Permanently marking PCBs

[artag]

I often have a need to write on PCBs, typically to record a serial number or mod level. But all the markers I've tried (includes Sharpie, Lumocolor, and pens rated for glass) seem to convert into dry-wipe when they encounter solder resist.

Has anyone found a reliable marker that will resist fingers, alcohol etc.  ?
Is there a surface treatment (such as silkscreen ink) that will make an area more resistant to cleaning than solder resist ?

[PlainName]

Tungsten scribe

[artag]

lol. Good permanence but low contrast.

Also - I didn't put this in the original requirements but polythene is another material that I have difficulty marking permanently, and although tungsten will indeed work it degrades the material badly.

[mikeselectricstuff]

I find permanent markers fine on resist - I use Staedler Lumocolor fine markers, but pretty much any permanent marker I've used is fine.

The only issue I see is finding a marker that's impervious to solvents when cleaning/reworking.

Also I always put a white silkscreen block for marking

[artag]

It may be that colour is also an issue. I've tried various black ones for marking channel number on some radio transmitters. They get a lot of handling and it eventually (ie too quickly) rubs off.

I remember that when we used to make PCBs with hand-applied etch resist many years ago, lumocolor red was recommended and, further, was not useful in the USA because they used a different ink formulation there. So it could be that some pigments are tougher.
 

[asmi]

Some label thermal printers can "print on" (more like burn into) a plastic tape which should be resistant to chemicals. Have you tried something like that?

[voltsandjolts]

Permanent marker then paint some clear electronics lacquer / conformal coating over the top of it.