You could use it as the logic board for a micro drone, something the size of a dime perhaps. Or other applications where weight or space are extremely limited. Another example might be a medical implant of some sort, this is small enough that it could be a part of a device that is meant to be placed inside an artery, or an eyeball, or an ear canal.
I make specialty vehicle electronics. My immediate thought was very small and cheap sensors. Similar to tire pressure monitoring but wired with CAN or something similar.
How would you ever actually practically use this
You could use it as the logic board for a micro drone, something the size of a dime perhaps. Or other applications where weight or space are extremely limited. Another example might be a medical implant of some sort, this is small enough that it could be a part of a device that is meant to be placed inside an artery, or an eyeball, or an ear canal.
Maybe an actual useful smart ring?
In small things. Probably not very feasible for hobby projects unless you can get it soldered on when the PCB is built.
BGA, like in the photo, isn’t the only option. There are options only slightly larger with hand-solderable packages (if you’re good at soldering)
This is already technically hand solderable with the right equipment.
I make specialty vehicle electronics. My immediate thought was very small and cheap sensors. Similar to tire pressure monitoring but wired with CAN or something similar.
In any use where size and or weight is important. For example wearables and flying drones
fly-sized spy drone
Wrist watch.
see comment from @Lumberjacked (it is complicated !)