Thanks, Istvan. We have introduced stitching the ground planes all the way around the pcb. Edge plating has been put on ice for the moment. The cost may increase and we do not really know how many dB it will help us right now.
We might run a seperate project on edge plating. Oh yea, thare are many other potential places for EMI leakage. We will use a sniffer to check out. Best regards Amund Fra: Istvan Novak Sendt: 21. februar 2020 14:28 Til: Amund Westin <am...@westin-emission.no>; EMC-PSTC@LISTSERV.IEEE.ORG Emne: Re: [PSES] SV: [PSES] Ground copper fill on signal layer on multilayer PCB Hi Amund, Since your potential problem appears to be at relatively low frequencies, an alternative to edge plating would be stitching the ground planes along the board edges with closely spaced vias. We have done this at SUN Microsystems also as a preventive measure. On the other hand, you should also consider the possibility that the leaking happens not through the edge of the board but through components connected to internal traces but sitting on the top or bottom of the board. What I am saying is that it is not necessarily the edge of the board that radiates. You could check this by poking around with a close-field probe, even uncalibrated unshielded home-made small loop or monopole antennas might give you a useful hint where the noise is coming from. You could also put absorbing sheets to the edge of the board to see if it makes a difference in the overall radiation. Best regards, Istvan Novak Samtec On 2/19/2020 1:50 AM, Amund Westin wrote: Hi Ken No, I have not considered edge-plating. I’ll look into this now. We have some high frequency noise (400-500MHz) from differential lines leaking out from an inner layer of a multilayer pcb. Edge-plating might be a good solution. Thanks for the tip. BR Amund Fra: IBM Ken Sendt: 18. februar 2020 23:18 Til: EMC-PSTC@LISTSERV.IEEE.ORG <mailto:EMC-PSTC@LISTSERV.IEEE.ORG> Emne: Re: [PSES] Ground copper fill on signal layer on multilayer PCB Hi Amund! Have you also considered edge-plating? Are you trying to reduce radiated noise outside your product, or cross-talk within the product (or both)? On Tue, Feb 18, 2020 at 3:03 AM Amund Westin <am...@westin-emission.no <mailto:am...@westin-emission.no> > wrote: Between two solid ground planes, we have a signal layer, routing high speed differential lines. What do you recommend: I. fill the remaining area with copper in the signal layer II. fill only the border of the layer (5mm ground copper trace around the layer edge) III. no fill at all Best regards Amund - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. 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