A simple formula to estimate the natural convection heat transfer coefficient on a flat plate was presented in a preceding column [1]. If, instead of a single plate, we wish to consider a closely spaced array of vertically oriented parallel flat plates, a different formula is required. The geometry to be considered appears in Figure 1 and is typical of that for a vertically … [Read more...]
The Role of Natural Graphite in Electronics Cooling
Graphite is available as a variety of different material forms, the most useful in the electronics cooling market being pyrolytic graphite, graphite fiber reinforced carbon and polymer matrix composites, graphite foams and, the subject of this brief, natural graphite. The basic structure of graphite is shown in Figure 1. Figure 1. Structure of graphite crystal. The … [Read more...]
Future trends in heat sink design
In today's electronics equipment, total system dissipated power levels are increasing with every new design. Increases in power levels combined with the market expectation of reduced package sizes lead to heat problems that, if uncontrolled, can significantly shorten the life of the electronics. Although this "increased power - decreased size" scenario has been prevalent for … [Read more...]
The treacherous streams
During the development of a telecommunications product, an unpredictable phenomenon of air streams within the maze of cards and module was encountered. It could only be compared to suddenly confronting powerful inner streams in a calm ocean. Unlike the ocean, however, these streams appeared in a man-made machine. It seemed as if someone had rewritten the laws of physics. It was … [Read more...]
Thermal characterization of power ICs using virtual junction temperature
Thermal experts generally view thermal resistance as a measurable property of a semiconductor device. A system designer, who designs an appliance, is usually not a thermal expert. The system designer just needs a way to determine the size of the external heat sink. At high heat sink temperatures, less power dissipation is allowed in the device. The ratio at which case … [Read more...]
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