[sdiy] square pads

[ASSI]

On Wednesday 13 October 2010, David G. Dixon wrote:
> Concerning orienting ICs, I line them all up straddling the power rails,
> so I always orient them with the +V pin on the same side.  This means
> that most quad opamp chips are upside down relative to most other chips.

You use quad opamps? Heretic! :-)

Seriously, if all IC of the same type get the same orientation that's good 
(people will likely stuff them at the same time and the go to the next 
type).  It is still bad if the board looks something like that if the IC are 
all the same DIL16:

  ==< ==> ==< ==> ==<

  ==< ==> ==< ==< ==<

  ==> ==< ==< ==< ==>

I did board inspection and repair (the stuffing was done by hand) for a 
while and boards looking like the above were always the ones with the most 
errors and slipping through inspection most easily.  For inspection I've 
started to use paper masks that left only a single orientation open so that 
a wrong part orientation would jump right out at me.  For the stuffing, we 
moved the parts at different orientations to separate stuffing places 
whenever possible, but that's not an option for kit builders, obviously.  
Something like this would usually be OK, but still sometimes someone would 
just "keep going with the flow" and put in a complete row in the reverse 
orientation:

  ==< ==< ==< ==< ==<

  ==> ==> ==> ==> ==>

  ==< ==< ==< ==< ==<

Instead of centering the parts over the two rails you could maybe slightly 
shift them depending on orientation, that would also make it easier to "line 
up the dots" after stuffing.

>  Hence, the desire to use square pads for some clarity.

You don't see them from the component side and from the solder side the pins 
all look the same anyway. :-P

And don't make people look under a board that's stuffed, but not soldered 
yet. :-)


Achim.
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