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By highly
I purchased four MicroMod Teensy in order #2984276 along with an ATP for the development of a product. All four boards functioned properly on arrival. Over time all four boards began having functional errors that degenerated to bootloader flash codes and the following responses from Teensy Loader
Code: Select all
07:59:50.074 (loader): nxp_write: success
07:59:50.089 (loader): HAB open mode, bootcfg=80018
07:59:50.092 (loader): Opps, NXP ROM in open mode, but we do not yet have code for this case :(
07:59:50.095 (loader): start ignoring usb:0/140000/0/3/2
07:59:50.098 (loader): end operation, total time = 0.144 seconds
Once in this state the CPU would not communicate with the bootloader. The 15-second recovery would cause the boot LED to illuminate briefly but would not reload the blink program. One of the four would not communicate over USB.

3 of the boards were resurrected by reflow. For each board I first reflowed the bootloader chip with CQ4LF-0.5 flux at 260c air temperature, cooled and tested. I then reflowed the flash chip, cooled and tested. I then reflowed the other components, cooled and tested. Lastly I reflowed the CPU, cooled and tested. Reflowing the CPU corrected the three boards I have attempted so far.

I am very interested in using the Teensy MicroMod as the basis for a commercial product, but seeing these boards stop working after heat cycling in use is not reinforcing that as a good choice. Looking over the forum posts there appear to be others that have also experienced similar issues with the Teensy boards that were corrected by reflow. Was there a known issue with the reflow profile on early batches that has since been corrected?
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By highly
I only performed surgery on 3 of 4 devices. All 3 that were reflowed work properly. A pin-test verified all pins function. The fourth board that was not reflowed does not connect to USB and does not self-program with the Blink recovery program. It blinks a 7-code on startup.

I'm much more interested in the likelihood that this sort of failure might be prevalent moving forward than of the one board not working today :)
User avatar
By TS-John
Thanks for posting on our forums about this issue, highly.

We are going to look into the build process for this product and see where we can improve on.

If you wish to get a replacement MicroMod Teensy, feel free to fill out a return ticket here:

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