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Hi I am wondering if a PCB silkscreen layer can be printed directly onto a copper layer without a solder mask. I don't see this often but I have a design for which this would be useful. Has anyone done this?

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  • \$\begingroup\$ I haven't personally but I've talked to people who have, and apparently it doesn't adhere very well and it just comes off, possibly even while it's being manufactured or shipped. \$\endgroup\$ – Hearth Oct 30 '18 at 18:52
  • \$\begingroup\$ @Felthry: That's interesting. I thought they were both just epoxy paint, only the silkscreen is opaque and nearly always white. \$\endgroup\$ – TimWescott Oct 30 '18 at 19:56
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    \$\begingroup\$ @TimWescott I imagine there's a wider variety of silkscreen formulations than soldermask formulations. I know there's at least one PCB fab that has inkjet printers to do the silkscreen for small batches, even. \$\endgroup\$ – Hearth Oct 30 '18 at 20:00
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    \$\begingroup\$ Do you specifically want to print on copper, or do you simply want to print on a PCB without soldermask, i.e., mostly on the bare FR4 but might occasionally land on a copper trace? \$\endgroup\$ – Evan Oct 30 '18 at 20:21
  • \$\begingroup\$ @Felthry: "Well, sonny, it's called the silk because a long time ago there was this process called..." Will it still be the silk layer when Wesley Crusher is making boards for his History of Technology class? \$\endgroup\$ – TimWescott Oct 30 '18 at 20:44
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I've done this in the past, but it was unintentional and before the silkscreen actually got printed on the copper, the manufacterer removed it before it got to production

The best people to talk to about this would be the manufacturer, usually when you do print on copper they'll send you an email or just remove it. They'll be able to tell you if it will work or not and since every manufacuterer used different silkscreen formulations and ways to print (some are like a dot matrix printer) they would be the one to ask.

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