How strong is the solder paste surface tension?

[poorchava]

I'm working on a design, that involves several stacked PCBs, which are connected with curface-mount 1.27mm pitch high pin count (50 pins) headers. Supplier for the connector is not known yet, but they will be similar to 20021321 series from FCI.

The question is: I have those connectors on both side of the PCB, will the surface tension be strong enough to prevent connectors from falling off the bottom side of the PCB during second reflow or should I specify some sort of glue to hold them in place?

[T3sl4co1l]

During what process, a second reflow?

It could be calculated, I think, but my instinct says it will fall.

I don't think components necessarily need to be glued for reflow, but under a wave soldering step, they do.

You could also hand solder the bulkier components after the fact, assuming the pins are hand-solderable of course.

Tim