Many readers of ElectronicsCooling are probably familiar with the use of fin efficiency formulas to estimate the thermal resistance of the commonly used parallel plate fin heat sink. Given the heat transfer coefficient, h, acting on a fin and the dimensions of the fin, the thermal resistance of an individual fin is given by: where Af and η are the surface area and … [Read more...]
Estimating Temperatures in an Air-cooled Closed Box Electronics Enclosure
Introduction In the majority of air-cooling applications, openings or vents are provided in the enclosure or box in which the electronic components are housed. The required cooling air is drawn in from outside the box by fans or blowers. In some applications, however, there may be airborne particulates or other substances in the air that would be injurious to the electrical … [Read more...]
Entrance Effects For Heat Flow Into A Multi-Layer Printed Circuit Board
Introduction Since their introduction, multilayer printed circuit boards have provided a significant benefit to the thermal management of IC packages. As is widely recognized, the power and ground planes in these boards function as fins and spread the heat beyond the package footprint and enhance heat transfer to the air. Heat can flow into these planes by conduction either … [Read more...]
Thermal Vias – A Packaging Engineer's Best Friend
Introduction In the 1990's, with the advent of surface mounting of semiconductor packages, multilayer printed circuit boards and multilayer substrates for Ball Grid Array packages were introduced. In order to create electrical interconnections between the different metal layers, vias are fabricated [1]. In most cases vias are hollow cylinders of copper, created by plating a … [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...]
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