Electronic – Is solder mask a valid electrical insulator

insulationpcb-design

I had some PCBs manufactured prior to ordering all of my components 🙁

It turns out that the surface mounted 1W LEDs I'm going to use have the heat slug connected internally to the LED's +ve terminal. Unfortunately I have a copper pour over the entire top of my boards, and it's part of the GND net.

Can I rely on the solder mask to insulate the +ve voltage (~3V ish) from GND? Long term?

Edit following comment:-

  • Simple home project to run in my man cave.
  • Once built, will not really be moved.
  • The led will only run @ 100 mA. I just like their size and spread.
  • If insulation fails, it will be a direct short across a modern 5.1V/2.5A wall brick switcher. Not really a biggie as there's a dropper resistor.

I'm just curious for the future…

Best Answer

No, I would not rely on solder mask as an insulator. It is very thin and can be nicked easily.

I think the bigger issue is going to be how to properly heat sink the LED without a good thermal connection to the heat slug. High power LEDs usually want the heat slug soldered or thermally epoxied to a heatsink. This can be PCB copper, but since you stated that the pcb copper is connected to the GND net you can't connect to it.

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