At 02:13 PM 3/7/00 -0500, Ron James wrote:
> To sum up my questions:
> 1) Does your company use standard hole size symbols across all
> designs?
As an independent service bureau I wouldn't be doing this. I can see the
purpose of doing it where all design is coming from a single source and is
being checked by the same engineers. But there is, in my view, a better way.
> 2) If so, does your software accommodate this, or is it a manual
> process for you?
I used to use Tango DOS PCB, and you could assign specific flash apertures
to drill symbols, and these definitions could be used by other designs. I
never did this; I always used the drawn drill symbols. I don't recall how
this is handled in OrCAD, but in Protel Advanced PCB 99SE, there is no
option, as far as I can tell, to use flashed symbols. However, there *is*
an option to plot the hole size numerically, and I find this far more
useful for checking than symbols or a letter code (which are the other two
options).
Drill symbols were invented for films so that they had a readily locatable
center which could be bombsighted to determine hole positions. With the
common use of CAD-generated drill files, this step is bypassed and it is no
longer necessary that the drill drawing *precisely* indicate hole position;
typically the drill drawing will be overlaid for checking with another
layer which shows position....
> 3) If so, do your end users (design, manufacturing or process
> engineers) find this to be valuable?
Fabricators have their own tools and I would expect that they would be
checking the drill *file*, not so much the drawing. For others who might
need to know what hole sizes are used and where, I highly recommend, if it
is available, using the hole size directly; no translation is required. I
use pretty small text, particuarly on boards with small holes close
together, but it is generally, as used, printed or plotted at 2:1 or better
for checking.
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Abdulrahman Lomax
P.O. Box 690
El Verano, CA 95433
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