Bob,

The answer to your question depends somewhat on your supplier.  However, in general, most non-plated holes are drilled at the same time as the plated through holes. They are prevented from plating by tenting plating resist over them -- the
same resist that is used to form the circuitry image.   Large holes or non-plated holes with a pad right up to the edge of the hole can not be successfully tented.  These will require a second drill process.  This means that the drill
machine must be set up a second time just to drill a relatively small quantity of holes.

So, in most cases, your supplier only needs one drill file because that is all they will use.  It is probably easier for them to sort out the holes that need second drill on an occasional part number than it is to combine two drill files
for the majority of part numbers.   However, I'm sure they appreciate the fact that you asked and were trying to make their life a littel easier!

Jay Soderberg
Holaday Circuits


Legal Notice:  All opinions are mine and mine alone.  The opinions expressed do not necessarily reflect the opinions of the management or ownership of this station.

>   ------------------------------------------------------------------------
>
> Subject: drill files-plated/non-plated holes
> Date: Thu, 24 Sep 1998 16:45:01 -0400
> From: Bob Walker <[log in to unmask]>
>
> Hi All,
>
>  I'm trying to better understand the process of drilling holes in a PCB
> and the files that are used by the board fabricators to do this. I am a
> PCB designer and presently send gerber files (fabrication gerber
> included) and a drill file (excellon format) to my board house for boards
> to be made. The fabrication drawing contains a drill table with symbols
> that represent each hole size and whether or not it is a plated or
> non-plated hole. I never allowed a plated and non-plated hole to be the
> same size in any of my designs because my CAD tools couldn't recognize
> that a plated and non-plated hole could be the same size and thus
> couldn't generate 2 different symbols for each. Well now my CAD vendor
> has provided me with the ability of tagging my padstacks as either a
> plated or non-plated hole so that I can generate a different drill symbol
> for my fab drawings. And I can also generate different drill files that
> can either include all hole styles, only plated holes or only non-plated
> holes which I thought would help my board fabricator out by not having to
> separate out the plated from the non-plated hole coordinates in the drill
> file. But when I called him to see if he could make better use of 2 drill
> files (plated and non-plated), he said he only wants the 1 file that
> contains both the plated and non-plated hole locations. Wouldn't it be
> better to have the 2 files? What don't I know? I would greatly appreciate
> all feedback from any designers or board fabricators.
>
> Regards,
>
> Bob Walker
> [log in to unmask]
>
>   ------------------------------------------------------------------------

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