On Nov 25, 2010, at 4:05 PM, Rick Collins <gnuarm.2006@xxxxxxxxx> wrote:
> At 05:01 AM 11/25/2010, you wrote:
>>> I am missing the reason you must mirror the footprints, however.
>>> Aren't the pins still in the same orientation they would be with the
>>> standard footprint? Since your DIP packages are mounted in the
>>> "normal-side-up" orientation, it seems the pins should be in the right
>>> order, unless you have placed the IC on the "component" side of the
>>> board in pcb... ?
>>
>> Yes, the component is at the same position, but traces are on
the opposite side of board so something must be mirrored. SMD
traces are at component layer. Through hole components have traces
on solder layer. Or both of them? Well, you confused me now :-)
Maybe I did not have to mirror the footprints.
>>
>> regards,
>> Jan
>
>
> Yes, of course you have to mirror the ICs that you are changing
from through hole mount to surface mount. As you say they are on
the opposite side of the board from the pads, so now the pads need
to be mirrored, unless the software is capable of moving the pads
from one layer to the other without changing how they look on the
screen. But normally it treats this as moving the part from one
side to the other and you have to mirror the footprint to keep pin
one oriented correctly.
>
> Heck, if it wasn't needed to mirror the footprint, it wouldn't
work correctly after you do mirror it.
>
> Rick
Rick,
Carefully look at an so8 and a dip 8
And really explain why you need to mirror a footprint.
Because the top side of a dip footprint is identical pinout as so8.
(At half of the pitch). Just remove the bottom pads.
Another way to think of it, if you took an dip package and made it
into a gullwing and soldered it to the dip footprint. You would have
vias through the board to that "mirrored" footprint so that
mirrored footprint was put on the wrong side of the board and you
had to move it through the layers.