The care with which we express the dimensions of important parameters makes the difference between conveying useful information or conveying useless or misleading data. Taking the issue of units one more step, the purpose of this article is to suggest that we occasionally organize our work to get rid of dimensions altogether. We must live in a dimensional world. A critical … [Read more...]
Simplified Formula for Estimating Natural Convection Heat Transfer Coefficient on a Flat Plate
Although most of the emphasis today in the electronics cooling community is devoted to extending forced convection cooling capability, many applications still depend upon natural convection cooling. Basically, natural convection cooling combined with radiation is what results when a fan is not used in the cooling design to move air. Instead, movement of the air is induced by … [Read more...]
The Anisotropic Thermal Conductivity of Plastics
The easiest way to tailor thermal conductivity of plastics is to incorporate some highly thermal conductive filler material into the plastic molding compound. Here the filler particles act as heat carriers in the thermally isolating media. Roughly, if more filler is used, then higher thermal conductivity is achieved. Phenomena related to manufacturability and strength often … [Read more...]
An alternative approach to junction-to-case thermal resistance measurements
As more and more integrated circuits dissipate power at levels once reserved for power discrete devices, junction-to-case thermal resistance (JC or RJC) remains as important as ever. The difficulties in making JC measurements often leads to values that do not accurately indicate true junction temperature (TJ). The measurement difficulties are usually two-fold. First is … [Read more...]
Characterizing a package on a populated printed circuit board
This column has emphasized methods of analyzing packages in the JEDEC-standard test environment. A thermal metric that lends itself to analyses of system applications is the junction-to-board thermal characterization parameter, JB. If one knows the board temperature (TB), then the junction temperature (TJ) can be determined by a simple application of the following formula: TJ … [Read more...]
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