The point 6.56 and the Teensy's testing are examples about testing, also the pictures below. Now suppose you want to do a SMD board to the size of fingerprint or smaller. The earlier video mentioned things such as "automatic optical inspection" about 4.20. I think the Teensy-style physical testing with pressing to some conductive golden pikes is impossible with very small SMD boards — or production/testing boards should be larger to have some testing holes that are cut out later.
How can you test some very small SMD boards?
Examples about testing with pikes
Best Answer
In the semiconductor industry these are called DUT (for Device Under Test) or Load boards and they map from the ide pins to the tester standard connection format. They can be fairly expensive because of size and thickness (to ensure stiffness).
However, you don't need most of that. at the center of a DUT board are cantilevered comb like structures that are very stiff but are spaced at the 100 um pad pitch with 50 um tips. These are relatively inexpensive, no more than the cost of a single pogo-pin.
Here is a super fancy, RF matched and reinforced version:
If you look closely you can see a bunch of very fine fingers. Of course you can only use these under a microscope as you will bend the crap out of them if you hand place them.
here is what a old style DUT board looks like. A lot of the design is the interface to the system electronics, which you don't care about.
Originally pogopins were developed to contact the DUT board to the tester.
Here is a picture of wafer probe or probe fingers taken from UP patent 7688097 B2
This is still very fancy. I have seen these "combs" go for only a few $100's
Here are some picoprobe probecards from GGB industries which I've used.
And finally if you search on probecards you get lots of hits.