FreeLists / pcdlist / [pcdlist] Re: Component Polarity

[William Gilman <williamwgilman@xxxxxxxxxxx>]

Jack,

Part of what the IPC standards say in regard to legend whether it is
silkscreen or not is to make sure everyone knows what you're talking about.
You can use about any symbology you want as long as you have it documented
in appropriate locations...like an assembly drawing.  So, if you want a
rhombus (or whatever) for a pin 1 marking on a particular component type,
define it as such, and document it.

William W. Gilman, CID


Well, the intent of my question was identifying polarity WITHOUT A
SILKSCREEN.
Using the IPC standard recommendations without a silkscreen will be useless
as far as determining polarity down the road.
Modifying the recommendation COULD cause soldering problems, and I'm no
expert when it comes to solder fillets.

Anyway, yeah, I'm sure many of you picture a farmer sittin' on a tractor
when you hear "Caterpillar", but this day and age we have high resolution
displays and GPS systems and operators sitting in soundprooof environmental
chambers with 5-speaker stereo systems, emission control, maintenance
records, etc etc etc.
In the new millenium there's a lot more to tractors than a choke pull...

thanks to all,
jack






Doug Boone <dboone@xxxxxxxxxxxx>@freelists.org
30May2002 06:48 PM

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Strange, most Caterpillar's I see are pretty big! Guess all those pig iron
ballast take up most of the room.  Anyway my two
bits worth is to make whatever marking you use very clear.  Nothing is more
frustrating than to encounter a code or mark
which does not have a common meaning.  Why not go ahead and use the IPC
standards?  They were created with some forethought
for both assembly and for troubleshooting and test after assembly.  And if
the collective memory of all involved fails, they
can always reference the published standards.  In my experience shortcuts
are not short.  Meanwhile we will all get out of
your way when you field test those beautiful yellow brutes.
grins.
doug.

"Jack C. Olson" wrote:

> Here at Caterpillar we are starting to do some designs that are dense
> enough that the silkscreen gets in the way.
>
> We would like to have some method of identifying component polarity even
> without a silkscreen and without a drawing, and about the only thing we
can
> think of  is to lengthen the "pin one" pad for ICs, and cut the corners
off
> the anode or positive side of diodes and caps. What worries me is the
> shaved corners. After preaching to everyone the value of having some kind
> of standard land patterns, I'm now advocating six sided geometries?
>
> but anyway,
>
> Have any of you seen soldering or reliability problems by cutting the
> corners off a pad?
> Is there a "trimming ratio" I should maintain?
> Any other ideas?
>
> Jack




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