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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 OSTI2015

Materials Analysis and Modeling of Underfill Materials

The thermal-mechanical properties of three potential underfill candidate materials for PBGA applications are characterized and reported. Two of the materials are a formulations developed at Sandia for underfill applications while the third is a commercial product that utilizes a snap-cure chemistry to drastically reduce cure time. Viscoelastic models were calibrated and fit using the property data collected for one of the Sandia formulated materials. Along with the thermal-mechanical analyses performed, a series of simple bi-material strip tests were conducted to comparatively analyze the relative effects of cure and thermal shrinkage amongst the materials under consideration. Finally, current knowledge gaps as well as questions arising from the present study are identified and a path forward presented.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Experiments and modelling of adhesive failure initiation of an epoxy underfill: a study of electronic packaging survivability

Epoxy underfills can be implemented in electronic packaging to enhance solder joint reliability of surface mounted components. However, it is important for an engineer to have a failure criterion that can be used for failure predictions and redesign of electronic assemblies. For this study, data from epoxy bond failure in mock electronic part assemblies were correlated to finite element analyses to predict adhesive failure initiation. Experiments were performed to determine failure loads for various loading locations and nonlinear viscoelastic analyses were performed for the same loading locations to determine a maximum principal strain failure parameter. Predictions showed that a maximum principal strain failure parameter defined from one test could be used as an indicator of adhesive failure of an epoxy bond undergoing other modes of loading. Failure initiation predictions matched experimental data using a maximum principal strain failure parameter for an epoxy bond undergoing mixed modes of loading for both unfilled and alumina oxide filled 828DEA epoxy. Such experimental setup is deemed appropriate for future epoxy testing.

42 ENGINEERING↗
DOE OSTI2016

Thermal Testing Quality Assurance of 24LCC & 3LCC Electronic Packages

The purpose of this project is to experimentally validate the thermal fatigue life of solder interconnects for a variety of surface mount electronic packages. Over the years, there has been a significant amount of research and analysis in the fracture of solder joints on printed circuit boards. Solder is important in the mechanical and electronic functionality of the component. It is important throughout the life of the product that the solder remains crack and fracture free. The specific type of solder used in this experiment is a 63Sn37Pb eutectic alloy. Each package was manufactured with conformal coating along with and without an underfill material below the device. Conformal coating helps protect the board from environments such as electrostatic discharge and humidity. It is commonly used in broad types of engineering disciplines such as commercial, military, research and development, etc. Conformal coating can also pose a risk for the life of the board because of its high thermal expansion coefficient. This can greatly decrease the life of the product if it regularly sees high temperature variations. This leads to a shorter fatigue life of the solder. The fatigue life is a common mechanical problem in the field of electronic devices. Adding underfill can help increase the fatigue life of the solder. However, applying underfill adds time to manufacturing and production. This ultimately increases the cost per unit. The study of conformal coated printed circuit boards with and without underfill was done on two different surface mount electronic packages. The electronic packages studied were 24 and 3 contact Leadless Ceramic Chips packages. When the package was not underfilled, the coating was allowed to flow underneath. The assembly was analyzed and tested to obtain the best available combination of conformal coating, underfill, and potting to design the most robust and reliable circuit board while keeping in mind certain factors such as cost, manufacturing time, and need. Different types of conformal coatings were considered with and without underfill for each device. 29 of each component were manufactured to have a large sample size and for the sake of individual defects and imperfections. Finite Element Analysis (FEA) was performed by an engineer at Sandia National Laboratories for both Leadless Ceramic Chips. From the FEA results, a test acceleration profile was derived and the number of temperature cycles to fail the solder interconnects were found for three different cases. Experimentation was done as a secondary measure to validate this data to show confidence in the theoretical analysis. Accelerated testing functions as a quality check for the product. Accelerated testing is extremely useful in the research and development phase of engineering. It can save money from the potential of early life defects and the costs that come along with warranties. Accelerated testing makes a weaker design more robust and checks the reliability of a strong design in a shorter period of time. It is extremely helpful in a world where deliverables are in high demand and scheduling is tight. Accelerated testing helps the engineer gain an understanding of what needs to be improved and what works well. There are many different types of accelerated tests. Our circuit boards were accelerated inside a closed thermal chamber because of the high number of use cycles. The ultimate goal of this experimentation is to help identify what will prevent any premature cracking or fracturing in the solder alloy. It is important to understand that underfilling each component may or may not be needed. If underfill is not needed, there are several production benefits.

42 ENGINEERING↗
DOE OSTI2018

Delta size and plant patchiness as controls on channel network organization in experimental deltas

Understanding the feedbacks between water, sediment, and vegetation in deltas is an important part of understanding deltas as ecomorphodynamic systems. Here, we conducted a set of laboratory experiments using alfalfa (Medicago sativa) as a proxy for delta vegetation to investigate (1) the effects of plants on delta growth and channel network formation and (2) the timescales controlling delta evolution in the presence of plants. Experiments were conducted with fluctuating discharge (i.e. flood and base flow periods) and variable seeding densities. We found that when deltas were small, channels had no memory across flood cycles, as floods could completely fill the incised channel network. When deltas were large, the larger channel volume could remain underfilled to keep channel memory. Plant patches also helped to increase the number of channels and make a more distributive network. Patchiness increased over time to continually aid in bifurcation, but as vegetation cover and patch sizes increased, patches began to merge. Larger patches blocked the flow to enhance topset deposition and channel filling, even for the case of large deltas with a high channel volume. We conclude that both plant patchiness and delta size affect the development of the channel network, and we hypothesize that their influences are manifested through two competing timescales. The first timescale, T v , defines the time when the delta is large enough for channels to have memory (i.e., remain underfilled), and the second, T p , defines the time when vegetation patches merge, amplifying deposition and blocking channels. Finally, when run time is between these two timescales, the delta can develop a persistent distributary network of channels aided by bifurcation around plant patches, but once T p is reached, the channel network can again be destroyed by vegetation.

58 GEOSCIENCES↗
DOE OSTI2019

Numerical analysis of temperature and stress fields in hybrid indium antimonide arrays detector with laser irradiation

Thermal-stress effects are the major cause of failure in infrared focal-plane arrays detector, during laser irradiation. Based on the established three-dimensional structural model of hybrid indium antimonide infrared focal-plane arrays, the temperature and stress fields of hybrid indium antimonide detectors irradiated by 1.064-μm Gauss pulsed laser are studied, considering the temperature-dependent material parameters. The results indicate that the temperature increase and thermal stress effects are different, in each layer. Especially in indium antimonide chip, which is the uppermost layer of the indium antimonide detector that directly absorbs laser energy, the temperature shows not a smooth decrease as laser intensity from centre to outside, but a concentric-ringed ripple decrease with discontinuous high temperature extremum areas; which induces its own unique stress distributions: during the laser irradiation region, the thermal stress in areas above indium bumps is much lower than that in areas above underfill, but the stress distribution outside the laser irradiation region is exactly the opposite. The temperature and stress distribution in other materials are also different from that in indium antimonide chip. The main reason is that each material has different thermal properties, especially indium bump and underfill, which are alternative distribution in middle layers, have quite different thermal parameters. All these make the temperature and stress distribution in each layer having own characteristics. In addition, the change trend of the maximum temperature and stress in each layer in accordance with the laser pulse number are also studied. The maximum stress as well as temperature always occurs in the indium antimonide chip.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2025

Predictive dynamic wetting, fluid–structure interaction simulations for braze run-out

Brazing and soldering are metallurgical joining techniques that use a wetting molten metal to create a joint between two faying surfaces. Here, the quality of the brazing process depends strongly on the wetting properties of the molten filler metal, namely the surface tension and contact angle, and the resulting joint can be susceptible to various defects, such as run-out and underfill, if the material properties or joining conditions are not suitable. In this work, we implement a finite element simulation to predict the formation of such defects in braze processes. This model incorporates both fluid–structure interaction through an arbitrary Eulerian–Lagrangian technique and free surface wetting through conformal decomposition finite element modeling. Upon validating our numerical simulations against experimental run-out studies on a silver-Kovar system, we then use the model to predict run-out and underfill in systems with variable surface tension, contact angles, and applied pressure. Finally, we consider variable joint/surface geometries and show how different geometrical configurations can help to mitigate run-out. This work aims to understand how brazing defects arise and validate a coupled wetting and fluid–structure interaction simulation that can be used for other industrial problems.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Real-Time Defect Correction in Large-Scale Polymer Additive Manufacturing via Thermal Imaging and Laser Profilometer

Defects can result in a failed part and are costly in terms of time and material. This cost is even greater in the context of large-scale additive manufacturing where the objects can be very large. As a result, a great deal of research has focused on defect identification and mitigation. To address defects during object construction, researchers at Oak Ridge National Laboratory’s Manufacturing Demonstration Facility investigated an in-situ control system comprised of two sensors: a thermal camera and laser profilometer. This control system adjusted material flow and build speed to mitigate three types of defects: low layer times, underfill, and overfill. Several test objects were constructed. The control system was found to adjust build parameters to handle low layer times of approximately 15 seconds and height deviations from -100% underfill (the absence of a layer) to 50% overfill. Within two layers, height deviations could be returned to within 10% of the expected layer height. Further, preliminary results suggest the system can compensate for uneven build surfaces.

Borish, Michael↗
DOE OSTI2025

Defect Detection Model Development for Large Scale Thermoplastic Printing

Large-format additive manufacturing (LFAM) offers several advantages, including high throughput, cost-effective pellet-fed extrusion, and the capability to produce large-scale structures. The main pain points of LFAM include start and stops during the printing process, warpage, long layer times that lead to bead freezing, and bead separation due to shrinkage. These issues can lead to overfill, underfill and buildup of material in different sections of a print. This can lead to hidden defects embedded within the printed layers, or even ultimate failure of the printed structure. This ensures these defects can only be identified through nondestructive testing (NDT) inspection methods after printing, which can be timely and costly. Aligned Vision work specializes in 2D projectors with visual inspection systems and machine learning. Traditionally system is used for composite layup and layup inspections. In this work we used the LFAM system at Oak Ridge National Laboratory to create defect rich samples. The Aligned Vision inspection system then performed in-situ monitoring of the print process after each part was printed. This in-situ vision inspection system was used to develop a layer-by-layer inspection model that looks for overfill, underfill, and the buildup of defects using only a camera-based vision system. This leads to the assurance of high-quality production components.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Smart CNG Dispenser Deployment

This final technical report documents the work performed under DOE Award DE‑EE0008799 by GTI Energy over the course of the project period. The project focused on advanced fueling methods for compressed natural gas (CNG) vehicles which have historically suffered from underfilling.

03 NATURAL GAS↗
DOE OSTI2019

Function reconsideration of indium bump in InSb IRFPAs

Indium bumps are generally accepted to possess functions of electrical connection, mechanical support and heat transfer in flip-chip devices. After comparing the distribution of stress components along different paths in InSb infrared focal plane arrays (IRFPAs), we ascertain that local enhancement effects of the stress components are remarkable in regions where the indium bumps are. More specifically, the local enhanced tensile stress in InSb chip connected with the indium bumps can lead to the local fracture of the InSb chip, and the locally enhanced shear and peeling stresses may give rise to the local interfacial delamination between the InSb chip and the indium bumps. These inferences are confirmed by the observed local failure characteristics, such as the distribution of the local delamination, the distribution of the crack widths, and the distribution of the cracks. In addition, the simulated Z-component strain distribution in InSb IRFPAs is also consistent with the backside surface profile of the InAs/GaSb IRFPAs fabricated in America with the identical structure, that is, the InSb chip glued with the indium bumps is concave downward, and the InSb chip glued with the underfill is convex upward. Judging from all these confirmed simulation results, we are confident that the indium bumps play a pivotal role in inducing the local failure of InSb IRFPAs. So the role of the indium bumps in causing the local failure of InSb IRFPAs needs to be supplemented and emphasized to comprehensively evaluate the structural reliability of InSb IRFPAs.

42 ENGINEERING↗
DOE OSTI2025

Phenomena Identification and Ranking Table (PIRT) for heat pipes

Heat pipes are advanced passive thermal management devices that utilize phase change and capillary action to achieve efficient heat transfer. However, due to the complexity of the phenomena coupled in heat pipes, including capillary, phase change, turbulence, and compressibility effects, there are high uncertainties in the predictability of their operational regimes and performance. This PIRT exercise, conducted as a collaborative effort involving the Department of Energy (DOE) Microreactor Program (MRP), the Nuclear Regulatory Commission (NRC), and university partners systematically identifies, reviews, and prioritizes critical phenomena affecting the operation of heat pipes based on their importance and knowledge levels. Additional analyses and discussion are provided for phenomena with high importance and low knowledge, such as wick de-wetting, critical heat flux, contact angles, and pressure dynamics. The discussions included the recognizing challenges and proposing future research directions for both modeling and simulation and experimental efforts. Additionally, the report addresses phenomena with medium importance and low knowledge that could impact heat pipe operation during non-normal or transient operation, including frozen startup, laminar to turbulent transition, geyser boiling, wick priming, underfilling conditions, surface roughness of the wick, NCGs trapped in the wick, and the timescales of startup and shutdown. In conclusion, this comprehensive evaluation serves as a valuable resource for guiding future research and development efforts, supporting the successful integration of heat pipes into critical applications such as nuclear reactors, and contributing to the advancement of heat pipe technologies in safety-critical industries.

21 - SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLAN↗
DOE OSTI2020

Water Uptake by Silica Nanopores: Impacts of Surface Hydrophilicity and Pore Size

Water uptake at 298 K by two mesoporous silicas with different pore sizes was studied using volumetric vapor sorption. Here, through variation of sample pretreatment temperature and time, the number of surface hydroxyl groups was varied, leading to marked changes in the water sorption behavior. With increasing surface hydroxyl density, the adsorption of water to the pore surfaces increases, leading to formation of a thicker and denser water sorption layer. The BET model was used to measure surface hydroxyl density from low pressure parts of water adsorption isotherms. Adsorption of water molecules scales with the number density of surface hydroxyl groups, and monolayer coverage is reached at reduced pressure of ca. 0.3. The onset of adsorption pore condensation of water shifts to lower reduced pressure with increasing surface hydroxyl density, indicating growing thickness of adsorption layers. However, the water pore condensation step of the desorption branch shifts to smaller reduced pressure with increasing surface hydroxylation, reducing the adsorption-desorption hysteresis width. An adsorbed phase model is utilized to calculate the distribution of pore water molecules between adsorbed and pore condensation phases, and characterize the density and thickness of the water sorption phase. In the smaller pores, the adsorbed phase forms a sparse monolayer, while approximately a bilayer is formed in the wider pores. The previously reported silica nanopore underfilling by water is confirmed and rationalized by a significantly reduced water density in the adsorbed phase with respect to bulk, while the pore core is filled with water of approximately bulk density.

36 MATERIALS SCIENCE↗
DOE OSTI2015

THE K2-ESPRINT PROJECT. I. DISCOVERY OF THE DISINTEGRATING ROCKY PLANET K2-22b WITH A COMETARY HEAD AND LEADING TAIL

We present the discovery of a transiting exoplanet candidate in the K2 Field-1 with an orbital period of 9.1457 hr: K2-22b. The highly variable transit depths, ranging from ∼0% to 1.3%, are suggestive of a planet that is disintegrating via the emission of dusty effluents. We characterize the host star as an M-dwarf with T{sub eff} ≃ 3800 K. We have obtained ground-based transit measurements with several 1-m class telescopes and with the GTC. These observations (1) improve the transit ephemeris; (2) confirm the variable nature of the transit depths; (3) indicate variations in the transit shapes; and (4) demonstrate clearly that at least on one occasion the transit depths were significantly wavelength dependent. The latter three effects tend to indicate extinction of starlight by dust rather than by any combination of solid bodies. The K2 observations yield a folded light curve with lower time resolution but with substantially better statistical precision compared with the ground-based observations. We detect a significant “bump” just after the transit egress, and a less significant bump just prior to transit ingress. We interpret these bumps in the context of a planet that is not only likely streaming a dust tail behind it, but also has a more prominent leading dust trail that precedes it. This effect is modeled in terms of dust grains that can escape to beyond the planet's Hill sphere and effectively undergo “Roche lobe overflow,” even though the planet's surface is likely underfilling its Roche lobe by a factor of 2.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2025

Pressure suppresses the density wave order in kagome metal LuNb 6 ⁢Sn 6

The density waves that develop in kagome metals ScV 6 ⁢Sn 6 and LuNb 6 ⁢Sn 6 at low temperature appear to arise from underfilled atomic columns within a V-Sn or Nb-Sn scaffolding. Compressing this network with applied pressure in ScV 6 ⁢Sn 6 suppressed the structural transition temperature by constraining atomic rattling and inhibiting the shifts that define the structural modulation. We predicted that the density wave transition in LuNb 6⁢ Sn 6 at 68 K would be suppressed by pressure as well. In this Letter, we examine the pressure dependence of the density wave transition by measuring resistance vs temperature up to 2.26 GPa. We found the transition temperature is smoothly depressed and disappears around 1.9 GPa. In conclusion, this result not only addresses our prediction, but strengthens the rattling chains origin of structural instabilities in the HfFe 6⁢ Ge 6 -type kagome metals.

Charge density waves↗
DOE OSTI2020

K-space algorithmic reconstruction (KAREN): a robust statistical methodology to separate Bragg and diffuse scattering

Diffuse scattering occurring in the Bragg diffraction pattern of a long-range-ordered structure represents local deviation from the governing regular lattice. However, interpreting the real-space structure from the diffraction pattern presents a significant challenge because of the dramatic difference in intensity between the Bragg and diffuse components of the total scattering function. In contrast to the sharp Bragg diffraction, the diffuse signal has generally been considered to be a weak expansive or continuous background signal. In this paper, using 1D and 2D models, it is demonstrated that diffuse scattering in fact consists of a complex array of high-frequency features that must not be averaged into a low-frequency background signal. To evaluate the actual diffuse scattering effectively, an algorithm has been developed that uses robust statistics and traditional signal processing techniques to identify Bragg peaks as signal outliers which can be removed from the overall scattering data and then replaced by statistically valid fill values. This method, described as a 'K-space algorithmic reconstruction' (KAREN), can identify Bragg reflections independent of prior knowledge of a system's unit cell. KAREN does not alter any data other than that in the immediate vicinity of the Bragg reflections, and reconstructs the diffuse component surrounding the Bragg peaks without introducing discontinuities which induce Fourier ripples or artifacts from underfilling `punched' voids. The KAREN algorithm for reconstructing diffuse scattering provides demonstrably better resolution than can be obtained from previously described punch-and-fill methods. The superior structural resolution obtained using the KAREN method is demonstrated by evaluating the complex ordered diffuse scattering observed from the neutron diffraction of a single plastic crystal of CBr 4 using pair distribution function analysis.

36 MATERIALS SCIENCE↗
DOE OSTI2015

A Process and Environment Aware Sierra/SolidMechanics Cohesive Zone Modeling Capability for Polymer/Solid Interfaces

The performance and reliability of many mechanical and electrical components depend on the integrity of polymer-to-solid interfaces. Such interfaces are found in adhesively bonded joints, encapsulated or underfilled electronic modules, protective coatings, and laminates. The work described herein was aimed at improving Sandia’s finite element–based capability to predict interfacial crack growth by 1) using a high fidelity nonlinear viscoelastic material model for the adhesive in fracture simulations, and 2) developing and implementing a novel cohesive zone fracture model that generates a mode-mixity dependent toughness as a natural consequence of its formulation (i.e., generates the observed increase in interfacial toughness with increasing crack-tip interfacial shear). Furthermore, molecular dynamics simulations were used to study fundamental material/interfacial physics so as to develop a fuller understanding of the connection between molecular structure and failure. Also reported are test results that quantify how joint strength and interfacial toughness vary with temperature.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Thermal Testing and Quality Assurance of BGA LCC & QFN Electronic Packages

The purpose of this project is to experimentally validate the thermal fatigue life of solder interconnects for a variety of surface mount electronic packages. Over the years, there has been a significant amount of research and analysis in the fracture of solder joints on printed circuit boards. Solder is important in the mechanical and electronic functionality of the component. It is important throughout the life of the product that the solder remains crack and fracture free. The specific type of solder used in this experiment is a 63Sn37Pb eutectic alloy. Each package was surrounded conformal coating or underfill material.

36 MATERIALS SCIENCE↗