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Thread: Teensy 3.2: soldering carrier board directly to Teensy using vias

  1. #1
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    Teensy 3.2: soldering carrier board directly to Teensy using vias

    Has anybody created a Teensy 3.2/3.5/3.6 carrier board that is soldered directly to the Teensy using pads with plated through-holes for soldering?

    I have a larger board I embed Teensy 3.2 onto. To get easy access to the pads (both pin pads and the USB D+ and D-), I was considering I could use exposed pads with vias through them, so I could solder the Teensy directly to the carrier board. I don't need any routing on the carrier underneath the Teensy on the Teensy-facing side, nor any extra vias, so this seems to me like this might work better than soldering short wires or pins to Teensy. For alignment, I can use pins like the USB panel mount breakout board. (However, that board uses castellated holes to solder the D+ and D- lines to, not vias.)

    Anybody done this yet? Experiences? Opinions?

    The other approach I know would work, would be to use castellated holes on the carrier board. (It does not matter *which* board has the castellated holes...) However, it looks like inside castellated holes are problematic for the cheap prototype PCB makers, so I'd probably have to hand-file the castellations. I'd rather use vias/plated through holes instead, if that has a moderate chance of working.
    Last edited by Nominal Animal; 07-19-2019 at 03:47 PM.

  2. #2
    Senior Member+ MichaelMeissner's Avatar
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    There are these two boards you can order from OSH park. Unfortunately these boards do not provide addess to the D-/D+/reset pads at the front:


    There is also this board which allows you to mount a USB-B connector. I imagine it can be combined with the FrankB carrier above:


    Talldog sells more complete carriers at his/her tindie store. It includes access to the bottom pads as well as pogo pins for the USB D-/D+ pins and the reset pins. If your soldering skills aren't that great, Talldog will also solder a 3.2 onto the carrier for $40 more:


    I'm not sure whether shipping to Finland would make things too expensive however. You might want to send a private message to Frankb which is regular on this site about using a different PCB vendor.

  3. #3
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    It's that Odroid HC1 carrier board of mine. Flux, leaded solder, acetone, and a toothbrush make me the solderer I ain't, to borrow a saying from welders.

    That is, I can do an one-off with pins (surface mount 2x7 pins work for the 14 pads underneath), but if I want it to be something anyone else can do if they wish, I might have to do a jig, a separate board to help with positioning when soldering the pins to the Teensy, before soldering the pinned Teensy to my carrier board.

    It looks like inner castellated holes aren't something normally done. That is, having a cutout in a board, with castellated holes on the inner edge of that board. I probably could do those myself, using a high-speed router with a sharp milling bit, with acceptable yield (not too many boards botched) and a little hand filing.. Won't help anyone else, though.

    The reason I am interested in the USB D+ and D- pads, is that an ADuM3160-based isolator fixed to full-speed mode (12 Mbit/s) is really simple (here's mine). For Teensies with external power, the circuit is even simpler, as the DC-DC converter is not needed. Since in my case, the USB on the Teensy can be connected to another computer for serial console access, and I have the room on the board, adding a footprint for the ADuM3160, four caps, and four 24 Ohm resistor just makes sense to me; well worth the effort to have the added safety.



    As an aside, it would not take much effort to take the existing USB panel connector board, and extend it a bit to include the isolator, placing the bulky DC-DC converter just in front of the existing USB connector on the Teensy, and the ADuM3160 chip. Perhaps using say Recom R2SX-053.3-R isolated DC-DC converter, which can provide 600mA at 3.3VDC (from 500mA at 5VDC input), with just 10F and a 100nF capacitors and a 10H inductor for bypass and EMI filtering. I wonder if others have as often ground loop issues as I do?

  4. #4
    Senior Member+ KurtE's Avatar
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    Again I am not an electronics expert or the like, but I believe a lot (most? all) vendors will now allow you to do some internal cutouts on boards.

    For example, I did this for a castellated test board for T3.5/6...

    So in my case I used Diptrace program and used the instructions from I believe OSHPark and marked the board outline layer with the cutouts. The stuff looked sort of like:

    Click image for larger version. 

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    Then had the boards fabricated, maybe not the greatest picture, but shows the outcome

    Click image for larger version. 

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    I believe most of the details are in: https://docs.oshpark.com/submitting-...board-outline/

  5. #5
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    Quote Originally Posted by KurtE View Post
    I used Diptrace program and used the instructions from I believe OSHPark and marked the board outline layer with the cutouts.
    Very interesting; OSHPark does say that they basically do what I said I could do myself, simply route out the cutout afterwards, and one has to deburr and test them oneself. Not bad, works for me!

    I can do the same in EasyEda according to OSHPark guidelines (EasyEda allows direct drawing on the outline gerber layer, and I've used EasyEda for a couple of boards already -- I'm just a a hobbyist myself, though; much better on the software side). It was just that I could not find any information or advice about internal castellations, but seeing that was exactly what you have done, is excellent to know! Thanks a lot; I owe you one!

    Essentially, my board is very similar, just much larger, as it straddles an Odroid HC1; and I'll add two castellated holes for the D+ and D- pads for Teensy 3.2 so I can connect to an ADuM3160. (The Teensy itself is connected to the HC1 via level shifters to 1.8V UART.)

    Just out of interest, did you have any issues with the quality, or when soldering the castellated holes? Any hints as to what the optimal pad size for the castellated holes is, now that you have practical experience?

    (I'm one of those with quite a bit of theoretical knowledge, even electronics courses, but in real life, I'm an uncle bumbleflug; so, any practical experience and advice is invaluable to me.)

  6. #6
    Senior Member+ KurtE's Avatar
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    I am also mainly a Software guy as well. I am a retired Software Engineer who did take several EE classes when I was working on my BS and MS in Computer Science, but that was over a few decades ago... Or to give a time frame, I did my masters project using a Franklin Ace computer. 8)

    So I also borrow as much from others as possible!

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