Electronics Protection - June/July 2011 - (Page 8)

Feature The Benefits of Using Thermal Simulation Software in Electronics Design Sherman Ikemoto, General Manager Future Facilities USA Managing heat flow in electronics resembles managing an investment portfolio. Sound financial management requires knowledge not only of financial goals, but also the statistical performance characteristics and relative weightings of the asset classes within the portfolio. Similarly, when managing electronics’ heat flow, you have to get inside the box to understand the characteristics of the device’s various components. You must understand precisely where heat is generated, how it flows and potential heat removal mechanisms. Just as risk and return must be balanced in the financial world, cost and effectiveness must be balanced in the thermal management of electronic devices. Maintaining this thermal balance has never been so challenging. Performance improvements in electronic devices have rendered them ubiquitous. More of modern life, perhaps even your own heartbeat, depends on electronics. But the increasing density of logic gates on silicon substrates in accordance with Moore’s law has caused a proportional increase in electronics’ power density. Because the power input of electronics is released as heat, chip and device designers have struggled to find increasingly efficient heat-removal strategies. To make matters worse, strategies for removing heat in one particular application environment may not work in another. Intense pressure from management, market, materials, manufacturing, regulators and the public increasingly focuses electronics engineers on solving the thermal problems of new electronics designs. This demand for thermal solutions that perform in real-world conditions means that designers must consider increasing numbers of design parameters as they work. Designers need to find overstressed junctions. They need to identify hotspots, because each hotspot creates potential design weaknesses. They need to find low cooling zones, and they need to consider carefully each structure that is sensitive to heat build-up. These objectives demand significant design analysis time. As a project progresses, the temptation grows to move to physical production. To avoid the high costs of developing physical prototypes and stay on the design schedule, designers should consider using thermal simulation to develop an optimal design before the product heads toward manufacturing. Thermal simulation of electronics during the early design phase has become a best practice because thermal simulation allows electronics design work to address design issues comprehensively, quickly and accurately at low total cost. Let’s assume that a designer has just loaded his team’s thermal simulation software with the circuitry, devices, board material and supporting structures for an electronics design project. The best thermal simulation software offers extensive component libraries that allow the designer to rapidly populate the chip, board or larger device. This software also accepts custom device designs from the popular solid modeling programs, which include Autodesk 8 Inventor, proE, Hyperdesk, Ansys, Rapidform, Geomagic and Solidworks. Whether one is working on a packaged chip, a PCB, a larger-scale device or an entire box, the process is the same. Once the initial proposed design is specified, the designer must determine where heat is generated. Designers can look to the software for 3D temperature and air-velocity maps under a variety of usage scenarios. In simplest terms, the software critiques design work by creating a synthetic reality check at each step. This allows the designer to place cooling resources in the right locations to create an optimal mechanism for escorting heat out of the device. Heat transfer paths often improve in proportion to the sophistication of the heat sink, but that sophistication increases costs. Fans greatly improve heat-sink performance but create noise and reliability problems. Greater heat-sink mass improves reliability, but weight adds cost and is undesirable in many applications. Weight particularly affects the newest applications such as medical devices and small computing platforms such as tablets and smart phones. The high-level design problem is finding the optimal balance among these rules of thumb. Facing so many possibilities for creating the heat pathway, a designer needs narrow the choices quickly and predict performance accurately. The trick is using a simulation tool that predicts the junction temperature of every device under consideration. Good software reveals to the designer the exact locations that will benefit from more work. Good thermal simulation tools calculate the conduction, convection and radiation profiles of each device and predict conditions at each location under analysis. The assembly of all these observations into one graphic display constitutes a thermal map. From these predicted observations the software summarizes temperature, thermal stress and airflow. Together these summaries give the designer insight not otherwise attainable by traditional means. Future Facilities’ 6SigmaET contains several hundred standard library entries. 6SigmaETallows the designer to describe solution elements that include integrated chip electronics, memory, appurtenances, power supply paths, circuit boards, heat sinks, fans and other heat-path elements. The designer then lets the software map the heat that results, calculate critical measures for each of the design elements, and compare those results with the software’s derivation of the upper thermal limits each element will be exposed to. Usually a thermal simulation of a PCB containing 100 components takes less than a minute. If the temperature for each element is within limits, then the designer has achieved an effective solution and the search is on for cheaper solutions, different shapes, cheaper materials and finishes, and simpler manufacturing. However, if the simulated junction temperature of any device exceeds the device’s design limits, then the designer makes iterative changes to establish a viable heat exit pathway. During the process the designer concentrates first on the thermal effectiveness of the pathway removing heat from chips, boards and enclosures, along with the June/July 2011 www.ElectronicsProtectionMagazine.com http://www.ElectronicsProtectionMagazine.com

Table of Contents for the Digital Edition of Electronics Protection - June/July 2011

New Material Adapts to Strain
XPAL Power Debuts PowerSkin Battery-Boosting Smartphone Cases
Ruggedizing Enclosures: From Military to Seismic to Mobile Applications
The Benefits of Using Thermal Simulation Software in Electronics Design
Designers Face a Potentially Confusing Assortment of Surge Protection Device Choices
Military’s Demands Drive Innovative Thermal Management Solutions
Integra Enclosures Releases new Product to Genesis Line of Enclosures
New LCR COTS Filters Perform in Extended Temperature Range for Added Reliability
Thermacore Introduces VME64x/VPX Cold Plates for Military Cooling Applications
Laird Technologies Expands Thermal Gap Filler Line
ASI New Line of 13mm MCB’s offer UL 1077 Supplemental Protection
New Deutsch HDP Series Electrical Connector
Industry News
Calendar of Events

Electronics Protection - June/July 2011