I made a thread in another forum section a while back asking about quantity and size of vias I would need for a trace to survive a 20A surge, and I came away with a conclusion of 9 x 0.6 mm diameter vias. It was suggested to me that filling the vias with solder would enhance the current-carrying capacity. I wondered whether that would be possible to do during reflow soldering by leaving these vias unmasked and adding apertures for these vias to the solder paste stencil.
I had been looking around for any kind of advice, article, app note, etc. to see if this was possible and wasn't having much luck until I stumbled upon the magic term: "pin-in-paste". That is, the practice of soldering THT components by reflow. So I found and was following
this application note from Littlefuse where they recommended a paste volume twice that of the volume of the hole to be filled (I'm ignoring subtracting the component lead volume and adding volume for fillet).
But my resulting numbers seem quite... extreme, and I'm not sure whether I've made a mistake or not.
By my calculations, for a 0.6 mm diameter via in a 1.6 mm PCB, I need a paste stencil aperture of
2.76 mm diameter!
Via volume works out at 0.45 mm^3, making 0.9 mm^3 paste; using a typical stencil thickness of 0.15 mm then gives radius of paste 1.38 mm.
There's no way I could use such a large area of paste on these vias. For a start, there would be overlap because I have multiple in close proximity. I'm also sceptical of the ability of such a relatively huge area of paste to reflow properly down in to the via's hole.
Am I on a hiding to nothing with this? Should I forget it? It's really just a 'nice to have' to get these vias solder-filled, and I thought it'd be convenient to get it done with the solder paste; perhaps not.