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...]
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...]
Estimating Natural Convection Heat Transfer for Arrays of Vertical Parallel Flat Plates
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...]
High Resolution, Real Time Micro-thermal Imaging — Steady State and Pulse Measurements on Microscopic Semiconductor Targets
Thermal imaging of microscopic targets has evolved over the past 20 years to the point where real time "true-temperature" mapping with 50 milliKelvin sensitivity and 2.75 �m spatial resolution is possible. Recently, the capability to study and evaluate high frequency transient pulses has been added. Infrared imaging methods provide unequaled ease and flexibility for … [Read more...]
The Many Flavors of Ball Grid Array Packages
By now, it is a tired truism to say that the consumer electronics industry has consistently delivered on its promise to provide products that are smaller, faster, and more feature-rich at an ever cheaper price. The main driver for these trends has been the increasing integration of more functions on a single chip. In spite of its greater performance, the PC of today has far … [Read more...]
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