In the May 2001 issue, this column discussed the thermal conductivity of unfilled plastics. The interested reader may have noticed that the category of rubbers/elastomers was missing. This was not without reason. The user of these elastic materials should be aware that the final thermal resistance (which is, of course, from an engineering point of view, the more important … [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...]
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...]
Use of Naphthalene Sublimation Technique for Obtaining Accurate Heat Transfer Coefficients in Electronic Cooling Applications
The naphthalene sublimation technique has been demonstrated by a number of investigators to be an excellent method for obtaining heat transfer results [1,2] and a few have applied this technique to applications focused on electronic cooling [3-6]. These investigators have found that the mass transfer process can be set up with cleaner boundary conditions and can be studied more … [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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