thermal management in electronic equipment

Thermal Management in Electronic Equipment

February 2010

Thermal Management in Electronic Equipment | February 2010�

© 2010, HCL Technologies. Reproduction Prohibited. This document is protected under Copyright by the Author, all rights reserved.

Abstract

Development in the electronics industry has come a long way from nascent low performing devices to advanced devices with high computational speed and power. The advancement in the industry led to an exponential increase in power densities, which in turn drove the innovation of smarter and smaller products. These advanced technologies, coupled with miniaturization requirements, guided innovation-driven thermal management in electronic devices. Thermal management is essential in electronics, as it improves reliability and enhances performance by removing heat generated by the devices.

This paper highlights the development and challenges faced in the thermal management of electronic equipment in various domains. It gives an overview of innovative cooling solutions developed over the years. It presents HCL case studies in various domains such as medical, consumer, aerospace and defense, and automotive electronics. It also gives a process flow chart which demonstrates the thermal methodology of electronic equipment in general.

Contents

AbsTRACT 2

InTRoduCTIon 3

MARkET TREnd And ConsuMER dEMAnd 3

nEEd FoR THERMAL MAnAgEMEnT 4

THERMAL MAnAgEMEnT: CHALLEngEs And soLuTIons 6

MEdICAL ELECTRonICs 9

ConsuMER ELECTRonICs 11

AERo & dEFEnsE ELECTRonICs 13

AuToMoTIvE ELECTRonICs 15

PRoCEss FLow 16

ConCLusIon 17

APPEndIx 18

ACRonyMs 18

REFEREnCEs 19

AuTHoRs 19

AbouT HCL 20



Introduction

The phrase thermal management encompasses the technology of the generation, control and dissipation of heat generated in electronic devices and systems. Heat is an inevitable by-product of every electronic device, and is usually disadvantageous to performance and reliability. The electronic packaging trend has been to reduce size and increase performance of the product, both of which contribute to exponential increase in power consumption of the system.

Figure 1: World thermal management market trend (Source: BCC Research, USA)

BCC Research[6] has estimated that global thermal management technology spending increased to an estimated $6.8 billion by the end of 2008 and should reach $11 billion by 2013 [Fig.1]. Report[6] highlights are given below.

The largest end-markets for thermal management technologies in 2007 were the computer industry (57% of total revenues) and telecommunications (16%)

By 2013, medical and office electronics should move into a tie for second place with telecommunications, each with a 12% market share

Market Trend and Consumer Demand

In the past two decades, the conventional electronic industry has become digital savvy, where consumer needs and demands are driving the design and manufacture of products. The electronic industry responded to consumer demand with innovation, offering products which were more powerful than conventional ones, and matching the endless needs of the consumer. The electronic industry can be divided into four broad categories. These categories represent all of the electronic devices in the industry. This section gives the market trend and consumer demands for the aforesaid categories.

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Medical Electronics

According to Prismark Partners[13], approximately $53 billion was spent on non-IT medical electronics equipment in 2006, accounting for 4% of the global electronics industry

This amount is expected to reach $66 billion in 2010

Consumer Electronics

Consumer electronics[14] sales are expected to hit 724 billion dollars in 2009, That’s up 4.3 percent from the 694 billion dollars in 2008

Flat panel displays were accounted for 57.2% of materials by 2003, and then to grow to 82.3% of the total by 2013

The value of worldwide shipments of display materials were reached $13.6 billion by 2003 and then to the growth of $30.8 billion by 2013

The value of CRT glass represented more than 88% of all CRT materials used

Aero & Defense Electronics

The performance of the market[10] is forecast to decelerate, with an anticipated CAGR of 3.6 percent for the five-year period 2006-2011, expected to drive the market to a value of US$1,096 billion by the end of 2011

The US and European markets will grow over the same period with CAGRs of 3.4 percent and 3.9 percent respectively, to reach the values of US$594.5 billion and US$284.3 billion respectively in 2011

Automotive Electronics

The automotive ASIC market[11] was worth $2.99 billion in 2006, and a compound annual growth rate of 8.2 percent would put it at $4.10 billion by 2010

Need for Thermal Management

If we observe the statistics of market trends and consumer demand in electronics, there has been an explosive growth in the industry. The tremendous growth in electronic equipment demands innovative solutions to the new challenges of thermal management. The major challenges on the thermal management front can be understood by the heat dissipation of electronic devices, which vary from 5 W/cm2 on a PWB to 2000 W/cm2 for a semiconductor laser. Providing cooling solution for former heat flux is manageable, but for later heat flux is very difficult, and needs novel cooling solutions. This will be further explained in Fig. 2.

In general, a vehicle re-entering the Earth’s atmosphere will have the highest heat flux on its surface. Figure 2 shows the heat flux variation with comparative technologies trend. VLSI electronics heat flux can be comparable with that of re-entry heat flux; this heat flux is very high. Thermal management must be provided for these electronics.

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Figure 2: Heat flux vs. comparative technologies trend (Source: Charlespoint Group Boston, MA)

Further, the junction temperature of the chip has to be maintained below the allowable limit specified by the vendor in most cases for both performance and reliability factor. Reliability[1] is defined as the probability that a device will perform its required function under stated conditions for a specific period of time. Product reliability is seen as the single most important factor to determine the quality and superiority of product technology. Stringent standards and guidelines to ensure user safety have revolutionized development in the packaging industry The need for increased reliability has energized the industry to seek the latest cutting-edge technology solutions.

From a reliability and performance point of view, thermal management needs to be carried out for every electronic device which dissipates heat. This is essential for modern electronics, for as they consume more power, they also generate more heat. This has led to the development of computational fluid dynamics (CFD) simulation software and advances in thermal management techniques. The increasing complexity and power density of modern electronics has challenged the traditional approach of using prototypes and testing. The modern CFD simulation software developed for challenging environments and high power dissipation devices has led to a reduction in the product development cycle.



Thermal Management: Challenges and Solutions

This section describes various challenges faced in thermal management and the novel solutions for the ever growing challenges.

Thermal Management Challenges

The following are thermal management challenges in electronic equipment:

Reduced form factors

Ever growing power densities

Harsh environments

Product miniaturization

Reducing product cost

Reliability and performance constraints

Meeting stringent standards

Development of advanced technologies and materials

Increasing consumer demands and needsThe next section explains some of the thermal management solutions developed over the years.

Thermal Management Solutions

Solutions were developed based on thermal requirements of electronic equipment. Thermal management of electronic devices can be classified on two broad-based parameters, i.e. product level and industry level. The product level can be further classified into two levels.

Printed wire board (PWB) level DIMMs, power cards, processors, chips and various components

System level Single rack (e.g. servers, etc.)

Multiple racks (e.g. data center, etc.)

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Figure 3: Analysis level vs. industry trend (Source: HCL Technologies Ltd)



Figure 3 shows the distribution of thermal management in industry levels with that of component, board and system level analysis. The comparative data highlights the focus of industry led innovation. For instance, the medical electronics industry is more focused on making products at system level, whereas consumer electronics focuses more on component level analysis (like the semiconductor industry).

The latest technologies in the thermal management arena function in and around the basic heat transfer modes, i.e. conduction, convection (natural and forced) and radiation. Development has reached a stage where the technologies overlap the basic functional industrial domains. Figure 4 gives the usage percentage of each mode of heat transfer technology in various domains. Depending upon the requirement in the respective domains, a different mode of heat transfer will be chosen accordingly. For example, the medical electronics domain will use primarily conduction cooling technology, whereas consumer electronics will mostly use natural convection heat transfer technology.

Figure 4: Industry vs. heat transfer technologies trend (Source: HCL Technologies Ltd)

Figure 5: Heat flux vs. year of cooling technology development (Source: IBM USA[7])



The chip cooling technologies are evolving over the years to accommodate steep increase in heat flux. Figure 5 shows the plot between advancement in cooling technology and chip heat flux. The exponential curve shows the increase in the heat flux and changes in the cooling technologies. Future cooling solutions are being developed around multi-phase heat transfer technologies. The cooling technologies such as thermal vapor chamber, cold plates and jet impingement mechanisms have revolutionized the future of the thermal management landscape.

The solution for these challenging thermal tasks has led to novelty in thermal management. The development of technologies is moving from single-phase heat transfer to multi-phase heat transfer, which has led to the design of advanced cooling solutions. The latest cooling technologies leverage nanotechnology and the advancement in smart materials. Figure 6 briefly explains the various innovative cooling solutions available in the thermal management industry.

Figure 6: Innovative cooling solutions



Medical Electronics

The medical electronics area has traditionally included implantable medical devices, medical diagnostic tools and monitoring devices. Today, however, the market is being fueled by an explosive growth in personal medical equipment. Driven by the need to reduce healthcare costs, patients’ desires to manage their own health, and an increased emphasis on preventive medicine, the adoption of consumer based, portable and often wearable medical products is increasing at a substantial rate. The major medical products can be classified into two categories.

Large infrastructure equipmentMedical imaging systems (e.g. X-ray and MRI)

IT equipment (e.g. picture archival communication systems)

Biochemical analysis equipment (e.g. lab instruments and DNA analyzers)

Small stationary - portable equipmentPatient monitoring systems

Bedside monitoring units

Challenges

Meeting stringent medical standards

Overall reliability requirements, including component reliability, test methods and standards

Limited space and closed-case environment

The acoustic design standards limit the use of moving parts

Advancement in printed circuit board (PCB) substrate technology provides a new challenge when using conduction cooling technique

In-depth understanding of RF technology and potential communication interference between medical devices and other products

HCL Case Study: Thermal Analysis of Bed Side Monitor Unit

The bedside monitor unit is designed for high packaging factor, plus low EMI/EMC and noise levels. It consists of multiple input output boards dissipating 90W of heat, and was designed to meet Ingress protection standards. A typical bedside monitor unit is shown in Fig. 7.

Thermal Challenges

Low EMI/EMC design

High packaging factor

Very low noise levels

Power dissipation is 80W

Qualifying for ingress protection standards

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Thermal Management in Electronic Equipment | February 201010


Cooling Solution

Special baffles were designed to divert the flow from fans to heat sink as the EMI/EMC shields were obstructing the flow

With the help of dedicated ducts, pressure drop was optimized inside the system

To reduce the temperature of the unit, low thermal conductive material was used between heat dissipating chips and the unit surface

A low-noise fan was chosen to meet noise and vibration standards

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Figure 7: Bedside monitor unit

Thermal Management in Electronic Equipment | February 201011


Consumer Electronics

In this era of communications and entertainment, growth of consumer electronics is exploding. Consumer demand for increased mobility, wireless connectivity and advanced features demand has paved the way for a variety of new products, including servers, laptops, ruggedized laptops, hybrid routers, data centers and cameras. The silicon solutions driving these products are more highly integrated than ever before, as advancements in process technology are delivering system-on-a-chip (SoC) solutions that are smaller, faster, and lower cost. These trends, along with the broad range of emerging equipment, require diversity in new IC package types to meet specific applications.

The evolution of the microprocessor from a 486 Intel chip to a multi-core processor shows the exponential increase in power density needed to achieve superior computing power. Figure 8 shows the comparative changes in processor wattage over the years. The obvious change in the processors is the amount of power consumption, which has increased from 70W to 250W in the last decade. This power consumption has challenged the industry to create cutting edge technologies to deal with thermal management.

Consumer electronics thermal management is one of the most challenging and innovative in the entire technological landscape. The semiconductor which involves chip cooling to server and datacenter cooling has led to innovation of some of the finest cooling technologies in the field of thermal management (Fig. 6).

Figure 8: Power vs. chip development (Source: HCL Technologies Ltd)

Challenges

Harsh environment

High power dissipation

Miniaturization

Competitive packaging factor with overall high heat flux

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Components with a lower form factor pose a challenge due to obstructed flow passage

Acoustic and vibration standards

Ineffective and insufficient airflow distribution

HCL Case Study: Thermal Management of Multi-Core Processor

Until now in the electronic industry, a passive cooling solution has dominated previous generation processors. This solution is very cumbersome and noisy because it contains a big heat sink, heat pipes and a dedicated fan. This system consists of a multi-core processer. The total power consumption of the unit is 220W. Since it is a next generation processor (number of cores and power dissipation was more), the thermal management is even more cumbersome and challenging. There is a need to provide a feasible thermal cooling solution for this processor at high ambient temperature. Thermal management in a multi-core processor is shown in Fig. 9.

Thermal Challenges

High ambient temperature

High power dissipation = 220W

Pressure drop should be minimum

Cooling Solution

A novel cold plate has been designed for the multi-core processor

The number of passes for the cold plate was optimized with a constraint on minimizing the pressure drop

A simple, reliable, hassle-free and optimal cold plate has been designed for next generation processors

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Figure 9: Cold plate technology for multi-core processor cooling



Aero & Defense Electronics

The Aero and Defense industry is entering a transformational change with more power efficient and higher power density components. Thermal and power management are widely considered to be the crucial links in the ability to embrace high performance advanced technology. The development in directed-energy weapons and UAVs is growing, and these innovations require ultra-efficient energy systems. The products include electric power generating, distribution, management and control systems, auxiliary power units, LRUs, and environmental control systems

Current and future generation processors are making it difficult for military systems designers to efficiently manage thermals in mission critical systems, forcing thermal engineers to devise novel methods of thermal management.

Aero and Defense electronics thermal management is one of the most sensitive to the environment and most stringent in the entire technological landscape. The lightweight carbon thermal-management systems, fuel cells, CNT thermal interface and spray cooling are innovations of the decade which are meeting the tough requirement of Aero standards.

Challenges

Require more power, but have less space

High functional density

Compatibility with two-level maintenance

Ability to facilitate insertion of new technology and mitigate component obsolescence

Harsh environment conditions with high product reliability

Adherences to RTCA DO Standards

HCL Case Study: Thermal Simulation of Line Replace Unit

In Aero and Defense, the typical field problem in line replacement units (LRUs) of an aircraft involves the rapid thermal runaway in electrical components due to the high power density of 6,750W. It consists of electrical components including IGBTs, transformers, inductors and bus bars. There is a need to consider the joule heating effect on bus bars while optimizing them. A detailed modeling of these components was done, and the LRU is shown in Fig. 10.

Thermal Challenges

Altitude condition

Cooling high power density components such as IGBTs, transformers and inductors

High power dissipation = 6,750W

Bus bars design and optimization with joule heating effect

Pumping power should be minimum

Detailed modeling of transformers, inductors and bus bars

Preventing thermal runaway

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Cooling Solution

Detailed modeling was done for complex transformers, inductors and bus bars

The cooling solution was provided using liquid technology

The cold plate was designed for optimum velocity and pressure drop

Complex bus bars were designed and optimized

Joule heating effect was evaluated with respect to optimum bus bar design

Transformers and inductors were cooled by routing the flow through the optimized channels

Cold plate has been optimized with respect to pressure drop

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Figure 10: Line replacement unit



Automotive Electronics

The quantity, value and complexity of electronics in passenger vehicles continue to rise. This brings a corresponding increase in shielding, grounding and thermal management challenges for the automotive design engineer. Vehicle electronics can be loosely split into ‘in cab’ and ‘out of cab’ applications.

In cab applicationsHeating ventilation and air conditioning (HVAC)

Instrument panels

Radios

Infotainment

Satellite navigation

Head-up displays

Out of cab applicationsEngine management ECUs

Braking ECUs

Diverse array of sensor units

The emergence and evolution of thick, soft thermal gap fillers in either die-cut sheet or form-in-place formats range has enabled engineers to effectively couple surface-mount devices to a chassis or enclosure. At the same time, this approach can often simplify and speed module assembly by removing the need for some mechanical fixes.

Challenges

High engine temperature environment

Harsh operating conditions

Stringent automobile standards

Use of commercially available, off-the-shelf items to control product cost

Electronics modules in passenger vehicles, particularly those mounted out-of-cab, are often sealed to prevent moisture ingress, which makes it very challenging to provide a cooling solution

Cooling techniques are limited to conduction and “limited” convection

Under-bonnet modules are often exposed to extreme temperatures coupled with smaller footprints

Protecting modules from damage or malfunction due to spurious electrical signals through EMI/EMC shielding

HCL Case Study: Thermal Analysis of Motor Control Unit

The development of the electric car has propelled the need for thermal management in the electric motor. The electric motor couples inductors and a rotating hub to produce wheel motion.

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Heat is a by-product of this mechanism. The thermal wattage is around 1.5kw A typical motor control unit is shown in Fig. 11.

Thermal Challenges

High thermal dissipation = 1.5kw Modeling of inductors

Design of an optimal flow channel

Selection of a coolant

Pumping power should be minimized

Complexity of the model and flow

Cooling Solution

Glycol-based water cooling jackets were designed to transfer the high wattage

Optimal coolant pumping rate was found where pumping power is minimized

Coolant fluid flow channels are optimized for maximum heat transfer and minimum pressure drop

Complex inductors were modeled

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Figure 11: Motor control unit

Process Flow

A thermal engineer makes use of industry-wide best practices and his judgment for engineering design decisions. The three most important proponents in making engineering decisions: 1. Understand the heat transfer circuit of the system (i.e. convection, conduction and radiation); 2. A thermal equivalent model for analysis needs to be identified for mimicking the exact model; 3. A process flow chart must be designed to reduce errors in the model and analysis, and to obtain the results quickly. Figure 12 shows the indicative best practice for the thermal simulation of board level and system level product designs.



Figure 12: Thermal management methodology (Source: HCL Technologies Ltd)

Conclusion

This paper highlights the importance of thermal management (reliability and performance of devices) in electronic equipment with respect to ever increasing product packaging factors, thermal wattages, and consumer needs. A glimpse of market trends and consumer demand for electronics was presented, with a view of the increasing importance of thermal management. Thermal management needs, challenges and solutions were also highlighted. An overview of specialized cooling solutions has been given with respect to product advancement. Case studies were presented in various domains (medical, consumer, aero & defense and automotive electronics) to illustrate HCL’s capabilities. A thermal management methodology flow chart was designed using best practices, and simulation approaches from the industry were also presented. As needs and demands grow every day, thermal management technology will continue to evolve.



Appendix

Source HCL Technologies Ltd: The data represented in this paper is from the vast experience of HCL Technologies in Thermal Management. The data is collected from 100 different products in each of the following domains (Medical electronics, Consumer electronics, Aero/ Defense electronics and Automotive electronics).

Acronyms

CFD Computational Fluid Dynamics

CNT Carbon Nanotubes

CRT Cathode Ray Tube

DIMM Dual In-line Memory Module

ECU Engine Control Unit

EMI/EMC Electromagnetic Interference/ Compatibility

IC Integrated Circuit

IGBT Insulated Gate Bipolar Transistor

LRU Line Replace Unit

PWB/PCB Printed Wiring Board/ Printed Circuit Board

RF Radio Frequency

UAV Unmanned Aerial Vehicle

VLSI Very Large Scale Integration



References

1. Scott Speaks Vicor, ‘Reliability and MTBF Overview’, Vicor Reliability Engineering, Europe

2. Tai Phan and Joseph Steinman, ‘AMC/ATCA Thermal Management: A Case Study’, Interphase Corporation

3. Dr. Robert Hannemann, ‘Thermal Control of Electronics: Perspectives and Prospects’, Charlespoint Group, Boston, MA

4. Joseph Fjelstad, ‘Thermal Management Challenges’, Verdant Electronics

5. Roger Schmidt, ‘Data Center Trends and Power Management’, IBM USA

6. BCC Research, http://www.bccresearch.com/report/SMC024E.html

7. Richard C. Chu, ‘Thermal Management Roadmap: Cooling Electronic Products from Hand-Held Devices to Supercomputers’, IBM USA

8. http://www.omai.com.cn/en/shownews.asp?id=165

9. http://en.kioskea.net/news/11734-growth-in-consumer-electronics-sales-to-slow-in-2009

10. http://www.ebis.com.sg/Portals/0/pdfs/InfoByte/Public/Aerospace%20&%20Defense.pdf

11. http://www.eetasia.com/ART_8800480602_499501_NT_d2dce9db.HTM

12. http://www.ti.com/research/docs/SemiconductorPackagingWP.pdf

13. http://www.prismark.com/

AuthorsJagadish Thammanna is a Manager and Heads the CFD and Thermal team at HCL Technologies. He has 15 years of experience in Thermal management in all the niche domains and various cross-application industries. His areas of interest include Computational Fluid Dynamics, heat transfer and scientific programming. In his vast experience, he has presented and published many national and international papers at technical symposiums.

Ambuj Srivastav is a Thermal Analyst at HCL Technologies. He has 5 years of experience in designing and developing innovative solutions for the thermal management of electronic devices, and his core domain areas expertise lies in thermal management of aerospace and automotive lines of products. His experience in industry wide practices has given him insight to work on the cutting edge and the latest technologies in thermal management.

Thermal Management in Electronic Equipment | February 2010�0


About HCL Enterprise

HCL is a $5 billion leading global Technology and IT Enterprise that comprises two companies listed in India - HCL Technologies & HCL Infosystems. Founded in 1976, HCL is one of India’s original IT garage start-ups, a pioneer of modern computing, and a global transformational enterprise today. Its range of offerings spans Product Engineering, Custom & Package Applications, BPO, IT Infrastructure Services, IT Hardware, Systems Integration, and distribution of ICT products across a wide range of focused industry verticals. The HCL team comprises over 62,000 professionals of diverse nationalities, who operate from 26 countries including over 500 points of presence in India. HCL has global partnerships with several leading Fortune 1000 firms, including leading IT and Technology firms. For more information, please visit www.hcl.in

ABOUT HCL

HCL Technologies

HCL Technologies is a leading global IT services company, working with clients in the areas that impact and redefine the core of their businesses. Since its inception into the global landscape after its IPO in 1999, HCL focuses on ‘transformational outsourcing’, underlined by innovation and value creation, and offers integrated portfolio of services including software-led IT solutions, remote infrastructure management, engineering and R&D services and BPO. HCL leverages its extensive global offshore infrastructure and network of offices in 26 countries to provide holistic, multi-service delivery in key industry verticals including Financial Services, Manufacturing, Consumer Services, Public Services and Healthcare. HCL takes pride in its philosophy of ‘Employee First’ which empowers our 55,688 transformers to create a real value for the customers. HCL Technologies, along with its subsidiaries, had consolidated revenues of US$ 2.5 billion (Rs. 11,833 crores), as on 31st December 2009 (on LTM basis). For more information, please visit www.hcltech.com

thermal management in electronic equipment

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