Designers that pass the IPC test KNOW that led's of the PTH variety should be designed to use a square or
rounded rectangular pad to designate ANODE.  I have vendors that have long leads that are anode,  others
use long lead for cathode, some claim that the leads are the same but one is slightly larger than the other
at the base etc.  That is why we designate on the PCB with a square pad and have an SOP in place that
describes that LED completely to avoid just what happend to you.  Anywayz happy holiday and call in sick
all next year and claim you have an early version of the year 2000 bug flu!

Mark Ross
Sr. Design Engineer
Whistler Automation Products Inc.


Stephen R. Gregory wrote:

> Hey ya'll...
>
>      Thanks for all the responses! Most of them were related to the part
> getting too hot or something along those lines, such being mounted flush to
> the board and having failures, but then standing them off and the problem
> going away. But what confused me at first with that reasoning, was that these
> LED's that were failing were being stuffed with stand-offs...but then I
> remembered something...the first 3 or 4 panels that we waved, we stuffed the
> LED's in the wrong way...and the ones that were failing were the ones that we
> reworked correcting our little faux pax...two heat cycles... makes sense.
>
> You know that old saying; "Long lead goes in the square hole."?...not on this
> board it don't...it bit me AGAIN! Dammit!! Why is it that there are a only a
> very few board designers that go against the rest of the world when it comes
> to going along with the same kind of polarity markings or conventions that
> everybody else uses? It seems to be more with LED's too...this is not the
> first time this has happened to me, and I'm sure it won't be the last. But
> that's what it wuz...
>
> -Steve Gregory-
>
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