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For various reasons, I need to pad a bit more solder paste onto a fixed-size pad, and I cannot change the stencil thickness without messing up other footprints.

The pad is a 1.2mm diameter circle, and I've drawn the paste to be 1.36mm diameter, so about 0.16mm of the paste extends paste the pad. On my 120um stencil, this 0.16mm "extension" increases the solder on the pad by my target amount of about 28%.

But this is only true if this extension of solder sucks into the pad during reflow. Is it reasonable to expect this to be the case?

In green is the copper, and in teal, is the solder paste.

Solder paste

Copper

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    \$\begingroup\$ Generally yes, but you would also want the boards to go through a good washing process to clean the remaining solder balls. Best bet is to ask the assembly house though. \$\endgroup\$
    – Wesley Lee
    Commented Nov 13, 2020 at 14:03
  • \$\begingroup\$ ^^^ Second that - Talk to your assembly house for guidance. This kind of thing is process-dependent. Don't guess your way into it. \$\endgroup\$
    – Kyle B
    Commented Nov 13, 2020 at 18:46
  • \$\begingroup\$ I've done this for pin-in-paste parts, and it worked without a hitch, albeit with a small number of boards, and TH parts. Still, I was pleasantly surprised how little (none) solder was balled up around the PCB. I was prepared for some cleanup, that didn't need to happen. Good luck! \$\endgroup\$
    – Chris Knudsen
    Commented Nov 13, 2020 at 21:41

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