I seem to recall that there are some specifications for the insulating coating in the IEC 60384-14 standard for Y1 caps, but I have not worked with that standard for a while.
I agree with John Woodgate that a quick fix might be to place a piece of insulating tape on the surface of the board in the area under the cap. I have seen Kapton tape used quite often to convert a clearance problem into “distance through solid insulation.” Another quick fix that I have seen (possibly for the same reason) is to slide a piece of heat-shrink tubing over the cap and then apply heat to shrink the tubing. The shrinkage of the tubing at the top and bottom of the rounded cap does a nice job of retaining the tubing on the cap. So, if there is a production schedule to be met, some form of added insulation can probably solve the immediate problem. In the long run, it may be possible to change the board layout so that there are no surface traces under the cap. Note that the construction requirements for implementing basic or reinforced insulation within a circuit board provide several easy-to-meet options. This is because the circuit board can be treated as “solid insulation”. Joe Randolph Telecom Design Consultant Randolph Telecom, Inc. 781-721-2848 (USA) <mailto:j...@randolph-telecom.com> j...@randolph-telecom.com <http://www.randolph-telecom.com> http://www.randolph-telecom.com From: John Woodgate [mailto:j...@woodjohn.uk] Sent: Monday, March 11, 2024 1:36 PM To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] Y-capacitor body material - considered to be insulating? I think you have to ask the manufacturer of the capacitors about the insulation quality of the coating, and also test what happens if the insulation does break down; the result might be 'safe' but destructive. At that point, high-voltage spikes on the AC input have to be taken into account. It looks as though changing the PCB would be a simpler solution than trying to prove that it's already OK or than adding a piece of insulating material and checking that it is still there. On 2024-03-11 17:13, James Pawson (U3C) wrote: Hello Group, We are assessing a system that uses class Y1 capacitors for EMC filtering. Because of space constraints, they are laid down horizontally on the PCB. This is causing a problem (at least in my mind) where the capacitor body is now resting on top of the AC input trace. The side of the capacitor connected to PE is the side closest to the AC mains input trace. <https://unit3compliancecouk-my.sharepoint.com/:i:/g/personal/james_unit3compliance_co_uk/EaXJSK9bMYRItCXbdutLJKsBORjTOA5_7Kh0bpPXDC5taw?e=aT7pfK> y-cap-body-insulation-question.jpg One of those pieces of received wisdom that has been passed down to me is that “the body of components is not considered to be insulating” for the purposes of assessing creepage and clearance. Common sense says “danger danger Will Robinson” and to change the PCB and/or to add some insulating material, but some technical back up would be welcome. 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