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...]
Vapor Compression Cooling for High Performance Applications
Vapor compression refrigeration is being adapted to cool computer and telecommunications equipment in a limited number of high performance applications. Vapor compression can lift large heat loads and can heat sink at below ambient temperatures. Cold plates can offset high case-to-junction temperature gradients to keep high power integrated circuits from overheating and/or can … [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...]
General aspects on fan selection and layout
Introduction and Description of Fan Types Small ventilators are generally called fans. Depending on the geometrical design of the impeller, various constructional types are distinguished to indicate the main direction of the airflow. Here are the descriptions of the most important types of fans: Axial Fans Axial fans are characterized by their typical impeller form, which … [Read more...]
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