Dom,
That is fine but it is no reason to create SMT pads off-center for the
purposes of creating a PCB. In designing PCBs for over 25 years now, your query
is the first time I have heard of such reasoning for off-centering SMT pads.
There are any number of methods by which assembly/fab facilities create their
test fixturing and probe points, none in my years of designing boards was ever
accompanied by any request to off-center SMT pads.
I would have to believe that the software for flying lead probes
normally has this functionality built into their software/utilities. Whenever I
have had blank or assembled PCBs tested by a shop, the probe points are always
off-center near the external edge of the pad where the probe dimple will not
interfere with coplanarity of the lead attachment. I have never been asked for
any modifications or off-center pads, nor will a lot of CAD packages accomplish
this feat. That said, I have to wonder if you are possibly doing something
like creating your own flying probe tester and as such it doesn't have that
functionality built into it. Maybe an improvement in that test software is
needed, rather than "munging" up the PCB design with additional hurdles/burdens
and compromising the other core functions of the PCB design package. Not that I
am promoting tossing designs over the wall to manufacturing but your request
just doesn't fall within the expected norms within the industry. Offsetting SMT
pads is just not common and Protel is definitely not a package that supports it.
Sincerely,
Brad Velander
Senior PCB Designer
Northern Airborne Technology
#14 - 1925 Kirschner Road,
Kelowna, BC, V1Y 4N7.
tel (250) 763-2329 ext. 225
fax (250) 762-3374
-----Original Message-----
From: Dom Bragge [mailto:[EMAIL PROTECTED]
Sent: Tuesday, March 14, 2006 8:27 PM
To: Protel EDA Discussion List
Subject: Re: [PEDA] off-center pads
Abd ul-Rahman Lomax <[EMAIL PROTECTED]> wrote: At 09:46 PM 3/12/2006, Dom
Bragge wrote:
> Does anyone know of a way to create off-center SMT pads in protel?
Pad center is not really relevant to SMT pads.
It is for us (hence the question) so why assume it is not relevant?
The pad origin/centroid/xy gets stripped out as a location of the pad w.r.t.
the rest of the board & that position gets hit (+/-tol) with BBT Flying probe
tester. I don't wish the tester to hit the centre of the pad, I'd like it
toward the outermost edges. This is my reason to offset. Instead of specially
munging the board data if it is built into the library part, it will work
forever more (or V6, whichever comes first).
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