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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

Peripheral end face attachment of exposed copper layers of a first printed circuit board to the surface of a second printed circuit board by surface mount assembly

A printed circuit board (PCB) structure and mounting assembly for joining two PCBs. A first PCB has a top and bottom surface faces and a peripheral end face separating the top and bottom surface. The first PCB has one or more conductive wire ends exposed at a surface of the peripheral end face; the exposed conductive wire ends forming multiple separate electrical contacts across the thickness and length of the PEF surface. A second PCB has a top surface face and one or more conductive pads exposed at the top surface at locations corresponding to locations of the multiple electrical contacts. A surface mount solder material is disposed on one or more exposed conductive pads for electrically connecting with corresponding the multiple electrical contacts. The disposed solder material stably joins the PEF surface of the first PCB to the top surface of the second PCB in a relative perpendicular orientation.

Takken, Todd E.↗
DOE OSTI2021

Peripheral end face attachment of exposed copper layers of a first printed circuit board to the surface of a second printed circuit board by surface mount assembly

A printed circuit board (PCB) structure and mounting assembly for joining two PCBs. A first PCB has a top and bottom surface faces and a peripheral end face separating the top and bottom surface. The first PCB has one or more conductive wire ends exposed at a surface of the peripheral end face; the exposed conductive wire ends forming multiple separate electrical contacts across the thickness and length of the PEF surface. A second PCB has a top surface face and one or more conductive pads exposed at the top surface at locations corresponding to locations of the multiple electrical contacts. A surface mount solder material is disposed on one or more exposed conductive pads for electrically connecting with corresponding the multiple electrical contacts. The disposed solder material stably joins the PEF surface of the first PCB to the top surface of the second PCB in a relative perpendicular orientation.

Takken, Todd E.↗
DOE OSTI2018

Leaching Studies for Copper and Solder Alloy Recovery from Shredded Particles of Waste Printed Circuit Boards

Printed circuit boards (PCBs) comprise various metals such as Cu, Sn, and Pb, as well as platinum group metals. The recovery of metals from PCBs is important not only due to the waste treatment but also for recycling of valuable metals. In the present work, the leaching process of Cu, Sn, and Pb from PCBs was studied using fluoroboric acid and hydrogen peroxide as the leaching agent and oxidant, respectively. Pertinent factors including concentration of acid, temperature, liquid-solid ratio, and concentration of oxidizing agent were evaluated. The results showed 99 pct of copper and 90 pct solder alloy were dissolved at a temperature of 298 K (25 °C) for 180 minutes using 0.6 M HBF{sub 4} for the particle size range of 0.15 to 0.4 mm. Moreover, solid/liquid ratio had insignificant effect on the recovery of metals. Kinetics analysis revealed that the chemical control regime governs the process with activation energy 41.25 and 38.9 kJ/mol for copper and lead leaching reactions, respectively.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Solder assembly of pins to the peripheral end face of a printed circuit board

A printed circuit board (PCB) and PCB assembly. The PCB is formed of a laminate substrate of at least two layers of a non-conductive material forming at least one peripheral end face (PEF) surface separating top and bottom PCB surfaces. Embedded conductive wiring at one or more multiple layers carry energy to or from PCB surface mounted devices. The conductive wiring provides multiple conductive wire ends exposed at multiple locations along the PEF. A conductive contact structure is formed at the PEF surface to connect with one or more of the exposed conductive wire ends. One or more conductive pins are attached to the conductive contact at the PEF and are configured to mount the PCB on, and in a vertical and perpendicular orientation or a coplanar orientation relative to, a surface of a second PCB surface. The conductive pins provide one or more of: an electrical, thermal and/or mechanical contact.

Takken, Todd E.↗
DOE OSTI2014

Evaluation of gold and silver leaching from printed circuit board of cellphones

Highlights: • Printed circuit boards (PCB) of mobile phones have large amounts of metals with high economic value such as gold and silver. • Dissolution of gold was done with a cyanide-based reagent and silver with nitric acid. • Leaching of PCB with Na{sub 2}S{sub 2}O{sub 3} and (NH{sub 4}){sub 2}S{sub 2}O{sub 3} to examine the feasibility of using these reagents was done. - Abstract: Electronic waste has been increasing proportionally with the technology. So, nowadays, it is necessary to consider the useful life, recycling, and final disposal of these equipment. Metals, such as Au, Ag, Cu, Sn and Ni can be found in the printed circuit boards (PCB). According to this, the aims of this work is to characterize the PCBs of mobile phones with aqua regia; obtaining “reference” values of leaching, to gold and silver, with cyanide and nitric acid, respectively; and study the process of leaching of these metals in alternative leaching with sodium thiosulfate and ammonium thiosulfate. The metals were characterized by digesting the sample with aqua regia for 1 and 2 h at 60 °C and 80 °C. The leaching of Au with a commercial reagent (cyanide) and the Ag with HNO{sub 3}were made. The leaching of Au and Ag with alternative reagents: Na{sub 2}S{sub 2}O{sub 3,} and (NH{sub 4}){sub 2}S{sub 2}O{sub 3} in 0.1 M concentration with the addition of CuSO{sub 4}, NH{sub 4}OH, and H{sub 2}O{sub 2}, was also studied. The results show that the digestion with aqua regia was efficient to characterize the metals present in the PCBs of mobile phones. However, the best method to solubilize silver was by digesting the sample with nitric acid. The leaching process using sodium thiosulfate was more efficient when an additional concentration of 0.015 and 0.030 M of the CuSO{sub 4} was added.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2015

Toward environmentally-benign utilization of nonmetallic fraction of waste printed circuit boards as modifier and precursor

Highlights: • Environmental impacts of electronic waste and specifically waste printed circuit boards. • Review of the recycling techniques of waste printed circuit boards. • Advantages of physico-mechanical recycling techniques over chemical methods. • Utilization of nonmetallic fraction of waste printed circuit boards as modifier/filler. • Recent advances in the use of nonmetallic fraction of waste printed circuit boards as precursor. - Abstract: Electronic waste, including printed circuit boards, is growing at an alarming rate due to the accelerated technological progress and the shorter lifespan of the electronic equipment. In the past decades, due to the lack of proper economic and environmentally-benign recycling technologies, a major fraction of e-waste generated was either destined to landfills or incinerated with the sole intention of its disposal disregarding the toxic nature of this waste. Recently, with the increasing public awareness over their environment and health issues and with the enaction of more stringent regulations, environmentally-benign recycling has been driven to be an alternative option partially replacing the traditional eco-unfriendly disposal methods. One of the most favorable green technologies has been the mechanical separation of the metallic and nonmetallic fraction of the waste printed circuit boards. Although metallic fraction, as the most profitable component, is used to generate the revenue of the separation process, the nonmetallic fraction (NMF) has been left isolated. Herein, the recent developments in the application of NMF have been comprehensively reviewed and an eco-friendly emerging usage of NMF as a value-added material for sustainable remediation has been introduced.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2018

Design and dynamic modeling of printed circuit heat exchangers for supercritical carbon dioxide Brayton power cycles

Due to the unique geometries and hydraulics of printed circuit heat exchangers and rapidly changing properties of supercritical carbon dioxide, the effective design and rating of printed circuit heat exchangers is an essential requirement for their use in supercritical carbon dioxide power cycles. In this study, one-dimensional design and dynamic models have been developed in Aspen Custom Modeler for printed circuit heat exchangers utilized in printed circuit heat exchangers Brayton power cycles. The design model is used to determine the optimal geometry parameters by minimizing the metal mass. The dynamic model is used to predict transient behavior and can be easily implemented into system-level models developed in Aspen Plus Dynamics for cycle performance evaluations. In these models, the heat transfer coefficient and friction factor are calculated using data reported by Heatric, a prominent printed circuit heat exchanger manufacturer. Both models are validated by comparing with the data from a small-scale exchanger used in the 100 kWe facility operated by the Naval Nuclear Laboratory, and then applied to design and simulate low- and high-temperature recuperators for a 10 MWe supercritical carbon dioxide indirect recompression closed Brayton cycle, which is of interest to the U.S. Department of Energy. The designs and dynamic responses of the printed circuit heat exchangers are compared with conventional shell-and-tube exchangers and microtube shell-and-tube exchangers for the same applications. Here, the simulation results indicate that the proposed printed circuit heat exchangers have fast dynamic responses due to their small metal masses and high heat transfer coefficients compared with the conventional shell-and-tube exchangers. Even though the metal masses of the designed PCHEs are slightly higher than those of the microtube shell-and-tube exchangers, the printed circuit heat exchangers are still promising candidates for heat recuperation because of their mature manufacturing procedures and abundant laboratory and industrial operating experience.

42 ENGINEERING↗
DOE OSTI2011

Recycling of WEEE: Characterization of spent printed circuit boards from mobile phones and computers

Highlights: > This paper presents new and important data on characterization of wastes of electric and electronic equipments. > Copper concentration is increasing in mobile phones and remaining constant in personal computers. > Printed circuit boards from mobile phones and computers would not be mixed prior treatment. - Abstract: This paper presents a comparison between printed circuit boards from computers and mobile phones. Since printed circuits boards are becoming more complex and smaller, the amount of materials is constantly changing. The main objective of this work was to characterize spent printed circuit boards from computers and mobile phones applying mineral processing technique to separate the metal, ceramic, and polymer fractions. The processing was performed by comminution in a hammer mill, followed by particle size analysis, and by magnetic and electrostatic separation. Aqua regia leaching, loss-on-ignition and chemical analysis (inductively coupled plasma atomic emission spectroscopy - ICP-OES) were carried out to determine the composition of printed circuit boards and the metal rich fraction. The composition of the studied mobile phones printed circuit boards (PCB-MP) was 63 wt.% metals; 24 wt.% ceramics and 13 wt.% polymers; and of the printed circuit boards from studied personal computers (PCB-PC) was 45 wt.% metals; 27 wt.% polymers and ceramics 28 wt.% ceramics. The chemical analysis showed that copper concentration in printed circuit boards from personal computers was 20 wt.% and in printed circuit boards from mobile phones was 34.5 wt.%. According to the characteristics of each type of printed circuit board, the recovery of precious metals may be the main goal of the recycling process of printed circuit boards from personal computers and the recovery of copper should be the main goal of the recycling process of printed circuit boards from mobile phones. Hence, these printed circuit boards would not be mixed prior treatment. The results of this paper show that copper concentration is increasing in mobile phones and remaining constant in personal computers.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2020

Measured Energy-Dependent Neutron Attenuation Through the Stacked Printed Circuit Boards

Engineers often stack printed circuit boards (PCBs), populated with semiconductor devices, one behind the other in neutron beams to improve the error statistics in radiation-effects tests. As the neutron beam traverses through the boards, the neutron flux is both attenuated and the energy spectrum changes, which may have a significant impact on the results of such tests. In this work, we have developed a technique to measure the energy-dependent neutron attenuation due to the PCBs and to determine the energy-dependent effective cross section of neutron interactions with a single PCB. With this effective cross section, engineers can calculate the change in the neutron energy spectrum and the total neutron attenuation after any number of identical PCBs in the stack. This information will allow test engineers to partially correct inaccuracies in soft error tests.

42 ENGINEERING↗
DOE OSTI2018

X-ray Computed Tomography Imaging of Printed Circuit Boards

Nondestructive inspection of printed circuit boards (PCB) can be efficiently carried out with xray Computed Tomography (XCT). However, image artifacts can obscure some of the PCB details. As a demonstration of LLNL’s XCT capabilities, an internally-funded effort was recently executed that acquired XCT data for a PCB. These data were reconstructed with both traditional and physics-based iterative techniques to illustrate the use of advanced algorithms to reduce artifacts and thus improve image quality.

42 ENGINEERING↗
DOE OSTI2026

Recycling of Printed Circuit Boards to Recover Critical Materials

The printed circuit board (PCB), a central component of most electronic devices, represents a significant fraction of the electronic product waste stream. The complex composition of PCBs, consisting of metals, polymers, and fiberglass, requires specialized recovery steps to reclaim valuable and critical materials and the safe disposal of brominated compounds. In this review paper, we describe the current state of critical material recovery and traditional recycling technologies and identify key obstacles to large-scale implementation. Metals present at high concentrations, such as copper, lead, and iron, are conventionally recovered from PCBs using hydrometallurgical, pyrometallurgical, or electrometallurgical processes. Hydrometallurgical methods achieve high selectivity through chemical leaching but pose significant challenges for effluent and reagent recovery. Pyrometallurgical methods facilitate rapid metal separation through smelting but require substantial energy and may release harmful gases. Electrometallurgical techniques produce high-purity metals but are constrained by pretreatment requirements and the consumption of energy. The non-metallic fraction of PCB waste is recycled using thermochemical conversion, microwave-aided heating, and direct recycling of epoxy–fiberglass composites, enabling material or energy recovery. The recovered polymer from direct recycling may have reduced mechanical strength and poor compatibility with new polymer matrices, and the resulting products from the thermal conversion suffer from incomplete conversion, degradation of quality, and residual contamination, as compared to synthetic polymers. Recent process developments have focused on extracting rare earth and supply-critical materials present at lower concentrations in the waste stream. The literature on existing and emerging approaches for recycling PCB wastes is reviewed to identify sustainable, economically viable, and environmentally responsible strategies for the recovery and reuse of critical materials from waste streams.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Delamination mechanism study of large size waste printed circuit boards by using dimethylacetamide

Highlights: • Dimethylacetamide (DMA) dissolved the epoxy resin of printed circuit boards (WPCB). • PCBs of 1, 4, 9 and 16 cm{sup 2} were delaminated in 150, 180, 300 and 420 min, respectively. • Peaks of epoxy resin and DMA were evident in the NMR spectra. • Shift in C=O, OH peaks of DMA & resin, respectively was registered w.r.t. time. • Hydrogen bonding between C=O of DMA and OH of resin results in the dissolution. - Abstract: Present work investigates the recycling of waste printed circuit boards (PCBs) by cracking of its multi-layered structure by using dimethylacetamide (DMA). The study shows that cracking and separation of layers of PCBs increases as the temperature increases; and decreases as the surface area of PCBs increases. After separation of layers, the used solvent was analyzed by proton and carbon nuclear magnetic resonance spectroscopy (NMR) to understand the dissolution phenomenon of resin. Further, NMR and Fourier transform infrared spectroscopy analysis of DMA sample after 1 h, 2 h, 3 h, 4 h and 8 h of reaction with PCBs at 433 K and PCB:DMA ratio (wt/vol) of 3:10 has been carried out to investigate the mechanism of dissolution of resin. These studies revealed that hydroxyl group of PCBs polymeric chain participates in hydrogen bonding with parent carbonyl group of DMA molecule that results in the solvation of resin. Possible chemical reaction based on the above finding has been discussed. Using this technique, separation of the metallic fraction without application of any energy intensive mechanical pre-processing is possible.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2013

Analytical Study on Thermal and Mechanical Design of Printed Circuit Heat Exchanger

The analytical methodologies for the thermal design, mechanical design and cost estimation of printed circuit heat exchanger are presented in this study. In this study, three flow arrangements of parallel flow, countercurrent flow and crossflow are taken into account. For each flow arrangement, the analytical solution of temperature profile of heat exchanger is introduced. The size and cost of printed circuit heat exchangers for advanced small modular reactors, which employ various coolants such as sodium, molten salts, helium, and water, are also presented.

42 ENGINEERING↗
DOE OSTI2021

A Novel Approach for Bounding the Stress Experienced by the Core of Utility-Scale Printed Circuit Heat Exchangers Under Thermohydraulic Loads

Printed circuit heat exchangers (PCHEs) have rapidly gained popularity since being introduced nearly three decades ago, and they are currently widely deployed in the petrochemical and aviation industry. Their compactness, thermohydraulic efficiency, inherent suitability for high temperature/pressure fluids containment, and demonstrated durability are some of the reasons the nuclear industry is seeking to adopt this technology as well. However, the relatively strict nuclear-related regulatory design code, especially when classified as critical to the safety of the reactors, is posing challenges to adopting the technology. From stress analysis point of view, one undesirable feature of PCHEs is their geometrical complexity, which is implied by their multilength-scale features. As a result, a full-scale model of a utility-scale exchanger cannot simply be solved on a computer because meshing such components results in a vast number of degrees-of-freedom. Here, this work seeks to address the challenge of stress analyses to PCHEs by presenting a method to simplify the geometry of PCHE designs. The models proposed by this work can be practically analyzed on a standard computer and provide a path for implementing ASME design rules. The analyses presented herein are divided into five separate investigations. Each is carried out to incrementally simplify the analyzed model by addressing features such as the shapes of the flow passages, the complex distribution of stress in large components, the three-dimensionality of the stress and strain, the thermal stresses caused by thermohydraulic operation observed experimentally and more.

42 ENGINEERING↗