FreeLists / pcdlist / [pcdlist] Re: Component Polarity

["T.L. Dlouhy" <td.cad@xxxxxxx>]

At a couple of places I worked, we used "chamfered" pads and experienced no
solder problems or reliability issues. The only thing depends on the size of
the chamfer compared to the pad size for square pads. It could make the pad
look circular at a quick glance. From what I remember, a chamfer of 0.010 to
0.015 x 45 degrees was used on pads 0.060 and larger. If you have no room
for a silkscreen marking, but have room on the conductor layer, you could
place a marking in the conductor pattern. I have done this a few times.

Tom Dlouhy

0-----Original Message-----
From: pcdlist-bounce@xxxxxxxxxxxxx [mailto:pcdlist-bounce@xxxxxxxxxxxxx]On
Behalf Of Jack C. Olson
Sent: Thursday, May 30, 2002 6:37 AM
To: pcdlist@xxxxxxxxxxxxx
Subject: [pcdlist] Component Polarity


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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