Surface flatness is an important issue for thermal designers as it is directly related to thermal contact resistance between surfaces. In this column, the definitions of surface flatness related parameters are discussed. These definitions are presented here as in the ASME B46.1-1995 standard [1]. Surfaces are characterized by three main parameters: roughness, waviness, and … [Read more...]
Simple Formulas for Estimating Thermal Spreading Resistance
A problem commonly encountered in the thermal analysis of electronic packages is that of thermal spreading resistance. Thermal spreading resistance occurs as heat flows by conduction between a source and a sink with different cross-sectional areas. Examples of two situations involving spreading heat flow are shown in Figure 1. One example is that of a chip mounted on the bottom … [Read more...]
Nostradamitech
The big electronics design show was in town. Gino suggested we blow off work for the day and check it out. I was a little short on promotional pens and key chains, so I fell in with him. Gino is OK, even if he's one of those Reliability Engineers. The cavernous convention center was packed with flashy booths of the usual component, CAD-tool and test equipment vendors. It's … [Read more...]
Modeling Heat Conduction in Printed Circuit Boards Using Finite Element Analysis
Introduction Heat transfer in and around a printed circuit board (PCB) is generally very complex. Some of the heat generated in components is conducted away through the multiple conducting (trace) layers, vias, and dielectric layers of the board; and some is dissipated by convection and radiation from the exposed surfaces. There has long been a focus on characterizing the … [Read more...]
Critical Cooling Issues in High Power Radio Frequency Transmitter Amplifiers
Introduction While emerging methodologies correctly insist that thermal engineers should be involved right from the early conceptual stages of electronics product design [1], many situations still require thermal analysis well after the introduction of the product to its intended application. Military transmitters installed in the 1980's and 1990's and still in operation today … [Read more...]
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