In the Tech Data series on thermal conductivity, gases - especially air - have been the subject of a few contributions. So far, the influence of two important parameters has been covered: temperature and pressure. However, people regularly ask: "What exactly is the influence of humidity?" And my standard answer has always been: "Nothing to worry about." Some time ago, one of … [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...]
Thermal Capacitance
When time enters the equations, the ability of a material to store or release heat becomes a crucial parameter. This issue's technical data column is devoted to a basic understanding of thermal capacitance. Thermal capacity (or heat capacity) is defined as: Cth = V � � cp [J/K] where: V =Volume (m3) = Density (kg/m3) cp = Specific heat (J/kgK) at constant pressure (the … [Read more...]
The Thermal Conductivity of Air at Reduced Pressures and Length Scales
In several earlier issues of Electronics Cooling, I discussed the thermal conductivity of air as a function of temperature and pressure. Therein, it was stated that the temperature dependence cannot be neglected, but that the pressure dependence, under 'normal' conditions, is virtually absent. But what is 'normal' these days? In 'normal' electronic systems we, indeed, need … [Read more...]
Dynamic Measurements: A Cornerstone of the European PROFIT Project
This article presents an overview of a number of dynamic measurement methods as part of the European PROFIT project. Due to lack of space, details cannot be given, but the interested reader is invited to consult the references at the end of the article. Because the majority of a product's cost and performance are committed in the early phases of a design cycle, it is envisioned … [Read more...]
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