Tiny PCBs vs. large ISP headers — Pogo-pins to the rescue

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As of late I’ve been making smaller and smaller circuit boards, fighting for every mm² of space. The typical 6pin ISP connector used for programming a lot of the AVR micro-controllers has been getting in the way more and more.

In one of my recent projects, Serial-Knob I was forced to use a smaller header (2.00mm raster), and was ‘punished’ by having had to make an adapter for every single board that had found a new home. That was a pretty unpleasant experience, as it involved too much improvisation and it was way too fiddly work.

One of the latest projects required an even smaller programming header, 1.27mm raster, and I just couldn’t see myself soldering wires to such tiny pins. So I went looking for pogo-pins and was lucky to find a pack of suitable ones (“P50 – E2”) on ebay.

As the images might show, it was quite a task to assemble this tiny tiny thing. Pin alignment is crucial and it is really hard to do it just by hand. I had to make a little jig to hold the pins in place while soldering.

I tried plastic first, but that failed miserably.

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The one that worked was made from hard wood, I think oak. The 3×2 hole pattern, holes spaced 1.3mm, was drilled 10mm deep using a 1.0mm drill.

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The pogo-pins have a weak spot. I couldn’t mount them to minimize stress or put a sleeve over it, so I added a small blob of solder to reenforce it.

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A later revision comes with a little spacer/reinforcement board, which should be placed far enough down to keep stress away from the weak spot. I didn’t quite manage that in this photo, so I resorted to the solder-blob-method again.

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Some time later…

I received another set of boards from OSHPARK, and there was something wrong with the drills sizes. Apparently the fab had done something, and some vital holes were 5mil under-sized. Not good.

After a couple more board revisions hammered into my git repository, I had a eureka moment: why not use the apparently useless sub-boards (meant to slide over the pogo-pin shafts) as an alignment tool. The pogo-pin heads fit very nicely. Totally obvious in hindsight – of course – but it makes assembly so much easier. All that is now needed for assembly is a spacer block (wood, plastic, metal…) of the right height and a bit of glue or tape. Gone is the need to drill straight 0.7mm holes! Before I forget, poke holes into the tape. Otherwise the pogo-pin heads won’t align properly.

This little project may be found tindie.

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3 Responses to Tiny PCBs vs. large ISP headers — Pogo-pins to the rescue

  1. Pingback: Using Pogo Pins to Shrink 6-Pin ISP Connectors « adafruit industries blog

  2. I was unable to locate this on tindie. Is the PCB on OSH Park? Thanks!

    • robert says:

      Dear David,

      the latest version is on tindie.com, but the shop is offline at the moment. Oshpark.com wouldn’t help, as it requires 0.6mm board thickness.

      The old version shown here should work though. Assembly is trickier.

      You can find the gerber files on github. I can’t be of much more help now. Sorry.

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