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Thread: Teensy 4.0 (iMX1062) assembly and M0 chip functionality

  1. #1
    Junior Member
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    Teensy 4.0 (iMX1062) assembly and M0 chip functionality

    Came across your very impressive product Ė the Teensy 4.0. Congratulations!

    Iím thinking of building a robot using the iMX1064 and since it is similar to the iMX1062, I'm hoping I can learn from your experience.

    1. How are you assembling the Teensy 4.0 board? Do you think hand placing an iMX1062/4 in the 10mm x 10mm, 0.65mm pitch package would work?
    2. In the Teensy 4.0 schematic, you show an M0 chip connected up to the JTAG port. Iím not getting what you are using it for.


    Thanks!

  2. #2
    Senior Member+ defragster's Avatar
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    The M0 'bootloader' chip on JTAG port is what makes it a PJRC Teensy. It enables upload of HEX files over USB port. Giving full access to CPU and its function in a usable and ideally UnBrickable way as configured on the shipping Teensy 4.0 PCB.

    The only addition of the 1064 is internal 4MB Flash - where that chip wasn't ship ready soon enough to consider so the FLASH is 2MB external chip.

    Swapping the chip and having the M0 willingly program it isn't likely but PJRC can answer that - and the FLASH internal versus external may have conflicts you should discover in reading the RefMan's as the 1064 wasn't considered. And any follow on teensy after the T4 will be a chip for a niche chosen by PJRC either lower end or yet unannounced higher end - but not seeming to be a 1062/1064 based update.

  3. #3
    Senior Member PaulStoffregen's Avatar
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    We use a professional contract manufacturer for the board assembly. They have the usual pick and place machine and reflow oven used for surface mount soldering. They also have a solder paste printer, in addition to the normal solder stencil process. I believe they have been using a stencil to apply the solder paste for everything except the BGA, then using the much slower paste printer for the 196 BGA pads.

    Hand placing the BGA chip might work. Whether you're able to apply the paste properly to those tiny pads is probably the bigger question. Doing it well with a stencil is very difficult, even if you have professional equipment. Odds of it working for hobbyist building are probably quite low.

    Even just designing the PCB is quite a challenge. Teensy 4.0 uses a 6 layer PCB, where the top layer has 4 mil traces and 4.4 mil spacing in the BGA area, and 5/5 trace/space outside the BGA and on all 5 other layers. Vias in the BGA are 8 mils, with a 4 mil ring on the top layer and 5 mil ring on all other layers. Vias on the rest of the board are 10 mils, with 5 mil rings on all layers. Just routing the PCB with those specs was incredibly difficult. NXP's reference PCB uses significantly tighter specs, which push the limits of what most PCB fabs can reliably manufacture.

    If you value your sanity and don't have over 1 year to develop your board (as was spent on Teensy 4.0), I would recommend using the 0.8 mm pitch BGA part. It didn't exist when we started the Teensy 4.0 design. It's also 44% larger...

    The MKL02 chip implements the bootloader.

  4. #4
    Quote Originally Posted by PaulStoffregen View Post
    We use a professional contract manufacturer for the board assembly. They have the usual pick and place machine and reflow oven used for surface mount soldering. They also have a solder paste printer, in addition to the normal solder stencil process. I believe they have been using a stencil to apply the solder paste for everything except the BGA, then using the much slower paste printer for the 196 BGA pads.
    [.....]
    If you value your sanity and don't have over 1 year to develop your board (as was spent on Teensy 4.0), I would recommend using the 0.8 mm pitch BGA part. It didn't exist when we started the Teensy 4.0 design. It's also 44% larger...
    To echo what Paul said, using either of those parts is not a trivial solder-at-home task. That .65mm pitch is going to be a pain in the butt to hand place, even if you have an oven. You'll never know for sure that you soldered it right even if it looks stuck in place, and without some electrical verification tests at each pin you may never know if you did it right -- will the bugs in your system be from software or soldering problems? It'll be hard to tell. Pros would use x-ray inspection on the BGA, but even that is limited past the outer ring.

    Honestly, I don't even like doing PCB layout with 1mm pitch parts because there's not a ton of room for vias and breakout traces. Oh it's easy for pros, sure, but I only build prototypey stuff at work and these designs can bite you if you're not working in your layout tool daily. I know you'll really start to push the tolerances of the "cheap" prototyping rapid-turn fabs below 1mm BGA pitch.

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