Why don't you do it proffesionaly at the component mounting factory?
They have a sort of stamp which looks exactly like the silk screen.
The other way is engraving with a high speed drilling machine (like
protomax) but looks ugly.

Vasile

On 5/7/06, Wouter van Ooijen <wouter@voti.nl> wrote:
> I want to give PCBs a serial number (for visual inspection only). I
> could write the number with a marker pen, or use a printed sticker, but
> I am afraid such markings won't last for too long.
>
> Do any of you have experience with using scratch-away markings using the
> silk or component-copper layer? Or maybe solder pads that are soldered
> to make the marking? I have a small area available on the component
> side, maybe I can even get rid of all copper there, but I can't free the
> solder side.
>
> Wouter van Ooijen
>
> -- -------------------------------------------
> Van Ooijen Technische Informatica: www.voti.nl
> consultancy, development, PICmicro products
> docent Hogeschool van Utrecht: www.voti.nl/hvu
>
>
>
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