> Olin:  When you spec a hole as "unplated" in the PCB layout program,
> how does that information get passed to the PCB maker (given just
> Gerber and Excellon files)?

Protel specifies it in the drill tool listing. Other CAD programs produce
an unplated drill file.

> What are some times this would be a problem?

I have used some SMT LEDs that shine through the PCB from the other
side. To asist in manufacture I want the hole to be as large as possible.
If the hole gets plated, I need to add in another tolerance to prevent the
plating shorting the pads on opposite sides of the hole.

In cases like that, I make sure it is pointed out on the mechanical
drawing and the read.me file that it is important that these holes aren't
plated.

Even though I expect a fab house to question anything ambiguous, I
agree with Olin that if you explicitly state "plate them" with a check box,
they should be plated regardless.

OTOH, the local morons have just delivered several hundred boards
with the assembly instructions silkscreened on them. Sigh !

Steve.

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