I am planning to pre-program the flash memory of STM32 for production, how will the reflow oven affect the data retention of the flash memory? According to the datasheet the data retention is specified to 15 years @85°C and 1kcycles. Thanks!

[Javier1]

We have a reflow oven production overhere but we programm the boards after reflowing the chips in the PCB.

I found out (the bad way) that different density stm32 devices have different temperature sensibility when woking with my hotair gun.

stm32f1xx/stm32f0xx can tolerate higher temperature than stm32f2xx.

It is my understanding the stm32 bootloader is already inside the Flash memory(not accesible by user), so if that remains unchanged after reflowing so does your code?

[ALage.2]

Hi Javier,

Thank you for your answer.

My understanding is that the STM32 boot loader is stored in the boot ROM (system memory), which manages the reprogramming of the Flash memory.

So I guess that it is not necessarily true to say that the data retention of the flash memory is the same as the data retention of the boot ROM.

The question is: Can the reduced flash memory data retention due to the reflow oven process be negligible?

Thanks!

[Javier1]

Youre 100% right.

[Tesla DeLorean]

You could always have the code be capable of erasing/rewriting itself, whilst at room temperature, post-soldering

The original question is perhaps better posed to the FAE assigned to your account, who might have appropriate data/reports.

[ALage.2]

Hi Tesla,

Thank you for your reply.

You are probably right. I thought that technical representatives from ST would be present on this forum to answer my question.

[TDK]

This a primarily a user forum, not a direct link to ST. If you're looking for technical information that is beyond the scope of the datasheet, it's unlikely to get an ST response here. It might not even be something they have tested or are willing to guarantee.

Anecdotally, I have reflowed many chips and never had a problem with corrupted flash.

[ALage.2]

Hi TDK,

Thanks for your reply,

I have reached out to the ST technical support with my matter instead.

Yes, I have never heard of anyone with such problems. It would still be good with some data that support our experiences :smiling_face_with_smiling_eyes: