Failure Lifetime Research Articles

Structural characteristics and evolution in the crack propagation process of NiCrAlY/YSZ gradient coatings through thermal shock at 900 °C

In this study, four different thicknesses of NiCrAlY/8YSZ gradient coatings were fabricated using atmospheric plasma spraying (APS) technology. The failure behavior and lifetime of coatings were subsequently compared and analyzed through thermal shock experiments. The results revealed a pronounced correlation between the initiation and propagation of internal cracks within the gradient coatings and the thickness of the gradient region at a thermal shock temperature of 900°C. Both horizontal and vertical cracks were observed to propagate and interconnect, with horizontal crack propagation being the primary cause of coating failure. Notably, samples featuring a gradient region thickness of 150μm exhibited superior thermal shock resistance, suggesting promising prospects for enhanced coating durability.

Creep Behavior and Fracture Mechanisms of the Dissimilar Inertia Friction Welded Joints of Deformed and Powder Metallurgy Ni‐Based Superalloys

ABSTRACTIn this research, the microstructure and precipitate characteristics of the dissimilar inertia friction welded (IFW) joints of deformed and powder metallurgy (PM) nickel‐based superalloys were studied using optical, scanning electron, and transmission electron microscopy. In addition, several creep tests were conducted. The high‐temperature mechanical properties of the IFW joints were systematically analyzed. Under the creep testing condition of 680°C, the specimens exhibited creep fracture at the thermomechanically affected zone (TMAZ) of the PM superalloys. Further, the failure lifetime is enhanced with a reduction in the applied creep loading. Owing to the IFW process, various γ′ precipitates and carbide distributions were observed in the various zones of a dissimilar IFW joint. Undissolved powder particle boundary (PPB) defects in the TMAZ of the PM superalloy initiated creep cracks under creep loading. Based on the experimental results and theoretical analysis, the creep fracture mechanisms of the dissimilar IFW joints were revealed. Thus, the findings of this study provide guidance for controlling the microstructures and properties of dissimilar deformed/PM nickel‐based superalloy IFW joints.

High temperature fatigue behavior of coated and uncoated nickel-based single crystal superalloy DD6: Microstructures evolution, damage mechanisms and lifetime prediction

Thermal barrier coatings (TBCs) are widely used to further extend the lifetime of turbine blades by protecting the blades from high temperature corrosion and oxidation. However, the mechanical behavior of turbine blades is obviously affected by the TBCs. In this study, microstructures evolution, damage mechanisms and life prediction of coated and uncoated nickel-based single crystal (NBSX) superalloy DD6 under isothermal fatigue load were investigated at 980 °C. The effects of TBCs on fatigue failure behavior and lifetime of DD6 were addressed. The results showed that the fatigue lifetime reduced with the increase of load. The effect of TBCs on the fatigue lifetime was related to the stress amplitude, as the effect was beneficial at high stress but almost negligible at low stress. Fracture morphologies showed that the cracks more likely initiated and propagated from basal defects for both coated and uncoated DD6, and the microstructure evolution also showed stress amplitude dependence. The crack density of uncoated DD6 increased first and then decreased with the increase of stress amplitude. However, the TBCs reduced the number of cracks that penetrate into the DD6 substrate, and the stress amplitude exerted a significant effect on crack propagation paths. In addition, the rafting behaviors of the DD6 substrate of coated and uncoated samples was compared, and results showed that TBCs could reduce the rafting degree of DD6. Finally, the fatigue lifetime of coated samples was predicted based on the modified Basquin model, and the prediction results fitted well with the experimental results.

A Data-Driven Approach for Predicting the Lifetime of Lithium-Metal Batteries

Lithium-metal batteries (LMBs) are promising candidates for accelerating the implementation of electric vehicles in our society. LMBs comprise of a lithium-metal anode that possesses the highest theoretical specific capacity (3860 mAh/g) and the lowest redox potential (-3.04V vs standard hydrogen electrode).1 LMBs undergo repeated plating and stripping of lithium ions on the anode surface. The non-homogenous stripping process leads to the isolation of metallic lithium from the anode surface, forming dead-lithium.2 The parasitic reaction between the lithium-metal anode and the electrolyte leads to the formation of the solid electrolyte interphase (SEI) layer. These phenomena lead to the reduction of available lithium and a rise in cell impedance, causing a rapid reduction of lifetime for these batteries.3 , 4 In this talk, we present a diverse dataset collected from different LMBs of different capacities and voltage ranges, that includes features from the initial formation cycle, rest voltages and CV charging during cycling. A data-driven model from the LMB cycling data is presented to predict the remaining useful lifetime (RUL) of these cells. Insights from the model can be used to determine the bad cells in a batch, improve the designs of the cells and derive optimal charging protocols for their implementation in the BMS. References Lin, D., Liu, Y. & Cui, Y. Reviving the lithium metal anode for high-energy batteries. Nat. Nanotechnol. 12, 194 (2017).Xu, S., Chen, K.-H., Dasgupta, N. P., Siegel, J. B. & Stefanopoulou, A. G. Evolution of Dead Lithium Growth in Lithium Metal Batteries: Experimentally Validated Model of the Apparent Capacity Loss. J. Electrochem. Soc. 166, A3456–A3463 (2019).Liu, G. & Lu, W. A Model of Concurrent Lithium Dendrite Growth, SEI Growth, SEI Penetration and Regrowth. J. Electrochem. Soc. 164, A1826–A1833 (2017).Gao, N. et al. Fast Diagnosis of Failure Mechanisms and Lifetime Prediction of Li Metal Batteries. Small Methods 5, 1–11 (2021).

A New Rank Estimator for Least Squares Estimation of Weibull Modulus

The Weibull distribution is widely used in reliability analysis to evaluate the failure behavior and lifetime characteristics of various systems and components. One of the most commonly used methods for estimating the parameters of the Weibull distribution is the ordinary least squares (OLS) technique, which is based on fitting a linear regression model to the transformed data. This paper proposes a new rank estimator for ordinary least squares estimation of Weibull modulus, a key parameter used as a measure of variability in the data. The new rank estimator is a quadratic function of the order statistic number, with three parameters that are optimized by Monte Carlo simulations. Using relative efficiency as a criterion, the performance of the new rank estimator is compared with three commonly used rank estimators, mean, median and hazen rank estimators, which are linear functions of the order statistic number. The results show that the new rank estimator has a significant advantage over the other rank estimators for any sample size between 3 and 150. The findings also imply that other nonlinear functions, such as cubic polynomials, could be applied to further improve the efficiency of the parameter estimators of the ordinary least squares method.

The impact of titanium alloying on altering nanomechanical properties and grain structures of sputter-deposited cobalt for electromigration reliability enhancement

Cobalt (Co) has recently become a highlighted on-chip interconnection material for advanced metallization scheme of microelectronic circuits. Here, electromigration behaviors of sputter-deposited Co and Co(Ti; 0.9 at%) interconnection lines embedded in Si are comparatively studied. These lines were annealed (500 °C/30 min) prior to further accelerated electromigration testing under high current densities in the range of 3 × 107–9 × 108 A cm−2. A collection of the obtained electromigration failure lifetimes, current scaling factors and activation energies confirms a noticeable enhancement in the electromigration reliability of the Co lines by the added Ti. Results by scanning transmission electron microscopy (STEM) and nanoscratch testing reveal that 3–5 nm-sized Ti crystallites are uniformly dispersed in the Co-interconnect matrix, effectively inhibiting Co grain growth, promoting the formation of nanotwinned Co and elevating film’s mechanical properties for ensuring the electromigration reliability. With deteriorated hardness and adhesion energy, reduced planar defects and many big grains all spanning transversely the entire interconnect line, Co is vulnerable to electromigration failures, also giving accelerated thermally-induced interfacial diffusion and chemical reactions with the surrounding Si, as proven by depth-profiling secondary spectrometry and STEM analysis.

Identifying multiple synergistic factors on the susceptibility to stress relaxation cracking in variously heat-treated weldments

The 347H austenitic stainless steel has been widely used for pressure vessels and pipeline (PVP) applications due to its excellent creep and corrosion resistance, which fit ideally to the harsh conditions in petrochemical industries, fossil fuel or nuclear power plants, and modern energy storages. However, a failure mode has been commonly observed with cracks emerging at the heat affected zone (HAZ) of weldments during post-weld heat treatment (PWHT) or under intermediate to high temperature service conditions. This phenomenon is termed as Stress Relaxation Cracking (SRC) since the purpose of PWHT is to relieve the welding-induced residual stress fields, or as Stress Age Cracking (SAC) if failure happens during service. A leading literature explanation of this failure suggests that the residual stress relaxation and the precipitation dissolution and/or re-precipitation occur in the same temperature range, which can lead to locally high strains and thus to crack at the grain boundaries. Since in situ spatial measurements of residual stress fields, microstructural evolution, and failure processes are nearly infeasible, this work recourses to a micromechanical finite element framework that models the high temperature failure as the nucleation and growth of grain boundary cavities, whereas various parameters such as thermomechanical loading history and its evolution, the competition of grain-interior dislocation creep and grain-boundary diffusion in failure lifetime, and microstructural heterogeneities (such as the precipitate free zone near grain boundaries) can be quantitatively incorporated. It can be concluded from these microstructure-explicit simulations that an accurate knowledge of residual stress evolution and a carefully calibrated set of material constitutive parameters are the essential prerequisites for lifetime predictions. The understanding of individual governing factors also leads to a mechanistic interpretation of the observed SRC susceptibility C-curves. These results suggest that the criticality of residual stress evolution, but not the precipitation-induced local strains, be the leading factor for SRC.

Breakdown voltage and TDDB performance improvement by optimizing the PECVD dielectric film characteristics in MIM capacitors

The dielectric breakdown voltage (BV) and time dependent dielectric breakdown (TDDB) are the most important concerns for device reliability. In this study, the silicon nitride (SiNx) used as metal-insulator-metal (MIM) capacitor dielectric was successfully prepared by a dual-frequency plasma enhanced chemical vapor deposition (PECVD) method. Fourier transform infrared (FTIR) absorption spectra and electrical characterization results suggest that the SiNx film possesses higher dielectric breakdown voltage performance by decreasing SiH4/NH3 gas flow ratio or optimizing the interface layer among multiple layers. Similarly, the TDDB reliability test based on Weibull distribution indicates an increase in failure lifetime of the MIM capacitors by adjusting RF power and NH3 gas flow.

Practical Study to Demonstrate an Increase in the Reliability of Flip Chip Connections by Adding Nanoparticles to Solder

The aims of the research are to improve the reliability and lifetimes of solder joints to contribute to the green economy, by reducing waste and extending recycling times. The objectives of the work are; to improve the materials properties of various solders used for attaching die/flip chip packages to PCBs by adding nanoparticles to the mix, to fabricate industrial test samples using flip chips soldered to PCBs, to test the reliability of the solder through accelerated testing, to examine failure modes and lifetime extensions.

Grain boundaries-dominated migration failure of copper interconnect under multiphysics field: Insight from theoretical modeling and finite element analysis

As the feature size of Cu interconnects in microelectronic devices are miniaturized into micro- and even nano-scale, the effects of grain boundaries (GBs) on the electromigration (EM) failure become more and more obvious. It is of fundamentally importance to investigate the grain boundaries dominated failure mechanism and lifetime of Cu interconnects. In this work, the interconnection models containing different grain boundaries were constructed by using finite element simulations. The simulation results indicate that the current density at Cu grain boundaries is lower, but the current will be increased locally, when it is almost perpendicular to grain boundaries. However, the temperature is higher locally at grain boundaries. In the early stage of atomic diffusion, thermal migration and stress migration also occur near grain boundaries, resulting in significant atomic segregation near grain boundaries, particularly at the intersection of grain boundaries and near the inclined grain boundaries with small angles to the current direction. The atomic diffusion is considerably accelerated as the density of grain boundaries is increased, but is slowed down by poorly connected columnar grain boundaries.

High-Temperature Failure Mechanism and Lifetime Assessment of Silicone Gel Package Insulation for High-Power Electronic Devices Based on Pyrolysis Kinetics

High-Temperature Failure Mechanism and Lifetime Assessment of Silicone Gel Package Insulation for High-Power Electronic Devices Based on Pyrolysis Kinetics

Stability and reliability analysis of a non‐isolated high gain DC‐DC converter

AbstractThis paper investigates the stability and reliability analysis of a non‐isolated high‐gain DC‐DC converter. The proposed DC‐DC converter produces a high gain output voltage with a lower duty ratio and reduced voltage stress on the semiconductor switch. A reliability analysis is performed to predict the failure rate and lifetime of the individual components using the military handbook (MIL‐HDBK‐217F). A state space equation and small signal modeling of the proposed converter are derived to elucidate the performance of the proposed converter through stability analysis. A closed‐loop using PID controller is incorporated to attain the constant regulated output voltage during sudden parameter changes. The validation of the closed‐loop using the PID controller is verified with the wide range of variations in the different parameters, such as input voltage, load value, and reference voltage value. The laboratory‐based prototype is developed for the proposed converter and validated the performance with 250 W. The power density and efficiency of the proposed converter are 1.360 kW/L and 93%, respectively.

Discriminating among inverse Weibull, lognormal, and inverse Gaussian distributions

AbstractInverse Weibull, lognormal, and inverse Gaussian are some commonly used statistical distributions for modeling positively skewed failure lifetime data. These distributions share some interesting properties among themselves like they all have uni‐modal hazard rates. In this paper, we address the problem of discriminating among these statistical distributions to consider a more appropriate lifetime model. We first consider the complete samples and make use of the maximized log‐likelihood approach for choosing the correct model. We also obtain the expressions for logarithmic of defined test statistics, and associated asymptotic distributions. We then extend our discussion based on the observed sample in the presence of some censoring. We perform a simulation study in both cases to compare the probabilities of correct selection. Furthermore, for a given probability of correct selection and user‐specified protection level, we present a discussion to determine the minimum sample size required to discriminate among the three lifetime models. Finally, two real data sets are analyzed to illustrate the proposed methodology. In our findings, we observed that model parameters and methods of estimating unknown parameters play very important roles in the discrimination process, and sample size and the proportion of censoring become key factors to ensure a high probability of selecting a correct model.

Understanding electromigration failure behaviors of narrow cobalt lines and the mechanism of reliability enhancement for extremely dilute alloying of manganese oxide

Self-forming barriers for copper (Cu) interconnect metallization are well developed. However, the self-forming-barrier process and associated electromigration behaviors of narrow lines of cobalt (Co), a new interconnect wiring material for sub-10-nm semiconductor device nodes, are yet to be explored. In this study, we present an all-wet electroless trench-filling process to fabricate narrow (100 nm) lines of Co and MnO-added Co [Co(MnO)], then thermally annealed to some extent (400 °C/30 min) prior to electromigration testing. Empirical data obtained from accelerated electromigration testing, including failure lifetimes, current-density scaling factors, activation energies and physical failure profiles, consistently show that electromigration reliability of the Co lines is markedly enhanced by 0.1% added MnO. Transmission electron microscopy and focused ion beam imaging, along with dynamic adhesion strength data, reveal that the enhancement is related to annealing-induced segregation and dispersion of MnO particles at the interface with SiO2, ensuring adhesion of Co on SiO2, preventing interfacial interdiffusion and stuffing electromigration pathways. The adhesion strength, microstructures and Joule-heating data of Co and Co(MnO) are provided for the discussion of the differences in their electromigration performance and failure mechanism. Comments on electroless-plated Co as a new interconnect material are also given.

Influence of corrosion on failure modes and lifetime seismic vulnerability assessment of low‐ductility RC frames

AbstractCorrosion of reinforced concrete (RC) structures constitutes a critical form of environmental deterioration and may significantly increase the vulnerability of old non‐seismically designed buildings during earthquake events. This study proposes a probabilistic framework to evaluate the influence of corrosion deterioration on the lifetime seismic fragility of low‐ductility RC frame buildings. In contrast to limited past literature on this topic, the proposed framework offers novel contributions. This is one of the first study to consider potential alteration in failure modes of building components (from flexure to flexure‐shear) due to the time‐dependent aging process. Numerical models validated with past experimental test results are utilized to capture these failure modes, which are particularly relevant for low ductility RC frames designed prior to the introduction of modern seismic codes. Secondly, given the gamut of uncertainties associated with the corrosion process, this study develops condition‐dependent seismic fragility functions independent from an assumed exposure scenario, as often done in literature. These functions can be easily adopted by design engineers and stakeholders for prompt fragility assessment, and subsequent decision‐making without the need for computationally expensive finite element (FE) model runs. The proposed framework is demonstrated on a benchmark three‐story RC frame that considers time‐varying seismic demand models and damage state thresholds while accounting for the uncertain corrosion deterioration process and ground motion record‐to‐record variability.

Difference Between the PWM and Standard DC Power Cycling Tests Based on the Finite-Element Simulation

PWM power cycling, which has complex control strategies and high testing costs, received a lot of attention in recent years due to the test conditions are closer to the application of power modules than standard DC power cycling. Therefore, the root difference of the failure modes and lifetime of IGBT power modules between DC and PWM power cycling is the concern in this paper, based on the finite element simulation. For stimulating the PWM power cycling with high accuracy and fast speed, an IPWM power cycling is proposed and verified by a simple model. Then an electro-thermo-mechanical coupled model of a single chip is established for comparison. Mainly focus on the current distribution, temperature distribution and stress distribution. The current distribution comparison results show no difference while a higher temperature gradient is shown in PWM power cycling due to the additional switching losses. However, the stress distribution results show chip solder layer is still the main failure mechanism both in DC and IPWM power cycling. Therefore, a conclusion can be obtained that there is no difference in failure mechanism and lifetime between DC and PWM power cycling. And the same bond wire failure and similar lifetime of DC and PWM power cycling tests further verify this conclusion.

Load Current Injection Modes Affected Power Cycling Lifetime and Failure Mechanism of IGBTs

In this paper, the influence of load current injection modes (saturation mode and threshold mode), at standard DC power cycling, on the failure mechanism and lifetime of IGBTs is presented. 6 groups of power cycling tests, at almost the same test conditions, with 2 different current injection modes and 2 different packages are performed. The failure mode after power cycling is confirmed by on-line monitored electrical and thermal parameters (forward voltage drop <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CE</sub> and thermal resistance <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">thjs</sub> ) and further by SAM (Scanning Acoustic Micrography) pictures. Failure mechanism is then analyzed and the power cycling lifetime is compared and explained, with the help of finite element simulations. All results show that the threshold load current injection mode, with the gate and collector shorted, in power cycling can indeed reduce the load current to a large extent for the desired junction temperature swing. However, the power cycling lifetime and failure mechanism are changed, especially for devices with bond wire failure. It is not recommended for power cycling lifetime evaluation.

Comparative Investigation on Aging Precursor and Failure Mechanism of Commercial SiC MOSFETs Under Different Power Cycling Conduction Modes

Power cycling test (PCT) is an effective method to evaluate the SiC MOSFETs' long-term reliability, including lifetime and degradation mechanisms. Some of the aging precursors of PCT have been identified in previous literature. But when multiple failure mechanisms compete with each other, the individual precursors are nullified. Although PCT is mainly used to evaluate the package reliability, there are still unresolved problems due to the gate oxide reliability of SiC MOSFET, the repeated gate stress of the power cycling has different effects on the devices with different gate structures. This paper presents a comprehensive investigation of the aging precursors and failure mechanism of three typical commercial SiC MOSFETs with different gate structures through PCTs under two different conduction modes. Degradation-related essential precursors and possible causes behind them are discussed. The failure mechanisms and correlation with the degradation state of different devices are studied in depth. In addition, the effects of PCT under different conduction modes on failure mechanism and lifetime have been investigated.

Workbench Study Concerning the Highest Reliability Outcome for PoL Converters with Different Output Capacitor Technologies

The last decade’s studies show that the PoL (point-of-load) converter’s output capacitor is an important component for reliability, implying that its careful selection may determine the overall converter’s failure rate and lifetime. PoL converters are commonly found in many electronic systems, usually as part of the Intermediate Bus Architecture (IBA). Their important requirements are a stable output voltage at load current variation, good temperature stability, a low output ripple voltage, high efficiency, and reliability. If the electronic system is portable, a small footprint and low volume are also important considerations. These were recently well accomplished with eGaN (enhancement gallium nitride) transistor technology, whose VUFoM (vertical unipolar figure of merit) is 1.48 compared to 1.00 for silicon. This ensures a higher converter power density (watts/area). This paper reviews the most-used capacitor technologies, highlighting the reliability of these components as part of the converter’s output filter by presenting original data related to their best performance. The test was set up with EPC’s eGaN FET transistor, which was enclosed within a 9059/30 V evaluation board with a 12 V input and 1.2 V output. Different output capacitor technologies were evaluated, and reliability was calculated based on measurements of the ripple of the output voltage and thermal scanning.

Failure modes analysis and reliability enhancement of wind turbines

AbstractThe transition of the global energy system to affordable, reliable and clean sources is an important target of several international climate change accords and conferences such as the United Nations Framework Convention on Climate Change (UNFCCC) and its Conferences of parties (COP), Kyoto protocol and the UN Sustainable Development Goals (SDGs). The wind power is at the heart of these energy systems transformation and climate change mitigation. Indeed, the global capacity of wind turbines has seen tremendous growth, especially, during the past two decades which has made wind energy the fastest growing renewable source in the world. Nevertheless, the problem of premature failures and low‐reliability level of wind turbines have been increasingly noticed. This paper presents a new systematic analytical approach for failure modes and reliability analysis of wind turbines. The approach is a combination of three aspects which are qualitative and quantitative analysis using the fault tree method, reliability assessment as well as lifetime estimation and enhancement. Firstly, the various failure modes are presented. Then, mathematical modeling and reliability evaluation have been developed and simulated. Afterward, the actions that can be considered to improve the reliability and, consequently, the lifetime of wind turbines have been presented and analyzed. The results of the developed approach revealed that major reliability improvements, failure rate reduction and lifetime extension can be achieved, leading to a better return on investment, reduced maintenance as well as a safer and more reliable clean energy production.