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For my product I'm designing an enclosure and I thought that I could use a PCB to make the cover. I can place copper traces as touch buttons, and remove solder mask and copper to make semi-transparent holes for LEDs. However, I've never seen a commercial product have an exposed PCB, except some products directly sold to makers (e.g. https://teenage.engineering/products/po).

Is there a reason for this?

The only reasons I can come up with are:

  • cost for big quantities vs. plastic (not my case right now)
  • less "refined" aesthetics vs. plastic

Are there any other reasons? Possible safety risks? Certifications needed? Note that my product has 380V AC inside, but the front PCB is galvanically isolated.

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Are there any other reasons? Possible safety risks? Certifications needed? Note that my product has 380V AC inside, but the front PCB is galvanically isolated.

In Europe, if your case has conductive parts, it needs to be grounded. So, unless you're only using a single-sided PCB with no metal going through the PCB substrate, that will require a three-pin connector, which is a big no-go in a lot of situations. In the other situations, using a bit of shaped sheet metal as enclosure is probably a lot easier (not necessarily cheaper material-wise, since you'd need a tool made to build the exact shape of metal, but easier to mount things in, easier to handle, store, test). I am not a lawyer or product design expert – but probably there are more reasons than these.

Also, 380V AC sounds a lot like you want a stable enclosure. PCBs aren't meant for this kind of applications – they are relatively brittle / not shock resistant.

In all cases, a letal-voltage enclosure will be required to be "reasonably foolproof". Dropping the thing shouldn't expose the internals. Building that from PCBs sounds like a lot of structural elements (standoffs, guides/shafts/profiles…) need to be added to make a PCB enclosure reliable. That will have inhibitive complexity.

Also, and this will vary very much with legislation, exposed edges of fiber glass material themselves might be prohibited. You don't want to shave of fibers. Again, this can be solved with using non-PCB edges/guides and whatnot, but at that point, the PCB becomes more of a problem than a solution.

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  • \$\begingroup\$ You could probably design it with an exposed PCB surface, but with a proper structural cover under it. Also some PCB are made with lead, so you probably want to avoid that. \$\endgroup\$ – hekete Jun 4 at 13:41
  • \$\begingroup\$ @hekete these lead-containing PCBs would most probably be already problematic inside the device, under the RoHS directive. \$\endgroup\$ – Marcus Müller Jun 4 at 13:43
  • \$\begingroup\$ Thanks for the insight. To clarify: PCB will run on 5V and be galvanically isolated from the HV circuitry, there are no exposed copper surfaces, there is copper under solder mask but it's grounded. Enclosure is strong and solidly fixed to a wall, the PCB is mostly cosmetic and is not subject to strong forces. The PCB will have its edged exposed only during installation, as after that its border is hidden behind a snap-on plastic frame. \$\endgroup\$ – MGG Jun 4 at 14:07
  • \$\begingroup\$ Again, not a product design expert. But if you have something that is screwed to a wall, has a snap-on plastic frame: why expose the PCB at all? Also, as far as I can see, internal galvanic isolation doesn't matter. Metal enclosure parts == earthing requirement. \$\endgroup\$ – Marcus Müller Jun 4 at 14:19
  • \$\begingroup\$ It's for design customization and cost reasons. Plastic required an additional mold, and I'd still have to fabricate the PCB of a similar size for LEDs, touchpad and other stuff anyways. \$\endgroup\$ – MGG Jun 4 at 14:25

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