"Practically" smallest pin-pitch row of holes for programming and debug

Any idea on “practically” smallest pin-pitch row of holes for programming and debug. Need 7 to 8 pins. Rigid PCB double side, 0.6mm thick

0.05 inch pitch or others?? From drawing, this “pico” clip is 0.1 inch wide. Can they work with 0.05 inch hole with clip body ‘offsetting’ (upper/lower) from each other clip?


Pico-sized clip

Spring-pin clamp. Photo is 0.1 inch. Any finer pitch model?


I’ve used this a few times. Space efficient and cheap but needs to be on a board edge.

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You need more pins but for those who need 3…
I took 2x2 1,27mm pin header footprint. Deleted one pad. 3 left I shifted very little outside. Such 3 pin connector we use for debug and programming.
For debug we solder into it 2x2 pin header (with one pin removed) and use 2x2 socket to connect programmer/debugger with it.
For production programming we use 3 pins from 2x2 header just temporary inserted into these 3 holes. Thanks to holes being little shift this get enough good contact for few seconds needed for programming.
Thanks to having only 3 pins you can’t insert this pin-header wrongly.
You can see this solution (on the left) in PCB I showed here long ago:

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I use a 2x3 pogopin clamp in 1.27mm pitch with great succes. I do ICSP programming with it. As for a footprint I use the default 1.27mm male pin header in 2x3 layout.

I once chose for this footprint because I had some PCB’s which had to be somewhat small but my larger designs adopted a 1x6 pogopin clamp in 2.54mm. And so I lived long and happily afterafter with my 2 standards :+1:t2: .


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