Home | Business News | Browse by Publication | P | Printed Circuit Design & Manufacture

EMI/EMC and SI effects from ground-return vias on PCBs: at higher frequencies signal loss and noise is reduced when ground-return vias are placed close to the signal vias.

Article Excerpt
THERE IS OFTEN a lively discussion when it comes to the importance of "ground" or ground-return vias for high-speed signals that travel from layer to layer in a PCB. Many claim that there are many ground vias that stitch together the various ground layers, so there is little concern about their exact location. Others will insist that the ground-return vias are important to both EMI/EMC and SI performance for high-speed signals. The real truth lies some where in the middle. It depends on the data rate of the signals, and the amount of signal loss and/or noise generated between the planes.

The basic issue is that when a signal travels from one reference plane to another, it may travel through a pair or more of board layers. The return current must also travel from one plane to another. If a nearby metal conductor (ground-return via) is provided, the current will spread out between the planes, using the natural displacement current of the capacitance...

View this article FREE - Now for a Limited Time, try Goliath Business News
Free for 3 Days!