Evaluation Of Thermal Resistance Research Articles

Evaluation of the Thermal Resistance in GaN HEMTs Using Thermo-Sensitive Electrical Parameters

The thermal management of power converters is not only crucial for their own optimal operation and reliability, but also for the overall system in which they are operating. Reliability is a very serious aspect because power electronics systems are being increasingly widely adopted in mission-critical applications in the e-mobility sector, in smart grids, and other applications where safety and operational continuity are essential. The current trend towards miniaturization of power conversion systems and, consequently, towards high power density solutions is speeding up the diffusion of Gallium Nitride (GaN) High Electron Mobility Transistor (HEMT). GaN HEMT-based high power density converters must be properly managed, making the estimation of the thermal characteristics of these devices essential. This paper proposes the use of some Thermo-Sensitive Electrical Parameters (TSEP) for a simple and effective thermal resistance evaluation. The primary advantages and limitations of these TSEPs have been critically analyzed. The analysis highlighted that the use of the gate-source voltage is the best approach. However, it requires direct access to the gate pin, which may not be available externally in some system-in-package solutions.

Understanding Inherent Implication of Thermal Resistance in Double-Side Cooling Module

The double-side cooling (DSC) packaging becomes more and more popular with the great demands of high power and fast speed, especially for silicon carbide metal oxide semiconductor field effect transistors. Measurements and modeling of thermal resistance are critical for thermal management of DSC module. However, the thermal resistance of DSC module is still unclear due to the asymmetric dual thermal paths. In this article, a clear understanding of thermal resistance of DSC module measured by transient dual-interface method (TDIM) is explained. The thermal impedance of DSC module is analyzed through time- and frequency-domain response of the DSC thermal model. The cooling conditions in TDIM have no influence on the measured thermal resistance of DSC module. The measured thermal resistance from junction to top case (or bottom case) is half of the actual value. The important conclusions are verified by transient simulations and experiments. Based on the results, a new definition of thermal resistance of DSC module is proposed for exact evaluation of thermal resistance and reliability.

Theoretical and Experimental Evaluation of Thermal Resistance for Compression Bandages

Abstract The objective of this paper is to report a study on the prediction of the steady-state thermal resistance of woven compression bandage (WCB) by using three different mathematical models. The experimental samples of WCB were 100% cotton, cotton–polyamide–polyurethane, and viscose–polyurethane. The bandage samples were evaluated at extensions ranging at 10–100%, with two- and three-layer bandaging techniques. Experimental thermal resistance was measured by thermal foot manikin (TFM) and ALAMBETA testing devices. The obtained results by TFM and ALAMBETA were validated and compared with the theoretical models (Maxwell–Eucken2, Schuhmeister, and Militky), and a reasonable correlation of approximately 78%, 92%, and 93% for ALAMBETA and 75%, 82%, and 83% for TFM, respectively, was observed.

Numerical Evaluation of Thermal Resistance for Power MOSFET Packaged in Hermetic Method

Numerical Evaluation of Thermal Resistance for Power MOSFET Packaged in Hermetic Method

PET Foams Surface Treated with Graphene Nanoplatelets: Evaluation of Thermal Resistance and Flame Retardancy.

In this work, fire-retardant systems consisting of graphene nanoplatelets (GNPs) and dispersant agents were designed and applied on polyethylene terephthalate (PET) foam. Manual deposition from three different liquid solutions was performed in order to create a protective coating on the specimen’s surface. A very low amount of coating, between 1.5 and 3.5 wt%, was chosen for the preparation of coated samples. Flammability, flame penetration, and combustion tests demonstrated the improvement provided to the foam via coating. In particular, specimens with PSS/GNPs coating, compared to neat foam, were able to interrupt the flame during horizontal and vertical flammability tests and led to longer endurance times during the flame penetration test. Furthermore, during cone calorimetry tests, the time to ignition (TTI) increased and the peak of heat release rate (pHRR) was drastically reduced by up to 60% compared to that of the uncoated PET foam. Finally, ageing for 48 and 115 h at 160 °C was performed on coated specimens to evaluate the effect on flammability and combustion behavior. Scanning electron microscopy (SEM) images proved the morphological effect of the heat treatment on the surface, showing that the coating was uniformly distributed. In this case, fire-retardant properties were enhanced, even if fewer GNPs were used.

Energy saving in social housing through the implementation of regional materials

The materials with which the social housing envelope is usually constructed in sub humid warm climate are thermally inefficient because they lead heat to interior space which affects thermal habitability. To reverse the state of thermal inefficiency of the house was introduced in the construction industry the use of thermo-insulating materials that are evaluated for their ability to resist the heat flow (Thermal Resistance), however, this adequacy in the envelope involves an additional economic cost in a context of shortage. Therefore, the objective of this research was to determine the possibility of the use of materials from the region for potential use as an insulator. Selecting the configurations of roofing materials by their coefficient of thermal conductivity and evaluating by the insulation capacity according to the nmx-c-460-onncce involving the calculation of the Thermal Resistance (R); The performance of carrizo (Arundo Donax), corn cane (Mayz Zea) and the soil was evaluating to develop a roof for the region, according to the nmx-c-460-onncce meets for energy savings. Thermal analysis of materials is discussed only for their conductivity as there are other properties such as density and specific heat, that are dynamically related, independently that are not considered in the evaluation of thermal resistance. It is concluded that the analysis of pre-design thermal properties allows to select materials with adequate thermal response in the region to build efficient architectural envelopes.

Compact Thermal Modelling of Sub-20-nm Nanowire MOSFETs for Circuit Applications

Short channel effects (SCE) and self-heating be- comes more critical as the technology reaches on the nanoscale. Nanowire MOSFETs are an assuring candidate for coming CMOS technology. Due to the self-heating carrier mobility is decreased, which results in drain current degradation. Self- heating consequences in sub-20-nm Nanowire MOSFETs are studied and a compact thermal model is proposed in this work applying well-calibrated three-dimensional TCAD electro- thermal simulations. In this work, we observed that a different characteristic result of channel length towards thermal resistance. When the channel length is reduced, thermal resistance appears to be down gradually. The model is successfully implemented in BSIMCMG compact model. Compact thermal model for Nanowire MOSFET is proposed based on empirically extracted equations on different device parameters like channel length, nanowire thickness, nanowire height and fin pitch. The model may remain helpful for the evaluation of thermal resistance in Nanowire MOSFETs with large layouts.

Thermal Resistance Evaluation of a Low-Inductance Double-Stacked SiN-AMC Substrate for a High-Temperature Operation SiC Power Module

Two silicon nitride active metal brazed copper (SiN-AMC) substrates are double stacked and bonded to generate a five-layer structure that reduces the parasitic inductance of a power module. To investigate the heat dissipation characteristics of the double-stacked SiN-AMC substrates, the thermal resistance is measured using transient thermal analysis. The thermal resistance of each test vehicle is analyzed, and the thermal resistance of the SiN-AMC substrate is extracted. Further, the thermal resistance of the double-stacked SiN-AMC with a 0.3-mm thick Cu film is observed to be lower than the thermal resistance of a single SiN-AMC with a 0.1-mm thick Cu film. For a 3-mm square SiC die size, we observe that increasing the Cu film thickness is more effective to reduce the thermal resistance of the double-stacked SiN-AMC module as compared to increasing the SiN thermal conductivity.

Encapsulation of Lactobacillus acidophilus La-5 and Bifidobacterium Bb-12 by spray drying and evaluation of its resistance in simulated gastrointestinal conditions, thermal treatments and storage conditions

ABSTRACT: Lactobacillus acidophillus La-5 (ML) and Bifidobacterium Bb-12 (MB) microparticles were produced at different temperatures by spray dryer. The influence of different temperatures on the viability, encapsulation efficiency, water activity and moisture were evaluated. Microparticles that presented more viability were submitted to thermal resistance, gastrointestinal simulation, storage stability, morphology and particle size analyses. Drying temperature of 130°C showed higher encapsulation efficiency, 84.61 and 79.73% for Lactobacillus acidophillus (ML) and Bifidobacterium Bb-12 (MB) microparticles, respectively. In the evaluation of thermal resistance and gastrointestinal simulation, the microparticles of Lactobacillus acidophillus La-5 (ML) presented higher survival than Bifidobacterium Bb-12 (MB) under these conditions. In storage viability only the Lactobacillus acidophillus La-5 (ML) microparticles remained viable at all evaluated temperatures during the 120 days. The particle sizes reported were 4.85 for Lactobacillus acidophillus La-5 (ML) and 8.75 for Bifidobacterium Bb-12 (MB), being in agreement with the desired values for products obtained by spray dryer. Finally, the Lactobacillus acidophilus La-5 (ML) microparticles were shown to be more resistant under the conditions evaluated in this study.

Accurate and reliable U-value assessment of argon-filled double glazed windows: A numerical and experimental investigation

U-value assessment is a significant process to be able to evaluate the thermal insulation performance of building materials notably windows. About 60% of energy losses from building envelope is attributed to windows, hence accurate and reliable thermal resistance evaluation of glazed areas is of vital importance for a sensitive energy demand analysis of buildings. U-value assessment of windows is usually conducted through theoretical and numerical methods in literature. However, dwellers frequently complain about the insufficient thermal insulation performance of commercial glazing products when compared to the reported U-values in datasheets. This inconvenience arises from the lack of comprehensive experimental tests which simulate the actual operating conditions. Therefore, in this research, argon filled double glazed windows, which is one the most common fenestration products in market, is numerically and experimentally analysed in terms of U-value performance. Although computational fluid dynamics (CFD) analyses reveal that the U-value of the reference sample (4 mm pane + 20 mm argon + 4 mm pane) is 0.89 W/m2K, which is in good accordance with the theoretical data (0.80 W/m2K), it is observed from the environmental chamber tests that the U-value in simulated operating conditions is 1.25, 1.18 and 1.32 W/m2K for top, centre and lower positions of the window sample. The tests are repeated for accuracy verification, and the U-value is found to be 1.23, 1.18 and 1.31 W/m2K for the said points. In this respect, it is concluded that thermal bridges and edge effects play a key role in actual U-value performance of glazing products. Therefore, experimental performance figures are recommended to be utilised in energy demand analyses of buildings.

過渡熱解析による3次元積層IC内のアンダーフィル層の熱抵抗の評価

過渡熱解析による3次元積層IC内のアンダーフィル層の熱抵抗の評価

Evaluation of thermal resistance and mechanical properties of injected molded stereocomplex of poly(l‐lactic acid) and poly(d‐lactic acid) with various molecular weights

AbstractPoly(l‐lactic acid) (PLLA) and poly(d‐lactic acid) (PDLA) with various molecular weights (MW) were melt blended in equivalent proportions, and then followed by injection molding to form polylactide stereocomplex (sc‐PLA). The crystalline structures, thermal resistance, and mechanical properties of the formed sc‐PLA were then investigated in detail. The results showed stereocomplex crystallites (sc) were formed predominantly in all the sc‐PLA regardless of the MW of the PLLA or PDLA pellets, and a small amount of homocrystallites (hc) also coexisted in sc‐PLA. The MW of PLLA and PDLA pellets displayed significant effects on the crystallinity, thermal resistance, and mechanical properties of sc‐PLA. PLLA and PDLA with low and similar MW facilitated the formation of sc, and also improved the onset degradation temperature and Vicat softening temperature of sc‐PLA. For a similar degree of crystallinity, high MW was found to be more favorable in improving the thermal performance of sc‐PLA. Although sc‐PLA prepared from PLLA and PDLA with low MW showed decreased mechanical properties, the mechanical properties of sc‐PLA increased with an increase in the MW of the PLLA or PDLA pellet. When PLLA and PDLA pellets with high and similar MW were used, the mechanical properties of sc‐PLA could even exceed those of pure PLLA.

Influence of internal heat sources on thermal resistance evaluation through the heat flow meter method

Buildings energy performance is evaluated using codes which reproduce the building behavior, employing technical information about the structure. Wall thermal resistance can be measured using a heat-flow meter in compliance with the ISO 9869, which suggests avoiding proximity to particular points such as thermal bridges, but it does not give suggestions about how to deal with internal heat sources. Thermal resistance measurements are based on 1D models and the internal heat sources cause the departure from one-dimensional conditions. In this study we employ a FEM code to reproduce the heat-flow meter method within a 2D model. Walls include an internal pipe, inside which hot/cold water flows. Models were generated considering different stratigraphies and heat-flow plate positions along the inner side of the wall, in order to reproduce the thermal conditions that affect the flowmeter and the wall, respectively. Thus, it is possible to compare the thermal resistances of the different walls and to find the best heat-flow plate positions in order to minimize the influence of the internal heat source. A preliminary experimental evidence of the problem has been finally presented and the results of this case study have been compared with those of its corresponding FEM model.

Fabrication of Al-Based Metal Printed Circuit Board Having Excellent Heat Dissipation Characteristics Using Polyimide/AlN Powder and Evaluation of Thermal Resistance of Light-Emitting Diode Module

Fabrication of Al-Based Metal Printed Circuit Board Having Excellent Heat Dissipation Characteristics Using Polyimide/AlN Powder and Evaluation of Thermal Resistance of Light-Emitting Diode Module

Evaluation of Thermal Resistance of the Military Sleeping Bags

Military sleeping bags are envisaged for intensive use during military actions. They have extra properties that provide protection for military staff. In cold climatic conditions when sleeping bags are used for rest soldiers’s combat ability and survival depends on the thermal insulation properties of material technical resources (gear) and clothing.Aim of the research is to establish the extreme temperature of military sleeping bags and military uniforms complete sets, to find the optimal set and define conformity to NATO AECTP-230 “Climatic conditions” cold climate categories C0 – C1.

Evaluation of thermal resistance of carbon nanotube film fabricated using an improved slope control of temperature profile growth

We have successfully improved the weight density of a 40-µm-long carbon nanotube (CNT) to 0.27 g/cm3 by improving the slope control of temperature profile (STEP) growth. It was found that the CNT growth is reaction-limited in the early stage of STEP growth and supply-limited in the late stage. We succeeded in doubling the CNT density over the conventional method by optimizing the raw material supply and temperature slope during the reaction-limited and supply-limited periods. A CNT thermal interface material was fabricated using a CNT film prepared by this method. Thermal resistance was 11% below a conventional indium thermal interface material. Owing to the above reasons, CNTs show promise as heat dissipation materials.

Windows thermal resistance: Infrared thermography aided comparative analysis among finite volumes simulations and experimental methods

The correct estimation of the energy performance of windows represents a fundamental issue in the buildings heat losses assessment, since both accuracy and simplicity requirements have to be fulfilled.The most common approaches proposed consist of finite element simulations and laboratory measurements. The reliability of numerical methods results is still an open issue: the general policy of Standards requires for the calculated values to be on the safer side but it is not clear if this assumption is always verified and which is the difference between measured and simulated values. Standards allow the implementation of numerical simulations also in a two-dimensional domain, while windows are composed by zones with a definite three-dimensional geometry such as corners.Two types of windows (wood and aluminum framed) were analyzed, showing that the difference between two-dimensional and three-dimensional simulations is not so high to justify the vast difference that exists instead in terms of calculation time.By means of a hot box apparatus, a comparison term was given to evaluate the finite volumes method adherence to the experimental values. Infrared thermography gives the possibility of a better understanding of the differences between the simulation results and the measured values.The experimental measurements indicated a good data coincidence with simulations for both types of windows, with an expected thermal window performance underestimation of the numerical approach. The reasons lie in the use of thermal conductivity cautionary values in simulations, and on the stratification phenomenon (highlighted by the infrared camera), that brings a decrease to the convection heat transfer. It emerges therefore that, if a window manufacturer strives for achieving high performance certified products, the test on an experimental hot box setup becomes more appropriate, since it brings to a thermal resistance evaluation around 10% higher than the one obtained from a simulation procedure.

B132 繰り返し計算による電子機器の熱抵抗算出手法

B132 繰り返し計算による電子機器の熱抵抗算出手法

Three dimensional temperature field in a conducting sphere due to an arbitrarily located split ring heating source

Thermal control of spacecrafts plays an important role in space missions. In the design stage the preliminary thermal analysis of the spacecraft requires an estimate of the conductive thermal resistance between the various spacecraft components. With this in mind, the fully three dimensional problem of determining the thermal field in a conducting sphere with an asymmetric split ring current carrying heating source is resolved in an analytical or almost analytical form, implying either a closed form solution or utmost expressions involving a simple numerical integration. This has immediate application for evaluation of thermal resistance in spacecrafts. Green's function integral techniques are used. Comparisons are made with series solutions and also with purely numerical solutions to contrast the simplicity and highlight the elegance of the present method. Parametric studies reveal expected behavior.

Thermally efficient and highly scalable In2Se3 nanowire phase change memory

The electrical characteristics of nonvolatile In2Se3 nanowire phase change memory are reported. Size-dependent memory switching behavior was observed in nanowires of varying diameters and the reduction in set/reset threshold voltage was as low as 3.45 V/6.25 V for a 60 nm nanowire, which is promising for highly scalable nanowire memory applications. Also, size-dependent thermal resistance of In2Se3 nanowire memory cells was estimated with values as high as 5.86×1013 and 1.04×106 K/W for a 60 nm nanowire memory cell in amorphous and crystalline phases, respectively. Such high thermal resistances are beneficial for improvement of thermal efficiency and thus reduction in programming power consumption based on Fourier's law. The evaluation of thermal resistance provides an avenue to develop thermally efficient memory cell architecture.