Syed Bokhari, Lead SI and EMC Specialist, Fidus Systems
Cristian Tudor, Signal Integrity Specialist, Fidus Systems

A common approach to reducing radiated emissions from heat sinks is multipoint grounding. These reduce PCB routing area and can become impractical. This paper examines the effect of using a dissipative-edge termination scheme. This consists of resistive loading of the edges of the heat sink. Analysis carried out using a 3D EM field solver shows that 10–20 dB of reduction in the near-field strength is feasible with a proper choice of resistance. Heat sinks of the blade fin and pin fin types have been analyzed in detail and the advantages and limitations of this method will be presented.