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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Power Electronics Materials and Bonded Interfaces - Reliability and LIfetime

The emergence of wide-bandgap (WBG) devices in power electronics packages has brought significant attention to the reliability and thermal performance of the bonded interfaces. These interfaces, such as die-attach and substrate-attach, need to withstand the severe stress induced on them by the high-temperature (> 200 degrees C) operation of the WBG devices. Sintered silver and transient liquid phase alloys are key bonded interfaces that can enable the high-temperature operation of WBG devices, however it is essential to evaluate their reliability and study the possible failure mechanisms before they can be used in power electronics packages. Sintered silver is already being adopted in commercial packages as a die-attach, but large-area substrate-attach offers additional reliability challenges. In this project, we investigate the reliability of these interface materials under accelerated thermal cycling and correlate these results with finite element simulations to develop lifetime prediction models. The failure mechanisms of these bonded interfaces are also studied.

33 ADVANCED PROPULSION SYSTEMS↗
DOE OSTI2020

Power Electronics Materials and Bonded Interfaces - Reliability and Lifetime

The emergence of wide-bandgap (WBG) devices in power electronics packages has brought significant attention to the reliability and thermal performance of the bonded interfaces. These interfaces, such as die-attach and substrate-attach, need to withstand the severe stress induced on them by the high-temperature (> 200°C) operation of the WBG devices. Sintered silver and transient liquid phase alloys are key bonded interfaces that can enable the high-temperature operation of WBG devices, however it is essential to evaluate their reliability and study the possible failure mechanisms before they can be used in power electronics packages. Sintered silver is already being adopted in commercial packages as a die-attach, but large-area substrate-attach offers additional reliability challenges. In this project, we investigate the reliability of these interface materials under accelerated thermal cycling and correlate these results with finite element simulations to develop lifetime prediction models. The failure mechanisms of these bonded interfaces are also studied.

47 OTHER INSTRUMENTATION↗
DOE OSTI2024

Power Electronics Materials and Bonded Interfaces - Reliability and Lifetime

Advanced packaging technologies are currently being designed and developed by the power electronics industry however, the maximum operating temperature is still limited to 175 degrees Celsius for the silicon carbide devices. Bonded materials such as sintered copper and polymeric materials are potential candidates for high temperature operation, but it is critical to characterize and evaluate its reliability under harsh operating conditions. In this project, we discuss the results of the accelerated experiments conducted on sintered copper and polymeric materials. Additionally, a novel framework to develop the lifetime prediction model of bonded interfaces through employing statistical and machine learning models are described. In this task, scanning acoustic microscope images of bonded interfaces obtained under thermal cycling experiments are used as the data.

ENGINEERING↗
DOE OSTI2023

Power Electronics Materials and Bonded Interfaces - Reliability and Lifetime

High temperature operation of wide bandgap devices continue to be a challenge for the power electronics packages. Thermal performance and reliability are important factors that determine the viability of a bonded interface for operation at high temperatures. In this presentation, we present the technical approach and key results from the research on sintered silver, transient liquid phase alloy, and polymeric materials. A lifetime prediction model that incorporates the thermomechanical behavior of sintered silver at 200C was developed. The copper-aluminum transient alloy completed 350 thermal cycles from -40C to 200C and little increase in the defect level was observed. In addition to material research, we initiated a time-series analysis on the scanning acoustic microscope images of eutectic solder to explore statistical forecasting methods and machine learning techniques. Initial results that report the accuracy of a few different statistical models are presented.

ADVANCED PROPULSION SYSTEMS↗
DOE OSTI2022

Power Electronics Materials and Bonded Interfaces - Reliability and Lifetime

Wide-bandgap devices have pushed the operational limit of semiconductor devices in automotive power electronics packages to higher temperatures (>200 C). While a higher efficiency can be achieved through the use of wide-bandgap devices, the entire package must be re-designed with components that can withstand the higher temperature limits. Sintered silver and transient liquid phase bonds are potential candidates as bonded materials for use in higher temperatures however, the underlying mechanics of deformation under thermal loads and the resulting failure mechanisms in these materials are not well understood. Accelerated experiments conducted at NREL reveal that high-lead solder joints have better reliability than sintered silver under extreme thermal cycling conditions. Furthermore, efforts to develop a crack propagation model for the high-temperature materials are described.

ADVANCED PROPULSION SYSTEMS↗
DOE OSTI2024

Power Electronics Materials and Bonded Interfaces - Reliability and Lifetime

The need for reliable bonded interface materials is critical to realize the performance benefits of wide-bandgap devices in power electronic modules, especially in operating temperatures greater than 150 degrees Celsius. In this paper, we investigate the thermomechanical performance of sintered copper (Cu) as a large-area attachment, bonded between Cu baseplates and active-metal-bonded substrates, under accelerated thermal shock (-40 degrees Celsius to 200 degrees Celsius) conditions. In the fabrication phase of the samples, we used different stencil patterns and found out that the grid and stripe patterns resulted in a better outgassing of the residual organics during the sintering process, thereby ensuring a substantially improved bond quality than a full-area print. The paste consisted of Cu microflakes and we performed sintering using a Budatec SP300 sintering press at 275 degrees Celsius with 15 MPa of bonding pressure for 5 minutes in a nitrogen atmosphere. Under accelerated experiments, we monitored the degradation of the sintered Cu bond in the samples through C-mode scanning acoustic microscope (C-SAM) images. To quantify the defect percentage in C-SAM images, we investigated image denoising techniques to exclude the pattern prints. Finally, we cross-sectioned a sample and obtained digital microscope images, which revealed adhesive fracture as the dominant failure mechanism.

ADVANCED PROPULSION SYSTEMS↗
DOE OSTI2018

Calculating electronic stopping power in materials from first principles

From the early models of electronic stopping power to the current first principles simulations, the techniques evolved to increase the range of validity and to reduce empiricism. Thanks to a combination of theoretical advances provided by Time Dependent Density Functional Theory and the development of numerical codes, it is currently possible to predict electronic stopping power for realistic materials by performing direct simulations of the electron excitation processes beyond linear response, and including electronic band structure effects. Electronic stopping power is an important quantity used to predict and understand the effects of particle radiation in matter. First principles calculations of electronic stopping power can be applied to any atomistic system, solids, liquids and alloys. This review aims here to help graduate level students and researchers immerse themselves into state-of-the-art techniques to computationally model and calculate electronic stopping power.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Tailoring Growth Interfaces of Virtual Substrates for Power Electronics

Power electronics materials are poised to play a critical role in fulfilling next generation energy needs, with up to 90% of future energy demand predicted to flow through power electronics at some point. AlxGa1-xN ranks high among candidate materials, having bipolar dopability, thermal and chemical stability and an ultra-wide bandgap. However, AlGaN growth is limited by a lack of lattice-matched substrates, ultimately stunting material quality at higher thicknesses needed for power electronics applications. Further, high power applications increasingly call for fully vertical device structures, necessitating a conductive substrate. Recently our group identified the (111) plane of TaC as a conductive surface lattice-matched to Al0.55Ga0.45N, taking inspiration from prior work of AlN and GaN binaries on carbide and boride substrates. In this talk we demonstrate the growth of (111)-oriented TaC by RF sputtering. We investigate the interface of TaC with sapphire and SiC substrates and identify means to suppress competing Ta2C nucleation in order to stabilize (111)-oriented TaC. Potential stacking sequences are identified with respect to crystal structure and observed twinning in the TaC films. We next assess structural changes and film recrystallization that results from face-to-face annealing of TaC thin films at high temperatures above 1500 degrees C. Changes to grain structure and domain size are assessed by x-ray diffraction and surface morphology is explored using atomic force microscopy. Figure 1 shows significant improvements to in- and out-of-plane strain following annealing along with the formation of terraced step edges at the film surface. Strain as a function of material composition and thickness is considered, as this may play a major role in future nucleation of AlGaN layers. (1) R. J. in a face-to-face configuration, as illustrated in the schematic at left. Kaplar et al 2017, ECS J. Solid State Sci. Technol. 6 Q3061; (2) D. M. Roberts et al 2022, https://arxiv.org/abs/2208.11769; (3) T. Aizawa et al 2008, J Crys Growth 310, 1 22; (4) R. Liu et al 2002, Appl. Phys. Lett. 81, 3182-3184.

ENGINEERING↗
DOE OSTI2023

Tailoring Growth Interfaces of Virtual Substrates for Power Electronics

Power electronics materials are poised to play a critical role in fulfilling next generation energy needs, with up to 90% of future energy demand predicted to flow through power electronics at some point.[1] Among a number of candidate materials, AlxGa1-xN is the strongest, having bipolar dopability, thermal and chemical stability, an ultra-wide bandgap, and demonstrated experimental feasibility. However, AlGaN growth is limited by a lack of lattice-matched substrates, ultimately stunting material quality at higher thicknesses needed for power electronics applications. Further, high power applications increasingly call for fully vertical device structures, necessitating a conductive substrate. [1] Recently our group identified the (111) plane of TaC as a conductive surface lattice-matched to Al0.55Ga0.45N, taking inspiration from prior work of AlN and GaN binaries on carbide and boride substrates. [2,3,4] In this talk we demonstrate the growth of (111)-oriented TaC by RF sputtering. We investigate the interface of TaC with sapphire and SiC substrates and identify means to suppress competing Ta2C nucleation in order to stabilize (111)-oriented TaC. Potential stacking sequences are identified with respect to crystal structure and observed twinning in the TaC films. We next assess structural changes and film recrystallization that results from face-to-face annealing of TaC thin films at high temperatures above 1500 degrees Celsius. Changes to grain structure and domain size are assessed by x-ray diffraction and surface morphology is explored using atomic force microscopy. Figure 1 shows significant improvements to in- and out-of-plane strain following annealing along with the formation of terraced step edges at the film surface. Strain as a function of material composition and thickness is considered, as this may play a major role in future nucleation of AlGaN layers.

CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SU↗
NASA NTRS2021

Center for High-Efficiency Electrical Technologies for Aircraft (CHEETA)

The aeronautics industry has been challenged on many fronts to increase efficiency, reduce emissions, and decrease dependency on carbon-based fuels. With subsonic transports serving as the dominant contributor to the fuel consumption and carbon footprint of global aviation, the need for environmentally-responsible transportation has been met with a boom of research in the field of aircraft propulsion electrification across industry, government, and academic organizations. However, adoption of electrified propulsion systems for large commercial aircraft today is unattainable, due to the lack of motors and power electronics appropriately sized for these vehicles, high weight requirements of conventional electrical energy storage systems, and new principles required to design these classes of aircraft. The mission of the Center for High-Efficiency Electrical Technologies for Aircraft (CHEETA) program is to develop, mature, and design disruptive technologies for electric commercial aviation. The associated technologies being researched include distributed aero-propulsion system integration, high-efficiency electrochemical power conversion, flight-weight electric machines and power electronics, materials and systems for superconducting high-efficiency power transmission, and methods for complex system integration and optimization. Additionally, the current program is investigating the use of unconventional energy storage and power generation architectures, such as liquid hydrogen fuel and high-efficiency fuel cell systems. The research program provides a direct line-of-sight to not only achieving, but potentially even exceeding the aviation community goals for transition to alternative propulsion and energy through convergence of various novel technologies. The end result of maturation and integration of these technologies is an aircraft system with a quiet, efficient propulsion system that produces zero carbon dioxide, nitrogen oxides, and particulate matter emissions at the vehicle level.

Koushik Datta↗
DOE OSTI2019

High Temperature and Power Dependent Photoluminescence Analysis on Commercial Lighting and Display LED Materials for Future Power Electronic Modules

Commercial light emitting diode (LED) materials - blue (i.e., InGaN/GaN multiple quantum wells (MQWs) for display and lighting), green (i.e., InGaN/GaN MQWs for display), and red (i.e., Al 0.05 Ga 0.45 In 0.5 P/Al 0.4 Ga 0.1 In 0.5 P for display) are evaluated in range of temperature (77–800) K for future applications in high density power electronic modules. The spontaneous emission quantum efficiency (QE) of blue, green, and red LED materials with different wavelengths was calculated using photoluminescence (PL) spectroscopy. The spontaneous emission QE was obtained based on a known model so-called the ABC model. This model has been recently used extensively to calculate the internal quantum efficiency and its droop in the III-nitride LED. At 800 K, the spontaneous emission quantum efficiencies are around 40% for blue for lighting and blue for display LED materials, and it is about 44.5% for green for display LED materials. The spontaneous emission QE is approximately 30% for red for display LED material at 800 K. The advance reported in this paper evidences the possibility of improving high temperature optocouplers with an operating temperature of 500 K and above.

36 MATERIALS SCIENCE↗
NASA NTRS2004

Advanced Power Electronics Components

This paper will give a description and status of the Advanced Power Electronics Materials and Components Technology program being conducted by the NASA Glenn Research Center for future aerospace power applications. The focus of this research program is on the following: 1) New and/or significantly improved dielectric materials for the development of power capacitors with increased volumetric efficiency, energy density, and operating temperature. Materials being investigated include nanocrystalline and composite ceramic dielectrics and diamond-like carbon films; 2) New and/or significantly improved high frequency, high temperature, low loss soft magnetic materials for the development of transformers/inductors with increased power/energy density, electrical efficiency, and operating temperature. Materials being investigated include nanocrystalline and nanocomposite soft magnetic materials; 3) Packaged high temperature, high power density, high voltage, and low loss SiC diodes and switches. Development of high quality 4H- and 6H- SiC atomically smooth substrates to significantly improve device performance is a major emphasis of the SiC materials program; 4) Demonstration of high temperature (> 200 C) circuits using the components developed above.

Schwarze, Gene E.↗
NASA NTRS1991

Dual ion beam processed diamondlike films for industrial applications

Single and dual beam ion source systems are used to generate amorphous diamondlike carbon (DLC) films, which were evaluated for a variety of applications including protective coatings on transmitting materials, power electronics as insulated gates and corrosion resistant barriers. A list of the desirable properties of DLC films along with potential applications are presented.

Mirtich, M. J.↗
DOE OSTI2016

A High-Efficiency, Low Cost, High-Temperature Nanocomposite Soft Magnetic Materials for Vehicle Power Electronics.

The charge components for each gas atomization experiment (GA-1-230, GA-1-232, and GA-1-238) was provided by Aegis and consisted of elemental materials, while MPC provided the master alloy arc melted button castings that were added to yield a charge composition of (Co35Fe65)88Zr7B4Cu. The atmosphere in the melting chamber and connected atomization system was evacuated with a mechanical pump prior to backfilling with ultrahigh purity (UHP grade) Ar. The melt was contained in a bottom tapped zirconia crucible with an alumina stopper rod to seal the exit while heating to a pouring temperature of 1550 – 1575oC. When the desired superheat was reached, the stopper rod was lifted and melt flowed through a yttria stabilized zirconia (YSZ) pour tube with a 3.2 mm orifice and was atomized with Ar from a 45-22-052-409 gas atomization nozzle (or atomization die), having a jet apex angle of 45 degrees with 22 cylindrical gas jets (each with diameter of 1.32 mm or 0.052 inches) arrayed around the axis of a 10.4 mm central bore. The Ar atomization gas supply regulator pressure was set to produce nozzle manifold pressures for the series of runs at a pressure of 450 psi. Secondary gas halos of Ar and He also were added to the interior of the spray chamber at various downstream locations for additional cooling of the atomized droplets and to prevent coalescence of the resulting powder. Powder size analysis and size classification were performed with a full set of ASTM sieves, starting with the 106 µm screen and proceeding down through the 20 µm screen. A Microtrac particle size analyzer was used to verify the size classification results of the particulate resulting from the runs. The resulting powder size distribution results are provided with this report labeled with their respective run numbers (GA-1-230, GA-1-232, and GA-1-238). It should be noted that the size distribution results of the first atomization run were quite acceptable and the same parameters were used for the second and third runs to test the reproducibility for technology transfer purposes.

33 ADVANCED PROPULSION SYSTEMS↗
DOE OSTI2020

Dielectrics for Power Electronics Applications

This presentation discusses the role of dielectric materials in power electronic packages. Two dielectric technologies - a dielectric material film-based substrate for insulation and a dielectric coolant - are discussed. The thermal performance benefits of dielectric film-based substrate in comparison with traditional direct-bond-copper substrates are studied through finite element analysis. Also, a novel cooling concept based on dielectric liquids that can contact electrically active surfaces are presented.

30 DIRECT ENERGY CONVERSION↗