Question: what pads and connector to use for production ICSP

Community PCB Design
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I’ve designed a board for production. Initially I will do a couple of small runs (10-50) before going to larger quantities. My design includes a microcontroller which needs to be programmed (PIC 18F series, with the 6-pin header for In Circuit Serial Programming).

Once we go to larger quantities, we’ll pre-program the devices before SMD assembly, but up to a point, in the smaller runs, we intend to assemble the boards with blank devices, then program them on the bench, as we will be doing some development and reprogramming, etc.

At this point, I have a 6-pin, 0.1" through-hole header designed into the board, and for the first one or two prototypes, I’ve soldered the standard .025" square pin headers for ICSP, as we’re likely to be reprogramming these first couple units a fair amount.

For units 3 and up to something around 50 or 100, (i.e. before we go to assembling with pre-programmed devices), I’d like to avoid having to solder in that 6-pin header during assembly, because we will eventually get to the point where we’ll have the firmware somewhat locked down, and we should only need to touch each board one time for programming. If I leave those through-hole pads (for the 6-pin header) unpopulated, I’d like to make a cable with an appropriate connector/contacts on the board end that I could just “press into place” on those ICSP pads for the few seconds it will take to program my device, and I’m wondering what kind of a connector would be best to use there.

I’m imagining I could just cobble up a cable with that standard 6-pin male header with the .025" square pins, and then during programming, place them in the PCB holes and kinda wedge it in at a bit of an angle (remember, I’m expecting to hold this in with one hand during programming), hoping that this will make sufficient contact on the 5 of the 6 pins that are important to ICSP on the PIC.

I’m just wondering if anyone has any ideas as to something that might work better. Doesn’t have to be super cheap, as I just need one or two to make up programming cables. In my fantasy world, I’m imagining a 6-pin connector with individual spring-loaded conical pins that would each seat into one of those empty through-holes on the PCB - kinda like the “bed of nails” pins used in test fixtures. With that as inspiration (or going off in a completely different direction…), does anyone have any interesting ideas to kick around?

I’m assuming for now that I’m stuck with my existing .100", 6-pin header pad pattern, and am looking for a solution for that, but I also welcome ideas for future designs, if a different pad pattern for the PCB would facilitate a different approach…

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svoynick:
In my fantasy world, I’m imagining a 6-pin connector with individual spring-loaded conical pins that would each seat into one of those empty through-holes on the PCB - kinda like the “bed of nails” pins used in test fixtures.

You mean something like this?

http://www.microchip.com/stellent/idcpl … e=en541943

http://www.microchip.com/stellent/group … 0584-3.png

Or the version that has additional support legs:

http://www.microchip.com/stellent/idcpl … e=en541939

http://www.microchip.com/stellent/group … 0581-3.png

-Bill

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Oh dang - yeah, like something exactly like that… Thanks for the reference. I did do some searching, but I was probably not being creative enough with my search terms, and I didn’t come up with any leads. Thanks so much for the suggestion; I’ll check it out!

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Checked out that “Tag Connect” product, exchanged Emails with them, within an hour or two. Looks good, and I may do it on my next board, but I’m stuck this time with a 6-pin single-row configuration. Found the word “pogo” and searched on “pogo spring contacts” and got to Mill-Max (of course! How could I forget?) and ended up ordering some of their 829-22-006-20-001101, wihch is in stock at a couple common distributors. (This is a 6-position, .100" header with right-angle tails, and spring loaded contacts. Should do the job for me - I’ll build it onto the end of a piece of perf-board or something…

Thanks, phalanx for the lead - it got me started down the right path!

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You know Sparkfun sells pogo pins yeah? http://www.sparkfun.com/search/results? … t=products

Also they have a tutorial discussing how they do production/testing using pogo pins http://www.sparkfun.com/tutorials/138

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No problem. I know I had seen it a while back and it took me a while to find it on the Microchip website since there was no direct path to it. I had forgotten about them until you started this topic. I may finally invest in one and start using it on my boards. Right now I usually use Picoblade 1.25mm connectors for ICSP similar to this: http://search.digikey.com/scripts/DkSea … =WM1746-ND

-Bill

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You could knock up a little bed of nails test board with sprung test pins and pegs for the mounting holes that the board sits into.

We did this a lot at my last employers and it worked fine for prototypes and small runs instead of paying oodles for the proper test bed.