by light transmittance measurements on human atrial tissue. Results: AF could be effectively terminated in the remodeled atria of aged rats (97%, n = 6). Subsequently, ex vivo experiments using human atrial auricles demonstrated that 565-nm light pulses at an intensity of 25 mW/mm² achieved the complete penetration of the atrial wall. Applying such irradiation onto the chest of adult rats resulted in transthoracic atrial illumination as evidenced by the optogenetic cardioversion of AF (90%, n = 4). Conclusion: Transthoracic optogenetic cardioversion of AF is effective in the aged rat heart using irradiation levels compatible with human atrial transmural light penetration.

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Integrated Circuits and Electronic Modules experience concentrated thermal hot spots, which require advanced thermal solutions for effective distribution and dissipation of heat. The superior thermal properties of diamonds are long known, and it is an ideal material for heat-spreading applications. However, growing diamond films to the electronic substrate require complex processing at high temperatures. This research investigates a heterogeneous method of integrating diamond heat spreaders during the back-end packaging process. The semiconductor substrate and the heat spreader thicknesses were optimized based on simulations to realize a thermally enhanced Power Quad-Flat No-Lead package. The performance of the thermally enhanced PQFN was assessed by monitoring the temperature distribution across the active device surface and compared to a standard PQFN (without a heat spreader). Firstly, the thermally enhanced PQFN indicated a 9.6% reduction in junction temperature for an input power of 6.6W with a reduced thermal gradient on the active device surface. Furthermore, the diamond heat spreader's efficiency was observed to increase with increasing power input. Besides, the reliability of the thermally enhanced PQFN was tested by thermal cycling from -55°C to 150°C, which resulted in less than 2% thermal degradation over two-hundred cycles. Such choreographed thermal solutions are proven to enhance the packaged device's performance, and the superior thermal properties of the diamond are beneficial to suffice the increasing demand for high power.

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SnBiAgCu solder alloy is an attractive soldering material for temperature-sensitive electronic devices due to its excellent creep properties. This study firstly reports the creep properties of SnBiAgCu solder alloy under different temperatures. Results show that the addition of Bi resulted in better creep resistance compared with that of commercial SAC305 (Sn-3.0Ag-0.5Cu). Secondly, dynamic mechanical analyses were performed to get the storage modulus and glass transition temperature of potting compounds. Finally, a finite element modeling based analysis were used to figure out the different failure mechanism due to the presence of potting materials. The accurate simulation data offers an optimization reference for the selection of solder and potting materials.

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The objective of this article is to investigate the thermal-fatigue properties of a commercially available lead-free solder alloy (SnBiAgCu) under the use of different types of potting compounds. Solder alloys with lower silver content are expected to substitute the conventional solder alloys SAC305 (Sn-3.0Ag-0.5Cu). First, the tensile behavior and creep behavior of the SnBiAgCu solder alloys were studied at three temperatures (25, 75, 125). Results show that this type of solder alloys presented higher tensile strength and creep deformation endurance than conventional SAC305 solder alloys. Second, a dynamic mechanical analysis was performed to get the storage modulus and glass transition temperature of three types of potting compounds, which were used in the thermal-fatigue simulation. Third, the experimentally determined material data was used for the averaged strain energy density increment calculated by the finite element method. This simulation approach was selected as damage metrics to evaluate solder interconnect reliability under different combinations of materials. It is found that the application of potting compounds will increase strain energy density significantly when compared with the strain energy density calculated without potting compound, which means that potting compounds will deteriorate the thermal-fatigue reliability of solder interconnects. These accurate data-driven simulation models can in the future form the basis for compact digital twins for predicting useful remaining lifetime.

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High-performance IC-to-antenna interconnection is one of the key enablers for the mass production of high-end millimeter wave (mmW) radar systems above 100 GHz. In this work, a radar system with an on-package antenna array working at 122 GHz is presented. The antenna is placed on top of the molded package and the antenna-to-chip interconnection is realized by through-polymer via (TPV) technology. The detailed fabrication process of the radar antenna-in-package (AiP) with TPV is discussed. The results from the functional tests of the radar AiP are presented and benchmarked to a commercial quad-flat no-leads (QFN) package with an open antenna cavity. The detection margin between the echo signal and the constant false alarm rate (CFAR) threshold is approximately 10 dB higher for the TPV radar AiP compared with the benchmarked commercial QFN package.@en

AIMS: Ventricular tachyarrhythmias (VTs) are common in the pathologically remodelled heart. These arrhythmias can be lethal, necessitating acute treatment like electrical cardioversion to restore normal rhythm. Recently, it has been proposed that cardioversion may also be realized via optically controlled generation of bioelectricity by the arrhythmic heart itself through optogenetics and therefore without the need of traumatizing high-voltage shocks. However, crucial mechanistic and translational aspects of this strategy have remained largely unaddressed. Therefore, we investigated optogenetic termination of VTs (i) in the pathologically remodelled heart using an (ii) implantable multi-LED device for (iii) in vivo closed-chest, local illumination. METHODS AND RESULTS: In order to mimic a clinically relevant sequence of events, transverse aortic constriction (TAC) was applied to adult male Wistar rats before optogenetic modification. This modification took place 3 weeks later by intravenous delivery of adeno-associated virus vectors encoding red-activatable channelrhodopsin or Citrine for control experiments. At 8-10 weeks after TAC, VTs were induced ex vivo and in vivo, followed by programmed local illumination of the ventricular apex by a custom-made implanted multi-LED device. This resulted in effective and repetitive VT termination in the remodelled adult rat heart after optogenetic modification, leading to sustained restoration of sinus rhythm in the intact animal. Mechanistically, studies on the single cell and tissue level revealed collectively that, despite the cardiac remodelling, there were no significant differences in bioelectricity generation and subsequent transmembrane voltage responses between diseased and control animals, thereby providing insight into the observed robustness of optogenetic VT termination. CONCLUSION: Our results show that implant-based optical cardioversion of VTs is feasible in the pathologically remodelled heart in vivo after local optogenetic targeting because of preserved optical control over bioelectricity generation. These findings add novel mechanistic and translational insight into optical ventricular cardioversion.

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