Accelerated Lifetime Testing Research Articles

Impact of thermal crosstalk on dependent failure rates of multilayer ceramic capacitors undergoing lifetime testing

Several research studies have investigated the degradation of BaTiO3-based dielectric capacitor materials, focusing on the impact of composition, defect chemistry, and microstructural design to limit the electromigration of oxygen vacancies under electric fields at finite temperatures. Electromigration can be a dominant mechanism that controls failure rates in the individual multilayer ceramic capacitor (MLCC) components in testing the reliability of failures with highly accelerated lifetime testing (HALT) to determine the mean time to failure of MLCCs surface mounted onto printed circuit boards (PCBs). Conventional assumptions often consider these failures as independent, with no interaction between components on the PCB. However, this study employs a Physics of Failure (PoF) approach to closely examine transient degradation and its impact on MLCC reliability, emphasizing thermal crosstalk and its influence on dependent and independent failure rates. Finite element analysis thermal modeling and infrared thermography were used to assess the impact of circuit layout and component spacing on heat dissipation and thermal crosstalk under various electrical stress conditions. The study distinguishes between dependent and independent failures under a HALT, quantified through a β′ factor reflecting common cause failures due to thermal crosstalk. Through a series of experimental and statistical analyses, the β′ factor is evaluated with respect to temperature, voltage, and component spacing. These insights highlight the importance of understanding the nature of the data in reliability testing of MLCCs and optimizing the layout design of high-density circuits to mitigate dependent failures, improving overall reliability and informing better design and packaging strategies.

Mechanical wear characteristics of 170 kV gas-insulated switchgear circuit-breaker contacts before arc initiation: An accelerated lifetime test approach

Mechanical wear characteristics of 170 kV gas-insulated switchgear circuit-breaker contacts before arc initiation: An accelerated lifetime test approach

Advanced Design Validation Planning Techniques for Commercial Vehicle E-Axles

<div>Design validation plays a crucial role in the overall cost and time allocation for product development. This is especially evident in high-value manufacturing sectors like commercial vehicle electric drive systems or e-axles, where the expenses related to sample procurement, testing complexity, and diverse requirements are significant.</div> <div>Validation methodologies are continuously evolving to encompass new technologies, yet they must be rigorously evaluated to identify potential efficiencies and enhance the overall value of validation tests. Simulation tools have made substantial advancements and are now widely utilized in the development phase. The integration of simulation-based or simulation-supported validation processes can streamline testing timelines and sample quantities, all the while upholding quality standards and minimizing risks when compared to traditional methods. This study examines various scenarios where the implementation of advanced techniques has led to a reduction in the e-axle design validation plan (DVP), particularly in relation to the start of production (SOP) decision-making quality gates.</div> <div>Many DVPs incorporate tests in a specific order to enhance the validation impact of each sample and to guarantee that preconditioning tests are implemented when necessary. An instance of preconditioning is subjecting a system to thermal cycling. Thermal cycle preconditioning ensures that the sample accurately represents a real-world system when undergoing sealing-related tests, such as ingress protection testing according to ISO 20653 [<span>1</span>]. Assessing the necessary thermal cycling to “bed-in” a sample would be highly elaborate using a physical sample, but it is a straightforward aspect to extract from modern finite element analysis (FEA). A case study will be presented to evaluate the minimum required thermal cycling and determine the cost savings for the DVP.</div> <div>Furthermore, the validation supported by simulations will be showcased in the context of accelerated lifetime testing. Often, accelerating such tests necessitates a balance between the distribution of damages and the overall testing duration. By incorporating safety factors from simulations as an initial input, the distribution of damages can be adjusted to allow for some over-testing on more secure components, thereby reducing the overall testing time.</div> <div>Efficiency assessment will additionally be considered for virtual validation due to the complexity of the measurement and data acquisition, contributing to measurement uncertainty. Furthermore, simulation-based validation will be considered for the case of lubrication testing, which can be hampered by a largely qualitative assessment criteria.</div> <div>Overall, these scenarios will be evaluated for their potential to streamline the overall DVP process in terms of testing time, sample quantity, and critical path duration. This underscores the potential benefits of leveraging advanced DVP techniques for cost and time savings.</div>

Accelerated Life Tests for Time-Dependent Response Characterization of Functionalized Piezoelectric Microcantilever-Based Gas Sensors

This article explores the accelerated lifetime test approach to characterize the time-dependent response of a piezoelectrically driven microcantilever (PD-MC) based gas sensor. The novelty here relies on demonstrating how accelerated lifetime tests can be useful to differentiate sensing mechanisms for non-linear gas sensors. The results show the determination of the sensor’s optimum operation time while maintaining result validity. The approach is demonstrated for 1,5-diaminopentane (cadaverine), a volatile organic compound (VOC) whose concentration in meat and fish products has been proven viable for determining the shelf life. A PD-MC functionalized with a cadaverine-specific binder was therefore incorporated into a hand-held electronic nose, and the response was found to be highly reliable within a specific resonance frequency shift, enabling the accurate prediction of meat and fish expiration dates. To identify the limits of detection in terms of cadaverine concentration and sensor lifetime, this study applies the results of accelerated life tests into a Weibull distribution analysis to extract the expected time to failure. For the accelerated life tests, a functionalized PD-MC was exposed to high concentrations of cadaverine, i.e., 252.3 mg/kg, 335.82 mg/kg, and 421.08 mg/kg, compared to the nominal concentration of 33 mg/kg observed in meat and fish samples. Furthermore, we demonstrate the differentiation of the response mechanisms of the system accruing from the concentration-dependent interaction of cadaverine with the binder. This enables the determination of the upper limit of the analyte concentration for a stable response. The findings suggest that the functionalized PD-MC sensor exhibits a linear and predictable response when exposed to a standard cadaverine concentration of 33 mg/kg for up to 93.01 min.

Accelerated lithium-ion battery cycle lifetime testing by condition-based reference performance tests

Lifetime testing of lithium-ion batteries is time-consuming and costly. To reduce the time-to-market, application-specific accelerated lifetime tests are conducted. The test conditions must be carefully designed and controlled, both the test environment and load profile. During the lifetime test, measurable properties of the cell, most commonly the capacity and internal resistance, are tracked by a reference performance test (RPT). The frequency of RPTs is a variable of the number of test cycles or time. Setting the wrong frequency for the RPT results in either too many RPTs or, in the worst case, too few. To mitigate this issue, a test object capacity-driven approach has been developed. This new method is described and demonstrated in this article conducting the RPTs based on the cycling capacity of the cell. The method ensured the desired numbers of RPTs during the test period at the selected intervals corresponding to steps of 1% capacity loss. When compared to the most used traditional test method, using a fixed number of 200 cycles between RPTs, the method generated 44% more cycles over the initial 100 days.

Silver bridging TiO2 nanotubes (TNTs) bases and PbO2 active layers to accelerate electron transfer over PbO2/SnO2-Sb/TNTs-Ag/Ti anode for efficient organic pollutants removal

In this work, excellent conductor element Ag was employed to bridge TiO2 nanotubes (TNTs) and PbO2 to construct an “expressway” for rapid electron transfer between the bases and active layers over the fabricated PbO2/SnO2-Sb/TNTs-Ag/Ti anode. Physicochemical characterizations reveal that elemental Ag can fill into the gaps between the TNTs, thus stabilizing structure and improving conductivity of the anode. Electrochemical and accelerated lifetime tests show the expanded reaction area (0.049–0.173 cm2), decreased charge transfer resistance (42.32–4.03 Ω cm−2), and prolonged lifetime (0.29–6.28 years). Furthermore, relatively higher average current efficiency (ACE) and less energy consumption (Esp) can be achieved during electrochemical oxidation of acid gold G (AY36) and rhodamine B (RhB) synthetic wastewaters, as well as shortening their degradation pathways. Our research looks forward to providing a novel Ag bridging design strategy for the synthesis of highly active and stable multilayer anodes.

Effective rare-earth doping on semiconductor behavior for BaTiO3-based automotive MLCCs

Highly accelerated lifetime test (HALT) for lifetime evaluation was performed on the state-of-art automotive MLCC prototypes by varying Dy/Mg (donor/acceptor) ratio added to BaTiO3. The results clearly showed that the mean time to failure (MTTF) more than 280 times as the Dy/Mg ratio increased from 1.0 to 10.0. Since oxygen vacancies typically form in-gap state/defect at the donor level, the activation energy value under thermal activation process as a function of voltage was calculated and compared by non-destructive testing (I–V curve) for an accurate evaluation of the extrinsic behavior. It was found that barrier height at the Ni/BT interface decreases as the voltage increases, resulting in a decrease in activation energy. As the Dy/Mg ratio increases, the density of defects/in-gap states formed at the donor level in the bandgap by oxygen vacancies decreases, which may lead to a decrease in the number of electrons excited by the external voltage. Furthermore, it was verified that the calculated Schottky barrier height of the 10.0 Dy/Mg ratio under voltage has higher value than that of the 2.6 Dy/Mg ratio. Based on the results of this study, we propose a new indicator for the design of automotive MLCCs with high lifetime reliability that can be used for comparative analysis of additive compositions through non-destructive test (I–V curve) with low evaluation time/cost.

Performance Enhancement of Ti/IrO2-Ta2O5 Anode through Introduction of Tantalum-Titanium Interlayer via Double-Glow Plasma Surface Alloying Technology.

Ti/IrO2-Ta2O5 electrodes are extensively utilized in the electrochemical industries such as copper foil production, cathodic protection, and wastewater treatment. However, their performance degrades rapidly under high current densities and severe oxygen evolution conditions. To address this issue, we have developed a composite anode of Ti/Ta-Ti/IrO2-Ta2O5 with a Ta-Ti alloy interlayer deposited on a Ti substrate by double-glow plasma surface alloying, and the IrO2-Ta2O5 surface coating prepared by the traditional thermal decomposition method. This investigation indicates that the electrode with Ta-Ti alloy interlayer reduces the agglomerates of precipitated IrO2 nanoparticles and refines the grain size of IrO2, thereby increasing the number of active sites and enhancing the electrocatalytic activity. Accelerated lifetime tests demonstrate that the Ti/Ta-Ti/IrO2-Ta2O5 electrode exhibits a much higher stability than the Ti/IrO2-Ta2O5 electrode. The significant improvement in electrochemical stability is attributed to the Ta-Ti interlayer, which offers high corrosion resistance and effective protection for the titanium substrate.

A multi-channel stimulator with an active electrode array implant for vagal-cardiac neuromodulation studies

BackgroundImplantable vagus nerve stimulation is a promising approach for restoring autonomic cardiovascular functions after heart transplantation. For successful treatment a system should have multiple electrodes to deliver precise stimulation and complex neuromodulation patterns.MethodsThis paper presents an implantable multi-channel stimulation system for vagal-cardiac neuromodulation studies in swine species. The system comprises an active electrode array implant percutaneously connected to an external wearable controller. The active electrode array implant has an integrated stimulator ASIC mounted on a ceramic substrate connected to an intraneural electrode array via micro-rivet bonding. The implant is silicone encapsulated for biocompatibility and implanted lifetime. The stimulation parameters are remotely transmitted via a Bluetooth telemetry link.ResultsThe size of the encapsulated active electrode array implant is 8 mm × 10 mm × 3 mm. The stimulator ASIC has 10-bit current amplitude resolution and 16 independent output channels, each capable of delivering up to 550 µA stimulus current and a maximum voltage of 20 V. The active electrode array implant was subjected to in vitro accelerated lifetime testing at 70 °C for 7 days with no degradation in performance. After over 2 h continuous stimulation, the surface temperature change of the implant was less than 0.5 °C. In addition, in vivo testing on the sciatic nerve of a male Göttingen minipig demonstrated that the implant could effectively elicit an EMG response that grew progressively stronger on increasing the amplitude of the stimulation.ConclusionsThe multi-channel stimulator is suitable for long term implantation. It shows potential as a useful tool in vagal-cardiac neuromodulation studies in animal models for restoring autonomic cardiovascular functions after heart transplantation.

92‐1: Invited Paper: Wide‐Color‐Gamut and Stable MicroLED Displays Using UV‐Pumped Cd‐Free Quantum Dots

Applied Materials, Inc. has reported a novel and manufacturable microLED display architecture, featuring UV‐A microLEDs, 4‐subpixel layout, pixel isolation wells filled with inkjetted Cd‐free R/G/B quantum dots (QDs), and a blanket UV blocker on top. A 1.37” smart‐watch active‐matrix display prototype was assembled using such method. Our QDs, including blue QD and the matrix materials exhibit excellent stability under UV excitation, as verified by accelerated lifetime test under higher UV flux and elevated temperature. The emission properties of our R/G/B QDs was further optimized, paving a path to achieve 99% DCI‐P3 color space coverage. Our display demonstrates a highly uniform Lambertian emission pattern with minimal color shift at high viewing angles, attributing to all emissions originating from QD embedded in the same polymer matrix. Furthermore, we can eliminate the QD photon‐brightening effect and demonstrate display with high thermal stability up to 90⁰C.

Method for accelerated testing of wind turbine gearbox bearings based on frictional energy in the rolling contact

This paper investigates a method for a novel accelerated test procedure for rolling bearings in wind turbine gearboxes. Established test procedures e. g. highly accelerated lifetime tests (HALT) mainly reflect fatigue damage and not slip-induced damage patterns (e.g. smearing). A commonly used criterion to rate the severity of an operating point regarding slip-induced damage is the frictional energy. Frictional energy is introduced into the rolling contact as soon as there is a significant combination of simultaneously occurring slip and pressure. Up to now only critical thresholds for this criterion that must not be exceeded have been identified on small-scale component test rigs. However, the permissible amount and duration of overshoots of the critical threshold that lead to damage in the actual application are not understood yet. Therefore, the aim is to conduct tests on full-size test rigs in which frictional energy is applied until slip-induced damage occurs. In order to perform these tests in a reasonable time, it is essential to accelerate the test procedures. Thus, this paper introduces a method for accelerated test procedures based on frictional energy in the rolling contact. The requirement is that the same cumulated frictional energy as in field operation is applied in a shorter time on the test rig. A further requirement is that the frictional power in the accelerated test procedure never exceeds the maximum frictional power occurring in the field. This paper shows the theoretical background regarding frictional energy and the transfer to the test procedure.

Digitalization of Large-Scale Testing Facilities for the Wind Industry: DIGIT-BENCH Digital Twin

Testing of large wind turbine components plays a central role in delivering reliable yet cost-effective technology. However, these experiments are often lengthy and costly. Fatigue testing of a wind turbine blade might take up to 12-14 months, whereas highly accelerated lifetime testing of a nacelle demands 6-8 months. The exchange of simulation models and data between OEMs and test facilities is recognized as a critical factor in the planning of an experimental campaign. In fact, OEMs are typically very protective of their industrial secrets, and sharing such sensitive information may constitute a threat. It follows that the use of simulation models to enable more effective experimentation is not pursued efficiently.Digital twins are emerging as a key enabling technology to improve the operation & maintenance of test benches for the wind industry. A digital twin combines physical systems and their digital models into a cyber-physical system to provide functionalities that cannot be attained by either physical or digital assets independently. The seamless integration of the test bench with digital models offered by a digital twin is expected to enhance the interaction between OEM and test bench operators.This proceeding illustrates the status of the development of the DIGIT-BENCH digital twin developed by R&D Test Systems (R&D) and Aarhus University to serve large-scale test facilities for the wind industry. The digital twin utilizes FMI-based co-simulation to enable the coupling of physical/digital components in an industrial-secret-friendly environment. The digital twin concept is demonstrated on a 2-degrees-of-freedom test bench installed at Aarhus University.

Reliability of X7R MLCCs Under Alternating Polarity Highly Accelerated Lifetime Testing

Reliability of X7R MLCCs Under Alternating Polarity Highly Accelerated Lifetime Testing

Climatically Accelerated Material Processes Determining the Long-Term Reliability of Light-Emitting Diodes.

LEDs (Light-Emitting Diodes) are widely applied not only in decorative illumination but also in everyday lighting in buildings, flats, public areas, and automotive fields. These application areas often mean harsh environments, for example, regarding the humidity content of the surrounding air: besides outdoor and automotive illumination, even the household use cases (kitchen, bathroom, cellar) may represent extreme temperature and humidity variations (often reaching relative humidity levels close to 100%) for these devices; thus, their reliability behaviour in such circumstances should be better understood. Thermally activated processes were studied in several previous publications, but less information is available regarding high-humidity environmental tests. Moisture and temperature ageing tests with appropriate environmental parameter settings were performed as accelerated lifetime tests to investigate not only the effect of temperature but also that of humidity on the ageing and reliability of LED packages containing RGB (red green blue) chips and phosphor-converted white (pcW) LEDs. The ageing was followed not only through monitoring optical/electrical/spectral parameters but also with material analysis. Moisture-material interaction models were proposed and set up. It was found that humidity-accelerated ageing processes are more severe than expected from previous assumptions. RGB and pcW LEDs showed strongly different behaviour.

Disassembly of in-plastic embedded printed electronics

We explored a novel design-for-recycling method for encapsulated printed electronics in an injection-molded package that improves disassembly at End-of-Life (EoL). To this end, a non-adhering disassembly layer (NADL) was applied onto the printed circuitry and light-emitting diodes prior to injection molding. Surprisingly, the devices with a disassembly layer remained fully functional after injection molding, despite exposure to high shear forces and elevated temperatures. Facilitating the disassembly of an encapsulated electronic device using a weak link in the adhesion strength of the overmolded encapsulant invokes a contradiction: the possibility to remove the injected plastic from any underlying coating goes against the requirement of high adhesion over the entire surface area for structural strength and integrity during the harsh conditions expected by industry. To achieve balance between disassemblability and reliability, the adhesion strength of the overmolded encapsulant was tuned using vias in the coating design. To the author's best knowledge, this is the first time design-for-recycling principles were successfully applied to such in-mold structural electronics devices. Accelerated lifetime tests at 85 °C/85% relative humidity for 1000 consecutive hours were conducted to study the reliability of devices realized with this design-for-recycling method. Mechanical disassembly of molded devices proceeded uniformly along the intended interface of NADL with molded polycarbonate resin and exposed the printed Ag and surface-mounted components, thereby demonstrating the possibility to perform subsequent and dedicated recycling on plastics and metals separately.

Physics‐based and data‐driven approaches for lifetime estimation under variable conditions: Application to organic light‐emitting diodes

AbstractThe prognosis of organic light‐emitting diodes (OLEDs) not only requires early detection of a bearing defect, but also the capability to predict their life data under all operational scenarios. The use of sophisticated machine learning (ML) algorithms is undoubtedly becoming an increasingly exciting research direction, as these algorithms can yield high predictive models with minimal domain expertise. The central question of this perspective is: how well can ML models advance our ability to forecast the lifetime of OLEDs compared to the physics‐based models? In this paper, data‐driven methods, feed‐forward neural networks (FFNN), support vector machines (SVMs), k‐nearest neighbors (KNNs), partial least squares regression (PLSR), and decision trees (DTs), are used to predict the lifetime and reliability of OLEDs through analyzing the lumen degradation data collected from the accelerated lifetime test. The final predicted results indicate that both the data‐driven and our physics‐based OLED lifetime models fit well the experimental data. The main drawback of the former method is that their efficacy is highly contingent on the quantity and quality of the operational dataset. Among all these methods, much more reliability information (time to failure) and the highest prediction accuracy can be achieved by FFNN.

Degradation monitoring of multilayer ceramic capacitors during high accelerated lifetime testing using ultrasound

Multilayer ceramic capacitors (MLCCs) are vital circuitry components where long-term stability at high temperature and fields is critical to device operation. High accelerated lifetime testing (HALT) statistically investigates reliability and lifetime of MLCCs through exposure to temperatures and voltages exceeding normal operating conditions. The long-term reliability of the dielectric layers in MLCCs strongly depends on potential variability in the dielectric microstructure, such as cracking, which can be challenging to detect. Nondestructive ultrasonic evaluation is sensitive to microstructural changes through measurements of wave scattering. This work uses high frequency (100 MHz) focused ultrasonic scattering methods to nondestructively monitor structural and microstructural changes in MLCCs from the pristine to the failed state during HALT to understand structural origins of electrical failure. Printed circuit board mounted MLCCs were electrically and ultrasonically characterized in a pristine state and during various degraded states before and after electrical failure under HALT. Evidence of damage pre-HALT was ultrasonically indicated by high attenuation regions on the ultrasonic maps suggesting that the mounting process may induce damage. The high attenuation regions in the pristine samples evolved throughout HALT indicating that the damage in the pristine state might be the spatial origin of part failure, which underscores the impact and importance of detection of structural defects on the reliability of MLCCs.

A new Co-doped PbO2 anode for copper electrowinning: Electrochemical and morphological characterization

Anodic electrodeposition was used to create a high catalytic activity Co-doped PbO2 composite coating on Ti substrate, in order to reduce the overpotential and raising the electrocatalytic activity for oxygen evolution during the copper electrowinning process. The temperature, composition, and current density of the electrolyte were investigated in order to produce a composite anode with the best electrocatalytic behavior, stability, and efficiency in the electrowinning process. Scanning electron microscopy (SEM) was utilized to investigate the morphology of the coating, and electrowinning, cyclic voltammetry (CV), and the accelerated life time test (ALT) were employed to evaluate the electrodes' electrochemical behavior. The ideal conditions in this investigation involved 65 g.L−1 cobalt nitrate with a 5 mA.cm−2 current density at 65 °C for the electrodeposition of Co-doped PbO2 coating. Furthermore, the potential for oxygen evolution of the PbO2-CoOx anode was found to be approximately 180 and 220 mV lower than that of the PbO2 and Pb-Ca-Sn anodes, respectively, based on the results of the electrochemical test. The ALT test results showed that the PbO2-CoOx anode had a significantly lower initial cell voltage than the Pb-Ca-Sn and PbO2 anodes; however, this value increased after 165 h due to the anode's mechanical breakdown. The results showed that Cu electrowinning efficiency for Pb-Ca-Sn, PbO2, and PbO2-CoOx was 91.9 %, 98.4 %, and 100 % respectively.

Ultra-Stable Inorganic Mesoporous Membranes for Water Purification.

Thin, supported inorganic mesoporous membranes are used for the removal of salts, small molecules (PFAS, dyes, and polyanions) and particulate species (oil droplets) from aqueous sources with high flux and selectivity. Nanofiltration membranes can reject simple salts with 80-100% selectivity through a space charge mechanism. Rejection by size selectivity can be near 100% since the membranes can have a very narrow size distribution. Mesoporous membranes have received particular interest due to their (potential) stability under operational conditions and during defouling operations. More recently, membranes with extreme stability became interesting with the advent of in situ fouling mitigation by means of ultrasound emitted from within the membrane structure. For this reason, we explored the stability of available and new membranes with accelerated lifetime tests in aqueous solutions at various temperatures and pH values. Of the available ceria, titania, and magnetite membranes, none were actually stable under all test conditions. In earlier work, it was established that mesoporous alumina membranes have very poor stability. A new nanofiltration membrane was made of cubic zirconia membranes that exhibited near-perfect stability. A new ultrafiltration membrane was made of amorphous silica that was fully stable in ultrapure water at 80 °C. This work provides details of membrane synthesis, stability characterization and data and their interpretation.

Diagnostics of Piezoelectric Bending Actuators Subjected to Varying Operating Conditions

In applications of piezoelectric actuators and sensors, the dependability and particularly the reliability throughout their lifetime are vital to manufacturers and end-users and are enabled through condition-monitoring approaches. Existing approaches often utilize impedance measurements over a range of frequencies or velocity measurements and require additional equipment or sensors, such as a laser Doppler vibrometer. Furthermore, the non-negligible effects of varying operating conditions are often unconsidered. To minimize the need for additional sensors while maintaining the dependability of piezoelectric bending actuators irrespective of varying operating conditions, an online diagnostics approach is proposed. To this end, time- and frequency-domain features are extracted from monitored current signals to reflect hairline crack development in bending actuators. For validation of applicability, the presented analysis method was evaluated on piezoelectric bending actuators subjected to accelerated lifetime tests at varying voltage amplitudes and under external damping conditions. In the presence of a crack and due to a diminished stiffness, the resonance frequency decreases and the root-mean-square amplitude of the current signal simultaneously abruptly drops during the lifetime tests. Furthermore, the piezoelectric crack surfaces clapping is reflected in higher harmonics of the current signal. Thus, time-domain features and harmonics of the current signals are sufficient to diagnose hairline cracks in the actuators.