Ever flipped an op amp belly up?

[Christer]

I am working on a PCB layout, or rather a Veroboard layout, and
found that in this particular case it would be very useful if op
amps came in two variants, with symmetrically reversed pinouts.
Of course it is not realistic to manufacture dual versions, but
anyway, in this case it would make it possible to do a simpler
and better layout. So, I got this idea, why not just bend the
leads over 180 degrees and voilá, you have a mirrored op amp.
Of course once can put the op amp on the opposite side of
the board instead, but that seems a less preferrable way,
especially if using PCBS with groundplanes. I would be surprised
if I were the first to get this pretty obvious idea, so I am just
curios, have any of you used this trick already?

(Actually, I decided not to do it in this particular case, since I
will use sockets and will want to swap op amps frequently,
and don't like the idea of having a large bunch of flipped
op amps lying around. I will keep it in the back of my head
for future use, however.)

[purplepeople]

How about wiring up an adaptor using DIP sockets so that the stack looks like this:

PCB - DIP - Adaptor DIP - IC

:)ensen.

[Christer]

Yes, but that is a complex solution with bad electrical properties.
Just bending the pins is done in a few seconds, and shouldn't
be any problem if you're careful and don't bend them back
again.

[peranders]

You can bend the legs 180 deg but not too many times....

Only a few IC's have mirrored pinning. Some DAC's have it because they are intended for single sided pcb's and tne IC is SMD.

Have many has used this thick?.... have many have missed "top view" and "bottom veiw" when you have made a pcb, hands up?

To be honest I have never done that but I know a couple of people which have.

[DRC]

(Hand held up)
I managed to do this on a small number of 'horribly expensive to make' hexagonal PCB's . It would have been too embarassing to get them remade so bending the pins was the only option - luckily there were only a few DILs and there was no chance that anyone would ever see them again (too contaminated to ever handle again) !! They worked fine BTW ...

Dave /don't try this at home ...

[Christer]

DRC,
That's another reason to do it, of course. Didn't think of that.
I would probably have done the same in your situation.

[jackinnj]

Originally posted by Christer
Yes, but that is a complex solution with bad electrical properties.
Just bending the pins is done in a few seconds, and shouldn't
be any problem if you're careful and don't bend them back
again.

The technique is called "dead bug" -- i.e. the critter is like a roach on its back -- it's used a lot by ham radio guys.

[Christer]

Originally posted by jackinnj


The technique is called "dead bug" -- i.e. the critter is like a roach on its back -- it's used a lot by ham radio guys.

Interesting. Is it for layout reasons as I suggested, or does
it have some other radio-specific purpose?


BTW, it should also have the side-effect of slightly more efficient
cooling, since we end up with something like the Intel
flip chip package. This effect is probably negligible unless a
heatsink is used, however.

[jackinnj]

i think it's mostly to get some of the pins as close as possible to the ground plane.

the other popular technique is the "Manahttan" printed circuit board -- for point to point wiring of HF circuits you just tack your components "dot to dot" which are laid out like the streets of New York.

[Christer]

Originally posted by jackinnj
i think it's mostly to get some of the pins as close as possible to the ground plane.

Why would that make a difference? Doesn't the ground plane
usually run over the whole surface of the board so all pins are
equally close to it whatever way we mount it? Or do you mean
it is in order to get the return currents to go where you want
them in the ground plane? That would make sense.