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Showing 10 out of a total of 48 results for collection: 2006  Proceedings of 12th International Workshop on Thermal investigations of ICs. (0.025 seconds)

(TIMA Editions , Grenoble, France, 2006)In this work we present results of the analysis of thermal properties of highpower laser bars obtained by spatially resolved thermoreflectance (TR) spectroscopy. Thermoreflectance is a modulation technique relying on periodic facet temperature modulation induced by pulsed current supply of the laser. The periodic temperature change of the laser induces variation of the refractive index and consequently modulates probe beam reflectivity. The technique has a spatial resolution of about 1 m and can be used for temperature mapping over 300 m 300 m area. Information obtained in these experiments provide an insight into thermal processes occurring at devices' facets and consequently lead to increased reliability and substantially longer lifetimes of such structures....

(TIMA Editions , Grenoble, France, 2006)This paper presents a very straightforward method to compute the transient thermal response to arbitrary power dissipation profiles in electronic devices with multiple heat sources. Using cubic spline interpolation of simulated or measured unit power step response curves (Zthfunctions), additional errors due to model reduction can be avoided. No effort has to be spent on the generation of compact models. The simple analytic form of the interpolating splines can be exploited to evaluate the convolution integral of the Zthfunctions with arbitrary power profiles at low computational costs. An implementation of the algorithm in a spreadsheet program (EXCEL) is demonstrated. The results are in very good agreement with temperature profiles computed by transient Finite Element simulation but can be obtained in a fraction of the time....

(TIMA Editions , Grenoble, France, 2006)In this paper it is shown that multiport dynamic thermal networks admit four canonical representations which generalize the four canonical representations of passive lumped RC networks : Foster I and II canonical forms, Cauer I and Cauer II canonical forms. In particular the generalized Foster I canonical form is equivalent to the timeconstant representation and the generalized Cauer I canonical form is a passive multiconductor RC transmission line....

(TIMA Editions , Grenoble, France, 2006)Modern CPUs with increasing core frequency and power are rapidly reaching a point that the CPU frequency and performance are limited by the amount of heat that can be extracted by the cooling technology. In mobile environment, this issue is becoming more apparent, as form factors become thinner and lighter. Often, mobile platforms trade CPU performance in order to reduce power and manage the box thermals. Most of today's high performance CPUs provide thermal sensor on the die to allow thermal management, typically in the form of analog thermal diode. Operating system algorithms and platform embedded controllers read the temperature and control the processor power. In addition to full temperature reading, some products implement digital sensors with fixed temperature threshold, intended for fail safe operation. Temperature measurements using the diode suffer some inherent inaccuracies : ? Measurement accuracy  An external device connects to the diode and performs the A/D conversion. The combination of diode behavior, electrical noise and conversion accuracy result with measurement error ? Distance to the die hot spot  Due to routing restrictions, the diode is not placed at the hottest spot on the die. The temperature difference between the diode and the hot spot varies with the workload and the reported temperature dose not accurately represent the die max temperature. This offset is increasing as power density of the CPU increase. multiple core CPUs introduce harder problem to address as the workload and the thermal distribution changes with the different active cores. ? Manufacturing temperature accuracy  Inaccuracies in the test environment induce additional temperature inaccuracy between the measured temperature vs. the actual temperature. As a result to these effects, the thermal control algorithm requires to add temperature guard bend to account for the control feedback errors. These impact the performance and reliability of the silicon. In order to address the thermal control issues, the Intel® CoreTM Duo has introduced a new digital temperature reading capability on die. Multiple thermal sensors are distributed on the die on different possible hot spots. An A/D logic built around these sensors translates the temperature into a digital value, accessible to operating system thermal control S/W, or driver based control mechanism. Providing high accuracy temperature reading requires a calibration process. During high volume manufacturing, each sensor is calibrated to provide good accuracy and linearity. The die specification and reliability limitation is defined by the hottest spot on the die. In addition the calibration of the sensor is done at the same test conditions as the specification testing. Any test control inaccuracy is eliminated because the part is guaranteed to meet specifications at max temperature, as measured by the digital thermometer. As a result, the use of integrated thermal sensor enables improved reliability and performance at high workloads while meeting specifications at ant time. In this paper we will present the implementation and calibration details of the digital thermometer. We will show some studies of the temperature distribution on die and compare traditional diode based measurement to the digital sensor implementation....

(TIMA Editions , Grenoble, France, 2006)The aim of this work is to develop a simple optical method for the visualization of the natural convection flow generated in an electronic system during its normal operation. The presented experimental setup allows to reveal local refractive index changes in a phase objects. A fringe pattern is acquired, through the cooling fluid under analysis, with a digital camera two times : the first one with the fluid at rest, the second one with the thermal load due to the electronic device normal operation. By the means of the MATLAB processing of the acquired images it's possible to reveal the shape and the directions of the thermal flow lines for the cooling fluid. In this way we can obtain a deeper understanding of the optimal convection working volume or information for the optimization of the relative spatial positioning of the several electronic components in a complex electronic system, like a printed circuit board (PCB). The proposed technique has been tested on two typical heat extraction situations recurrent in the electronic devices. In this paper are presented the experimental results of the visualization of the convective flow, in air, for an heat sink and a power resistor....

(TIMA Editions , Grenoble, France, 2006)Multisource, Multichip, Thermal transient SimulationThis paper presents a very straightforward method to compute the transient thermal response to arbitrary power dissipation profiles in electronic devices with multiple heat sources. Using cubic spline interpolation of simulated or measured unit power step response curves (Zthfunctions), additional errors due to model reduction can be avoided. No effort has to be spent on the generation of compact models. The simple analytic form of the interpolating splines can be exploited to evaluate the convolution integral of the Zthfunctions with arbitrary power profiles at low computational costs. An implementation of the algorithm in a spreadsheet program (EXCEL) is demonstrated. The results are in very good agreement with temperature profiles computed by transient Finite Element simulation but can be obtained in a fraction of the time....

(TIMA Editions , Grenoble, France, 2006)The thermal response function given to a unitstep dissipation accurately characterizes the thermal system. Instead of the thermal response function the socalled structure function describing threedimensional as the equivalent model of onedimensional heatspreading, created from the thermal response function with the help of complex mathematical procedures, is often used. Using the structure function the partial thermal capacity and partial heat resistance of certain elements of the thermal system can be identified. If the geometrical measurements of a thermal system of simple geometry and homogeneous material (such as a homogeneous rod or board, etc.) are known, the coefficient of thermal conductivity of the material in question can be determined from two points of the structure function at 25 per cent of accuracy. In this paper a method is presented which applies a wide range/section instead of two points of the cumulative structure function to determine the thermal coefficient, thus reducing the subjective error deriving from the selection of the two points. The above method is presented and illustrated in simulated as well as measured thermal transient responses....

(TIMA Editions , Grenoble, France, 2006)Thermal ModellingThis paper presents a study of accuracy issues in thermal modeling of high power LED modules on system level. Both physical as well as numerical accuracy issues are addressed. Incorrect physical assumptions may result in seemingly correct, but erroneous results. It is therefore important to motivate the underlying key physical assumptions of a thermal model. In this paper thermal measurements are used to calibrate a computational fluid dynamics (CFD) model of a high power LED module model at a reference application condition, and to validate it at other application conditions....

(TIMA Editions , Grenoble, France, 2006)Prognostics is a process of assessing the extent of deviation or degradation of a product from its expected normal operating condition, and then, based on continuous monitoring, predicting the future reliability of the product. By being able to determine when a product will fail, procedures can be developed to provide advanced warning of failures, optimize maintenance, reduce life cycle costs, and improve the design, qualification and logistical support of fielded and future systems. In the case of electronics, the reliability is often influenced by thermal loads, in the form of steadystate temperatures, power cycles, temperature gradients, ramp rates, and dwell times. If one can continuously monitor the thermal loads, insitu, this data can be used in conjunction with precursor reasoning algorithms and stressanddamage models to enable prognostics. This paper discusses approaches to enable electronic prognostics and provides a case study of prognostics using thermal data....

(TIMA Editions , Grenoble, France, 2006)This work introduces a thermoreflectancebased system designed to measure the surface temperature field of activated microelectronic devices at submicron spatial resolution with either a laser or a CCD camera. The article describes the system, outlines the measurement methodology, and presents validation results. The thermoreflectance thermography (TRTG) system is capable of acquiring device surface temperature fields at up to 512 512 points with 0.2 ƒÊm resolution. The setup and measurement methodology are presented, along with details of the calibration process required to convert changes in measured surface reflectivity to absolute temperatures. To demonstrate the systemfs capabilities, standard gold microresistors are activated and their surface temperature fields are measured. The results of the CCD camera and our existing laserbased measurement approaches are compared and found to be in very good agreement. Finally, the system is validated by comparing the temperatures obtained with the TRTG method with those obtained from electrical resistance measurements....