Solder running on parts

[Marsupilami]

Hi Folks,

Anybody could tell me what's the proper name of this phenomenon?

Solder is running up and away on parts. What concerns me on this particular one is how it goes around the lip and gets inside the connector body.
Is there a property of solder to look for regarding how viscous it is or something that's related to this? I can't seem to find any related info but I might be using incorrect terms.
Another suspicion I have is that the solder might spend to much time above liquidus as I happened to notice it towards the end of the cycle. I obviously need to do my experiments but if there's some common knowledge I'd start tuning my parameters accordingly.

Thanks!

[ANTALIFE]

surface tension + adhesive forces = capillary action

https://en.wikipedia.org/wiki/Capillary_action

EDIT: One quick experiment you could do is adjust the paste shape & volume. Like rather than having a big "square" blob of solder paste you could adjust the shape to be a 2 or 4 small squares. As for what solder chemistry to be considerate of, flux would probably be a key one. But I think easiest thing to do would be to contact some solder manufacturers (chipquick, kester, MG...) and see what they recommend, as I am sure they would have run into this "issue" before

[AmnevaR]

I had experience with such phenomenon when assembling some prototypes on my previous job. Adjusting solder paste shape and plug in those holes with high temperature silicone did a trick.

[Marsupilami]

surface tension + adhesive forces = capillary action

https://en.wikipedia.org/wiki/Capillary_action

EDIT: One quick experiment you could do is adjust the paste shape & volume. Like rather than having a big "square" blob of solder paste you could adjust the shape to be a 2 or 4 small squares. As for what solder chemistry to be considerate of, flux would probably be a key one. But I think easiest thing to do would be to contact some solder manufacturers (chipquick, kester, MG...) and see what they recommend, as I am sure they would have run into this "issue" before

I'll try a different paste. That's a easy experiment. The paste shape... I'm not sure, it seems to me that there's no abundance of solder there so if I remove it I starve the joint. I might try something though.

[Marsupilami]

I had experience with such phenomenon when assembling some prototypes on my previous job. Adjusting solder paste shape and plug in those holes with high temperature silicone did a trick.

Yeah the via plugging is ongoing but there are no vias on the right side where I'm concerned. I might mask off the stancil farther from the board edge.

[Cerebus]

"Wicking" is the term I'd probably use.

You can probably alleviate this problem by reducing the amount of solder paste on the pad. You might even want to consider/investigate modified solder mask shapes in the same vein as these:



i.e. You might want to consider not putting paste onto the pads in areas where it's flowing away and around corners from.