I am working on a project which involves micro-controller and switches (triacs and EM relays). Due to size constraint, I need to stack one over the other. Here is unfinished relay and triac board which will go on top of micro-controller board of the same size:
PCB description: 220V to 5V offline switcher on the left. It has a switching frequency of 65 kHz. Two transistor driven electro-mechanical relays in between and 6 optically isolated triacs on the right. There are a few connectors for optional sensors.
I have given 4 holes in corners so that I can use spacers and nut bolts to put the two PCBs together. Electrical connection between the two will be made using either a cable or header pins (yet to be decided).
As such what should be the minimum distance between the two PCBs so that high voltage or whatever noise is there in ac lines don't disturb the delicate electronics below?
Is there something which I should use in between to provide added safety to my micro-controller board?
I was thinking of some plastic sheet the same size of PCB or two plastic sheets with a thin metal foil sandwiched between them but I am not sure whether they will have any impact or not.
Any suggestions regarding this will be much appreciated.