smps.us - Thermal design

Heat Sink Design, Calculators, Thermal Analysis Software

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Heat Sink Design, Calculators, ThermalWringerSoftware THERMAL DESIGN AN INTRODUCTION TO THERMAL MANAGEMENT OF ELECTRONICS HEAT EXCHANGERS GUIDES, FREE SOFTWARE AND CALCULATORS Let's uncork by defining the main terms. The goal of thermal management is to tenancy the temperatures of the electronic devices. But what is temperature? Technically speaking, on a microscopic level it is a measure of the stereotype molecular kinetic energy in the matter. The normal spritz of kinetic energy is from a higher temperature region (or an object) toward a lower temperature region (or an object). This spritz is referred to as heat transfer. Home Tutorial Topologies SMPS diamond Thermal diamond Software PCB diamond Computer PSU UPSSpinTransformers Formulas EE Reference Inverters Generators Solar In general, there are three types of heat transfer: conduction, convection, and radiation. Conduction is the collisional transfer of energy between atoms, which occurs in solids. Convection is the motion of molecules in air or fluids. Radiation is the energy spritz by electromagnetic waves. In practical electronics primarily only the first two types are usually taken into account. Why do electronic devices get hot? Electric currents and successive electromagnetic fields rationalization power dissipation in all electronic parts, which results in increase of their temperatures. This in turn affects the reliability and life expectancy of these components. The measures of the electronic system reliability are failure rate and its inverse, midpoint time between failures (MTBF). According to Arrhenius model, each 10oC rise increases the failure rate by 50%. At unrepealable point any electronic device can be irreversibly destroyed. Typical maximum operating temperature "T" for semiconductors and ICs is 125-175 oC at their junctions, capacitors- 85-125 oC, wire insulation- 105-200 oC. The thermal management and engineering whose task is to tenancy "T" of the product, is therefore an essential part of electronics design. When designing a heat sink for a semiconductor cooling, first of all you need to segregate the component's maximum operating junction temperature Tjmax (typically, we select 105-120 oC for commercial parts). Then, for convection cooling the required heatsink thermal resistance should be Rth-hs<(Tjmax-Ta)/P-(Rthj-c+Rthc-hs) oC/W, where Ta- ambient, Rthj-c - thermal resistance between junction and the specimen from the datasheet (typically 0.5-2.5 oC/W for conventional discrete power packages), Rthc-hs - thermal resistance between the device's specimen and the heatsink, P- power prodigal by the device in watts. Besides conduction cooling, there is flipside path for the heat- from the specimen of the device directly to the air. This path is specified by junction to ambient thermal resistance Rthj-amb. However, you can usually condone it when a device is mount onto a heatsink. See thermal spin diagram to the left for an illustration. Once you found the required Rth-hs, you can pick a stamped or extruded heat sink with equal or lower value of thermal resistance. Note that if you use an insulator between the device and the heatsink, you need to take it into worth as well. For off-the-shelf parts, Rth-hs is normally specified in the datasheet. Harry Lythall found empirically a "rule of thumb" numbering formula for Rth-hs of home made U-shape folded aluminum sheet. Based on his equation, the required surface zone in sq.cm is A=(50/Rth-hs)2.In general, the main optimization criteria are to maximize the exposed heat exchanger's surface area, and to minimize its weight and the midpoint loftiness of the exposed surface from the component to be cooled. Below you will find self-ruling calculators and useful information on the thermal design. HEAT AND THERMODYNAMICS BASICS THERMAL MODELING AND ANALYSIS SOFTWARE THERMAL DESIGN GUIDES, ANALYSIS & APPLICATION NOTES Heat conduction formulas A detailed heat transfer textbook for engineering students (conduction, convection, radiation) The First Law of thermodynamics PCB TRACE CALCULATOR FOR TEMPERATURE RISE Heat sink calculation, diamond and wringer Thermal conductivity units conversion Temperature units conversion Duct spritz velocity calculator Thermal resistance and fin efficiency online calculators THERMAL DATA OF ELECTRONIC COMPONENTS Basic thermal management of semiconductor devices Thermal conductivity in cal/sec and W/m*K for various materials The diamond of fan speed tenancy What you need to know well-nigh cooling fans HEATSINK PROPERTIES AND DESIGN NOTES How to select an extruded heat sink Analytical model for simulating electronic systems' thermal policies Heatsink diamond guide Disclaimer, Disclosure and Terms of Use | Contact Us |Well-nighUs | Privacy © 2004, 2008-2015 Lazar Rozenblat