Creating a good programming & test jig can be a daunting task if you’ve never attempted it before. Here is an example to demonstrate that it’s not that hard if you have a good plan.
I recently had to create a programming jig for an ATmega328PB based board. 1mm diameter test pads were placed on the bottom of the PCB to give access to the ISP pins. Normally one would add two 3mm diameter holes to locate the PCB on the jig, but this PCB was too small and only had two indents on each side to keep it in place. Here is a picture of the board placed on the jig and held in place with two M3 hex spacers on each side:
Here is a picture with the board removed. Note the spring loaded test pins sticking through the top mezzanine PCB:
The test board has 12 through-hole pins that would prevent it from sitting flat on top of the top mezzanine PCB. Holes are made in the top mezzanine PCB to accommodate these through-hole pins:
Here is a picture with the top mezzanine PCB removed. Note that the spring loaded test pins are not soldered to the bottom routing PCB. The gold coating of the test pins and the tight fit of the through-hole pads make a good electrical connection:
The ISP test pads are routed to a standard 2×3 header on the side. +3V3 is supplied with a bench supply via the blue screw terminal. Finally, here is a side profile view to show how it all stacks up:
As always, enjoy, and I hope a few pictures were worth a thousand words.
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