Most production line flash programmers have a facility to sequentially program a serial number into an IC from a given range. A problem is these are usually standalone so you have to be careful about duplicate assignments, especially if there are multiple assembly lines. This gets complicated when production is split between a local plant and an offshore contract manufacturer.
A second approach is to wait until you run the assembled PCB tests in an ATE fixture. Assuming the PCBA passes functional tests the ATE can write the serial number through the JTAG or a test port command to the board. I prefer this approach for a few reasons: non-functional scrapped PCBAs are not registered in the serial number database; the ATE (one or more across multiple assembly lines) retrieves a serial number from a database to guarantee unique identity; and the indelible STM32 internal ID can be retrieved and linked to the serial number in the quality assurance database. Scrapped boards can be assigned a tracking number outside the usual serial number range for QA purposes, though there's no link to the specific board in the QA database unless an external barcode is scanned on the PCBA.
It's a tradeoff between cost and QA statistics. A standalone is cheaper since it's offline, but you need a re-reeler to extract the IC, program it, and place it back on the tape reel for the SMT pick and place. ATE tester is more complex to set up and has a single point of failure in the database, though there are ways around this, but yields more precise QA statistics.
And as a last resort...hire an intern to do it manually.
Jack Peacock
