Hi Mark:
> let's assume there are 120VAC traces on the top layer of the PCB (AC comes > in from a detachable power cord) Right next to the trace (<1mm) > > there is a plastic stand with metal screw (washer build-in) in it. metal > washer lays on top of the AC trace, separated only by the mask. > > Screw is not connected to any grounds or circuits or any other conducted > part. It is untouchable to the user side. > > Is where any safety concern? Product is evaluated under 60950. One thing > came to my mind, is a plastic standoff, probably should be able to support > high voltage? is it valid concern? any others? The solder mask is NOT a suitable safety insulation (because its purpose is that of a solder mask). Therefore, you must consider that the screw is connected to the the PCB 120-volt trace. Now, you must evaluate the safety based on the screw being part of the mains circuit. That means you must evaluate the clearance and creepage distances from the screw to other parts of the equipment. And, you must evaluate the plastic standoff as a solid insulation, including distance through insulation as specified in 60950-1. Best regards, Richard Nute Product Safety Consultant San Diego - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <[email protected]> All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher: <[email protected]> David Heald: <[email protected]>
