Original Date: 11/01/2004
Revision Date: 01/18/2007
Information : Thermal Design and Analysis of Electronic Products and Systems
The Center for Advanced Life-Cycle Engineering has contributed to more timely and cost-efficient industry thermal design processes for electronic equipment through innovative thermal management solutions, improved thermal analysis and characterization methodologies, and professional development courses.
Increases in integrated circuit (IC) heat flux and power dissipation, combined with more stringent performance and reliability constraints in the future, pose challenges that will make thermal management a key enabling technology in the development of electronic systems. Many integrated circuit packaging failure mechanisms have been found to depend on spatial temperature gradients, temperature cycle magnitude, and rate of temperature change rather than absolute temperature, while die circuit electrical performance can be highly temperature dependent. Thus, electronics temperatures must be controlled through appropriate thermal management strategies to meet both performance and reliability requirements. Rising heat loads combined with ever-reducing product development times require increasing levels of engineering expertise, improved experimental facilities, and computing resources. Many companies are feeling the need to out-source their thermal design process and research.
Over the past 15 years, the Center for Advanced Life-Cycle Engineering (CALCE) has advanced the thermal management and reliability of electronic equipment by developing innovative thermal design solutions, efficient thermal design methodologies combining experimentation and numerical analysis, and by studying the dependency of electronics failure mechanisms on temperature. Electronics cooling strategies developed and optimized at the Center include passive and forced-air cooling solutions, and single- and two-phase liquid cooling solutions. Because of cost and reliability constraints, air-cooling will remain an important thermal management approach for many electronic products in the foreseeable future. CALCE has addressed key thermal management areas to extend the limits of air-cooling. Advances in heat sink cooling performance have been achieved by addressing the following areas, to optimize the complete heat transfer chain from the heat dissipating components acting as thermal source, to the environment external to the system enclosure: minimization of thermal contact resistance between component and heat sink, integration of heat spreading technologies (e.g., heat pipes and high-thermal-conductivity materials), hybrid cooling solutions such as phase change materials, and minimization of heat sink surface fouling. Liquid cooling-based solutions have been developed (both single- and two-phase) for applications where air-cooling alone is not sufficient enough to meet thermal design specifications. Liquid cooling solutions include advanced liquid cooled modules for cooling of high heat flux electronics, and high performance cold plates with porous and other micro-structures.
An efficient thermal design strategy requires a balanced combination of experimental and numerical efforts, applied to the development of high-performance cooling technologies. Over the last decade, thermal design practices within the electronics industry have progressed from basic analytical and semi-empirical calculations, applicable to systems in tandem with extensive physical prototype characterization, to a high reliance on virtual prototyping using numerical predictive techniques, such as computational fluid dynamics- (CFD-) based methods. Using experimental benchmarks, CALCE has assessed the predictive capability of CFD software dedicated to the thermal analysis of electronics, and highlighted the need for experimental verification due to inherent limitations in the codes used. CALCE has demonstrated the capability of alternative low-Reynolds number eddy viscosity turbulence modeling strategies, available in general-purpose CFD codes, to improve predictive accuracy for electronic component heat transfer. Apart from the prediction of operational temperature in application environments, the value of CFD in optimizing electronic component assembly processes (e.g., corrective re-flow soldering), and optimizing the thermal loads imposed in accelerated reliability tests (e.g., air temperature and power cycling), has also been demonstrated.
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