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Thread: Another day, another soldering failure

  1. #1
    Senior Member+ MichaelMeissner's Avatar
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    Another day, another soldering failure

    I was trying to solder wires to the underneath of one of my Teensy 4.0's. I had gotten some 7 pads soldered, and I was going back for pads 27 and 31, when evidently I put on a little too much solder in the wrong are, and now it won't turn on at all, and the 15 second push of the program button doesn't work either. Ah well. Tomorrow, I will use a bunch of solder wick to clean things up. Somedays I use a lot more solder than wick, and some days, I use more wick than solder.

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    Senior Member+ defragster's Avatar
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    Pin #27 and #31 have SMD components closer than anything else. Someone else noted he lost one of them soldering on either #25 or #27.

    Will be interesting if you can get it going.

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    Senior Member+ MichaelMeissner's Avatar
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    FWIW, by cutting off all of wires soldered on to the bottom, and using solder wick to remove the solder, I was able to get it to boot again. In testing each of the solder pads in turn, it looks like all pads are functional except for pad 31. Looking at the board, I suspect it was pad 31 that was the problematical one, since that pad's solder did extend, and there is some SMT component just beyond pad 31. Since pads 30/31 connect to CAN CRX3/CTX3, and I don't use CAN devices, it won't be a hardship if I can't use pad 31 (pads 26/27 which bring out the second SPI bus were the ones I was interested in).

    In a few weeks, I will probably order another fresh T4. I have another one that I didn't attempt to solder underneath the PCB along with the beta2 board.

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    Senior Member+ defragster's Avatar
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    Quote Originally Posted by MichaelMeissner View Post
    FWIW, by cutting off all of wires soldered on to the bottom, and using solder wick to remove the solder, I was able to get it to boot again. In testing each of the solder pads in turn, it looks like all pads are functional except for pad 31. Looking at the board, I suspect it was pad 31 that was the problematical one, since that pad's solder did extend, and there is some SMT component just beyond pad 31. Since pads 30/31 connect to CAN CRX3/CTX3, and I don't use CAN devices, it won't be a hardship if I can't use pad 31 (pads 26/27 which bring out the second SPI bus were the ones I was interested in).

    In a few weeks, I will probably order another fresh T4. I have another one that I didn't attempt to solder underneath the PCB along with the beta2 board.
    That is a tight spot! Glad it turning on and just the one pin/pad offline so far. Is there some prophylactic you can see helping? Not much room to get a strip of Kapton tape across there to dam the solder and heat away? Maybe a dot of conformal coating? Anything else come to mind that would insulate, isolate and take the heat?

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    Senior Member+ MichaelMeissner's Avatar
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    Quote Originally Posted by defragster View Post
    That is a tight spot! Glad it turning on and just the one pin/pad offline so far. Is there some prophylactic you can see helping? Not much room to get a strip of Kapton tape across there to dam the solder and heat away? Maybe a dot of conformal coating? Anything else come to mind that would insulate, isolate and take the heat?
    I was going to ask for suggestions of how to better solder those pads. For the 3.2 I like the FrankB castellated board which is fairly easy to solder (and the Bob Larkin board for 3.5/3.6 in the spirit of Frank's board). If I have problems with the 0.1" (2.54mm) pads in the back of the Teensy 4.0, I suspect I won't be able to tackle the 1mm pads for the SDIO card at the front of the board.


    One thought that I had was rather than snipping off the wire at the end before putting it on the pad, instead with wire strippers make a slight opening in the wire insulation and tape the wire down away from where it is being soldered, solder it, and then use diagonal cutters to remove the excess. I did the front pads first and repeated to do the back pads. The wires on pads 27 and 31 had come off, and I was trying to reapply them, and evidently applied a little too much solder.

    While I like the Talldog boards in design, getting up the courage to solder the male SMT pins (2x7 on the 3.2, and the 2x3, 2x4, and 2x5 on the 3.5/3.6) so that it would fit into the board seemed daunting. Much easier with a castellated design to solder the pins, and drip some solder to make the connection on the pins.

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    Senior Member+ defragster's Avatar
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    Those castellated PCBs when they fit and worked did go well. I had a couple of Onehorse boards that worked well like FrankB's did.

    I signed up for Beta T4 BB's from TallDog to try his first board will have to watch those 2x5 ends - maybe trim them some. Would be nice for alignment and support if they ran to the outside pin holes so the plastic strip gave continuity. Maybe a 2x6 or 2x7 with straight pins on the outside. Also ordered a T_3.6 one that would be nice to have Handy without powering up one of FrankB's Teensy64 units with display all the time - and have access to all the pins.

    Those bottom 10 pads on T4 with those close SMD parts will be a close call. A bit more clearance to the single CAP on the SDIO end. soldering the Flex ribbon there hopefully aligns easily and goes well. For a connector the solder mask will hopefully do its job rejecting bridges when touched up as needed. uTube videos make it look easy - I posted a link to one I saw that was a 0.8 or 0.6 MM pitch chip that came out well dragging a wet tip across. Practice would be good.

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    Quote Originally Posted by MichaelMeissner View Post
    I was going to ask for suggestions of how to better solder those pads.
    If you want to tackle the 1mm SDIO pads, i would suggest the following tools:

    1.2mm conical chisel tip for your soldering iron, anything bigger and you won't be able to solder one pad without touching the other.
    0.5mm diameter solder wire, anything larger and you won't be able to apply tiny controlled amounts.
    Curved or angled precision tweezers to make micro adjustments.
    A good desk magnifier.

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    Senior Member+ KurtE's Avatar
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    @MichaelMeissner and all - Been there, done that...

    I had one of the pads that would not work, and when I tried again, I must have gotten a little too ambitious and one of the small caps came off... I am not sure what all that CAP was used for, but so far I just have that poor abused T4 sitting on a shelf, looking sad at me.

    And yes I do have a small curved tip for that soldering station, and using the solder/flux that Paul recommends, plus a LED magnifying desk lamp.

    The main problem left is I have two older uncoordinated hands that are being controlled by eyes with progressive lenses :lol:

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    Senior Member+ MichaelMeissner's Avatar
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    Wink

    Quote Originally Posted by KurtE View Post
    The main problem left is I have two older uncoordinated hands that are being controlled by eyes with progressive lenses :lol:
    Yeah, my soldering iron doesn't have a thin tip. But yeah, the main problem I have is my computer/reading bi-focals the difference between the two lenses is about where I would want to use for soldering and the head mounted magnifier often gets in the way. And having two uncoordinated hands doesn't help.

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    @All - I wonder how many experimenters are in our shoes. I No longer can do point to point soldering. My hands and eyesight are not good enough for that any more. It's really disappointing having to rely on other people to create platforms for me to use. I guess maybe that is why I depend on all of the talented people in this forum for designing and building such great hardware and software. These are the things that make this forum so usable and worthwhile for me. The level of talent and skill here is what I use everyday to walk away from work and enjoy a moment of accomplishment.

    I have been using Teensy since I started with Teensy 2.0 to program a Motorola 68332 BDM board designed for fuel injected engine controllers. EFI332 to be exact. Now Megasquirt.

    Hopefully not off topic.
    Just saying thanks to all. Especially Paul. Great hardware and software!!

  11. #11
    Senior Member+ defragster's Avatar
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    this @loglow pic for T4 breakout board assembly gives an idea of the proximity when using those underpads - not a comfortable margin given too much flux, solder, tip, or ... the things @wwatson noted.
    Attachment 17418

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