Why are plated mounting holes connected to the ground ?
I read that if you are connecting your board to chassis ground, then it should be connected at only one point and connecting, say 4 mounting holes, to the ground then screwing it into the chassis seems to not be desired. Why ?
If you have 3 PCBs that fit into one large enclosure, what is the proper way to mount them ? Plated vs unplated ? Grounded ? Star configuration to chassis ?
It may or may not be a problem depending on the application and its operating environment. Using a single point of connection is a good idea if you want to avoid setting up ground loops (which will pick up AC mains interference). So for your scenario each PCB should be electrically connected at one point to the chassis, leaving the other points of attachment for each board as mechanical connections only.
In an electrical system, a ground loop refers to a current, almost always unwanted, in a conductor connecting two points that are supposed to be at the same potential, often ground, but are actually at different potentials.
With two or more points connected to ground you can have some measurement problem.
In order to avoid emc problems, there are some rules you must consider. First, you must estimate the spectrum of the signals involved and to consequentially consider the relative propagations and couplings; then, you must avoid to form any loops of current with meaningful areas; you must use short connections; You must pay attention to the ground connections: the currents return to their source on the paths of lowest impedance.
You know your case; so you can find the answer by looking the chapter 11 in the book od Clayton R. Paul, “Introduction to Electromagnetic Compatibility” second edition, A John Wiley & Sons, Inc. Publication.
Most of common answers you have already got. But if you need another theoretically-grounded view on what happens if you attach your PCB to chasis on multiple points please consider chapter 9.9 Chasis Connections ('chasis stitching') in the book Elya B. Joffe and Kai Sang Lock "Grounds for Grounding", IEEE Press and A John Wiley & Sons, Inc. Publication.
- Badges
- Science topic
- Similar topics
- Engineering
- Electrical Engineering