Slide 1 ME6204 Convective Heat Transfer Thermal Management of Electronic Components Mujumdar A S and Ravi K January 2006 Slide 2 Introduction Basic Thermal Problems in IC Packages and Electronic Systems Heat Transfer path in IC packages Thermal Definitions and JEDEC standards Basic Approaches for IC package Thermal Performance Characterization Analytical Approach Modeling approach* Experimental Approach* Thermal performance - Package level with examples - Heat sink selection with examples Summary Outline of Topics Outline of Topics * Covered basic details
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Slide 1
ME6204 Convective Heat Transfer
Thermal Management of Electronic Components
Mujumdar A S and Ravi K
January 2006
Slide 2
Introduction
Basic Thermal Problems in IC Packages and Electronic Systems
Heat Transfer path in IC packages
Thermal Definitions and JEDEC standards
Basic Approaches for IC package Thermal Performance Characterization
Analytical Approach
Modeling approach*
Experimental Approach*
Thermal performance
- Package level with examples
- Heat sink selection with examples
Summary
Outline of TopicsOutline of Topics
* Covered basic details
Slide 3
Needs of thermal management for electronic Needs of thermal management for electronic packages and systemspackages and systems
Basic concepts, definition and industrial Basic concepts, definition and industrial approaches for thermal characterization of approaches for thermal characterization of electronic packageselectronic packages
To understand the package thermal performance To understand the package thermal performance with different external cooling arrangementswith different external cooling arrangements
IntroductionIntroduction
Slide 4
Reynell, M. 1990
Source: U.S. Air Force Avionics Integrity Program
Major Causes of Electronic FailuresMajor Causes of Electronic Failures
Slide 5
Control of TJ = Goal of electronic coolingHigher TJ yields shorter device lifeHigher TJ poor image capture
Jc/TeLife
Lifespan Vs Junction TemperatureLifespan Vs Junction Temperature
Slide 6
Heat Fluxes For Various EventsHeat Fluxes For Various Events
Chu, Simons, et.al 1999
Heat Fluxes for Various ElementsHeat Fluxes for Various Elements
Slide 7
Increasing module and device heat fluxes
Declining thermal design-margins
Trends in Electronic CoolingTrends in Electronic Cooling
Slide 8
Packaging Controls
Size Weight Performance Reliability Cost
What is Packaging?What is Packaging?
Source: IEEE/CPMT
Slide 9
Today s electronics product are very complicated systems containing many thin layers, narrow conducting wires, tiny solder joints etc.
Because of the fine features and large number of parts involved in each design the probability of system failure is high unless all the design considerations are taken into account.
This presentation covers only some aspects of design, production, testing, and packaging of electronic products issues based on package structural considerations.
Why care about Packaging?Why care about Packaging?
Slide 10
To keep the maximum junction temperature To keep the maximum junction temperature within the specified limit (within the specified limit (TjTj < 125< 125 C)C)
Effective/Economic heat removal out of electronic Effective/Economic heat removal out of electronic systemssystems
Thermal Issues in ElectronicsThermal Issues in Electronics
Slide 11
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Various Electronic PackagesVarious Electronic Packages
Package size decrease Package size decrease ------> Hot> HotDie size decrease Die size decrease ------> Hot> HotSystem complexity increase System complexity increase -- HotHotClock speed in crease Clock speed in crease -- HotHotLower power process, lower Lower power process, lower volatgevolatgeI/O increaseI/O increase
Thermal Trends in Electronic Thermal Trends in Electronic PackagesPackages
Slide 14
Both are critical for thermal design of a system Both are critical for thermal design of a system and componentand component
Thermal characterizationThermal characterizationInvolves the determination of thermal fields Involves the determination of thermal fields
and its gradients (spatial and temporal), and its gradients (spatial and temporal), representative thermal parameters throughout representative thermal parameters throughout the system and component the system and component
Thermal managementThermal managementInvolves heat removal strategies from the Involves heat removal strategies from the
electronic package, PC board and systemelectronic package, PC board and system
Analysis and Technical skillsAnalysis and Technical skillsHeat transfer Heat transfer
Conduction, Convection and RadiationConduction, Convection and RadiationComputational Fluid DynamicsComputational Fluid DynamicsNumerical Numerical modellingmodellingExperimentExperiment
Thermal Analysis for ElectronicsThermal Analysis for Electronics
Slide 16
ConductionConductionheat transfer occur within the solid heat transfer occur within the solid
Convection Convection -- heat transfer by external fluid or gas that heat transfer by external fluid or gas that surround the surfacesurround the surface
Natural ConvectionNatural Convectionheat transfer based on the principle that hot air risesheat transfer based on the principle that hot air rises
Forced ConvectionForced Convectionheat transfer by forced air blown across the surface heat transfer by forced air blown across the surface
RadiationRadiationheat transfer calculation based on energy released by heat transfer calculation based on energy released by
radiation.radiation.
Heat Transfer Mechanism in Electronic Heat Transfer Mechanism in Electronic packagespackages
Slide 17
Source: www.electronics-cooling.com
Major heat pathsPackage top to AirPackage Bottom to boardPackage leads to board
Heat Transfer in Electronic packagesHeat Transfer in Electronic packages
Slide 18
Source: www.electronics-cooling.com
Heat Transfer in Electronic packagesHeat Transfer in Electronic packages
- Need for liquid cooling in the future of thermal management
Various Cooling in ElectronicsVarious Cooling in Electronics
Slide 22
Source: www.electronics-cooling.com
IC package with thermal conduction path to heat sink via TIMsFor high-power applications, TIM resistance becomes an important issueHigher thermal conductivities, BLT and CTEs
Conduction and Heat Spreading Conduction and Heat Spreading Cooling Cooling
- Effect of thickness on heat spreading for various heat source areas,- Material thermal conductivities and - Heat transfer coefficients
Heat Spreading Results Heat Spreading Results
Slide 24
Source: www.electronics-cooling.com
- Fan Cooling limits:- Std Fans with accepted noise level max. heat transfer co-efficient: 150 W/m2K- Heat flux of 1 W/cm2 with 60 C temperature difference
- Macro jet impingement- HTC: 900 W/m2K
- Non std fans/dedicated heat sinks for CPU cooling- Heat flux of 50 W/cm2- 10x better than 15 years ago
- Piezo Fans - Air coooling enhancement - Low power, small and relatively low noise fan used- 100% enhancement over natural convection heat transfer- Research: Perdue, " HeatTransfer Eng., Vol. 25, 2004, pp. 4-14 Synthetic Jet impingement
- Synthetic Jet Cooling
- Nanolightning
High performance Cooling in High performance Cooling in Electronics Electronics
- New approach to increasing the heat transfer coefficient called 'nanolightning , from Purdue . - Based on 'micro-scale ion-driven airflow' using very high electric fields created by nanotubes. - The ionized air molecules are moved by another electric field, thereby inducing secondary airflow [9]. - Cooling a heat flux level of 40 W/cm2 has been reported. - Technology is being commercialized through a start-up company (Thorrn).
- Liquid Cooling ( upto 2000 Kw/cm2 is possible), - Experimental value reported upto 200 kw/cm2- Micro coolers can handle upto 1 kw/cm2
- Direct cooling- Immersion cooling- Jet impingement
- Indirect cooling- Heat pipe - Cold plate
- Micro channels and Mini channels- Electrodynamic and electrowetting cooling- Liquid metal cooling- Thermo electric cooling- Thermionic and Thermotunneling cooling- Super lattice and Heterestructure cooling- Phase change materials and heat accumaltors
Slide 28
Heat Pipe: High Performance Cooling in ElectronicsHeat Pipe: High Performance Cooling in Electronics
Source: www.electronics-cooling.com
Indirect passive coolingEffective thermal conductivity range: 50 kw/mK to 200 kW/mKPerformance of heat pipe: 10 W/cm2 to 300 W/cm2
Simple water heat pipe heatt transfer capacity is 100 W/cm2 (Average):
In general the package therm al perform ance is characterizedbased on the following five different basic therm alparam eters based on heat dissipation requirem ents.
Therm al Resistance : JA, JC & JB
Therm al Characterization param eter : JB
& JT
What are different Thermal numbers?What are different Thermal numbers?
Slide 32
Thermal parameter - Notation
RJA or JA or JMA or JX or JR - Thermal Resistance:Junction to ambient (in still air or moving air)
RJC or JC - Thermal resistance: Junction to caseRJB or JB - Thermal Resistance: Junction to board
JT - Thermal characterization parameter: Junction to top center of the package top
JB - Thermal characterization parameter: Junction to the board
Where,R - Reference point X - Measured locationA - Ambient conditionsMA - Moving air
Slide 33
In general the package therm al perform ance is characterizedbased on the following five different basic therm alparam eters based on heat dissipation requirem ents.
Therm al Resistance : JA, JC & JB
Therm al Characterization param eter : JB
& JT
What are different thermal numbers?What are different thermal numbers?
Slide 34
JA - Junction-to-Ambient Thermal ResistanceDefinition
What does it mean?
- It reflects how well heat flows easily from junction to ambient via all paths.- Relevant for packages used without external heat sinks.
Use of Junction to Ambient Thermal Resistance?
- Used to compare thermal performance of packages for selection of packagetype, materials and package supplier.
- If two packages with same JA
should perform equally well in an actualapplication.
- A package with a lower value of JA
should perform better in an applicationthan one with a higher value. Lower is good.
- Used to calculate package power capability. If package JA is knownpackage power capability can be calculated for a particular application.
- Used to calculate die temperature when environment is similar to the testenvironment. (Formula should be used with great caution).
How to measure this value?
- Mount package on standard JEDEC thermal test board- Put package in standard test environment Wind tunnel or JEDEC enclosure- Apply known amount of power- Measure temperature of chip TJUNCTION and temperature of air TAMBIENT
-
Perform calculation using definition
POWER
TTR AMBINETJUNTION
JA
Slide 35
Junction to Ambient Thermal ResistanceJunction to Ambient Thermal ResistanceNatural ConvectionNatural Convection
Heat Flow In Still AirHeat Flow In Still AirJEDEC Still air boxJEDEC Still air box
Thermal Measurement Thermal Measurement
P
TTR AJ
JA
DefinitionDefinition
Slide 36
Junction to Ambient Thermal ResistanceForced Convection
Heat Flow In Forced AirHeat Flow In Forced Air
P
TTR AJ
JA
DefinitionDefinition
Wind TunnelWind Tunnel
Thermal MeasurementThermal Measurement
TA
TJ
Die
Package
Slide 37
Definition
What it means?
- It measures ease of heat flow between the die and the surface of the package- Relevant for packages used with external heat sinks
Application of Junction to case thermal resistance?
- It applies only to situations in which all or nearly all of heat is flowing out oftop or bottom of package.
- Low value means that heat will flow easily into external heat sink.- It is not a useful thermal characteristics to predict junction temperature
How to measure this value?
- Mount package on standard JEDEC thermal test board or socket- Put package in contact with water-cooled cold plate
- Insulate package from air- Force all heat to flow to cold plate though package surface
- Apply known amount of power- Measure temperature of chip TJUNCTION and temperature of package surface
(case) TCASE.
-
Perform calculation using definition
POWER
TTR CASEJUNTION
JC
JC
Junction-to-Case Thermal Resistance
Slide 38
Measurement of RJC
P
TTR CJ
JC
Thermal MeasurementThermal Measurement
DefinitionDefinition
Heat flow with heat sinkHeat flow with heat sink
Slide 39
Definition
What it means?
- It provides overall thermal resistance between die and the PCB.- Defined to be the difference in the junction temperature and the PCB
temperature closer to the package at center.
How to measure this value?
- Mount package on standard JEDEC thermal test board- Mount thermocouple on board at edge of the package- Applies only for 2S2P test board.- Measure temperature of die TJUNCTION and temperature of the board near to
the package at center location.- Perform calculation using definition.
POWER
TT BOARDJUNTIONJBR
JB
Thermal Resistance: Junction-to-Board
Slide 40
P
TTR BJ
JB
DefinitionDefinition
Measurement FixtureMeasurement Fixture
Thermal Measurement Thermal Measurement
Measurement of RMeasurement of RJBJB
Slide 41
JT Therm al Characterization Param eter:Junction-to-Package Top
Definition
What it means?
- It provides correlation between die temperature and temperature of packageat top center.
- It is not true thermal resistance. Also, is not RJC. Variable with air flow.- It is about 5-10X smaller than RJC.
Application of Junction to Package top thermal characterizationparameter?
- Used to estimate the junction temperature from a measurement of top ofpackage in actual applications environment.
How to measure this value?
- Mount package on standard JEDEC thermal test board- Mount thermocouple on top center of the package- Put package in standard test environment Wind tunnel or JEDEC enclosure- Apply known amount of power- Measure temperature of die TJUNCTION and temperature at top center of
package TTOP
- Perform calculation using definition
POWER
TT TOPJUNTIONJT
Slide 42
Measurement of JT
P
TT TSSJJT JAJTJAR
Thermal MeasurementThermal Measurement
DefinitionDefinition
Thermocouple LocationThermocouple Location
Relationship with RjaRelationship with Rja
Slide 43
JB Therm al C haracteriza tion P aram eter:Junction -to -B oard
Definition
What it means?
- It provides correlation between die temperature and board temperature nearto the package.
- It is not true thermal resistance. Very close to RJB since 80-90% of an diepower flows into the PCB.
- New parameter does not have wide usage yet.- It is defined for both natural and forced air coditions.
Application of Junction to Board thermal characterization parameter?
- Used to estimate the die junction temperature from a measurement of boardin actual applications.
How to measure this value?
- Mount package on standard JEDEC thermal test board- Mount thermocouple on board at edge of the package- Put package in standard test environment Wind tunnel or JEDEC enclosure- Apply known amount of power- Measure temperature of die TJUNCTION and temperature of the board near to
the package.-
Perform calculation using definition.
POWER
TT BOARDJUNTIONJB
Slide 44
Measurement of JB
P
TT BJJB
Thermal MeasurementThermal Measurement
DefinitionDefinition
Thermocouple LocationThermocouple Location
TB
Slide 45
Other related equations
SACSJCJA
JAJTJA
Note: Package jc is very important for heat sink selection
Slide 46
Package with Heat Sink
Silicon DiePackage
Interface MaterialResistance(Assumed 0.2°C/W)
Rja = Rjc+Rcs+Rsa
Ta
Rsa - Heat sink
Rcs - Interface
Rjc - Package
Slide 47
How to select a Heat Sink How to select a Heat Sink
Simulated data of FC package shows case to junction thermal resistance as (Rjc) 0.2°C/W.
Assume the heat sink interface material thermal resistance to be (Rcs) 0.1°C/W
Case 1: Required Rja = 1.67°C/W (P=15 W, Ta = 85°C, Tj = 110°C)
Case 2: Estimated Rja=4.00°C/W (P=15 W, Ta = 50°C, Tj = 110°C)
HDI(Magazine High Density Interconnect)Advanced Packaging magazineASME, Int. Jl. of Electronic PackagingIEEE Trans. on Advanced PackagingIEEE Trans. on Components and Packaging TechnologiesIEEE Trans. on Electronics Packaging Manufacturing