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ON Semiconductor Is ON Semiconductor Is Now To learn more about onsemi™, please visit our website at www.onsemi.com onsemi and and other names, marks, and brands are registered and/or common law trademarks of Semiconductor Components Industries, LLC dba “onsemi” or its affiliates and/or subsidiaries in the United States and/or other countries. onsemi owns the rights to a number of patents, trademarks, copyrights, trade secrets, and other intellectual property. A listing of onsemi product/patent coverage may be accessed at www.onsemi.com/site/pdf/Patent-Marking.pdf. onsemi reserves the right to make changes at any time to any products or information herein, without notice. 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Should Buyer purchase or use onsemi products for any such unintended or unauthorized application, Buyer shall indemnify and holdonsemi and its officers, employees, subsidiaries, affiliates, and distributors harmless against all claims, costs, damages, and expenses, and reasonable attorney fees arising out of, directly or indirectly, any claim of personal injury or death associated with such unintended or unauthorized use, even if such claim alleges that onsemi was negligent regarding the design or manufacture of the part. onsemi is an Equal Opportunity/Affirmative Action Employer. This literature is subject to all applicable copyright laws and is not for resale in any manner. Other names and brands may be claimed as the property of others. Basic Thermal Properties of Semiconductors HBD856/D Rev. 0, June−2009 © SCILLC, 2009 “All Rights Reserved” ACE Loop, AnyLevel, BERS, Bullet−Proof, CHIPSCRETES, DUOWATT, E−FET, EASY SWITCHER, ECLinPS, ECLinPS Lite, ECLinPS MAX, ECLinPS Plus, EpiBase, Epicap, EZFET, FASTMOS, FLEXMOS, FULLPAK, GEMFET, GigaComm, HDPlus, ICePAK, ICEPAK*, L2TMOS, MCCS, MDTL, MECL, MEGAHERTZ, MHTL, MicroIntegration, MicroLeadless, MiniGate, MiniMOS, MiniMOSORB, MRTL, MTTL, Multi−Pak, NOCAP, ON−Demand, PInPAK, PMODE, PowerBase, POWERSENSE, POWERTAP, PureEdge, Quake, SLEEPMODE, SMARTDISCRETES, SMART HotPlug, SMARTswitch, Soft−Skip, SUPERBRIDGES, SuperLock, SWITCHMODE, ThermalTrak, Thermopad, Thermowatt, TMOS Stylized, TOCCATA, Toccata Plus, TOCCATA PLUS, mCool, Unibloc, VPower, XtreMOS, Z−Switch and ZIP R TRIM are trademarks of Semiconductor Components Industries, LLC (SCILLC). A/M/I, AMI, AMI SEMICONDUCTOR, AMIS, ASTRIC, BelaSigna, BELASIGNA, CATALYST, dbCOOL, DSPFACTORY, Ezairo, EZAIRO, FPGASIC, FREEPROM, From−the−Socket−to−the−Pocket, GreenPoint, HDTMOS, HVTMOS, MOSORB, NETRANS, Orela, ORELA, QUAD−MODE, SENSEFET, SignaKlara, SIGNAKLARA, SMALLBLOCK, SURMETIC, TMOS, TMOS & Design Device, UNIWATT, WAVEFET, XLARRAY, XPRESSARRAY and XTREMOS. are registered trademarks of Semiconductor Components Industries, LLC (SCILLC). All brand names and product names appearing in this document are registered trademarks or trademarks of their respective holders. ON Semiconductor and are registered trademarks of Semiconductor Components Industries, LLC (SCILLC). SCILLC reserves the right to make changes without further notice to any products herein. SCILLC makes no warranty, representation or guarantee regarding the suitability of its products for any particular purpose, nor does SCILLC assume any liability arising out of the application or use of any product or circuit, and specifically disclaims any and all liability, including without limitation special, consequential or incidental damages. “Typical” parameters which may be provided in SCILLC data sheets and/or specifications can and do vary in different applications and actual performance may vary over time. All operating parameters, including “Typicals” must be validated for each customer application by customer’s technical experts. SCILLC does not convey any license under its patent rights nor the rights of others. SCILLC products are not designed, intended, or authorized for use as components in systems intended for surgical implant into the body, or other applications intended to support or sustain life, or for any other application in which the failure of the SCILLC product could create a situation where personal injury or death may occur. Should Buyer purchase or use SCILLC products for any such unintended or unauthorized application, Buyer shall indemnify and hold SCILLC and its officers, employees, subsidiaries, affiliates, and distributors harmless against all claims, costs, damages, and expenses, and reasonable attorney fees arising out of, directly or indirectly, any claim of personal injury or death associated with such unintended or unauthorized use, even if such claim alleges that SCILLC was negligent regarding the design or manufacture of the part. SCILLC is an Equal Opportunity/Affirmative Action Employer. This literature is subject to all applicable copyright laws and is not for resale in any manner. ON Semiconductor Handbook − Basic Thermal Properties of Semiconductors Chapter 2 Table of Contents Abstract Page In applications requiring wide ambient temperature ranges, Introduction. 3 compact form factors, limited airflow, or high power Thermal Models. 3 dissipations, thermal design can pose a significant challenge. Thermal Resistance. 3 The basic concepts behind heat transport and thermal modeling Thermal Resistance and Thermal Characterization are very straightforward, and device datasheet parameters and Parameters. 3 thermal response curves provide valuable tools to estimate Example 1: Differentiating q and Y . 4 device junction temperatures. Steady−state, transient, and Case−Mounted Rectifiers. 4 periodic power inputs can all be modeled, and the results allow Lead−Mounted Parts. 5 for accurate estimation of resulting temperatures and Example 2: Calculating Junction Temperatures from a heatsinking requirements. In addition, thermal models can be Generic Thermal Model. 7 used to assess the likelihood of thermal runaway and to Thermal RC Networks. 8 demonstrate the thermal stability of a design. Grounded and Non−Grounded Thermal Models. 8 Thermal Response Curves. 9 Superposition of Thermal Responses. 11 Example 3: Calculating Transient Junction Temperatures by Superposition. 11 Superposition of Rectangular Pulses. 12 Example 4: Temperature Changes Due to a Set of Pulses. 13 Periodic Responses and Duty−Cycle Curves. 14 Non−Rectangular Power Transients. 15 Example 5: Maximum Junction Temperature During Overload. 17 Thermal Runaway. 18 Thermal Design. 20 http://onsemi.com 2 ON Semiconductor Handbook − Basic Thermal Properties of Semiconductors INTRODUCTION commonly used as a temperature reference point for thermal Three basic processes govern the removal of heat from the calculations involving semiconductors. The other reference rectifier junction to the ambient air: conduction (heat point is the case for case−mounted parts or a specified point traveling through a material); convection (heat transfer by on a lead for axial lead mounted parts. These reference physical motion of a fluid); and radiation (heat transfer by points are denoted with subscripts. For example, qJC electromagnetic wave propagation). Heat flows by signifies junction−to−case thermal resistance, and qJL conduction from the die to the package mounting surface in signifies junction−to−lead thermal resistance. The stud−, base−, or surface−mount pads, but it flows from the corresponding temperature differences are denoted DTJC die through the leads to the mounting terminals in a and DTJL, respectively. lead−mounted part. This thermal conduction can be modeled and designed for, so that the devices in question do Thermal Resistance and Thermal Characterization not exceed their maximum junction temperatures. Steady Parameters q state, periodic and transient thermal conditions can all be Thermal resistance ( ) denotes the resistance along a modeled and solved, allowing the design to maintain proper specific path. When using true thermal resistances all paths thermal operating points, ensure device lifetimes and must be taken into account to compute power and prevent thermal runaway. temperature relationships. There is a related set of characterization parameters (Y) that denote the relationship THERMAL MODELS between power dissipation and temperature, ignoring
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