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We present results of modeling for the design of microgaps for the removal of high heat fluxes, i.e., 1 kW/cm2, at low wall temperature (∼ 85°C) via a strategy of very high mass flux (>1000 kg/m2s), high quality (outlet vapor mass quality >90%), two-phase forced convection. Modeling includes (1) thermodynamic analysis to obtain performance trends across a wide range of candidate coolants, (2)...
This study investigated how passive and active cooling methods dissipated the heat from a remote phosphor layer in an LED system. The focus was on quantifying the amount of cooling contributed by each heat dissipation mechanism, namely, conduction, convection, and radiation.
Industry migration to leadfree solders has resulted in a proliferation of a wide variety of solder alloy compositions. The most popular amongst these are the Sn-Ag-Cu family of alloys like SAC105 and SAC305. Electronics subjected to shock and vibration may experience strain rates of 1–100 per sec. Electronic product may often be exposed to high temperature during storage, operation and handling in...
Global warming highlights the effect of light-emitting diodes (LEDs), the advantages of which include lo w pollution and power consumption, as well as a long operation lifetime. However, LED research and development is limited by Illuminating Engineering Society of North America (IES) LM-80-08. This standard reliability test, which is utilized by most LED companies, is time-consuming and prolongs...
Microfluidic cooling shows promise in cooling next generation 3D microsystems when integrated with through-silicon-vias. In this work, electrical and thermal effects of staggered micropin-fin heat sink dimensions are analyzed using deionized water. An experimental study of five different silicon micropin-fin arrays with a nominal height of 200 µm and diameters down to 30 µm was conducted at flow rates...
The ever-increasing demand for more functionality of electronic and optoelectronic components led to increased packaging and thermal power densities. Higher processing density can be reached by developing thermal management solutions. The current technology in electronic packaging is to attach the die to heat spreader, using materials known as Thermal Interface Materials (TIM), such as solder or silver...
The macroscopic stress dependence of bipolar junction transistors (BJTs) can be modeled by three transport model parameters as a function of stress: saturation current IS, forward current gain βF, and Early voltage VA. Recent research has shown that Early voltage VA is independent of stress, so it is not discussed in detail in this paper. Unfortunately, accurate extraction of model parameters IS and...
Numerical and experimental investigations of water microdroplet evaporation on polymer substrates are reported. The study is focused on validating numerical models with experimental data. The experimentally measured evaporation rates are compared to the predictions of a commonly reported model based on a solution of the Laplace equation, providing the local evaporation flux along the droplets liquid-vapor...
AlGaN/GaN high electron mobility transistors (HEMT) semiconductor technology holds promise for revolutionary improvements in the cost, size, weight, and performance of a broad range of military and commercial microelectronics [1]. However, exploiting the true capabilities of GaN is a compromise between the desired RF performance and the realities of current thermal solutions. In this work we present...
In this study, we report a new experimental method to independently and simultaneously measure the capillary pressure and permeability of wick structures and a simulation framework to establish their theoretical limits. The maximum liquid transport rates through different micropillar wick geometries operating against gravity are determined at various wicking lengths by measuring the dryout threshold...
A High frequency wall temperature measurement approach at the microscale is demonstrated. This experimental approach was implemented to study the transient effect of bubbles in a slug flow regime. Air stream was injected into liquid water flow in a 210 µm deep and 1.5 mm wide horizontal microchannel to form a slug flow regime (with bubble frequency of ∼280 Hz) and the associated wall temperature variations...
Thermal assessment of AlGaN/GaN heterostructure on diamond substrate is presented. To emphasize the advantages of diamond substrate for GaN, results of test devices on GaN-on-Diamond material are compared to those on GaN-on-SiC and GaN-on-Si materials. Mesa resistors and High Electron Mobility Transistors (HEMTs) fabricated using a 0.25 µm gate length process are characterized. Infrared thermography...
Development of nano-electromechanical relays (NEMRs) has led to a new focus on the thermal behavior at nano-scale contacts. The asperity-asperity contacts in NEMRs are susceptible to deformation and melting due to high pressures and temperatures at the contacting surfaces. Furthermore, because of their small size, these contacts are very difficult to analyze either experimentally or theoretically...
Data centers consume a significant amount of energy in the US and worldwide, much of which is consumed by the cooling infrastructure, particularly the chiller plant and computer room air conditioners and air handlers. To enable energy efficient data center designs, ASHRAE added two new IT environmental classes, A3 and A4, with associated allowable inlet air temperatures of 40C and 45C respectively...
A lot of effort has been put to develop the next generation cooling technologies for Insulated Gate Bipolar Transistor module of hybrid vehicles. Two phase cooling has been identified as a potential solution for cooling of such modules. This paper explores the viability and implementation of a two phase cooling scheme and its comparison with single phase cooling. For this inverter module of Toyota...
This paper describes the effect of cooling from a surface of power Si MOSFET on hot spot temperature. In traditional thermal design of electronics, the temperature distribution of chips is assumed to be uniform for simplicity of thermal design. However, in recent years, thermal problems of electronics are more serious, because electronics have been downsizing. Therefore, we should consider the temperature...
Electric-drive systems, which include electric machines and power electronics, are a key enabling technology to meet increasing automotive fuel economy standards, improve energy security, address environmental concerns, and support economic development. Enabling cost-effective electric-drive systems requires reductions in inverter power semiconductor area, which increases challenges associated with...
This study evaluates a jet impingement based cooling strategy combined with microfinned enhanced surfaces as a means of improving thermal management for power electronic devices. For comparison, a baseline channel flow heat exchanger and jet impingement on plain surfaces are characterized. The jets, augmented with enhanced microfinned surfaces, provide localized cooling to areas heated by the insulated-gate...
Air-cooled Data Centers absorb heat in central room air conditioners or air handlers and most commonly reject the heat through cooling towers to ambient air. The energy efficiency of the overall cooling system is determined by the energy efficiency of its components, its thermodynamic design and layout, and the protocol for its control, operation and its operational set points. The current work is...
Operational expenses of servers and the data center to support them account for a significant part of the total cost of ownership of a data center and potentially the total business. Manipulating the inlet temperature to the servers can provide a possible method of lowering the operating cost of a data center. Conventional wisdom regarding management of the cold aisle temperature in the data center...
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