I'm not sure why this happens or if anyone else has experienced this but
sometimes ExpressPCB will slightly shrink or enlarge the job being
printed.
Most of you probably know to print out the PCB layout on regular paper
and test the layout before wasting a board. Im just learning my lesson.
If anyone knows why Ive experienced this, please chime in.
Best Regards,
Steve Maroney
Business Computer Support, LLC
Mobile Phone:504-914-4704
Office Phone: 504-904-0266
Fax: 866-871-7797
From:
expresspcb@yahoogroups.com [mailto:
expresspcb@yahoogroups.com] On
Behalf Of Dennis
Sent: Thursday, July 15, 2010 7:04 AM
To:
expresspcb@yahoogroups.comSubject: [expresspcb] Re: Unplated hole
Well, there is more than one way to make a board. Plated through holes
are a bit of a trick though. The method I am familiar with is that the
double sided board is drilled before anything else. Then the board is
dipped in a catalyst solution that makes the fiberglass conductive. Then
the whole board receives a thin copper electroplating. Then the negative
etch mask is applied. Then the board gets electroplated with more copper
followed by tin. The tin also plates inside the holes. The etch mask is
removed. Then the board gets etched. The etchant used only dissolves
copper and not tin so the tin becomes a positive etch mask. Then you
have a board.
That works for simple double sided boards. I am not sure how the
multi-layer boards are made.
But if this process is used, the only way to make an unplated hole is to
drill it after the board is complete.
Dennis.
--- In
expresspcb@yahoogroups.com <mailto:expresspcb%40yahoogroups.com>
, "Nick Alexeev" <kender_a@...> wrote:
>
> Hello Jim,
>
> Before reading your post, I thought that drilling and plating occur
before copper is etched. I've got that idea from the PCB design book by
Craig Mitzner. Probably, I've interpreted the book incorrectly.
Probably, there's more than one sequence.
>
> - Nick
>
>
>
> --- Jim Drew wrote:
>
> That is simply not true. I have been working with PCBs for 35 years,
so
> if someone tells you simple drilled holes are difficult and require a
> secondary drill, do not believe them! A non-plated hole is very simple
> to create and costs nothing extra. To create a non-plated hole, you
> simply pull back the copper from around the hole. This leaves a ring
of
> non-copper around the hole and no possibility of creating a hole
during the plating process.
>
>
> --- Nick Alexeev wrote:
> >
> > > ...
> > > - even a simple unplated hole drill!!
> > > ...
> >
> > By the way, an unplated hole is not that simple. Drilling holes
without
> > plating is an additional step at the end of the process. In fact,
PCB
> > fabs that take gerbers charge extra for unplated holes.
>
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