The heat transfer coefficient is used to describe convective heat transfer between a solid and a fluid, as in Equation (1). The heat transfer coefficient is a defined parameter, not a physical property like thermal conductivity, and different definitions are used for different situations. The preferred definition for use in the electronics-cooling situation is … [Read more...]
The Temperature Ratings Of Electronic Parts
Introduction Semiconductor parts are most often specified for use in the "commercial" 0 to 70°C and, to a lesser extent, in the "industrial" -40 to 85°C operating temperature range. These operating temperature ratings generally satisfy the demands of the dominant semiconductor customers in the computer, telecommunications, and consumer electronic industries. There is also a … [Read more...]
Prediction of Thermal Contact Resistance
All engineering surfaces exhibit some level of microscopic roughness. The resistance to heat flow through a contact interface occurs because only a small portion (usually 1-2%) [1] of the nominal surface area is actually in contact. Heat may pass through the interface via three paths: conduction through the contact spots, conduction through the gas present in the gap between … [Read more...]
Problems with Thermal Interface Material Measurements: Suggestions for Improvement
Preface Increasingly it is apparent that measuring the thermal properties of Thermal Interface Materials (TIMs) causes much irritation for vendors and users alike. This article focuses on various measurement and standardization aspects and offers a strategy to overcome the problems. It is essentially an abbreviated version of a paper presented at SEMITHERM '03 … [Read more...]
The 45° Heat Spreading Angle – An Urban Legend?
Ever hear about the 45° heat spreading angle? Most of us have. However, no one I've talked to seems to know where it came from. Is it an urban legend, such as alligators in the sewers of Manhattan, or is it an eternal truth deposited into the collective subconscious of the thermal engineering community? However fascinating it might be to explore the historical origins of this … [Read more...]
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