August 9th 2017- Day 1
7:00 am – Registration Open/Breakfast
8:00 am – Welcome/Keynote Address
Fanless Thermal Solution Design Guide for IoT Applications
The internet of things (IoT) network of interconnected devices is driving an explosion of integrated-electronic components (IC) for embedded applications. Transceivers and computers in this segment are adapting a module based approach, where the memory, logic or RF, and power regulating components are placed on a single board. These module based systems and sensors will be deployed at the IoT edge, where environmental considerations have challenging implications for thermal and mechanical design.
In order to function reliably in harsh environments with extended operating ambient temperature ranges, electronics housings for IoT solutions that support low-power components with fan-less designs in sealed enclosures will be desirable. This paper is intended to be a practical guide for the thermal designer to quickly size and implement an optimized fanless thermal solution. We review the boundary conditions applicable to various segments relevant to IoT applications. We then present a guide for fanless thermal solution design, with an overview of analytical free-convection plate-fin heatsink optimization, radiation considerations, TIM selection, as well other relevant fanless boundary condition concerns.
We begin with simplified equations for back-of-the envelope sizing calculations and then dive into analytical expressions for optimizing the heatsink fin spacing. We then compare the simplified computations with extensive simulation results and provide heatsink size dimensions based on segment ambient specifications for a typical IoT compute module with varying thermal design power, fin height aspect ratio, and heatsink material. Finally, we present a simplified example of an automotive software defined cockpit (SDC) design to demonstrate the application of these design considerations.
Mike Schroeder, Thermal Mechanical Systems Engineer - Intel Corp.
8:45 am – Featured Presentation from Minteq International, Inc.
High Flux Flow Boiling Microchannel Heat Exchanger for Compact Electronic Systems
Microchannel flow boiling is an attractive thermal management strategy for ever-growing volumetric heat dissipation demands associated with electronic systems. For example, modern laser diodes can yield heat fluxes of greater than 1 kW cm-2, and packing constraints push the volumetric heat dissipation rates above 10 kW cm-3. Cooling large arrays of laser diodes using single-phase convection heat transfer has been investigated for more than two decades by multiple investigators. Unfortunately, either large fluid temperature increases or very high flow velocities must be utilized to reject heat to a single phase fluid, and the practical threshold for single phase convective cooling of laser diodes appears to have been reached. In contrast, liquid-vapor phase change heat transport can occur with a negligible increase in temperature and, due to a high enthalpy of vaporization, at comparatively low mass flow rates.
In the present study, flow boiling heat transfer at heat fluxes up to 1.1 kW cm-2 was investigated in a microchannel heat sink with plurality of very small channels (45 × 200 microns) using R134a as the phase change fluid. The high aspect ratio channels (4.4:1) were manufactured using MEMS fabrication techniques, which yielded a large heat transfer surface area to volume ratio in the vicinity of the heating element. To characterize the heat transfer performance, a test facility was constructed that enabled testing over a range of fluid saturation temperatures. Due to the very small geometric features, significant heat spreading was observed. The performance of this heat sink was investigated using a detailed computational modeling utilizing FEA with Comsol combined with Matlab to examine the applicability of available heat transfer correlations for use to determine the performance of packaged electronic systems with high heat flux dissipation requirements.
Dr. Todd Bandhauer is an Assistant Professor in the Department of Mechanical Engineering and the Director of the Interdisciplinary Thermal Science Laboratory – Colorado State University
10:15 am – Networking Break and Dedicated Expo Time
Advanced Thermal Material Solutions
Thermal issues in printed circuit boards and their related assemblies are becoming as important as the Signal Integrity that typically dominate discussions of design and manufacture of said printed circuit boards. The relationship between the materials used and the thermal functionality is being sharply focused as the industry sectors tackle issues of reliability, aging and functionality.
Costs and the value analysis between thermal transfer rates and materials used, are fast becoming a design discipline that has huge effects on final assembly cost, and thermal functionality. Martin’s presentation sets out to show firstly what these new generation materials are, their background and how we got to the current solutions being used in various market sectors. Discussion on the next generation of Insulated Metal Substrates (IMS) and pre-pregs for printed circuit boards and hybrid constructions will be covered. Design and the value analysis required to lower cost in the final assembly while maintaining thermal function will be reviewed. Finally, the myths and misunderstandings around thermal materials and how to use them will be explained.
Martin Cotton, Director OEM Technology – Ventec International Group
High Efficient Heat Dissipation on Printed Circuit Boards
This paper describes the various techniques for effectively dissipating heat from heat generating electrical components on printed circuit boards. Small copper coins that are matching the shape of the electrical components are located underneath the component and are integrated in the PCB construction. The heat from the component will be dissipated by the copper coin to a heat sink. The thermal conductivity of such kind of copper coin is about 10 times higher than usually achieved with so called thermal via arrays. Several different methods of integrating copper coins into the construction of PCB’s have been developed and will be presented.
New developments such as the “Chip-on-Coin” technique are providing solutions for highly miniaturised electronic circuits and micropackaging. The integration of copper coins into PCB’s is suitable for all common substrates including RF and microwave substrates as well as for conventional PCB substrates. Just recently also rigid-flexible circuit boards can be equipped with copper coins.
Markus Wille ∙ R&D Manager – Schoeller Electronics Systems GmbH
12:20 pm – Networking Lunch
Thermal Conductivity Measurement by Steady-State and Flash Diffusivity Methods and Instruments
The thermal managements of any systems require reliable thermal conductivity data of the components that are employed. Understanding both the advantage and limitation of various measurement methods and instruments associated with the thermal conductivity range of materials, geometries and sizes of the samples available for testing, sample status (solid, powder, liquid) is essential to choose the proper methods in accordance with ASTM, ISO standards to obtain reliable thermal conductivity data.
The presentation will cover the measuring principles and instrumentations of heat flow thermal conductivity meters, and flash diffusivity analyzers, and their applications on various materials such as polymers, metal/alloys, carbon/graphite, ceramics, liquids/pastes/powders in different shapes, sizes, and status in the temperature range -150°C to 1600°C. The comparisons between different methods and the cautions that must be taken for the correct measurement are discussed.
Kadine Mohomed, Ph.D, Applications Manager – TA Instruments
Piero Scotto, Manager, ThermoPhysical Properties Product line – TA Instruments
Heng Wang, Ph.D., Sr. Product Marketing Specialist, Thermophysical Properties - TA Instruments
Detailed PCB Trace Modeling with Thermal Territories
Electronics today are designed into dynamic and miniaturized products. The dynamic thermal behavior of the electronic system influences its operation, reliability, and in some circumstances the end-user experience. The PCB copper distribution plays a significant role in the cooling of a miniaturized product to efficiently conduct the heat away from the heat generating components.
Accurately modeling detailed PCB traces in a system level thermal analysis is challenging. Historically the process involved the creation of 3D MCAD geometry from a set of 2D drawings. Other methods involve processing the PCB layout images to determine effective material properties. More recently thermal analysis tools have been able to convert PCB layout files directly to thermal models but generally lack the ability to control the models resolution of detail. The ability to resolve a PCB layout file directly greatly reduces the model development time but modeling an entire PCB with expicit traces is computionally inefficient for most system level thermal design scenarios. The current best approach balances thermal model accuracy with computational expense through the concept of Thermal Territories. A Thermal Territory represents the distance away from the critical IC component, both laterally and PCB layer depth, that the copper will be resolved explicitly.
A brief overview of the methods of capturing PCB copper distribution is discussed including the advantages and disadvantages of each process. Examples of the thermal predictions based upon these methods will be shown. The concept of Thermal Territories will be introduced and examples shown that compare the relative accuracy gain when explicitly capturing the copper distribution from the heat source outwards.
John Wilson, Electronics Product Specialist - Mentor Graphics Corp.
Modeling of Thermal-Mechanical Instabilities: from Macroscale to Microscale
High-speed sliding systems involve contact interfaces with frictional heat generation. A disturbance might change the otherwise uniform temperature distribution, and hence the thermal expansion and the rate of heat generation. If the sliding speed is sufficiently high, the thermal-mechanical feedback is unstable, leading eventually to the localization of high temperature in small regions of the contact area, known as hot spots. This phenomenon, generally named as thermoelastic instability or TEI, can cause vibration, excessive wear, material damage and fatigue failure.
To mitigate the effects of TEI, a finite element code HotSpotter is developed for evaluating the susceptibility of sliding systems to the phenomenon. In HotSpotter an eigenvalue scheme is employed to find the exponential growth rate of temperature. The critical sliding speed is then determined by searching for the lowest speed at which at least one thermal mode has a positive growth. The parametric studies are performed to find the optimal designs for brakes and clutches against TEI.
On the other hand, MEMS resonators are important electromechanical devices that can resonate at certain ranges of frequencies for a variety of applications. Minimizing the energy loss (damping) or achieving a high quality factor is often a key design objective for these devices. Recently it is strongly evident that thermoelastic damping (TED) is a dominant source of intrinsic damping in silicon resonators operating at high frequencies. It has been found that the mechanism of TED is analogous to that of TEI. Briefly the phenomenon is induced by the irreversible heat dissipation during the coupling of heat transfer and thermoelastic strain rate in an oscillating system. A computational model is developed to elucidate the geometrical, material and multiphysical effects on the TED energy loss in silicon resonators. This research will potentially impact the internet technology, biomedical sensors and digital electronics.
Yun-Bo Yi, Ph.D., Associate Professor, Mechanical & Materials Engineering
University of Denver
3:20 pm – Networking Break and Expo Time
Digital Temperature Sensors are Revolutionizing the safety and Reliability of Electronic Products
It seems like almost daily a news flash talks about some electronic product overheating, causing potentially catastrophic problems. While an overly hot product can, of course, cause problems, the correct thermal management of the inevitable heat should be a part of sensible and prudent product design. This session will explain the internal user-programmable registers contained in Digital Output (I2C protocol) temperature sensors as well as the two main issues when using these registers and possible design solutions.
The first issue is that most user-programmable registers are volatile memory type registers which means once power is removed, the register’s stored data values are not saved or retained. The second issue is, since these volatile memory registers have to be updated upon each system power up and initialization sequence, this could create a high risk and unreliability timing event allowing the opportunity for these registers to be inadvertently misconfigured and set to the wrong settings which could cause run away heat issues in the product.
We’ll discuss how integrating non-volatile memory registers inside the temperature sensor to store these data settings, even after power is removed, can solve both of these critical issues. Furthermore, being able to either reversibly or permanently lock down the integrated nonvolatile registers such that it would prevent any register data changes against any future erroneous misconfiguration or data tampering would significantly increase the non-volatile register value in a product. This also increases system reliability and safety while helping to reduce any product liability exposure issues.
Bryce Morgan, Product Manager, Mixed Signal and Linear Division
Microchip Technology Corp.
Heat Pipes as Thermal Solution for PCBs
Rapidly ongoing miniaturization in combination with increasing electronic functionality -particularly in high end applications- leads to the need of progresses in the PCB cooling technology. Improved thermal performance of PCBs should allow -with lowest possible additional cost- to remove the power loss from components in such a way that their maximum temperature during operation does not exceed allowed levels. Heat decentralization, i.e., heat spreading and heat guiding in the PCB is one opportunity to achieve high cooling effectiveness from passive systems. In order to provide an effective heat transport from the chip into the lateral direction of the PCB, embedded miniaturized heat pipes are a promising solution for the heat spreading problem.
Jonathan Silvano de Sousa, PhD, Project Leader R&D – AT&S Austria
5:00 pm – Cocktail Reception
August 10th 2017 – Day 2
7:30 am – Registration Opens and Breakfast
8:00 am – Day 2 Keynote
Lightweight Thermal Management Solutions with Carbon Fiber
This session will discuss thermal interface materials (TIMs) that consist of sparse carbon fiber velvets attached to a film of polymer or metal. The fiber packing density and orientation are selected to serve a wide range of applications, including hostile thermal and chemical environments, sliding interfaces, and interfaces with widely varying gaps. They can be coated for electrical isolation. They require low contact pressure and provide high thermal conductivity. Their light weight and high compliance make them uniquely suited for aerospace, industrial and high performance commercial devices.
These phase change material (PCM) composite heatsinks consist of a conductive carbon fiber velvet embedded with a suitable alkane (“paraffin”) having high latent heat at its melting point. Such heatsinks offer passive thermal control for instruments that would otherwise overheat or undercool during periodic operations. A typical application involves lasers that dissipate heat but need tight thermal control where active cooling is unavailable.
Michael Mo, CEO – KULR Technology
Thermal Runaway Prevention of Li-ion Batteries by Novel Thermal Management System
Due to their energy density, higher voltage, and negligible memory effects, lithium-ion batteries are the popular choice for a wide range of applications. Larger power demands and increasing cell density of lithium-ion battery packs result in high operating temperatures, especially under peak loads. Because of the susceptibility of most commercial lithium-ion cell chemistries to degrade or age at or above 60°C, this leads to rapid loss of capacity over subsequent charge/discharge cycles as well as reduced overall power output. Reducing detrimental thermal effects through the use of latent heat system (LHS) materials that absorb and store thermal energy, has proven highly effective.
Another impressive feature of LHS Battery Materials is their ability to eliminate the potential for Thermal Runaway or Propagation in battery packs. Thermal Runaway and Propagation potential is a growing safety concern in many applications due to the possibility of serious fire in the event the cells are physically damaged or short circuited.
A novel thermal management system will be demonstrated which offers a solution to both these safety and performance concerns through the use of latent heat storage (LHS) material that are able to absorb and store significant thermal energy, substantially increasing the overall safety and thermal stability of a battery system. The ability of these LHS- based systems to maintain optimal cycling performance and inhibit thermal runaway will be explored and the benefits of these materials into a variety of application-specific design configurations will be detailed.
Mark Hartmann, CTO/R&D – Outlast Technologies LLC
Conductivity Enhanced Phase Change Materials for Transient Loads
Phase change materials (PCMs) provide significant heat absorption in a very small package, making them ideal for absorbing high transient loads in environments where heat transfer is challenging. A traditional downside of PCMs is low thermal conductivity, requiring external support systems to provide heat transfer to utilize the full PCM mass. This paper will discuss the usage of a composite phase change material-graphite matrix (PCC) that incorporates thermal absorption with thermal conductivity.
PCC can be found lithium-ion batteries in automotive, stationary, aerial, robotic, and marine applications. The combined heat absorption and conduction prove beneficial for normal thermal management and prevention of thermal runaway propagation, a growing concern in the lithium-ion industry. Results of testing and simulation will be shared.
AllCell will also discuss some novel concepts for the usage of composite phase change materials to get a blend of properties that can be optimized by application.
Greg Albright, Vice President of Business Development – AllCell Technologies
10:15 am – Networking Break and Expo Time
Performance Investigation of Fans Placed in Series
When designing equipment that use fans for forced convection cooling, the situation frequently arises when the airflow impedance through the system is high enough that one fan will not provide the pressure and consequently the airflow needed to cool the unit. When this situation occurs and there is no acceptable solution available that will provide adequate airflow with a single fan, two fans in series may be able to provide the needed airflow. Two fans in series should, in theory, be able to double the available static pressure of just one fan. However, if the second fan is simply placed downstream of the first fan, there will be a degradation in the theoretical static pressure developed by the fan pair.
This presentation will show the results of an investigation to determine how close a series fan arrangement can come to doubling the static pressure while minimizing the amount of space required for the two-fan combination. The presentation will consist of using CFD simulations with a rotating frame of reference around the impellers to predict the series fan performance and will also show how well the simulations agree with actual test data taken using an airflow test chamber to measure the pressure and airflow of the series arrangements.
Guy Wagner, Director - Electronic Cooling Solutions
Ultrathin Thermal Ground Planes for High Heat Flux
As electronic systems continue shrinking, the waste heat is generated at ever increasing power densities. Vapor chambers and thermal ground planes (TGPs) are passive thermal management systems which employ the evaporation of an encapsulated liquid to lift heat from a hot spot, convection of the hot vapor to spread the heat, condensation of the vapor to reject heat at a condenser, and capillary pumping of the liquid to return it to the hot spot; they offer an excellent solution to reduce the heat flux from a high-heat flux electronic system. However, TGPs suffer from two issues in high heat flux applications: first, the wick has a limited capillary pressure, and therefore there is a limit to the maximum power they can sustain; second, the liquid and wick introduce an evaporative thermal resistance.
We have developed TGPs with a thickness of <0.5 mm for high heat flux applications off of a 3 mm x 3 mm heat source. With a thin copper wick, we demonstrate a transition from thick-film evaporation to enhanced evaporation/boiling above 100 W/cm2 which reduces the evaporation resistance by a factor of 2. With low-area applications for electronic modules of 4 cm x 2.5 cm or 3.5 x 3.5 cm, the TGP cools a hot-source by >10°C compared to an equivalently sized copper heat-spreader, which corresponds to an effective thermal conductivity of >3,000W/m-K. We will cover models to show improvement of the TGP in terms of reducing thickness, increased power, and increased effective thermal conductivity.
Dr. Ryan Lewis, Director of R&D - Kelvin Thermal Technologies
12:15 pm – Networking Lunch
Comparison of Advanced Flexible Heater Technologies
The flexible heater market is a $3.1B industry worldwide, 1/3 of which is polyimide-based flexible heaters and the market is expected to reach $1.4B in 2021 . There are distinct advantages of polyimide heaters when compared with other heating element technologies. For example, they have a high temperature range (>200C), quick response times and are very lightweight. Due to the advantages of polyimide heaters, they are used in a number of different industries including medical, aerospace, automotive and industrial applications as well as a variety of applications such as comfort heating, freeze protection, process heating and composite curing.
This paper will outline property comparison among polyimide heater technologies including etched-foil heaters using a polyimide substrate and the dual layer all-polyimide film. Heaters with similar power densities will be selected and evaluated based on various criteria including voltage and current inputs as well as temperature outputs, time to thermal stability, temperature uniformity and heat up / cool down time. Other criteria that will be reported in this paper will include weight, thickness, resistance and flexibility. And conclusions will be drawn regarding the best use-cases for each type of polyimide-based heater technology.
Matthew Manelis, Application Engineer – DuPont Electronics & Communications
Nashay Naeve, Business Development Leader - DuPont Electronics & Communications
Fans are the Horses of the Digital Age
Total liquid immersion, when implemented appropriately, is a future-proof technology that uses no fans or other moving components within the chassis. All electronics are immersed in a dielectric liquid and 100% of the heat is removed from the chassis by direct contact between the fluid and heat generating components. Cool liquid is circulated directly to the hottest components first, and all the remaining components are cooled by bulk flow as the dielectric liquid circulates and then exits the chassis. Liquid submersion keeps component operating temperatures at least 20°C lower compared to air-cooling under comparable ambient conditions.
Directed flow creates predictable heat transfer for critical power components of the system, and all the electronics are protected from humidity, dust, oxidation, and corrosive gases, thereby extending product life of the server. The chassis can be reused during upgrades, significantly reducing e-waste.
In validating this type of technology, the National Renewable Energy Laboratory (NREL) confirmed that total immersion servers can recapture as much as 94 percent of the electricity generated at a temperature of at 55oC to provide hot water or heat for building systems. Additionally, this technology does not need any water or evaporative cooling if the outdoor temperature is cooler than 45oC.
Herb Zien, CEO - LiquidCool Solutions
Power Density and Thermal Management Roadmap of Next Generation Telecom Equipment
The network traffic in telecommunication industry has grown rapidly every year since its inception. With the extrapolation from current equipment, future nodes would consume and dissipate up to 100’s of kilowatts of power. In response to the projected growth, new design and architecture are needed in order to face the power-density challenges in the next generation telecommunication networks. There are two aspects of these issues. One is the network architecture and another is telecommunication equipment design. The thermal management of latter case is the focus of this paper
This paper first describes the trends and the critical thermal issues in the current telecommunication industry, and then follows with the possible solutions to the issues. The thermal technology map is developed as a general guideline to select the proper cooling schemes for the system under consideration. The discussion is then extended to the development of liquid cooled telecommunication equipment which is a must to meet power density challenge in the future systems. General design guidelines of liquid cooling are discussed in details. Because of the rapid growth in energy consumption and its related cost, the energy efficiency of the data center becomes a major issue to be considered in the industry. This paper also presents the critical steps needed to achieve the energy efficiency at the equipment and in data center by integrating thermal management into system design.
Lian-Tuu Yeh, Ph D & PE, ASME Fellow – Thermal Consultant
3:30 pm – Conference Conclusion and Closing Remarks