Adeel Malik wrote:

> Hi All,
>          Some FABs require that NC Drill data for PCB fabriaction should be
> given to them in Excellon Format. In Protel we have 2:3,2:4, 2:5 in Englich
> units and 4:2,4:3,4:4 in Metric Units. Can someone comment as to which of
> these formats supported by Protel correspond to Excellon Format (or Whats
> the definition of Excellon Format) ?.

All of them are "Excellon" format.  This is a variant format of the RS-274D
language specification, in fact a different variant of the same spec is also
used as
"Gerber" format!  Excellon format is quite easy.  There is a comment header
at the beginning that defines the format (%FSLAX43Y43) or something like that
means Format Spec. absolute coordinates, and both X and Y are implied
resolution of NNNN.NNN, with the decimal point supressed and the
leading zeroes (or is it trailing, I ALWAYS forget?) also suppressed.
Following the header, additional lines usually define the drill sizes.  Then,
a tool number (ie T01) is called for and then a list of X and Y coordinates
are given, these being the locations of the holes in that size.

Depending on the grid your holes are aligned to, the number of digits and the
unit definition (mm or Inch) can be selected to best define hole location.
If your holes are all on a .1" grid, 2.5 would just waste file size with a lot
of
zeroes.  If you have a mixed imperial/metric grid, with holes on .85/.6/.5/.4
mm
pitch, then you probably need to specify more significant digits to the right
of
the DP.  2.5 means there is a location for 0.00001" resolution, which is
rediculous,
as no drilling machine has a hope of hitting a spot with 10 u-Inch resolution,
not even a laser.

> Secondly, some FABSs specify different distances between Pad/Trace to Board
> Edge for 1) Routing Method 2) For V-Cutting (scoring). So whats the point in
> specifying different distances and What does the Terms "Routing Method" and
> "Scoring" refer to ?

You probably need to work out with YOUR board fabricator what they need in
this regard, and then see how it works out in your board design.  You probably
don't
want the router to trim the board right across a component hole, but maybe your

design really needs this.  As long as you say this is really what you want,
most
board houses can make it that way, but they will call back and say they think
you
have an error in the routing outline.  I put a trace on a mechanical layer and
have
it added to all layers, and tell the board maker to route the board outline to
that
trace.  That seems to satisfy most makers.

Scoring is how you have the router cut part way through the board, so you can
put large panels into your pick and place machine, and then break them apart
into single small boards after stuffing, soldering and testing.  Most makers
charge
extra for this.  If you are making them by hand, don't bother with scoring.

Jon


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