The SMD pad size is already smaller than the physical tab (someone in a former?post pointed this out as an error and the pad size should be made larger). I'm not sure how much smaller it should be made...?
Anyway there is going to be no problem here going forward; it's in the manual, in the troubleshooting, quite easy to fix generally, and we are testing all boards for it now before shipping; and for future PCB revisions I moved Q104 a little further away, for which there is plenty of space on the PCB at that location, so there is no further trouble.?
On Mon, Aug 21, 2023 at 9:35?PM John Z <jdzbrozek@...> wrote:
Totally agree with the above admonitions to reduce the tab size for
the component.
Tony S. nailed it when he referred to the float and tendency to be
randomly surface tension driven.
JZ
On Mon, Aug 21, 2023 at 2:27?PM Tony Scaminaci <tonyscam@...> wrote:
>
> Yes, I totally agree on reducing the tab’s footprint. It’s well known that SMD components move during IR reflow and will float freely within the copper region on the board. Where they finally settle is a random variable with component mechanical tolerances also being a factor.
>
> On Mon, Aug 21, 2023 at 1:11 PM Donald S Brant Jr <dsbrantjr@...> wrote:
>>
>> On Mon, Aug 21, 2023 at 12:57 PM, Hans Summers wrote:
>>
>> it would be nice if the manufacturers didn't have this degree of slop in the angle of the AOD403.
>>
>> Perhaps the PCB footprint of the part(s) needs to be changed, to shrink the ground pad and its solder mask opening, which will constrain the movement of the part.
>> Remember that during reflow soldering the part is literally floating on liquid solder and the only thing constraining its movement is surface tension.
>> I had a product with some large Mini-Circuits surface mount amplifiers; the first pass had ~25% shorts using the MCL-recommended pattern.? When we shrank the ground pad (by about 25%) and widened the solder mask clearances we had 0 shorts.? Making the pad and solder mask openings symmetrical with respect to the centerline of the part will also help avoid skewing.
>> 73, Don N2VGU
>
>
