bluuebunny/crossref_metadata_2025_split huggingface dataset:
Behavior of Printed Hybrid Electronic Assemblies With Embedded Components in Polymeric Substrates Subject to Extreme Acceleration Levels and Elevated Temperatures
Authors: Richards Hayden , Abusalma Hisham , Dasgupta Abhijit , Bujanda Andres , Tsang Harvey , Bowman Matthew 
Published: November 2024

Abstract
This study assessed the performance of printed hybrid electronic (PHE) assemblies subject to simultaneous exposure to elevated temperatures (up to 150 °C) and extreme mechanical shock (up to 100,000 g). The test specimens were rectangular beams measuring 3.2 mm thick, 12.7 mm wide, and 63.5 mm long, fabricated using injection molding from various polysulfone polymers. Several different electronic circuit elements — traces, passive components, and interconnects — were embedded into the largest flat surface of these substrates using a novel ‘mill-and-fill’ method. This method used conventional 5-axis CNC milling to generate pockets and channels into which the electrical elements were embedded. Traces were extrusion-printed with silver paste. The components used were 0-ohm resistors. Interconnects were formed using extrusion-printed tin-bismuth solder.
Testing was accomplished using an accelerated-freefall drop tower equipped with a shock amplifier and integrated furnace. Acceleration pulses (half-sine shape) ranged from 25,000 g to 100,000 g with pulse durations of ∼.03-.1 ms and velocity changes of 6–25 m/s. Elevated temperatures ranged from 88 °C to 150 °C in addition to room temperature (25 °C). The specimens were fixtured in a clamped-clamped configuration (largest flat face upright) and did not experience any secondary impact. Tests were instrumented with accelerometers, thermocouples / RTDs, and strain gauges with sampling grates of 1 MHz. Thermal cameras and high-speed optical cameras were also used. At the highest acceleration levels, peak strain values measured &gt; 14,000 microstrain. Drop degradation assessment was based on changes in electrical performance metric (such as overall circuit resistance) or based on structural failure of circuit elements. Measurements were made either in real time during the drop event or intermittently after a select number of drops. Global and meso-scale modeling was conducted to validate measured strain response data, facilitate generation of a damage accumulation model, explain observed failure modes, and predict physical and electrical response for future geometries and applications.
Component separation and interconnect failure were the primary failure modes observed. As expected, number of cycles to failure decreased with increasing acceleration level and increasing temperature. The polysulfone beams themselves survived at all tested temperatures and most acceleration levels except for 100,000 g. Optical microscopy observations throughout testing showed cracking present in sintered silver traces, but this was not the sole predictor of circuit failure. Additional work is ongoing to further explore the causes for these failure modes and understand the implications of the physical response on different embedded components and specimen geometries.
Experimental Investigation of Single-Phase Forced Convection Heat Transfer With Water in Compressed Copper Foam
Authors: Alade Bolape , Kisitu Deogratius , Battleson May , Schaffarzick Denver , Ortega Alfonso 
Published: November 2024

Abstract
Open-cell metallic foams exhibit properties that make them suitable for enhancing the performance of heat sinks in advanced electronics cooling applications. Metallic foams have high surface area and low density, making them ideal for dissipating heat efficiently. However, while much research has focused on uncompressed metallic foams, particularly in single-phase cooling with air, there remains a gap in understanding their behavior in single-phase forced convection with liquid or in two-phase flow. Recent investigations have indicated that compressed copper foams can offer significant improvements in two-phase cooling efficiency at high heat fluxes when compressed in the direction of flow, but this advantage has not been explored in single-phase forced convection. This paper presents an experimental study aimed at evaluating the thermohydraulic performance of copper foam using deionized (DI) water as a coolant. The study focuses on investigating how foam compression influences heat transfer and fluid flow characteristics in single-phase forced convection. The experimental setup involves square copper foam samples of different heights, heated from below with flow entering parallel to the heated surface. The tested foam samples include a baseline uncompressed sample (compression ratio (CR) = 1) and two other compressed samples with CR = 2 and 4, corresponding to porosities of 92%, 81%, and 64%, respectively. Each sample has a footprint area of 25.4 mm × 25.4 mm and heights of 2.5, 3.5, and 5 mm. The experimental data demonstrate that foam compression significantly enhances the apparent heat transfer coefficient, attributed to increases in both effective thermal conductivity and apparent fin efficiency. This improvement in thermal performance is accompanied by an increase in pressure drop. The data trends are predicted well by a simple homogeneous, equilibrium flow model that predicts NuL α PeL1/2 but the data reveal an independent dependence on sample height.
Basic Study on Transient Flow Control Technique in Narrow Flow Passage With Flow Separation Region for Maximization of Cooling Performance of Heating Elements
Authors: Kobayashi Daiki , Fukue Takashi , Wakitani Shin 
Published: November 2024

Abstract
This study describes a method to maximize cooling performance in narrow passages with flow separation regions by applying pulsating flow. Forced convection cooling using pumps and fans is a standard cooling method for electronic devices. In most densely assembled and complicated passages, there are separation regions when cooling is performed by this method. However, in these regions, cooling is not sufficient. This prevents the accessible design of immersion cooling in computers and other devices. In this paper, pulsating flow is used to cool the heating element more effectively and more widely. In general, the cooling with pulsating flow results in uneven temperatures and areas that are not cooled. Therefore, it is necessary to repeatedly change parameters such as the frequency and time-averaged Reynolds number of the pulsating flow. This study applied an extremum seeking control approach to achieve maximum cooling even when the heat generation point changes. The following results were obtained from this study. The cooling target cooled better with pulsating flow than with steady flow. The pulsating frequency for the best cooling was found to be limited. The optimal pulsating frequency can be automatically guided to various cooling targets by controlling the pulsating frequency.
Scalable Large-Area Two-Phase Capillary-Enhanced Micro-Cooler Using Silicon Microchannel Fin Array With 3D Silicon Manifold for High-Heat-Flux Electronics Cooling Application
Authors: Kwon Heungdong , Kong Daeyoung , Lee Hyoungsoon , Palko James , Dede Ercan M. , Asheghi Mehdi , Goodson Kenneth E. 
Published: November 2024

Abstract
We have developed a silicon-based capillary-enhanced two-phase micro-cooler capable of removing a high heat flux &gt; 200 Wcm−2 with water mass flow rate ≈ 28 g(min)−1 (vapor quality, xe ≈ 0.8) over a large area ≈ 2 cm × 2 cm at superheat &lt; 20 °C, resulting in a thermal resistance of phase change, R″mean,2-ϕ ≈ 0.08 cm2°CW−1. By increasing the flow rate to ≈ 150 g(min)−1, a hybrid single/two phase regime prevails resulting in a critical heat flux ≈ 285 Wcm−2 (1.1 kW/chip) with minimal pressure drop ≈ 10 kPa, achieving 100× larger Coefficient of Performance (COP), compared to the conventional forced convective microchannel cooling. In this work, we utilize dense silicon channel fin array (height 100 μm, width 15 μm and 15 μm spacing) as capillary wicking structure in combination with a 3D silicon open-microchannel manifold (channel width and period ≈ 100 μm and 570 μm, respectively) for capillary-based liquid delivery and vapor extraction over large, heated area of 2 cm × 2 cm. The micro-cooler performs the best at low flow rates and high heat fluxes where the capillary flow and two-phase boiling dominates, resulting in a very uniform temperature distribution over the large area of the micro-cooler. At the high flow rates (pressurized flow), the coolant bursts out of the gap between the 3D manifold and the cold plate, resulting in single-phase cooling near the inlets of the micro-cooler. The temperature profile and its uniformity, or lack thereof, strongly depend on the competing effects of the single-phase and two-phase cooling regimes, which in turn depend on the flow rate and applied heat flux.
Passive Direct Liquid Cooling for High-Power Processors
Authors: Tyryshkin Alexei , Kim John , Amalfi Raffaele Luca , Enright Ryan 
Published: November 2024

Abstract
Refrigerant-based two-phase cooling systems are leading candidates for adoption in high-power electronics thermal management due to their potential for enhanced thermofluidic characteristics relative to single-phase liquid cooling. Passive cooling, leveraging gravity and fluid-vapor density difference instead of mechanical pumps to drive the flow, have attracted particular attention by offering further benefits, including lower maintenance requirements and higher operational reliability. However, the industrial implementation of passive cooling, tuned to specific application requirements, is a non-trivial task due to the complex two-phase flow physics and intricate thermo-hydraulic coupling during the evaporation and condensation processes. Designing a passive two-phase cooling system is a complex task requiring rigorous optimization of each individual component in the loop to ensure stable cooling performance in the desired range of heat dissipation and temperature. This challenge is further compounded by the dimensional constraints imposed by the electronic equipment. Thus, accurate experimental data and computational support are of crucial importance to realize the optimal design of such cooling loops.
Computational Fluid Dynamics (CFD) Modeling and Optimization of Large-Scale (3 cm X 3 cm) Silicon-Based Embedded Microchannels With 3D Manifold Micro-Coolers
Authors: Kong Daeyoung , Kwon Heungdong , Lee Haeun , Lee Hyoungsoon , Asheghi Mehdi , Goodson Kenneth E. 
Published: November 2024

Abstract
The continuing increase in CPU and GPU performances can be attributed mostly to the rise in frequency, scaling of chip area (bigger dies), advancements in thermal management, and improvements in thermal design power, among other factors. Over the past two decades, the size of a typical GPU die has increased from 100 mm2 to ∼800 mm2 in the year 2020. Silicon-based single-phase embedded microchannels with a large area of 30 mmx30 mm, featuring three-dimensional (3D) manifold (MF) μ-coolers, can potentially remove heat and minimize pressure drop. However, previous computational fluid dynamics (CFD) simulation findings indicated considerable temperature nonuniformity resulting in increased thermal resistance and maximum temperature. The primary cause of temperature non-uniformity is the abrupt flow acceleration at the entrance and sudden deceleration at the end section of the 3D-manifold inlet channels. This leads to a significant temperature rise in the middle region of the microcooler. In this study, we introduce innovative microcooler designs and conduct extensive computational fluid dynamics (CFD) simulations to achieve low thermal resistance, low-pressure drop, and crucially, uniform temperature distribution across the entire surface area of the microprocessor. To deal with this issue, our initial approach involved integrating converging inlet and diverging outlet channels into the 3D manifold. Although this method effectively dealt with the nonuniformity throughout the u-cooler’s area, it still resulted in a large pressure drop. Consequently, we implemented a narrow opening at the end of the inlet channels in the 3D manifold. This allows a portion of the coolant (50–80%) to bypass the microchannels in the cold plate to the exit plenum. As a result, the pressure was reduced by ∼66% compared to the conventional 3D manifold microchannel cooler.
Advanced Thermal Aware Mobile SoC Floorplan Design Optimization by Integrating Proactive Design Rule Check Process and Evolutionary Algorithms
Authors: Lee Myunghoon , Arimpoor Pallan Ouseph Lindo , Yaddanapudi Vamsi Krishna 
Published: November 2024

Abstract
The increasing demands for advanced functionality and high performance in modern mobile devices continuously escalate power consumption in system-on-chips (SoCs), intensifying thermally induced challenges, the floorplan design of application processors (AP) from the initial design stage must optimize the placement of each Intellectual Property (IP) block through thermal aware design, minimizing IP Block area, timing delays, maximum die temperature, and hotspot areas. This paper proposes an optimal IP Block placement workflow that satisfies key design parameters such as Performance, Power, and Area (PPA), using Computational Fluid Dynamics (CFD) thermal analysis and evolutionary algorithms. Additionally, to validate the utility of the developed workflow, a comparison of Dynamic Thermal Management (DTM) performance between base line and optimized candidate design under specific operating scenario is conducted, confirming the effectiveness of the workflow.
Enhanced Passive Cooling in Thermal Interface Materials via Encapsulated Phase Change Material Additives
Authors: Kasitz Joshua , Ghufran Muhammad , Huitink David 
Published: November 2024

Abstract
Phase change materials (PCMs) offer significant upside in passive cooling potential, allowing them to be integrated in electronics as thermal buffers to prevent damaging localized heating effects. This impact can greatly improve the reliability of electronic packages and reduce the opportunity for thermal stress induced failures. Integrating passive cooling into electronics is difficult, especially in the case of PCMs, as additional packaging architectures are needed to facilitate PCM incorporation that often negatively affects the module’s power density. Encapsulated phase change materials (ePCMs) achieve a stable PCM system by creating spherical particles with a PCM core and a protective shell material. The shell contains the PCM through both solid and liquid phase, removing concerns of handling liquid PCM within an electronic stack. The particles contain most of the thermal energy storage capability of the PCM and are mechanically more reliable than the bulk system. These particles can be introduced into existing materials to form ePCM composites. Balancing the functionality of both material types is important for upgrading current materials in electronic packaging. Thermal interface materials (TIMs) are at the forefront of electronic packaging research as these are a significant bottleneck in the thermal management of electronics. This study introduces ePCMs into TIMs to create a more thermally capable interface material. These new composites will look to take advantage of ePCM fillers to provide passive cooling across the interface and be used as thermal conductivity fillers. In this study, ePCM particles with a paraffin core and a titania shell will be combined with three different TIMs of varying thermal conductivity and viscosity. The composites will be thermally and mechanically evaluated.
Thermal Performance of Common Cold Plate for Pumped Single- and Two-Phase Direct Liquid Cooling for Next Generation High Power Server Processors
Authors: Kulkarni Devdatta , Gulick John , King Jeff , Jarrett Brian , George Paul , Feldman Yoav 
Published: November 2024

Abstract
The rapid expansion of Generative AI and ML applications has led to a surge in demand for advanced accelerators. These next-generation accelerators require high power, with some reaching nearly 1kW and continuing to rise. Consequently, server power envelopes have expanded to 10kW and beyond, while rack-level power for AI applications is approaching 100kW. The high TDP (Thermal Design Power) and heat flux of these processors, combined with power-dense servers and racks, necessitate cooling technologies with superior thermal performance. As IT power consumption escalates, most data centers are transitioning to liquid cooling solutions that align with corporate sustainability objectives. This paper assesses the thermal performance of single and two-phase pumped direct liquid cooling technologies. It explores a unified cold plate construction approach, a COMMON cold plate, enabling both technologies to address cooling challenges faced by data center operators and to expedite the Time to Market (TTM) for server manufacturers’ cooling solutions. The paper outlines the design methodology, laboratory testing procedures, and thermal performance of a common cold plate design suitable for both single and two-phase pumped direct liquid cooling technologies. For single-phase liquid cooling, Propylene Glycol-25 (PG25) is the chosen fluid medium, while a medium-pressure refrigerant with a lower Global Warming Potential (GWP) is considered for two-phase cooling. Three types of Thermal Test Vehicles (TTVs) were utilized under uniform and non-uniform heat load conditions, with power levels up to and beyond 1kW and high heat fluxes up to 300W/cm∧2. Additionally this paper emphasizes the significance of characterizing non-uniform heat flux in thermal solutions by varying the heat flux at high heat flux locations. Understanding how to cool these high heat flux hotspots are crucial for the development of thermal solutions, as the heat fluxes of new generation accelerators are significantly higher than those of traditional processors. In conclusion, the paper highlights the need for further ecosystem development for various cooling loop components to enhance the adoption of two-phase liquid cooling solutions.
Additively Manufactured Cold Plate Integrated With Evaporator Wicks and Phase Separators for Thermal Management of Multiple High-Heat-Flux Heat Sources
Authors: Shaeri Mohammad Reza , Demydovych Maksym , Chen Chien-Hua 
Published: November 2024

Abstract
In this study, a Hybrid Two-Phase Cooling System (HTPCS) was developed, combining the advantages of capillary-driven evaporation from wick structures with pumped two-phase cooling. The cold plate, the core element of the HTPCS, was made of AlSi10Mg and incorporated seven heaters distributed in a non-patterned configuration across its surface. Each heater was assigned a wick structure as an evaporator. The key contribution of this study lies in (i) fabricating the entire cold plate through one single additive manufacturing (AM) process, and (ii) preventing the flooding of individual evaporators using an internal phase separator. The first merit results in a substantial reduction in fabrication complexity compared to traditional manufacturing processes, representing a crucial milestone in the path toward commercializing the developed HTPCS in this study. The second merit results in a further reduction in the thermal resistance of the cold plate. The HTPCS exhibited significant thermal performance, operating at heat fluxes exceeding 505 W/cm2 and achieving low and uniform thermal resistances of ∼0.16 K-cm2/W. Furthermore, the HTPCS operated within a low pumping power range, below 0.14 W. This study introduces a promising cooling technology for the thermal management of the next generation of miniaturized electronic devices, especially those integrating multiple high-heat-flux heat sources.
Study on the Impact of Prolonged High-Temperature Exposure on the Reliability of Lead-Free Solder Joint Assemblies Under Vibration
Authors: Lall Pradeep , Mehta Vishal , Suhling Jeff , Blecker Ken 
Published: November 2024

Abstract
The solder joint stands out as one of the most vulnerable elements in electronic components and assemblies. In automotive systems, including engine control units, variable valve sensors, and crankshaft-camshaft sensors, many electronic assemblies are located under the hood. These components are frequently exposed to elevated temperatures reaching up to +150°C. Moreover, they undergo drop-impact incidents, experience vibrations, and encounter shocks. In this demanding environment, electronic devices may also be subjected to strain rates ranging from 1 to 100 times per second. To enhance the durability of electronic packages in high-temperature and high-strain-rate conditions, it is imperative to focus on the mechanical properties and statistics of lead-free solder alloys. The combination of vibrations and elevated temperatures has the potential to accelerate the degradation of electronic components. Existing research on solder joints has primarily concentrated on either vibrational stresses in room temperature environments or thermal cycling, particularly for traditional and unaged solders such as SAC105 and SAC305. Previous studies involving Finite Element (FE) analysis have exclusively considered the linear-elastic behavior of solder materials. SAC-Q solder was employed in the assembly of the CABGA208 Package-PCB assemblies. Unaged and isothermally aged PCB-Package assemblies were tested for failure at different ambient test temperatures up to 150°C, with vibration loads of 5g and 10g applied. To model harmonic vibration loading on PCB-Package assemblies under various situations, finite element (FE) analysis was carried out. The first natural frequencies of test boards featuring CABGA208 packages were measured at different test temperatures (e.g., 25°C, 75°C, and 150°C) and vibration g-levels using a combination of experimental and Finite Element Analysis (FEA) based modal analysis. The number of cycles to failure was measured and compared across various test conditions (unaged and aged) through Weibull plots. Peak displacements under vibrations at different g-levels were measured and compared for the test vehicle using the 2D-DIC method. Hysteresis stress-strain curves and accumulated plastic work densities were extracted through FE analysis, and comparisons were made for various g-levels and ambient temperatures. Damage relationship model is established for life prediction of the PCB-Package assembly.