Thermal Management for Electronic Packaging 03 02 2006 Guoping Xu Sun Microsystems CSE291 Interconnect and Packaging UCSD Winter 2006 Outline Introduction Heat transfer theory Thermal resistance in electronic packaging Thermal design Thermal modeling Thermal measurement Page 2 CSE291 Interconnect and Packaging UCSD Winter 2006 Introduction Functions of Electronic Packaging Package protection Signal distribution Power distribution Heat dissipation Page 3 CSE291 Interconnect and Packaging UCSD Winter 2006 Introduction Packaging Hierarchy Chip Package Board System Rack Room Page 4 CSE291 Interconnect and Packaging UCSD Winter 2006 Introduction High end chip power trend 600 CPU Power W 500 400 UltraSparc 1 Power 4 2 Itanium 2 3 ITRS 2002 4 ITRS 2005 300 200 100 0 1990 1995 2000 2005 2010 2015 2020 Year Page 5 CSE291 Interconnect and Packaging UCSD Winter 2006 Introduction Cost performance chip power trend 160 140 ITRS 2005 CPU Power W 120 100 80 60 40 20 0 2004 2006 2008 2010 2012 Year Page 6 2014 CSE291 Interconnect and Packaging UCSD Winter 2006 Introduction Power density in datacom equipment Page 7 CSE291 Interconnect and Packaging UCSD Winter 2006 Introduction Power density in datacom equipment Total power 24KW Footprint 15 sq ft Power density 1600W sq ft Sun Fire E25K Page 8 CSE291 Interconnect and Packaging UCSD Winter 2006 Introduction Impact of Device junction temperature Computing performance Reliability Fire hazard and or Safety issues Page 9 CSE291 Interconnect and Packaging UCSD Winter 2006 Heat Transfer Theory Conduction Definition Conduction is a mode of heat transfer in which heat flows from a region of higher temperaure to one of lower temperature within a medium solid liquid or gases or media in direct physical contact Fourier s law Q KA dT dX 1 D conduction Q KA T1 T2 L Thermal resistance R T1 T2 Q L KA Page 10 CSE291 Interconnect and Packaging UCSD Winter 2006 Heat Transfer Theory Conduction Contact thermal resistance Page 11 CSE291 Interconnect and Packaging UCSD Winter 2006 Heat Transfer Theory Thermal conductivity of various packaging materials Material Aluminum pure Aluminum Nitride Alumina Copper Diamond Epoxy No fill Epoxy High fill Epoxy glass Gold Lead Silicon Silicon Carbide Silicon Grease Solder W mK 216 230 25 398 2300 0 2 2 1 0 3 296 32 5 144 270 0 2 49 3 Page 12 CSE291 Interconnect and Packaging UCSD Winter 2006 Heat Transfer Theory Convection Convection is a mode of heat transport from a solid surface to a fluid and occurs due to the bulk motion of the fluid Newton s law Q hA Tw Tf Convective thermal resistance R 1 hA Effects of heat transfer coefficient Convetion mode Natural convection Foreced convection phase change Flow regime Laminar Turbulent flow Flow velocity y Tf Fluid y Surface condition Fluid Velocity distribution u y Heated surface Temperature distribution Tw T y Page 13 CSE291 Interconnect and Packaging UCSD Winter 2006 Heat Transfer Theory Typical values of the heat transfer coefficient Page 14 CSE291 Interconnect and Packaging UCSD Winter 2006 Heat Transfer Theory Radiation Definition Radiation heat transfer occurs as a result of radiant energy emitted from a body by virtue of its temperature Page 15 CSE291 Interconnect and Packaging UCSD Winter 2006 Thermal Resistance Package without heat sink Ta Tb Chip Tt Tj Package PCB Rja Junction to air thermal resistance Rja Tj Ta P Low value is good thermal perfromance Rjc Junction to case thermal resistance Rjc Tj Tc P jt Thermal characterization parameter Junction to package top NOT thermal resistance jb Thermal characterization parameter Junction to board Page 16 CSE291 Interconnect and Packaging UCSD Winter 2006 Thermal Resistance Package with heat sink Ta Heat sink Package Die Ts Tc Tj Rja Junction to air thermal resistance Rja Tj Ta P Rjc Rcs Rsa Rjc Junction to case thermal resistance Rjc Tj Tc P Rsa External heat sink thermal resistance Rsa Ts Ta P Page 17 CSE291 Interconnect and Packaging UCSD Winter 2006 Thermal Resistance PBGA package example Tair Page 18 CSE291 Interconnect and Packaging UCSD Winter 2006 Thermal Resistance Impact factors for package without heat sink Die size Package size lead count Packaging material thermal condunctivity Material thickness in major heat flow path Number of vias Heat spreader or heat slug Air velocity and temperature PC Board size Board configuration and material Board layout Page 19 CSE291 Interconnect and Packaging UCSD Winter 2006 Thermal Design Conduction application Single material Q Die Substrate Tc Tj Tc Tj QL KA ti Composite material Kin plane Layer 1 Layer 2 Layer i Layer N KTthrough Uniform heating on the die Page 20 CSE291 Interconnect and Packaging UCSD Winter 2006 Thermal Design Conduction application Heat spreader Die Substrate Ab As kb Ab R ba tanh H b Rsb kb Ab As 1 kb Ab R ba tanh H b 23 1 Ab As Ab Heat spreader base area As Heat source area Hb Heat spreader thickness Kb Heat spreader thermal conductivity Page 21 CSE291 Interconnect and Packaging UCSD Winter 2006 Thermal Design Convection application Heat sink design Hf b H tf Fins Hb L Heat sink base W Page 22 CSE291 Interconnect and Packaging UCSD Winter 2006 Thermal Design Convection application Heat sink design Thermal resistance Heat transfer Rba Tb Tinlet Q hDh Nu 7 54 k air Fin efficiency o 1 At 1 f m c p 1 e hAt o m c p Laminar flow hDh Nu 0 024 Re 0 786 Pr 0 45 k air Af 1 Turbulent flow f tanh mH f mH f Page 23 CSE291 Interconnect and Packaging UCSD Winter 2006 Thermal Design Convection application Heat sink design Total static pressure loss U ch 2 L P K c 4 f app K e Dh 2 Culham and Muzychka 2001 Apparent friction factor fapp calculation Fully developed flow friction factor f f app Re 3 44 L L Dh Re 2 f Re 2 40 829 b H f 3 22 954 b H f 4 5 6 089 b H f f Re 24 32 527 b H f 46 721 b H f Contraction loss coefficient Kc Expansion loss coefficient Ke L 0 5 2 David Copeland 2000 12 1 f app Re 3 2 L 0 57 2 2 f Re b H f 2 1 f Re 4 7 19 64 b H f 1 2 K c 0 42 1 K c 0 8 0 4 2 K e 1 2 K e 1 2 0 4 Nt f W b tf b 12 Page 24 CSE291 Interconnect and Packaging UCSD Winter 2006 Thermal Design Convection application Heat sink design Impact factors Air flow rate Available space Heat sink base and fin material Fin pitch and fin thickness Heat flux Heat sink technologies Page 25 CSE291 Interconnect and Packaging UCSD Winter 2006 Thermal Design Design methodology Define requirements Analyze given package design Identify major heat paths and paths for improvements Consider and assess potential
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