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I am looking to incorporate a Teensy board on my PCB. I want to solder the Teensy PCB onto my PCB. But I also want to minimize the height above my PCB as much as possible. Hence, I DO NOT want to solder using regular header pins -- i.e. I DONT want this: enter image description here

I want the Teensy to sit as flush as possible on my PCB. Unfortunately, the Teensy does not come with castellated holes (like the Photon or most wireless boards): enter image description here

So I was thinking of the following options:

  1. Using low profile header pins like this one -- https://www.pololu.com/product/2663 (plastic height is 1.5mm instead of usual 2.5mm). But I want to avoid the 1.5mm as well

  2. Use straight pins like this - http://www.digikey.com/product-search/en?mpart=3560-2-00-15-00-00-03-0&vendor=54 -- and soldering the Teensy flat on my PCB. Is this a viable option?? A google search doesnt really show me examples of this being done.

What other tricks/tips can I use??

(I understand that the best way is to not use the Teensy board directly, and instead to design the Teensy ckt on my PCB. But for some reasons I do not want to get into that right now.)

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  • \$\begingroup\$ I once had to deal with a similar issue at my old job, there was some mains voltage through hole parts that needed to be flush underneath. We ended up just flipping the board after soldering it and passing it through a mill, it worked so well we could get the underside totally flush with the soldermask. If the underside doesn't need to be ultraflat, another tactic I've used is to just clip off the excess length with a good pair of side cutters and run the soldering iron over the pads, you end up with smooth little bumps rather than big pins sticking way out. \$\endgroup\$ – Sam Sep 24 '16 at 21:54
  • \$\begingroup\$ Actually I found a project online that does something similar, but for only a few pins ... this result -- github.com/macaba/Teensy-3.2-USB/blob/master/Images/Result.jpg THis link that has assembly steps -- github.com/macaba/Teensy-3.2-USB \$\endgroup\$ – O.K. Sep 24 '16 at 22:05
  • \$\begingroup\$ Have you considered the option of mounting the Teensy upside-down, so its components sit between its board and your board, effectively using the otherwise wasted space? \$\endgroup\$ – Jules Sep 27 '16 at 4:37
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  1. Stick the headers through your main board from the bottom, with the plastic on the bottom.
  2. Set your Teensy on top, with the headers going through its holes.
  3. Solder the Teensy to the headers.
  4. Using a small screwdriver, pry the plastic off the headers. You'll be surprised how easy it comes off.
  5. Solder the headers to the main board.
  6. Trim headers as necessary.
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    \$\begingroup\$ I suggest cutting the headers to 3 or 4 pin sections prior to doing this. Makes prying off the plastic much much easier, and lessens the risk of breaking a trace from the stress. \$\endgroup\$ – Passerby Sep 24 '16 at 23:15
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    \$\begingroup\$ I am going with this answer. Also pasting a link that does pretty much exactly the same thing and has Steps with pictures -- github.com/macaba/Teensy-3.2-USB @Passerby -- I agree, will keep that in mind \$\endgroup\$ – O.K. Sep 25 '16 at 15:57
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Have you considered simply surface-mounting the module onto your PCB? The header holes are big enough for solder to flow down and wet onto the main board. Or you could use some solder paste and reflow on a hot-plate or an oven.

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  • \$\begingroup\$ I am up-voting this, and will be giving this a shot as well, in the hope that it will be less work than the prying plastic off the headers business. I'll update how it goes (in a few weeks though) \$\endgroup\$ – O.K. Sep 25 '16 at 15:59
  • \$\begingroup\$ have you ever done this 'surface-mounting the module on PCB' thing before (using any of the methods you suggested)? I am asking since this option seems more attractive now, especially because it is going to make routing much easier --- with this method all the bottom layers will be available to freely route the signals. Instead, if I did the through hole mounting, I will have to route traces from between the 2.54mm gap between the through hole pins, which seems tricky (not even sure if DRC checks will allow it). \$\endgroup\$ – O.K. Sep 26 '16 at 3:26
  • \$\begingroup\$ I am worried about one more thing with the 'solder-paste and reflow the Teensy' idea. Could it mess with the already soldered components on the Teensy in any way? Perhaps I should use a 'lower-melt' solder paste for this -- not sure if this even exists \$\endgroup\$ – O.K. Sep 26 '16 at 4:30
  • \$\begingroup\$ @O.K. I haven't done this with a module, but I recently designed a PCB that has a bare PCB mounted in this way (although the holes are bigger). As for reflow, as long as you don't overheat the board too much, you'll be fine. Normal components are unlikely to be damaged by this. The only potential issues could be some connectors with plastic parts or the little tactile switch. \$\endgroup\$ – Armandas Sep 26 '16 at 5:55
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  1. A Kapton tape layer between the two boards to prevent accidental short circuits. (Must be Kapton to withstand soldering temperatures)

  2. Just use resistor legs (or other sources of tinned wire) through each hole, soldered both sides, trimmed to length.

This isn't something you'll do in any quantity, or else it would be worth re-laying out the board (or cloning the Teensy with castellated pins to suit your purpose)

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  • \$\begingroup\$ thanks for the Kapton tape tip .. actually TIL its called Kapton tape \$\endgroup\$ – O.K. Sep 25 '16 at 16:09
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Have your board made with a cutout that the "teensy" board fits into, and through-holes around the edge of that. Make a bunch of U shaped wires to make the electrical and physical connection. Add epoxy or hot-glue after soldering if you want more physical connection.

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  • \$\begingroup\$ do you mean something like this -- dl.dropboxusercontent.com/u/2486346/t3a/ap/all.jpg \$\endgroup\$ – O.K. Sep 24 '16 at 22:03
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    \$\begingroup\$ Nope. I mean a rectangular hole in the board which is larger than the rectangular board you want to insert, such that the two boards end up co-planar. Morally similar to how a butterfly laser diode mounts. \$\endgroup\$ – Ecnerwal Sep 24 '16 at 22:07
  • \$\begingroup\$ okay, I thnk i understand. But then I would need separate supports for the board that I insert (since its not connectd to the main pcb) -- right? Assuming I want to make sure everything is sturdy and snugly fit in my enclosure. \$\endgroup\$ – O.K. Sep 24 '16 at 22:13
  • \$\begingroup\$ I upvoted this, but man.. soldering those small wires won't be fun. @O.K. Assuming you use bent component leads or similar, this construction will likely be extremely sturdy without any extra support. You'll have 28 soldered-down metal supports, in fact. \$\endgroup\$ – pipe Sep 25 '16 at 0:22
  • \$\begingroup\$ The wires shouldn't be particularly tiny, given that the holes are sized for header pins. Soldering should be easy, and result should be sturdy (as mentioned, after the soldering is done you could add epoxy or hot glue, but wire of an appropriate size for a header pin hole will be quite sturdy when you have 24 or 28 of them holding the thing in place.) \$\endgroup\$ – Ecnerwal Sep 26 '16 at 15:18

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