I had trouble with this part with a solder mask defined pad.
Too little solder left to make joint relative to the rest of the pads.
Increased stencil aperture once we recognized the problem.


On Tue, Mar 27, 2018 at 1:19 PM, Wayne Showers <[log in to unmask]
> wrote:

> Graham,
> I have tested these using an Actual J-STD-002 Test System for which I have
> a procedure that I can share.  However, I moved away from the DIP & Look
> Tests and substituted Line Quality Tests which consisted of printing a
> liner on a board, placing the part in the paste and then running the part
> or parts through a cold reflow.  Since J-STD-002 is 245C +0C -5C, I would
> target a mixed alloy profile and send the parts through.
>
> If you are having solderability issues, I would try these actions in order:
> 1) Thicken the solderpaste deposit thickness and/or back off the depth at
> which the part is being pushed into the paste.  My most common failure was
> actually caused by the body of the part creating a rocking horse.
> 2) Try a M0 or M1 flux.  If you do this check instead of or before check
> (1) and you still have solderability issues, try hand tinning a couple of
> parts.  If M0 flux doesn't fix the issue, but you can hand tin the parts,
> it is almost certain that it is the rocking horse issue.
>
> Also, almost all SOT 666's are cut leads, so you are only looking for
> wetted connections, not side and toe fillets as they often will not form.
>
>