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I have a 96 pole connector and a 32 pole connector on one board which plugs into the mating connectors on another board.

What is the correct way (and hopefully easier way) of ensuring that they are aligned ?

I've dealt with 1 connector in the past and if it was slightly off, it wasn't a big deal because I had space to shift the board so that it aligns. In this case, I can't because if I shift the board up or down, I'm shifting the alignment of two connectors.

What I do, is carefully take measurements and and hope that my measurements are correct.

But maybe there is another way, and maybe an easier way.

I have the following

  • Datasheet with measurements
  • 3d step model of each connector
  • Altium
  • I also have access to Solidworks or Autocad (have to check to see which one) but I never use it.

Can I use something from the list that would give me a better sense of security that it's correct rather than just me figuring out lengths ?

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  • \$\begingroup\$ Couldn't you import both models into your CAD program and see if they align? \$\endgroup\$
    – Ignacio Vazquez-Abrams
    Commented Jun 20, 2015 at 19:35
  • \$\begingroup\$ What pitch are those connectors? Do you have a mechanical guide option for them? Are the boards in design or in production? \$\endgroup\$
    – Lior Bilia
    Commented Jun 20, 2015 at 19:39
  • \$\begingroup\$ @IgnacioVazquez-Abrams I suppose that could be done last, I'd have to spend some time figuring out to do it. But I'm also curious about the process before getting to cad verification. Is it really just, look at the datasheet measure measure measure. That's it ? That's what I do now, and I was hoping for a speedier way. \$\endgroup\$
    – efox29
    Commented Jun 20, 2015 at 19:41
  • \$\begingroup\$ AFAIK it's been one of those two ways for decades (although obviously dimensional verification was first). \$\endgroup\$
    – Ignacio Vazquez-Abrams
    Commented Jun 20, 2015 at 19:42
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    \$\begingroup\$ Assembly is going to love you with this :) If these are surface mount I hope they have some guide posts. I second the cad approach, but I also sometimes print out my top layer to a laser printer and then fit my connectors on paper to see how it looks. Or send out a 2 layer 2-3 day turn board with just the connectors in place so I can assemble it in the lab and see how it fits before committing to assembly. \$\endgroup\$
    – Some Hardware Guy
    Commented Jun 20, 2015 at 20:35

2 Answers 2

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The best thing you can do is use a single connector.

Verifying that the connectors are aligned on their nominal positions is only the starting point. Using a common origin for both boards will help. Double check that the part footprints are drawn correctly. Print out the two boards at the same scale and hold the stacked sheets up to the light. Everything good? The kinematic overconstraint means it's still going to be a pain.

Even with perfect alignment in the computer, real world manufacturing tolerance can make it hard/impossible to assemble two rigid boards with a pair of snug fitting connectors fighting each other. Some connectors are designed to allow for a small misalignment, but most aren't. If they are surface mount connectors, they will end up in slightly different positions and rotations from board to board. Same goes for through hole. Forcing a fit can easily crack solder joints and break traces off pads.

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  • \$\begingroup\$ +1. The tolerance stack-up for multiple connectors between rigid PCBs is a very nasty problem, particularly in a hi-reliability world (where I currently am) but it can be just as big an issue in consumer equipment. Adding more connectors gives an exponential problem. \$\endgroup\$
    – Peter Smith
    Commented Aug 18, 2015 at 13:35
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An easy way to achieve this is to align both board origin points to a known feature (Fiducial, center point of a connector etc) then checking the generated pick and place (XY) files of both boards for mismatches.

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