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diycore 30th August 2009 12:57 PM

Electrical safety with pcb mount transformer

I'm designing a PCB for a PCB mount toroidal transformer. However I could not find a good amount of articles on the internet which clearly states the safety standards involving mains circuit on a PCB.

I would use standard PCB mount IEC power inlet with fuse drawer and PCB mount transformer. I would like to insulate the solder joints on the bottom side of the board.

The component leads would be bent parallel to the solder pad before being soldered. I am looking for a practical method to insulate these pads.

I would appreciate any inputs.


DigitalJunkie 30th August 2009 03:55 PM

I've used fingernail polish before,it seems to work well.

Juergen Knoop 30th August 2009 04:09 PM

commercial equipment does not rely on coatings or lacquers for good reasons.
Insulation is provided by air/creeping distance and solid insulation materials such as plastic sheets.
Open some equipment for reference please.

amc184 8th September 2009 07:21 AM

The ones I know of:

- at least 10mm clearance between mains voltage and low voltage traces on the PCB.
- an insulating sheet between the underside of the PCB and the chassis, either fixed to the PCB or the chassis. This is probably only strictly necessary for a double insulated appliance though.

Shaun 8th September 2009 09:18 AM

I seem to remember a standard IEC 60950. There are various parts, but I think the ones that would be most helpful would parts 2 & 3.

AndrewT 8th September 2009 10:48 AM

I would insulate the chassis underneath the "mains" area with two layers of heavy duty adhesive tape.
I would place the "mains" area near an edge of the PCB.
I would ensure the trace layout meets the special requirements for creepage distance.
I would ensure that when the case is open, I cannot accidentally touch or drop any anything on the "mains" traces and/or soldered pads/joints.

wwenze 9th September 2009 09:35 AM

Paper, thicker and better quality types, fixed with tape,
Black/blue/red/yellow "electrical tape",
Hot melt glue - can be used to secure filmsy connections too, I find the glue-gun as "technician's best friend" beside blu-tack and strings.

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