Day 1 – Thursday, June 6th
7:00 am - Registration Opens/Continental Breakfast
8:00 am – Welcome and Opening Address
8:05 am – Opening Presentation
Multiphase Heat Transfer Using Jets and Sprays: Modeling and Devices
Jet/spray cooling with phase change has the advantage of removing relatively large amount of heat (100 W/m2 to 1,000 W/m2) from the hot surface of many power electronics system. Even though spray cooling is used in the industry for several years the overall theoretical knowledge available is limited due to complex interaction of liquid, vapor, liquid droplet impact and phase change.
In this presentation the heat transfer process in the jet/spray multiphase flow is explained using direct simulation as reported in Selvam et al. (2006 to 2009). The process of heat transfer when a bubble is growing in a 30 to 50 μm thin liquid film is explained systematically. In what form the droplet impact in a spray helps to increase the heat transfer is also explained by modeling a droplet impact over a thin liquid film when a bubble is growing. Overall the major process of heat transfer in multiphase heat transfer is due to transient conduction is concluded through modeling and illustration.
From this understanding efficient cooling devices were designed and tested. The performance of jets and spray devices will be presented and compared with other available work. The importance of controlling the thin liquid film on the hot surface for better heat transfer is illustrated. Further understanding of multiphase heat transfer at the interface of solid, liquid and vapor at the nano level will be presented. The effect of surface roughness on nucleation is investigated using molecular dynamics (MD). Recent results from the MD modeling will be presented.
R. Panneer Selvam, Womble Professor of Computational Mechanics and Nanotechnology Modeling,
Department of Civil engineering
University of Arkansas
Flexible Thermal Ground Planes
Different prototypes of the flexible thermal ground planes have been demonstrated with funding support from the DARPA Thermal Ground Plane (TGP) program. In addition to flexibility, these prototypes illustrate other appealing features such as: 1) effective thermal conductivities of more than 2,000 W/mK; 2) scalable with thicknesses ranging from 0.2 to 1 mm and lengths ranging from 3 cm to tens of cm; 3) two-dimensional distribution of chips (heating) with heat fluxes reaching over 200 W/cm^2; 4) two-dimensional distribution of heat sinking regions; and 5) low cost resulting from the fabrication processes compatible with printed circuit board (PCB) manufacturing infrastructure. This presentation will review these features with an emphasis on potential applications.
Y. C. Lee, S.J. Archuleta Professor, Department of Mechanical Engineering
University of Colorado/DARPA
10:00 am – Networking Break/Exhibit Hall Opens
Friction Stir Welded Heat Sinks and Liquid Coolers
Friction stir welding can provide strong, void free and leak proof joints with low thermal distortion. In addition, friction stir welding does not use filler metal so the parent material thermal properties remain unaltered. These characteristics make friction stir welding an excellent joining method for heat sinks and liquid coolers.
This presentation will cover the research and development efforts to utilize the friction stir welding technology in heat sinks and liquid cooler design and manufacturing. Topics include the advantages of friction stir welded heat sinks over conventional epoxy bonded fin heat sinks and a cost-efficient manufacturing method of liquid cooler using friction stir welding and aluminum extrusions.
Chunming Alex Chen, Sr. Project Engineer, North American Technical Center
Sapa Extrusions North America, USA
Equipment for Airflow Impedance Testing of Electronic Systems
With market pressures demanding reduced time to market of most electronic products, and packaging constraints restricting size of conduction and forced convection cooling methods, tools to measure thermal performance must become easier and faster to use, and provide the best accuracy in a short time frame.
Digital air velocity sensors now bridge this gap and allow for designing into board assemblies as surface mount devices. Fully digital sensors can self-calibrate and communicate. These sensors can be used in multiple critical flow locations on a single board, to product detailed and effective environmental sweeps. These sensors will be the basis for filter clog detection, intake obstruction detection and fan fail for board assemblies of the future, and can even operate as miniature closed loop fan controllers.
Phil Daniels, VP Thermal and Sensor Products
12:00 pm – Networking Lunch
1:00 pm -
Formable Phase Change Materials for Thermal Management in Portable Electronic Devices
In this presentation, the efficacy of a formable phase change material (PCM) as a passive heat sink in portable electronics will be inspected. Microencapsulated n-eicosane (C20H42) and n-docosane (C22H46) were chosen for their high enthalpy of fusion (>200 kJ/kg) and precise melting points (37°C and 42°C, respectively). The formable PCM was placed beneath the EMI shield of a top selling commercial phone and was subjected to two continuously run benchmark tests. Both internal and external temperatures were seen to be reduced by as much as 4°C in the device with PCM compared to the device without PCM. A second parameter, the time required before the firmware throttled down the CPU speed due to overheating, was compared with and without PCM present. A 100 percent increase in maximum CPU speed processing time was seen in the device with PCM over the device without PCM.
Jackson Sutherland, Materials Scientist
Outlast Technologies LLC
Advances in Silicone TIM Products
This presentation will discuss why silicone is suitable for a polymer binder of TIM, including how silicone TIM has added heat-resistance, is weatherproof, is electrically insulating and has good chemical stability compared with other organic polymer TIM. A silicone thermally conductive PCM is characterized by applying silicone resin as polymer binder. It shows high tackiness, improved heat stability and anti-pumping-out property compared to the conventional wax / olefin system PCM. Learn how silicone thermally conductive double-sided tape can be used in a wide temperature range; -40°C to 150°C.
Akihiro Endo, Researcher
Shin-Etsu Chemical Co. Ltd.
Too Hot to Hold: Determining the Cooling Limits for Handheld Devices
With the rapidly increasing performance in tablets and smart phones, the result is increased power consumption leading to devices that are uncomfortably hot. This is especially true when watching video or playing games since these operations are both CPU and graphics intensive. This presentation explores the limits of cooling for handheld devices based on both testing and simulation under various conditions and provides guidelines for maximizing the amount of power that can be dissipated in these small form-factor devices.
Guy Wagner, Director
Electronic Cooling Solutions
3:15 pm – Networking Break
Developments in Thermally Conductive Hybrid Adhesive
This session with cover work on a thermally conductive hybrid adhesive that combines both pressure sensitive adhesive functionality and structural cross-linking adhesive integrity. The hybrid adhesive provides instantaneous adhesion to rapidly marry electronic components to an adherend. Thermal initiation, via manufacturing or burn-in processes, crosslinks the hybrid adhesive into a thermoset structural adhesive that results in a permanent bond line. Utilizing a hybrid adhesive yields a greater return on investment versus a one dimensional adhesive because of lower fixturing costs and reduced energy consumption during the assembly manufacturing process. This benefit comes with long term bond line reliability for secure thermal management of electronic assembly packages.
Dr. Jianhua Zou, Senior Product Development Chemist
Arlon Silicone Technologies
Technology Scouting for Thermal Management
This presentation will center on technology scouting as applied to thermal management. The session will give an overview of what technology scouting is, and how the process works for companies that aren’t multinational corporations. Then these concepts of technology scouting will be applied directly to thermal management. The presenter will look at one or more specific thermal issues and address how technology scouting can be applied to solve them. Finally, specific examples of companies and universities doing work on thermal management problems will be discussed. Additionally, in the course of the presentation, emerging technologies in thermal management will be covered.
Kevin Closson, Senior Analyst
5:15 pm - Cocktail Reception
Day 2 – Friday, June 7th
8:00 am – Registration & Exhibit Hall Opens/Continental Breakfast
8:30 am - Opening Presentation
Graphene Thermal Properties and Applications for Thermal Management of Li-Ion Batteries
Lithium-ion batteries are superior to other types of batteries owing to their high-energy storage density. However, their applications are limited due to strong self-heating effects coupled with the adverse effect of temperature on the battery life-time. The battery packs utilize multiple Li-ion cells stored close together to provide high electric power. This arrangement leads to strongly increased temperature that degrades the battery life.
Prior work on thermal issues in Li-ion battery packs has demonstrated that a passive thermal management system based on the phase-change materials (PCM) is a promising approach. The PCM thermal management uses the latent heat stored in the material as its phase changes over a small temperature range. However, PCMs typically have low thermal conductivity. They store heat from the batteries rather than transfer it outside. For this reason, the usefulness of PCM passive thermal management for the high-power Li-ion batteries is limited.
In this talk we describe a possibility of using graphene and few-layer graphene (FLG) as fillers for PCM for increasing PCM’s thermal conductivity while preserving its ability for the latent heat storage. Graphene’s intrinsic thermal conductivity, flat geometry and demonstrated capability for integration with other materials make graphene very promising for thermal management applications. Our measurements revealed that the large-area (~ 10 – 20 µm long) single-layer graphene flakes have an extremely high room-temperature thermal conductivity exceeding that of diamond (~2000 W/mK).
Alexander Balandin, Professor of Electrical Engineering and the
Director of the Nano-Device Laboratory (NDL) at UCR
Pradyumna Goli , Research Associate
University of California-Riverside (UCR)
Using Infrared Cameras to Save Time, Money and Provide Thermal Management of Electronic Devices
With the prices of the infrared camera systems dropping dramatically over the last few years, infrared cameras have become a valuable tool in electronic and microelectronic design. Using these systems to find poor bonds, resistance issues, misplaced components and poor solder connections are just a few examples where they are essential to designing and manufacturing quality products.
Various wavelengths of infrared cameras such as short wave, mid wave and long wave length infrared cameras, and why one may be better than another for a specific application will be discussed in this presentation. Optics and why they are essential will also be discussed. These cameras allow the end user to see and measure temperature real time, non-contact, with incredible accuracy.
Gary Strahan, CEO
ICI – Infrared Cameras Inc.
10:00 am - Networking Break
Harnessing the Power of Phase Change for Efficient Thermal Management
Recent studies have shown that liquid cooling is a path to higher efficiency and power density, and many liquid cooling solutions are coming into the market. This session will discuss a method to objectively evaluate the thermodynamic efficiency of various thermal management schemes. This jet cooling technology uses specially designed modules to generate an array of boiling jets of a low-pressure dielectric refrigerant. These modules are scalable from single power transistors to CPUs to large power electronic modules and they can be placed in series to efficiently remove large amounts of heat with low flow rates of refrigerant (2,000 W using 1 lpm) while keeping all of the devices at a nearly uniform temperature.
Diego Arias, Co-Founder and VP of Engineering, Ebullient, LLC
A Revolution in Thermal Modeling – The Past, Present and Future of Thermal Modeling
This presentation will discuss the past, current and future trends in thermal modeling, which has not changed much in the past 10 years. Engineers take days to build geometry from scratch using primitives. They then spend considerably more time gridding and/or meshing the solution domain, making several simplification assumptions to get a solution that meets limited model size restrictions. However, the landscape has changed. Modern computing technologies, on both the hardware and software side have evolved, allowing for an evolution in thermal modeling practices.
Today it is possible import MCAD and ECAD models directly into the software. Instead of using a series of primitives to define the grid and then have the user refine it to an acceptable state, today’s gridding and solution algorithms use imported geometry to intelligently define the grid, and then simply map the geometry onto it. Multicore processing capabilities, and advancements in memory, allow for complex geometries, and large grid counts to be solved in practical engineering times. What will tomorrow’s advancements bring?
Marie Ross, Senior Applications Engineer,
Controlling Compaction in the Thermal Conductivity Characterization of Thermal Interface Materials
The increased power levels and minimization of electrical devices have substantially increased volumetric heat dissipated, which impacts considerably on the performance of electronic equipment and presents a design constraint in further miniaturization of electronics. To this end, many new thermal interface materials have been developed to improve the thermal management. A key performance parameter of these materials is the effective thermal conductivity.
Some of the variability in test data published on various thermal interface materials is rooted in variation in test conditions, specifically the compression of the sample. Most thermal interface materials such as greases or pads are compressible. In compressing the sample, the thermal conductivity changes with densification of the material. The presentation will highlight the design of a special Compression Test Accessory (CTA) for precisely controlling sample compression in characterizing the thermal conductivity of the material via the modified transient plane source technique. The advancement of the CTA enables researchers to obtain accurate, precise thermal conductivity data representative of actual application conditions.
Adam Harris, Managing Director
C-Therm Technologies Ltd.
12:30 pm – Networking Lunch