Continuing our discussion of different forms of carbon, this column addresses the topic of pyrolytic graphite, a material that opens up many interesting applications not only for cooling but also for scientific measurement equipment. Pyrolytic graphite - the finest forms of which are often called Highly Ordered Pyrolytic Graphite (HOPG) - is manufactured through a pyrolysis … [Read more...]
Optical instrumentation for the thermal characterization of electronic devices
What information does light, reflected from a running electronic device, carry? Our research team has been working upon this key question for almost a decade. As this magazine is dedicated to thermal issues, we will focus upon these aspects of optical probing. Figure 1 shows the general principle of our experimental method. Light is shone upon a running device. When the device … [Read more...]
Thermal joint conductance for graphite materials
The heat flow across a metal/interstitial elastic-layer/metal joint is a very important problem in many microelectronic applications. It is generally known that when two surfaces are brought together, intimate solid-to-solid contact occurs only at discrete parts of the interface. Therefore, the actual contact area of pressed surfaces represents a very small fraction of the … [Read more...]
Understanding Phase Change Materials
Although phase change materials (PCM) were introduced nearly twenty years ago, it was not until the development of the high-powered Pentium processor that this class of interface material gained widespread acceptance. The large quantities of heat produced by these processors necessitated a carefully designed thermal path where all of the thermal resistances were minimized. For … [Read more...]
Thermal Design Challenges in Automotive Alternator Power Electronics
Ever since the advent of the automotive alternator, or claw-pole alternating current generator, in the 1960's, there has been an ever-increasing thermal design challenge to cool the power electronics in these machines. Figure 1 depicts a typical cutaway section of a modern day alternator. At first glance one may think that cooling the diodes in a rectifier bridge of an … [Read more...]
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