There are tutorials on the website explaining how to use them. I've placed 10 or so BGA's using those having an X-Ray of each one taken after reflow. Each one has come back near perfect.
Although I have a 5 zone convection reflow oven. I imagine this could be reflowed with a heat plate and an air gun
I was confusing my Mils with mm
Yeah, I looked into those stickons, and I assume they do work (looks like they should). Unfortunately, for a PCB like mine that has a few (7) BGA components on it, the cost of those 7 stickers is more than the cost of the assembly house to assemble the PCB. So yeah, it does let you "assemble at home", but it isn't cost effective. It is potentially "time effective", assuming you order the stickers long before your bare PCBs arrive. Last time I checked they cost $7 each, assuming you don't accidentally mess any of them up. That's $50 per PCB for my PCB, and more for PCBs with more BGAs. And that still doesn't solve the same problem with QFN components (unless maybe they now have QFN equivalents... don't know).
My goal was to find a cheap and permanent solution that works for all mini-pitch, hidden-contact components. That's what my device is. I'm sure the stickers make more sense for some people, like if they only make a couple/few PCBs per decade. For others, not so much. In my case I need to make 25 of my larger PCBs (with 7 BGAs and lots of QFN-like components) to prototype larger systems and to provide [development] samples to others. So for me, even this one project justifies the manual place device and a reasonable reflow oven.