Model-based analysis of screw locations to reduce radiation from a PCB-chassis structure

The effect of the location of screws that connect PCB ground with the chassis has been studied using a SPICE circuit simulation model created by the multilayered finite difference method (MFDM). The model includes the power and ground planes of the PCB and the chassis. By using the created model, the impedance between the ground of the PCB and chassis at every location and the current flowing through the screw when it is placed to connect the ground with the chassis was calculated. The investigation results suggest that the node at which the higher impedance can be observed provides a lower screw current. Furthermore, it revealed that even just two screws connecting the ground with the chassis can provide a lower current than a single screw connection. Far-field measurements were performed to validate the investigation results.