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Using a simple analytical model we investigate the effect of thermal vias on the heat transfer through a printed circuit board (PCB) . We show that thermal vias can increase the heat transfer coefficient by orders of magnitude. The model considers the arrangement and the geometry of the vias, the metallization thickness and the solder fillets. The application part of the paper addresses three prototypes of high-power LED-based operating room lamps. The heat spreading ability of three types of PCBs - two FR4-based prototypes with thermal vias and one with an insulated metallic substrate (IMS) - is evaluated by using thermal simulation and single point temperature measurement with miniaturized thermocouples. All the three prototypes fulfilled the requirements for the thermal performance satisfactorily: the total thermal resistance of the FR4-based prototypes was below 1.2 K/W, and the one with the IMS even below 0.6 K/W.
Date of Conference: 13-17 May 2009