Abstract
Because of the current trend in manufacturing to pack a greater number of electronic components into a given volume, the thermal failure of microelectronic systems is becoming an increasingly difficult design problem. This paper describes heat-transfer research into the important case of air cooling by forced convection of an array of electronic modules on a printed circuit board (PCB). Because of the interrupted nature of the airflow over the surface and the complex three-dimensional nature of the heat flow path, theoretical analysis is difficult and heat-transfer data for design are relatively scarce.
A research rig was designed and constructed which provided control of module power dissipation and continuously monitored the temperature of individual packages. An automatic data-acquisition system was successfully developed to record the large amount of experimental data that was generated. Realistic finite element models of the electronic package, leads and substrate were developed and used to reveal the temperature distribution. These models were also used, in conjunction with the experimental data, to determine heat-transfer coefficients. Correlations were established that related the value of the heat-transfer coefficient to distance from the leading edge of the PCB. It is intended that these correlations, together with the thermal analysis contained in the paper, will provide useful data for designers.
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