N.B: I'm still a 14 years old boy that is just a beginner in electrical engineering.

I've just finished My first Successful Single Sided PCB Project, which was a Relay controlled wirelessly via an infrared remote, so a part of the PCB must handle a 220Vac.I made the traces which carry 220vac so thick so that it can carry high current and voltage.

My main Problem is that I want to isolate the copper side of the PCB to avoid electrical shock and short circuit but I don't know what is the substances I can use and How ?

And don't forget that these traces can become hot alittle bit.

  • 4
    \$\begingroup\$ I'm not sure if this is what your question is asking, but a good way to isolate the circuit board from a user is to put it in an insulating box (the circuit, not the user). \$\endgroup\$ Sep 11, 2018 at 17:34
  • \$\begingroup\$ @Andrew Morton And what is the material of the isolating box ? \$\endgroup\$ Sep 11, 2018 at 17:44
  • \$\begingroup\$ Typically it would be ABS; there are some examples here. \$\endgroup\$ Sep 11, 2018 at 18:17
  • \$\begingroup\$ @ Shams The electrical resistance of standard PCB foil (1 ounce per square foot) is 0.000500 ohms per square. Understanding why ANY SIZE SQUARE applies is a fun exercise, a bit of drawing and thinking. And the thermal resistance of a square of that same copper foil is 70 watts/ degree C, the heat flowing only in one edge and out the opposite edge. \$\endgroup\$ Sep 12, 2018 at 4:38

2 Answers 2


Great to be doing stuff like that at this age!

I think the previous answer did not address the question which was how to insulate PCB trace.

If you circuit runs 220V you probably want to put it inside a plastic box.

You can also insulate it by putting coating the trace with resin like epoxy or you can put the whole circuit inside silicone

There are also some spray to do so

pcb covered with silicone.

  • 3
    \$\begingroup\$ Since you mention silicone, it may be a good idea to link that other answer, which gives details about which kind of silicone is appropriate. \$\endgroup\$
    – dim
    Sep 13, 2018 at 14:48

N.B: I'm still a 14 years old boy that is just a beginner in electrical engineering.

Excellent! Get a head-start by starting electronics at a young age :-) I did the same and never regretted it.

Indeed for high current you want the traces to be wide

For high voltage you want the distance between traces to be large

And don't forget that these traces can become hot alittle bit.

If that happens then you might need thicker traces. If that's not possible a way around that is to make the copper traces thicker using ordinary solder. That will only work if there's no soldermask on those traces. If there already is soldermask, you could carefully scrape it away (don't damage the copper!).

How wide should your tracks be for a certain current? It depends on the current, copper thickness and how much temperature rise you allow. Yeah, not easy, there's a calculator here.

How large must the spacing between the tracks be? There are calculators for that, here is an example.

For 220 V AC you generally need about 1 cm of distance between the mains connected side and the "safe to touch" side. Ideally there would be a slot (a hole in the PCB) in between.

What you could also do is look for similar PCBs, that can even be old PCBs from discarded equipment like a microwave, PC power supply or a TV. Look at those PCBs to get a feeling for how it is done.

Last tip, if you do not know the EEVBlog yet then you should have a look. There are several videos regarding circuit and PCB design.

  • \$\begingroup\$ Bimpelrekkie, I appreciate your answer very much and I learned alot of your answer but Damien answer is what I need. sorry but I still learn English and I used incorrect word which is isolate instead if insulate.forgive me from my fault please. \$\endgroup\$ Sep 14, 2018 at 15:36

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