Intel - Thermal Design for Embedded Apps

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Thermal Design

Considerations for

Embedded

ApplicationsDecember 2008

White Paper

Chris Gonzales andHwan Ming Wang

Thermal/MechanicalEngineers

Intel Corporation


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Thermal Design Considerations for Embedded Applications

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Executive SummaryEmbedded Applications differ from the typical desktop, server and mobile

markets. Some of the different requirements for embedded applications

include higher ambient temperatures, need for higher max component

temperature spec, low platform power, long life support, small form

factors, and extended usage conditions (24 x 7 x 365 operation). Due to

these differences there are special considerations for component and

system level thermal solution design.

Thermal solution design requires an engineer to fully understand the

system and various form factor boundary conditions and component level

attributes. This document will define thermal cooling schemes: passive,

active and fanless thermal solutions and their difference via the three

modes of heat transfer (conduction, convection, and radiation). The

thermal performance metrology will be explained, using a thermal

resistance calculation and how to apply to Intel components. The

methodology will highlight typical Intel component specifications such as

TJ-MAX, TCASE-MAX, TAMBIENT and Thermal Design Power (TDP). In addition

some thermal features such as the Digital Thermal Sensor (DTS) and

Thermal Monitor will be explained.


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Introduction

Computing platform component power has decreased as a result of silicontechnology improvement. However, it is still critical to cool the components to

adequately ensure a products long-life reliability.

In embedded applications, there are challenges which are more demanding

than the general computing systems such as desktops, notebooks, andworkstations/servers. The major differences are the target usage model andoperating environment. Typically, embedded applications are in harsh

environments, such as outdoors, factory assembly lines, and telecomm basestations. Conversely, the usual desktop, mobile, and workstation/ server aretypically deployed in homes, offices, and data centers where there are

controlled environmental conditions.

Intel provides a wide variety of embedded processors and chipsets that havefeatures and specifications that are suited for embedded markets. These

components typically have high maximum temperatures limits, long lifeavailability and features such as Digital Thermal Sensor and Enhanced IntelSpeedStep Technology. All of these features will aid the embedded thermalengineer in designing robust thermal solutions for Intel Architecture.

Cooling Methods and Component

Specifications

There are three basic types of thermal solutions for electronics cooling:passive thermal solutions, active thermal solutions and fanless thermal

solutions. The type of cooling solution used in an embedded system will varydepending on the form factor, component specifications, and boundaryconditions. All thermal solutions rely on the three modes of heat transfer to

dissipate the heat from the component: conduction, convection and radiation.

The following sections will explain the different cooling methods as well asIntels component specifications.

Three Modes of Heat Transfer

Conduction

Thermal conduction is the process in which thermal energy transfers through

matter, from a region of higher temperature to lower temperature and acts toequalize the temperature difference. It can also be described as the heatenergy transferred from one material to another by direct contact.

Fouriers Law of Conduction states that the rate of heat flow equals theproduct of the area normal to the heat flow path, the temperature gradient


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along the path and the thermal conductivity of the medium. Heat flux, q is

the rate of heat transfer per unit area and it depends on the direction.

Consider a one dimensional block with one side at a constant T1 and the

other side at a constant T2, where T1 > T2.

Figure 1. One Dimensional Heat Conduction

The total heat flow in the x-direction is expressed by the following equation:

Where:

k - is the conductive heat transfer coefficient

A area of surface contact

L length

Rearranging this same equation you get:

Where conduction thermal resistance is:

In regards to cooling electronic components this equation can be used toexpress a conductive thermal resistance. Thermal resistance (Theta) is a


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method used to represent thermal systems. Thermal resistance is analogous

to electrical resistance.

Figure 2. Thermal Resistance and Electrical Resistance

The thermal resistance calculation will be used when determining thenecessary thermal performance for a keeping a component within its

temperature specification. Conduction is the main mode of heat transferthrough the package and how the heat is transferred out of the package to

the attached thermal solution and the printed circuit board. Typical

designation given for thermal resistance from package junction to ambient islabeled Theta-JA whereas from package junction to board (PCB) is labeled

Theta-JB.

Figure 3. Thermal Resistance of Package to Its Surroundings

Tambient

T unction

Tboard

Theta-JA

Theta-JB

Si die

Substrate

Board


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Convection

Convection is the transfer of thermal energy between two surfaces as a

consequence of a relative velocity between them. The most practical

application is where one surface is a solid and the other is a fluid.

Figure 4. Convection

Newtons law of convection cooling can be written as

)(

= TThAq SS Where:

h Convective heat transfer coefficient

AS Surface Area

TS Surface Temperature

T- Fluid Temperature

In this equation the complexity lies in the determination of the distribution ofthe convective heat transfer coefficient, h. The heat transfer coefficient willdepend on the boundary layer conditions, surface geometry and nature of the

fluid motion. These parameters can be modeled using CFD (ComputationalFluid Dynamics) software to optimize thermal solution design and determinethe amount of convective heat transfer.

Convective heat transfer can also be expressed as a thermal resistance asshown in Figure 5.


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Figure 5. Convective Thermal Resistance

On a basic level, the convective heat transfer can be improved with higherairflow and more surface area. However, it is not always possible to make

the thermal solution larger or increase the airflow, due the constraints ofembedded form factors. Therefore, the thermal solution designer must factorin all the boundary conditions in order to develop a suitable solution.

Convective heat transfer plays a very important role in electronics cooling.This mode of heat transfer (airflow over heatsink) will allow higher powerprocessors to be cooled in most applications.

Radiation

Radiation cooling is the transfer of heat by electromagnetic emission,primarily in the infrared wavelengths. While the transfer of energy byconduction and convection requires the presence of a material medium,

radiation does not. In fact, radiation transfer occurs most effectively in avacuum. Figure 6 graphically represents the radiation heat transfer betweentwo surfaces at different temperatures.


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Figure 6. Radiation

The calculation for radiation emitted from an object can be expressed by the

following equation:

4" STq = Where:

- Emissivity of the object ranges from 0 to 1

- Stefan-Boltzmann constant

TS Surface temperature (absolute temperature)

For the majority of embedded applications, radiation will result in a very smallpercentage of the total heat transfer. The only applications where it will have

significant impact are in fanless designs.

Active Thermal Solutions

An active thermal solution is a heatsink that incorporates a fan attacheddirectly to it. This is the most common type of thermal solution for desktopcomputers. In general embedded applications do not use this type of thermal

solution. These solutions usually require more height above the motherboardthan embedded form factors can provide.


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Figure 7. Active Fan Heatsink

Active solutions typically have very good thermal performance due to the

large volume of the heatsink and the directly attached fan which provides asignificant amount of airflow when compared to other types of thermalsolutions. Active solutions rely on the heat to be conducted from the package

into the heatsink and then removed by the forced air flow flowing in betweenthe heatsink fins. Since the fan is directly attached to the heatsink, the

velocity is usually high and thus results in an overall thermal solution withlow thermal resistance.

Passive Thermal Solution

Passive thermal solutions are the most common type of thermal solution for

embedded applications. This type of thermal solution employs a solid metalheatsink attached to the heat dissipating component and then with system

airflow the heat is removed. Since the airflow is provided by system fan(s),the velocity tends to be much lower than that of an active heatsink, resultingin a lower convection heat transfer coefficient. There could be obstacles, like

motherboard components, that are placed between the system fan and thepassive heatsink, which creates a resistance to the forced air flow from

system fan. In turn, this usually requires a larger heatsink to achieve thesame performance, since the thermal solution must rely on more conductiveheat transfer. The advantage of passive thermal solutions is that they can be

used in form factors where the z-height above the motherboard is limited. Insome usage models, the fans are grouped into an easily removable trayfastened to the system chassis air inlet, which allows for swapping of

defective fan(s) from the system chassis. Below is an example of a passiveheatsink:


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Figure 8. Passive Heatsinks

Fanless Thermal Solution

A fanless thermal solution refers to a solution that does not use a fan (systemor component level) to provide airflow. The only airflow is induced by the

buoyancy effect where hot air moves opposite the direction of gravity and

cool air moves towards the direction of gravity. This air movement is createdby the difference in air density and the resulting velocity is very low.

There are two basic types of fanless solutions:

Conduction Cooled Natural Convection System. This solution isusually referred to a thermal solution in which the heat dissipatingcomponents are attached to the system chassis (via direct contact

or heat pipe); therefore, the chassis acts as a big heatsink. All heatfrom various heat sources will have to be channeled out viaconduction to the chassis. The heat is conducted from the

components to the chassis and then out to the surroundingenvironment via natural convection and radiation. This type of

cooling scheme is very common in In-vehicle infotainment systemsand many military type applications.

The second type of fanless solution would be a standard naturalconvection heatsink mounted to a heat generating component. Anatural convection system chassis will typically have ventilation

slots or a grille to allow for minimal air flow to enter and exit thechassis. This prevents the internal temperature of the chassis

Passive Heatsink

Passive Heatsink on amini-ITX motherboard


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from becoming too high. This solution looks just like a typical fin

heatsink and it relies on natural convection to remove the majorityof the heat to its surroundings, although radiation can positively

impact the performance.

All fanless thermal solutions will be somewhat limited on the amount of heatthat can dissipate. There are many factors that impact the amount of power

that can be dissipated (e.g. max component temperature or ambienttemperature) but a good rule of thumb is to target components that are 10 Wor less.

Design Considerations for a Fanless Solution:

Below are some general recommendations and considerations for a fanlessdesign. The best way to optimize the thermal solution design is through CFDmodeling. Intel provides component level package models that a system

designer can use to develop a robust thermal solution. Through modeling,

the system designer can try many different approaches to solving the thermalchallenge, reduce prototype cost and decrease time to market.

Heat Distribution. Optimizing the heat distribution from the heat source(s)by using multiple heatpipes as a fast heat conduction path to larger area of

system chassis is a good method to improve thermal solution design. Pleaserefer to Figure 9 for illustration of channeling heat from sources tosurrounding environment in a conduction cool system solution.

Figure 9. Heat Transfer Path & Distribution

Heatsink Design. Fin pitch, height, and thickness for natural convectionthermal solution will be different from typical forced convection heatsink fins.

The fin-to-fin spacing should be optimized (larger fin pitch) for the amount ofair flow that is induced by natural convection. Fin height can limit the

Conduction

Convection & Radiation


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radiation of the heat from one surface to the surrounding. The fins on a

fanless solution are typically much thicker than forced convection fins thusallowing more conductive heat transfer from the chassis/heatsink base.

System Orientation. The orientation and mounting of a fanless system willplay a critical part in the heat dissipation effectiveness. Having multiple setsof fin orientations will allow the chassis more flexibility in the orientation in

which the chassis is mounted. The thermal solution will perform better whenthe fins are oriented parallel to the direction of gravity, so ideally it should bemounted in a vertical position to achieve maximum convective heat transfer.

Refer to Figure 10 for a better illustration.

Figure 10. System and Fin Orientation

Surface Emissivity. The amount of heat transferred through radiation from

the outer surface of chassis will be affected by the surface emissivitycharacteristics. The heat transfer via radiation is improved by surfaces withhigher emissivity. A surface's emissivity can be improved by painting the

surface a dark color, with black being the optimum color.

Hot Spot Determination. Through simulations, locating the hot spot(s) isfairly simple and the thermal solution can be optimized to eliminate hot spots.

For example, the heat is localized at one area on the conduction cooledchassis as shown in Figure 11. The fins on the cooler area can be re-assessedif they are necessary on system level cooling. If not then they could be

removed and thus eliminate weight and unnecessary cost.


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Figure 11. Hot Spot Identification

Exotic thermal solutionsThere are a number of other cooling technologies that can be used to remove

the heat from component, these include:

Heat pipes. A heat pipe is a device with highly effective heattransfer from one end of the pipe (hot side) to the opposite side(cold side). For a heat pipe to function properly, a temperature

differential must exist between the hot and cold sides. A heat pipewill be attached to a heat source on one end (evaporator) and aheat exchanger (condenser) on the opposite side. The way that it

operates is the fluid inside a heat pipe will evaporate (by absorbingthe heat from its surroundings) and then flow to the cool side. At

the cool side, the vapor will condense and turn back into fluid. The

fluid will then flow back to the hot side via the wick structure (incapillary action) at the inner wall of the heat pipes. This cycle will

continue to occur as long as the temperature differential exists.Heat pipes are generally used to transfer the heat fromvolumetrically constrained area to larger area where there is more

volume for the heat exchanger. See an example of heat pipe in anactive heatsink in Figure 12. In this case the heat pipes aid in the

removal of heat from the heatsink base and transport the heat tothe fin array where the heat is dissipated by the fins and active

fan.


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Figure 12. Active Heatsink with Heat Pipes

Vapor Chamber. A vapor chamber is very similar in function to aheat pipe. The vapor chamber is manufactured within the heatsinkbase. This in effect creates a heatsink base that is similar to aheat pipe and the vapor chamber increases the heat spreading

within the base. The hot side (component side) of the base will bethe evaporator where heat transforms the liquid in the base into avapor. The heat then moves towards the cooler side (heatsink fins

side). At the cooler side, the heat dissipation through the fins willcondense the vapor back into fluid. The fluid will then return tothe hot side and starts the cycle again. A vapor chamber base will

usually result in higher effective conductivity for the heatsink basewhen compared to copper, but manufacturing costs will increaseand is only effective in high power dissipating applications.

Liquid Cooling. Liquid cooling is very similar to a car radiator in aclosed loop system. A cold plate is attached to the heat generatingcomponent. Through conduction heat is transferred through the

cold plate to the fluid inside. The fluid, usually a water and glycolmixture, is pumped through tubing to a heat exchanger (radiator).The radiator is typically located on the system chassis wall and a

large fan will be attached to the radiator. The heat will be removedfrom the fluid and to the environment via the radiator fins andforced air flow from the fan. The cooled fluid will then flow back

towards the cold plate and continue the cycle. Liquid cooling hasthe advantage of high heat transfer efficiency and can besignificantly quieter that standard thermal solution. However,

additional space for the cooling solution and cost are the majordrawback. Most embedded applications cannot take advantage ofliquid cooling due to the required amount of volume needed for the

total solution.Figure 13 shows a diagram of a liquid cooling

solution.


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Figure 13. Single Phase Liquid Cooling Diagram

TECs (Thermo Electric Coolers). A TEC is a solid state heatpump based on Peltier Effect that moves heat from one end to theother due to an external energy (electrical energy). It is useful inelectronic cooling as well as heating. The polarity of the electrical

current supply will determine which side of the TEC will be hot andwhich will be cold. Depending on the application a computer

system could take advantage of both the hot and the cold. Thedownside of this cooling method is high cost, low efficiency, and it

requires external energy to move heat which in turn increases theoverall power of the system.

In most cases the cost of implementing these solutions will not improve thethermal solution enough to warrant the increase in cost over the typical

thermal solution, except for heat pipes which have become much morereasonable to cost effectively manufacture in the last couple of years.

Intels Component Thermal Specifications

The thermal specifications for Intels components are described below. Theseterms will be used to determine thermal budgeting for thermal solution

design and help determine if a component can be used in an application.

TJUNCTION-MAX Maximum temperature that the die is allowed toreach and still function reliably for the lifetime of the product. Thisis the typical thermal specification for bare die CPUs. It ismeasured at the hottest point within the die. System designers

can monitor the PROCHOT# signal to determine when the max TJhas been reached.


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TCASE-MAX Maximum temperature specification for components withan Integrated Heat Spreader (IHS) on top of the die. It is located

at the geometric center of the IHS. TCASE-MAX requirement alsoapplies to bare die FCBGA type MCH and PBGA type ICH products.

For server class products the thermal specification is called the

Thermal Profile. The Thermal Profile relates the TCASE-MAX value tothe power being dissipated. Refer to the processor datasheet formore information.

Thermal Design Power (TDP) TDP is the realistic-worst casepower dissipation for thermal solution design. TDP is NOTmaximum power nor is it the amount of power that a customersapplication will dissipate in normal operation.

The basic equation for TDP is:

[ ]SiccDiccVccTDP +=

Where:

Vcc - Voltage

Dicc Dynamic Current

Sicc Leakage Current

The dynamic current is determined by testing a wide variety of applicationsand benchmarks. The worst case realistic application will be chosen for thedynamic portion of TDP. The dynamic current will be consistent from part-to-

part of the same CPU (e.g. Intel EP80579 Integrated Processor at 600 MHz).One thing to note is that the dynamic current can vary greatly fromapplication to application. A customers application may not be able to

generate the same amount of power as the TDP application. It is highlyunlikely that an application will be more stressful and cause a part to exceedTDP, but the Intel Thermal Monitor feature is available to control the

processor temperature in the event that TDP is exceeded.

The static or leakage current portion of the TDP is determined by process

technology, temperature, and voltage. The leakage current will be differentfrom part-to-part, so for a given CPU, the power can vary. In order to getthe maximum amount of leakage current, components are tested at their

maximum temperature to ensure that the leakage current is at its highestpossible limit.

Processor Thermal Features

There are a number of features available on Intel processors that aid inprotecting the parts from thermal damage and also provide feedback to theuser on temperature status.

To ease the burden on thermal solutions, the Thermal Monitor feature and

associated logic have been integrated into the silicon of the processor. Onefeature of the Thermal Monitor is the Thermal Control Circuit (TCC). Whenactive, the TCC lowers the processor temperature by reducing power


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The case-to-local ambient thermal characterization parameter (CA) is used

as a measure of the thermal performance of the overall thermal solution. It isdefined by the following equation, and measured in units of C/W:

Equation 1. Case-to-Ambient Thermal Characterization Parameter (CA)

Power

TT AMBIENTCASECA

=

The case-to-local ambient thermal characterization parameter, CA, is

comprised ofCS, the thermal interface material thermal characterization

parameter, and ofSA, the sink-to-local ambient thermal characterization

parameter:

Equation 2. Case-to-Local Ambient Thermal Characterization Paramter Components

SACSCA

+=

CS is strongly dependent on the thermal conductivity and thickness of the

TIM between the heat sink and device package.

SA is a measure of the thermal characterization parameter from the bottom

of the heat sink to the local ambient air. SA is dependent on the heat sink

material, thermal conductivity, and geometry. It is also strongly dependenton the air velocity through the fins of the heat sink. Figure 14 illustrates thecombination of the different thermal characterization parameters.

Figure 14. Thermal Characterization Parameter


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Example: Calculating the Required Thermal Performance

The cooling performance, CA, is defined using the thermal characterizationparameter previously described. The process to determine the required

thermal performance to cool the device includes: Define a target component temperature TCASE-MAX and

corresponding TDP.

Define a target local ambient temperature, TLA. Use Equation 1 and Equation 2 to determine the required thermal

performance needed to cool the device.

The following provides an illustration of how one might determine theappropriate performance targets.

Note: The following example is just an illustration of how to calculate the thermal resistance.The TDP and TCASE-MAX used in the example may not be the actual specifications of the

device. See the component datasheet for actual power and temperaturespecifications.

Assume:

TDP = 13.0 W & TCASE-MAX = 100 C Local processor ambient temperature, TLA = 55C.

Then the following could be calculated using Equation 1 for the givenprocessor frequency:

WCTDP

TT AMBIENTMAXCASECA /46.3

13

55100=

=

=

To determine the required heat sink performance, a heat sink solutionprovider would need to determine CS performance for the selected TIM and

mechanical load configuration. If the heat sink solution were designed to

work with a TIM material performing at CS 0.1 C/W, solving fromEquation 2, the performance needed from the heat sink is:

WCCSCASA /36.31.046.3 ===

If the local ambient temperature is relaxed to 40C, the same calculation canbe carried out to determine the new case-to-ambient thermal resistance:

WCTDP

TTAMBIENTMAXCASE

CA /62.413

40100=

=

=

It is evident from the above calculations that a reduction in the local ambienttemperature has a significant effect on the case-to-ambient thermalresistance requirement. This effect can contribute to a more reasonable

thermal solution including reduced cost, heat sink size, heat sink weight, anda lower system airflow rate.


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More detailed information and reference thermal solutions can be viewed in

product specific thermal design guides located atwww.intel.com/embedded/edc.

Below is a list of typical form factors and the approximate thermalcharacterization parameters and TDP ranges that are achievable. This is justa basic guidance, the actual performance can change based on package

characteristics, and system boundary conditions. Each individual designshould be evaluated on a case by case basis. Take note that the typicalDesktop (ATX) and server (1U and 2U) form factors have much lower

resistance than the embedded form factors (ATCA, CPCI, and AMC).

Figure 15. Approximate Thermal Solution Performance by Form Factor

Cooling Challenges for Embedded

Applications

Thermal management for embedded applications can be more challenging

when compared with traditional markets like server, desktop and mobilecomputing. Some critical parameters to consider for designing embeddedcooling solutions will be discussed in the following sections.

Ambient Temperature

The target ambient temperature for thermal solution design plays a very

important part in the ability to develop an adequate solution. This was shownin the previous section on how to calculate the thermal characterizationparameter. Embedded applications will typically operate in higher than 45C

ambient temperature depending on the target market segment. Whereas
http://www.intel.com/embedded/edchttp://www.intel.com/embedded/edc


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solutions in traditional PCs rarely go beyond 45C, and usually are meant for

operating at below 38C (normal operating temperature for home or office).Some of these higher temperature requirements for embedded applications

are:

+55C for telecommunications equipment. This is requirement forNEBS level 3 qualifications.

+70C for in-vehicle infotainment and other commercialapplications

-40C to +85C for some industrial, military or aerospaceapplications in extended temperature range.

These high ambient temperatures affect the design of cooling solutions forembedded applications. The higher the ambient goes, the lower the

resistance of the thermal solution needs to be in order to meet the maximumcomponents temperature spec. In some cases if the ambient is too high thendesigning a viable solution will not be possible. Thermal solution designers

should understand their target ambient temperature requirements and if atall possible, try to reduce it.

Form Factor and Available Volume for Thermal Solution

The available volumetric solution space for many embedded applications isvery dependant on target application. It is usually smaller and more

constrained than the solution space of typical PC markets. There are multiplereasons for the difference in solution space; some are governed by industrialstandards and some are proprietary form factors that are unique and provide

a niche for certain customers. The following table shows the dimensions ofvarious form factors and the available height for thermal solution. Note that

the embedded form factors are smaller and therefore, the available volumefor a thermal solution is less. Based on lessons from earlier sections in thisdocument it should be noted that a larger heatsink will usually result in abetter performing thermal solution. Table 1 should provide a clearer pictureof space constraints for thermal solutions in embedded applications.

Table 1. Form Factor and Solution Space Height

Form Factor Dimension X, Y, and Z (mm) General Max. SolutionSpace Height1 (mm)

3.5 SBC or ECX 146 x 105 x z2


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uATX 244 x 244 x z3


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The thermal specification for Intel Xeon products is the thermal profile.

The thermal profile relates TCASE specification to the power dissipation. Thisspecification is required to ensure product long term reliability. The thermalprofile for embedded specific processors is different from server product

thermal profile. This is to allow for higher ambient temperatures required byembedded markets.

Figure 16 shows two thermal profiles, Profile A and B, that are meant for 1Userver and 2U standard server products. The standard server will only allowambient temperature of up to 43.5 C and a TCASE of 70C. Whereas, Figure

17 shows the thermal profile for an embedded processor that is targeted fordemanding telecommunication applications. The embedded specific processorhas low power, higher allowable Tcase and is divided into nominal and short

term operating conditions. The nominal operating condition will allow aTAMBIENT of up to 45C and the short term operation condition will allow aTAMBIENT of up to 60C. This thermal profile will allow this processor to meetthe NEBS requirement of short-term excursions to higher ambient operating

temperatures, not to exceed 96 hours per instance, 360 hours per year, anda maximum of 15 instances per year. By tailoring server class processors

with embedded friendly thermal specifications, Intel allows system architectsthe advantage of implementing the latest and greatest processors in theirembedded applications.

Figure 16. Thermal Profile of the Quad-Core Intel Xeon Processor X5400 Series


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Figure 17. Thermal Profile of the Quad-Core Intel Xeon Processor L5408

Extended Usage

The typical usage conditions for embedded computers are different when

compared to a typical PC. In some applications embedded computers will runcontinuously at maximum or very high bandwidth. For the PC environment,the usage is heavily dependant on the PC users, but the system will typically

spend a good amount of time in an idle state or turned off.

Thermal engineers designing for embedded applications will need to consider

the extended usage of the parts at high workloads. When a component

needs to be run in these types of conditions the reliability can be affected. Insome cases it might require a better performing thermal solution so that the

average temperature of the part will be lower. The extended usageconditions can also impact fan selection. Designers will have to choosehigher reliability fans which usually come at a premium price.

Long Life Support

Embedded applications are typically targeted for more than five years ofoperating life and in certain market segments they will require 10 years or

longer of operating life. The embedded components (CPU and chipsets) areavailable for sale for seven years from product launch date. Therefore, the

long term reliability of the thermal solution will have to be considered andincorporated in the design. For example, the thermal interface material (TIM)that sits in between the heatsink base and package must be able to meet the

thermal performance throughout the useful life of five to seven years fortypical embedded usage. Thermal engineers will need to evaluate the thermalperformance of the heatsink at the end of life time based not only on TIM

degradation but the potential for the fastening mechanism (springs, clips,etc.) relaxing over time and not providing enough force on the package.


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Conclusion

Thermal solution design requires a thermal engineer to fully understand thethree modes of heat transfer and how to apply them in their designs.Additionally, embedded markets have more challenges when compared to

typical computing markets (server, desktop and mobile computing).Embedded applications have much stiffer constraints such as, higheroperation ambient temperature, smaller form factors, and continuous

operation. The thermal solution design must take into account the componentspecifications (TCASE-MAX, TJ-MAX, and TDP) and develop a solution that will meetthe system boundary conditions and thermal targets.

Intels Embedded and Communications group provides processors andchipsets that are targeted for these markets and enable system designers tosuccessfully design a thermal solution that will meet both the components

and their systems requirements. For official product specifications, detailedthermal design guides, and embedded reference thermal solutions, visitwww.intel.com/embedded/edc.
http://www.intel.com/embedded/edchttp://www.intel.com/embedded/edc


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Authors

Hwan Ming Wang is a Sr. Thermal/Mechanical Engineer with

Embedded and Communications Group at Intel Corporation.Chris Gonzales is a Sr. Thermal/Mechanical Engineer with

Embedded and Communications Group at Intel Corporation.

Acronyms

SBC Single Board ComputerNEBS Network Equipment Building SpecificationTDP Thermal Design Power

ECX Embedded Compact extended form factorEPIC Embedded Platform for Industrial ComputingEBX Embedded Board expandableATCA Advanced Telecommunications Computing Architecture

DTS Digital Thermal SensorTDP Thermal Design Power


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Intel - Thermal Design for Embedded Apps