If I put a via (which normally would get “tented” with solder mask) in a SMT pad that is not covered with solder mask, does the via stay tented? I suspect not.
If not, how does one accomplish this?
Why would you want to do that? How would that pad then work?
It’s becoming a more accepted technique for via-in-pad:
Funny, there was a discussion about this topic a couple of years ago:
I suspect it is tented with solder mask at the other side.
Just looking thru the data sheet and it talks of the thermal pad and the vias and it specifically says “Do not cover the vias with solder mask which causes excessive voiding.” to me it makes sense as it’s a ‘Thermal’ connection. It then goes on to say “Vias may be plugged to prevent solder loss and protrusions. This often produces the best thermal
performances but is not necessary or recommended because of the increased cost of PCBs and because the solder tends to wet the upper surface first before filling the vias”
So I think you have to check with the manufacturer whether they can plug or ‘Tent’ the vias at the copper plating stage, but certainly you don’t want solder mask under there
I talked to my assembly house, and they said to leave the pads open on the top and tented on the bottom.
So, for this design KiCad has no problems.
But, I have seen tech notes that recommend solder mask covered vias in thermal pads. Of course, I can’t find the document to link to it now.
Oh, hey - I found it:
1 Like
Sorry to be a bore but your document is talking about ‘Paste Mask’ solder paste is a compound of solder in some sort of suspension that melts at reflow. But further down we get “The newly released IPC-7093A explains how to create a Solder Mask Defined Thermal Pad to create solder dams between the checkerboard pattern and around the vias to prevent solder from flowing down open via holes. No need to plug these vias and save fabrication costs at the same time creating a reliable solder joint.”
Honestly good luck with that one 
I would imagine that would be pricey and maybe the FAB houses will offer it in time, but it is interesting to see these techniques slowly being available to the hobbyist and professionals alike, I mean who would have thought 6 layer boards for dirt cheap 
Why? this is done with BGA based packages since years and not that much of a showstopper regarding the price BECAUSE it’s “just” about the solder mask.(instead of plugging)
Don’t tell me, tell the guy asking the question if you have something useful to add as it’s no use to me ! as I pointed out, in my experience the FAB houses I use don’t have this technique listed in their capabilities section. BECAUSE IF it’s “just” about the solder mask answer the bloody question.