The 12mil refers to the drill size, so it's the size of the actual drilled hole you get. This hole is then plated unless it's a purely mechanical hole. The plated inside diameter will be smaller than the drilled hole, of course.
Mine worked great, no problems with wicking. Hot air pencil reflowed perfectly with a small dab of paste on the thermal pad. (Boards were too small to bother with a stencil.) I also have an EMI shield on this board and the only screwup was I pasted the pads for the shield then realized I had to reflow the shield as a second step, leading to excess solder, but on the whole for a first try with a board shield and thermal pad it went surprisingly well!
Yep, thanks for the info guys - very helpful. I just went with a drill size of 13mil and added (I think) 4mil for the pad and called it a day. So 17mil/13mil. Will see how this works out, a little wicking isn't the end of the world as long as I get a reasonable thermal connection. (Experiments with the SOIC part shows it's not a huge consideration anyway.) 13mil is a pretty dang small hole and even less if plated. :) I was just confused since I couldn't make sense of the numbers. Pad size, drill size, yeah that makes sense.
Ah, the problem is I'm using KiCAD and it won't allow a via size <= drill size. Also, the drill size can't be left out or set to 0 - this will make it complain the drill size is smaller than the minimum size. My assumption, which is all it is since I can't find even a single example online of how to add custom vias, is that the via "size" in KiCAD includes the pad and maybe soldermask. (Which of course is pointless in my case since these vias are used for stitching.)
The minimum hole for a 2 layer PCB is spec'ed as 12mil. I'm curious if this can be used for a 13mil via?
I don't normally use such small vias, but this is for a TI PowerPAD device - basically an MSOP 0.65mm pitch with a grounded thermal center pad that needs to be soldered. I want to connect it to a ground pour on the bottom. TI recommends using 13mil or smaller vias to avoid wicking. But I assume this would actually refer to the hole size? If I want to use a 12mil hole what should set the via size to?
