Re: gEDA-user: How much to bulk up holes?

[DJ Delorie <dj@xxxxxxxxxxx>]

> I understand that I'm specifying a drill size,

It depends on the fab.  4pcb, for example, wants finished size because
only they know how their specific process for that board will affect
finished hole size.  Others want drill size, and tell you 0.1mm for
barrel thickness (2x = hole shrinkage), etc.

> and I'll lose about 3mil in finished hole diameter from the plating.

It depends on the process.

> If I look at a manufacturer recommended PCB layout and it calls for a
> hole dimension, do I bulk that up, or keep it?

It depends on the fab.  Yes, I'm repeating myself, because it does.
The spec wants a finished hole size.  If your fab wants finished hole
size, give them the size you want.  If it's drill size, see how much
they want you to oversize it.

Also, you need 5 mil for solder wicking.

> It looks like they're taking it into account, but I'd hate to make a
> board with holes too small for my connectors...

When I do a board here (no plating), I use smaller than average drills
so that the parts stay still when I put them in.  It also allows for
sloppier drill alignment.


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