Absorbing boundary for a multi-layer circuit board structure

Abstract

The invention comprises an improved PCB board design having particular utility for high frequency application, and especially useful to alleviate the problem of electromagnetic disturbance of signals switching through power and ground planes. In one embodiment, the PCB contains a magnetically loaded absorbing boundary to absorb the EM disturbances and keep them from resonating inside the cavity between the power and ground planes. The boundary is preferably placed at an edge or edges of the PCB, where it is unlikely to affect any other signals on the PCB. Exemplary materials for the boundary have a magnetic loss tangent of 1.0 to 1.5 with an attenuation constant of −20 dB/cm over frequencies of interest. Depending on whether the boundary material is solid or non-solid, it may be adhered to the edges of the PCB, or may be applied to the edge and cured. It is preferable that the boundary material span through substantially the entire height of the dielectric cavity between the power and ground planes to best absorb the electromagnetic disturbances.

Dependencies are inferred from the claim text.