Reliability Of Modules Research Articles

Study on Lifetime Modeling of IGBT Modules Considering Electric Frequency Influence Mechanism

Affected by the randomness of the wind speed, the output electric frequency (0 20Hz) of the rotor-side converter does not match the thermal time constant (about 100ms) of IGBT modules, which causes the different junction temperature stress. It leads that it is difficult for the traditional lifetime model to reflect the influence of multi-time constant thermal load and result in inaccurate reliability evaluation. Aiming at the characteristics of wind turbine-side converters bearing thermal loads with multiple time constants, this paper studies the influence mechanism of electric frequency on the reliability of IGBT modules through a multi-physics simulation model and power cycling tests, and an improved lifetime model considering the influence of frequency parameters is proposed. Finally, an example analysis of the reliability evaluation of the DFIG rotor side converter is carried out. This paper is intended for the health management of converter systems and is supposed to be in service reliably.

Modeling and analysis of the multiphysics transport parameters of a kilowatt-class multistack module of reversible solid oxide cells

Degradation and reliability-related issues are major obstacles in the large-scale commercialization of multistack modules of reversible solid oxide cells. Understanding various transport processes, the distributions of multiphysics parameters, and chemical/electrochemical reactions is critical for improving the performance and reliability of modules. In the present study, a simplified method based on the distributed resistance analogy approach was developed for constructing a three-dimensional model of a kilowatt-class multistack module comprising reversible solid oxide cells. The uniformity of the parameter distribution and the fuel gas conversion rate were predicted, and the effects of the number of stacks, number of cells, cascade configuration, and module scale were investigated under dual-mode operation. The uniformity factor of the gas flow ranges from 0.152 to 0.817 in modules of different sizes and configurations; this range is considerably greater than the uniformity factors of the other transport parameters under dual-mode operation. The uniformity factors of flow, temperature, and current density are 17.7%–78.1% lower under parallel stack configurations than under series stack configurations. Doubling the number of cells resulted in the flow uniformity factor increasing by 108%–212%, and doubling the active area of the cells resulted in the uniformity factors of the temperature and current density increasing by 107%–135%. High reactant conversion rates and low nonuniformity factors are achieved for parallel multistack modules with a power of 8–32 kW, which is appropriate for large-scale applications.

Research on Online Monitoring Method for Bond Wire Fatigue Applied to IGBT Module

Bond wire fatigue is a prominent problem affecting the reliability of IGBT modules and power electronic converters, and has thus received much attention in the research community. As bond wire fatigue leads to changes in the gate circuit parameters, it affects the IGBT turn-off process. Based on this finding, this paper proposes a fatigue evaluation method for bond wire based on IGBT turn-off time. This includes constructing a turn-off time-bond wire fatigue model that considers the impact of changes in collector current, and developing a control software that utilizes the coupling relationship between the Kelvin terminal voltage VeE and turn-off time for the online extraction of IGBT turn-off time. In summary, the proposed online monitoring method of IGBT bond wire fatigue based on turn-off time can help improve the reliability of power electronic converters.

Reliability of photo-voltaic power plants

The quest for alternative energy sources, replacing the environmentally impacting fossil fuels, has resulted in the growing need to develop various new strategies in the field of renewable energies. A possible energy source is clean solar energy. The most common technology used is a silicon semiconductor device, which generates electrical output while interacting with light, known as Photo-Voltaic (PV) System. The reliability of PV modules and systems is critical to the commercial success of Photovoltaic systems. The technology combines multiple components, each of which could cause a system failure or energy losses. The reliability characterization measurements of a PV power system are complicated and only a few studies succeeded to design and simulate an efficient PV system. In the current study, two relatively large-scale solar farms were designed with an output of 20 MW. A comparison of the solar farms' performances was conducted, with an emphasis on the reliability indices of the systems. The obtained reliability indices are 83% and 88% for the studied solar farms.

Characterization of packaging warpage, residual stress and their effects on the mechanical reliability of IGBT power modules

Injection-moulded power electronics are inevitably subjected to warpage and residual stress from anisotropic contraction and thermal mismatch during the assembly, which deteriorates their reliability in service. In this work, the packaging warpage and residual stress of an epoxy resin encapsulated Insulating Gate Bipolar Transistor (IGBT) module were characterized with X-ray Computerized Tomography (CT) and blind-hole drilling, supported with Finite Element Analysis (FEA). Their effects on the bonding quality after silver-sintered to an external heat sink were investigated with Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), and mechanical tests. The module exhibited a maximum warpage of 420 μm, which comprised a flexed midsection and localized bending at the edges of the internal circuit board. The residual stress distribution had high magnitudes up to −39 MPa near the edges and a nearly stress-free interior. The warpage had little effect on the chemical composition across the module-silver interface, but the area fraction of the sintering defects increased by 37.5%, and the mean shear strength dropped by 7.4 MPa compared to the warpage-free counterparts. This work characterized the negative influences of packaging warpage and located the critical geometrical features that dictated the warpage behaviours, providing valuable information for future design optimization.

Thermal Performance Optimization of Integrated Microchannel Cooling Plate for IGBT Power Module.

In high-integration electronic components, the insulated-gate bipolar transistor (IGBT) power module has a high working temperature, which requires reasonable thermal analysis and a cooling process to improve the reliability of the IGBT module. This paper presents an investigation into the heat dissipation of the integrated microchannel cooling plate in the silicon carbide IGBT power module and reports the impact of the BL series micropump on the efficiency of the cooling plate. The IGBT power module was first simplified as an equivalent-mass block with a mass of 62.64 g, a volume of 15.27 cm3, a density of 4.10 g/cm3, and a specific heat capacity of 512.53 J/(kg·K), through an equivalent method. Then, the thermal performance of the microchannel cooling plate with a main channel and a secondary channel was analyzed and the design of experiment (DOE) method was used to provide three factors and three levels of orthogonal simulation experiments. The three factors included microchannel width, number of secondary inlets, and inlet diameter. The results show that the microchannel cooling plate significantly reduces the temperature of IGBT chips and, as the microchannel width, number of secondary inlets, and inlet diameter increase, the junction temperature of chips gradually decreases. The optimal structure of the cooling plate is a microchannel width of 0.58 mm, 13 secondary inlets, and an inlet diameter of 3.8 mm, and the chip-junction temperature of this structure is decreased from 677 °C to 77.7 °C. In addition, the BL series micropump was connected to the inlet of the cooling plate and the thermal performance of the microchannel cooling plate with a micropump was analyzed. The micropump increases the frictional resistance of fluid flow, resulting in an increase in chip-junction temperature to 110 °C. This work demonstrates the impact of micropumps on the heat dissipation of cooling plates and provides a foundation for the design of cooling plates for IGBT power modules.

Reliability study on the half-cutting PERC solar cell and module

In the photovoltaic industry, there are three critical parameters such as module power, cost and reliability. For increasing module power, half-cutting technology on the cell is one of the technologies because this can reduce the heating power by reducing the current. Therefore, laser scribing and mechanical cleaving (LSMC) technology have been implemented. As a result, the power of the module did not show any loss during standard test conditions when electrical luminescence and powers were monitored for the laser dicing process. However, in field conditions, the cut side of the cells with the laser process can cause cell breakage by wind or snow if the side has cracks. And then these crack cells can finally cause module power loss. Therefore, in this study, the laser process quality of the cell has been investigated by microscope image and scanning electron microscopy with laser process parameters such as laser power, frequency, and pulse width. In addition, cell strength was also checked by the four points of bending force to find the optimized laser process condition. The module power loss was analyzed with a static mechanical load test (MLT), which can represent snow or wind effect in the field. Our analyses show a strong correlation between crack width by laser, cell bending force, and module power loss. This correlation can explain the module power loss estimation, which can affect the reliability in the field without making module-level tests for the first time. In addition, the encapsulant thickness combination test and the mid-rail effect were also presented to reduce the power loss. As a result, the module power loss reached -1.34%. Finally, this study can contribute to the better reliability of the big wafer size products with LSMC technology.

Research Trends for Improving Cell Efficiency and Module Reliability in Crystalline Si Solar Cells

Research Trends for Improving Cell Efficiency and Module Reliability in Crystalline Si Solar Cells

Development and thermo-mechanical reliability assessment of fiber reinforced polymers in lightweight PV modules towards vehicle-integrated photovoltaics

Weight reduction by omitting the use of bulky glass in c-Si photovoltaic (PV) modules is an important consideration of module development for vehicle-integrated photovoltaics (VIPV). Various approaches to achieve lightweight modules are proposed, yet there are many concerns regarding the reliability of such modules compared to standard glass-glass or glass-backsheet configurations. In this work, we investigate the thermo-mechanical behavior of LW modules with a multiwire design specifically aiming to VIPV applications. The developed modules consist of a commercially available carbon-fiber reinforced polypropylene backsheet and are compared to glass-fiber reinforced polypropylene backsheet modules. To enhance the thermo-mechanical reliability, polymer encapsulant and interconnection foil are substituted by glass-fiber reinforced composite encapsulant with the carbon-fiber reinforced polypropylene backsheet, thereby leading to ∼2.9% fill factor (FF) decrease with a limited degradation after 200 thermal cycles. A failure mechanism analysis using electroluminescence and X-ray-based micro-tomography is carried out after thermal cycling tests, clearly demonstrating that thermal stresses introduce deformation of wire interconnects. A modified high-temperature thermal cycling test (- 40 to 110 °C, 3.5 h) is implemented to observe the fast degradation of interconnects in compliance with VIPV conditions. The resulting fatigue stresses account for wire breakage in-between cells in the glass-fiber reinforced polypropylene module, while this effect is less pronounced in the carbon-fiber reinforced polypropylene backsheet module, indicating better thermo-mechanical reliability of the carbon-fiber reinforced polypropylene backsheet module. Herein, the current results could provide guidelines for lightweight PV module design (with a weight of 4.8 kg/m2) in the thermo-mechanical aspect. This research sheds light on the potential of lightweight modules specifically for VIPV applications.

In Situ Full-Field Deformation Characterization of Power Module and FEA Model Calibration Based on Stereo Digital Image Methodology

Due to the increasing concern for the global climate problem, the electric vehicle has drawn considerable attention. The power module with high reliability is the key to the deployment and development of the electric vehicle. However, in-depth evaluations, such as the tedious power cycling, are generally required to verify the reliability of the power module prior to putting it into the field application. Therefore, to determine the failure mechanism and evaluate the reliability of the power module, the in situ full-field characterization with 3-dimensional (3-D) deformation under the field application is essential. Besides, the characterization results can also provide a reference for the finite element analysis (FEA) model and further assess the reliability of the power module. In this paper, the deformation mechanism and multi-physics simulation of the power module are comprehensively studied. To achieve the 3-D full-field characterization of the deformation, the stereo digital image correlation (DIC) methodology is proposed to measure the out-of-plane and in-plane deformation. Additionally, in order to validate the feasibility of the proposed method, an active power cycle test rig that periodically heats up the power module by its own dissipation losses is constituted by the introduction of a front-to-front converter. The experimental results show that the maximum deformation occurs on the central surface of the focused zone while the edge bears a minimum deformation. Comparative evaluation indicates that the maximal error between experimental and simulation results is within 5%, thus enable the effectiveness of the FEA simulation model.

A direct bonding copper degradation monitoring method for insulated gate bipolar transistor modules: Boundary‐dependent thermal network combined with feedback control

AbstractThe direct bonding copper (DBC) substrates of insulated gate bipolar transistor (IGBT) modules degrade inevitably under cycling thermo‐mechanical stress, causing potential threat to the reliability of IGBT modules. However, little attention has been paid to monitoring their degradation. This paper proposes a DBC degradation monitoring method for IGBT modules, which combines boundary‐dependent thermal network and feedback control. A thermal network is employed to describe the internal material degradation of IGBT modules and can be extracted from a finite‐element method model. The boundary conditions including power losses and DBC degradation are considered, enabling the thermal network suitable for various working conditions and different DBC degradation conditions of IGBT modules. The DBC degradation is characterised by its equivalent thermal conductivities measured in the thermal cycling ageing experiments. On the basis of the boundary‐dependent thermal network, feedback control is applied to monitor DBC degradation by regulating boundary‐dependent thermal impedances. Finally, the proposed model is verified from the effectiveness and accuracy of DBC degradation monitoring and junction temperature calculation. This method casts new light on thermal network modelling and could provide a feasible method for the monitoring of DBC degradation.

Performance analysis of avionics devices based on electro-thermal-stress multi-physics coupling under immersion cooling

The present study aims to analyze immersion cooling for the work reliability enhancement of avionics devices based on electro-thermal-stress multi-physics simulation. A comprehensive performance indicator considering the maximum DC IR-drop of the power supply network (PDN), the maximum temperature of the electronic elements and the maximum deformation of the printed circuit board (PCB) assembly is constructed to evaluate the effect of different flow distributor structure styles and Reynolds number (Re) on the work reliability of avionics devices. The results show that the maximum DC IR-drop of 2.0 V PDN was 73.83 mV which was the largest value among 1.5 V, 2.0 V, 3.3 V and 5.0 V PDN. The DC IR-drop of design A, design B and design C was smaller than the supply voltage fluctuation in a real design, this indicates that the flow distributor has no significant effect on enhancing the power delivery capability of PDN. The reflow in the middle part of design C makes the average temperature of PCB assembly lower than that of design A and design B by about 1–3 °C. The flow distributor has a significant effect on the maximum temperature of electronic elements and the pressure drop of avionics devices with Re increase, but not viable to decrease the maximum deformation of PCB assembly for design A and design B. The minimum of comprehensive evaluation function f is 0.038 when Re = 43,000 for design C, this means the comprehensive working reliability of the avionics server module is the best. Due to different flow patterns, the average temperature of PCB assembly for design C was lower which improve the electrical and mechanical properties, thus the value of f for design C was always smaller than that of design A and design B. The method and results herein revealed the advantages and potential limitations of immersion cooling on the working reliability of the avionics devices.

Encapsulant Materials and Their Adoption in Photovoltaic Modules: A Brief Review

In the last two decades, the continuous, ever-growing demand for energy has driven significant development in the production of photovoltaic (PV) modules. A critical issue in the module design process is the adoption of suitable encapsulant materials and technologies for cell embedding. Adopted encapsulants have a significant impact on module efficiency, stability, and reliability. In addition, to ensure the unchanged performance of PV modules in time, the encapsulant materials must be selected properly. The selection of encapsulant materials must maintain a good balance between the encapsulant performance in time and costs, related to materials production and technologies for cells embedding. However, the encapsulants must ensure excellent isolation of active photovoltaic elements from the environment, preserving the PV cells against humidity, oxygen, and accidental damage that may compromise the PV module’s function. This review provides an overview of different encapsulant materials, their main advantages and disadvantages in adoption for PV production, and, in relation to encapsulant technologies used for cell embedding, additives and the interaction of these materials with other PV components.

Reliability of SiC MOSFET Power Modules under Consecutive H3TRB and Power Cycling Stress

Power semiconductor modules are subject to both thermo-mechanical stress and electro-chemical stress during field operation. Usually, those stressors are investigated separately and possible interaction of both degradation mechanisms is neglected. In this work, the effect of combined thermo-mechanical and electro-chemical stress is investigated by means of consecutive H3TRB and PCT testing. One test group had been subjected to power cycling before the H3TRB test was performed, while another test group had been exposed to H3TRB stress before the power cycling test. As a reference, devices without preconditioning were tested in both, H3TRB and power cycling and are also used to compare the H3TRB and power cycling performance of the SiC devices to similar silicon devices. The results show, that the SiC devices feature a significantly better H3TRB performance than comparable silicon devices, but are inferior in terms of power cycling performance. Furthermore, the results for both test groups of the combined tests indicate that the failure modes for the previously stressed devices were the same as for the pristine devices and no impact of either preceding stress on the devices' lifetime could be observed. Therefore, the results of this work suggest no interaction between both stressors, at least not for the devices used for this investigation.

Copper-Wire Stress Buffers for Extending Lifetime of Double-Sided Bidirectional SiC Modules

The mismatch of thermal expansion coefficients causes tremendous thermo-mechanical stress in die attachment of double-sided bi-directional modules (BMs), thus reducing the reliability of the module. The thermo-mechanical reliability of a double-sided power module is the most critical issue, which needs to be addressed. People proposed ways to improve the reliability by reducing the CTE mismatches using such as Moly spacer instead of copper or junction temperature rise using high conductive spacer. This work first proposed a composite buffer, namely copper-wire-spacer (CWS), with low elastic modulus, capable of reducing thermo-mechanical stress by >50%. The lifetime of the double-sided BM with the CWS buffer is 40.0% and 42.9% longer than that with the conventional solid copper buffer, and is only 6.67% and 6.25% shorter than that with the moly buffer under the thermal shocking tests and the power cycling tests, respectively. The novel method of reducing the elastic modulus of the spacer could be a novel and good concept to reduce the thermo-mechanical stresses as well as improving the reliability of double-sided power modules. It can provide new guidance to design and packaging reliable double-sided power modules.

P‐76: Development on the Improvement of Low Temperature Folding Performance of AMOLED Modules

Since 2019, more than 20 foldable products have been released, and the categories released increased year by year. It can be seen that foldable products are increasingly favored by consumers and mobile phone manufacturers due to their advantages in expandable display size. It is expected that there will be explosive growth in the future. However, there are still some technical challenges for foldable product, such as waviness, poor impact/press resistance, and low temperature folding failure. This paper focuses on the research on improving the low temperature folding reliability of AMOLED modules. The difficulties of folding, the main failures and improvement methods, and the analysis of bending force in low temperature are introduced. Finally, the reliability for 50k times at ‐30℃ of out‐folding R 5mm, in‐folding U form R 1.5mm, in‐folding water drop form R 2mm are achieved.

A Modified Bypass Circuit for Improved Reliability of PV Module Validated With Real-Time Data

Solar Power is a promising way of electricity generation but it comes with a drawback of low conversion efficiency which is caused by several factors, the most prominent being partial shading. Partial shading leads to mismatch of PV cells, resulting in formation of hot spot. This leads to power dissipation and physical damage to PV cells. Consequently, panel’s credibility is called into question. A bypass diode reduces the amount of power dissipated by a shaded cell, but it doesn’t entirely prevent hot spot formation. Moreover, bypass diode doesn’t bypass every small shade as it has a shaded area threshold at and above which it begins to bypass the shaded module. Whereas, the rise in temperature may also be triggered even by a small shaded area, like the area of falling leaves, which further creates reliability issues. A few hot spot mitigation strategies have been devised; however, it still has room for improvement. This paper presents a modified bypass circuit arrangement for reliability enhancement of PV systems and it is evaluated for a 3×1 PV string. A comparative analysis with bypass diode is carried out in an experimental study. The efficacy of the proposed methodology is verified based on four performance metrics, namely reverse voltage, power loss under partial shading, the sensitivity of the bypass circuit, and the temperature of the hot spotted module. The proposed technique ensures sensitivity enhancement of the bypass circuit towards shade effect; thus, enhancing the reliability of PV system.

Causes and Prevention of Photovoltaic Module Hot Spot Effect

The photovoltaic module is the basic link in the photovoltaic power generation system, which has an important impact on the economic operation of photovoltaic power plants. Hot spot effects account for a large proportion of photovoltaic module failures, so it is of engineering significance to study them and put forward suggestions for fault prevention. Firstly, this paper briefly introduces the composition of photovoltaic power generation system and the structure of photovoltaic modules then analyzes the working process and typical models of photovoltaic modules as well as the causes of the hot spot effects of photovoltaic modules. Finally, it puts forward some measures to prevent faults to improve the operational reliability of photovoltaic modules.

FEA-Dominant Reliability and Lifetime Model of Double-Sided Cooling SiC Power Module

Owing to the low parasitic inductance, high power density, and excellent heat extraction performance, double-sided cooling (DSC) is regarded as a promising packaging solution for the silicon carbide (SiC) power module. Nevertheless, given the unclear failure mechanism and missed lifetime model, the reliability assessment and lifetime prediction of the DSC SiC power module remains a concern. Besides, the accelerated aging test generally used for the reliability assessment of the SiC power module is extremely time-consuming and costly. Therefore, the obstacles mentioned before limit the development and deployment of the DSC SiC power module. Aiming to fulfill these research gaps, based on the aging mechanism and failure criterion of packaging materials, the lifetime model of the DSC SiC power module is proposed in this paper. Comparative experiments show that the relative error of the FEA-dominated model is less than 6%. Moreover, the stress property and creep principle of the solder layer in SiC and Si power modules are assessed, respectively. Besides, the lifetime models of SiC and Si power modules applying different packaging materials are created. It is found that the lifetime of the DSC power module is twice that of the single-sided cooling (SSC) counterpart. Furthermore, applying the same packaging, the lifetime of the SiC power module decreases by 70% compared with the Si counterpart. In addition, the lifetime of the DSC SiC power module affected by different materials such as ceramic and spacer is studied in order to enhance its reliability.

A Review of High-Speed GaN Power Modules: State of the Art, Challenges, and Solutions

Wide bandgap (WBG) devices are a desirable choice for high-density energy conversion systems. In high-speed hard-switching applications, voltage overshoot across device terminals, oscillations at gate loop and Electro-magnetic Interference (EMI) becomes harder to mitigate and overall system reliability is reduced. To address the key challenges and harness the benefits offered by these latest generations of devices, improved and advanced packaging structures are required, as packaging technology often has a critical impact on module performance and reliability. This paper summarizes the design procedure for power modules, essential parts, and available materials for the fabrication of a power module package. Moreover, it provides a review of commercially available gallium nitride based high electron mobility transistors (GaN HEMTs) and state-of-the-art module packaging technologies adopted for them with a focus on module layout, module integration trends, and identifying their impacts on the GaN HEMT’s performance. Through this review, the paper also discusses major challenges faced by designers with GaN HEMTs in power electronics applications and their potential solutions, which is critical for the mainstream adoptions of GaN HEMTs and defining the future technology roadmap.