Re: gEDA-user: PCB pin hole size

[Daniel Nilsson <daniel@xxxxxxxxxxxxxxx>]

On Tue, Jan 25, 2005 at 08:14:43AM -0500, DJ Delorie wrote:
> 
> > > > I think that 20mils hole was used to serve as drill guide for manual
> > > > drilling.
> > >
> > > crosses at hole centers.
> >
> > Ability to reduce holes would be usefull also for those who have to use 
> > postscript to cerate masks. 
> 
> None of these ideas is right.  The drill sizes should be the final
> hole sizes, and if you want a small dimple to help you get the hole
> centered, choose the "drill helper" option when you print your
> postscript files.  That puts an EXTRA circle in the middle of the hole
> just for this purpose.

I guess one can argue whether or not the drill size should be the
final size or not, it depends on the application of the PCB. For
through hole components and pressfit connectors I agree that the most
important size is the finished hole size. But for other types of
boards, I really don't care that much about the finished hole as I do
with the clearance between the via barrel and antipads on inner
layers for example. If I couldn't control the drill size that the PCB
manufacturer used I couldn't control the spacing between vias and
traces on inner layers either which becomes important for high-speed
applications.

So I think it's up to the board designer to agree with the fab shop
what the drill size means (finished hole or not), I don't see either
way as right or wrong.


-- 
Daniel Nilsson