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
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?
