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MSP430 - soldering temperature vs. flash retention

OscarM.
Prodigy 440 points

Dear all,

I know that storage temperature is lower for programmed devices (states datasheet), but is there any risk of damaging the flash content in production? I.e. when the part is preprogrammed before soldering? Do we have any "derating curves" for this phenomena?

 

thanks,

OskarM.

  • 0
    Guru 227245 points

    When mass-producing out wireless alarm transmitter for smoke sensors, we provided pre-programmed RfPIC processors for the soldering process (in-system programming after soldering was difficult due to the size of the device (connector space) and the triple-used processor pins).

    A significant fraction of the devices didn't work and we suspected the soldering process having erased or at least damaged the flash content. We couldn't check, as the devices were programmed with a read protection fuse burnt. But usually, reprogramming the flash (a rather difficult task, including removal of a resistor) solved the problem.

    So I'd answer your first question with a 'very likely', even though I never had an issue with MSPs since we program them after soldering.
    We lost, however, some flash contents due to accidentally applying a supply voltage above 4V (damaged/badly soldered stepdown regulator from 5 to 3.6V). Nothing else was harmed in these case and reprogramming fixed it (after fixing the regulator).

    I don't have any derating information. I'd say this must be supplied by TI, as almost nobody else has the material to do more than a simple "will/won't"-check.

  • 0
    TI__Expert 7775 points

    Hi OskarM,

    There is no difference for programmed vs non programmed parts in terms of maximum solder reflow temperature in production. The solder process is simulated during TI device qualification. As such, devices used for qualification must pass the maximum allowed solder temperature without any effect to flash memory content.

    The maximum allowed reflow solder temperature is specified for Pb-free and non Pb-free soldering per the international Standard JEDEC 020D. This standard describes the maximum Temperature versus Time for a reflow profile used in Pb-free and non Pb-free soldering. This conditions are used also for the qualification tests and had to be seen as the worst case allowed reflow profile. The allowed maximum reflow peak temperature is listed on the device label on the shipping boxes; it can also be found in the respective product folder at ti.com (ex: http://focus.ti.com/docs/prod/folders/print/msp430f2132.html#qualitydata)

    The exact recommendation for customer reflow profile should be done in cooperation with the solder paste supplier and possibly also with the equipment supplier if needed. The solder paste datasheet includes typical recommendation for the reflow profile to achieve good solder wetting on the component leads. The flux activity in the solder paste plays a contributing role for the achievable solder wetting of the parts joined in the solder connection.
     
    Be aware that there is a different solder joint mechanism for NiPdAu lead finish. Pls see http://focus.ti.com/general/docs/litabsmultiplefilelist.tsp?literatureNumber=szza026

    Additional Lead (Pb)-Free Application Notes are available at: http://focus.ti.com/quality/docs/gencontent.tsp?templateId=5909&navigationId=11750&contentId=5043 

    So, as long as the recommended industry standards are followed in production, there should not be risk of flash corruption at reflow.

    Hoping you find this helpful, Zack

  • 0
    Guru 58965 points

    Arrhenius equation gives an acceleration factor (AF) for data retention based on a temperature (K) difference. See: http://focus.ti.com/general/docs/litabsmultiplefilelist.tsp?literatureNumber=slaa334a

    But given that you are talking ~30 seconds of soldering at ~650K  vs. >100 years of retention at ~300K, I do not think there is any problem.

    -- OCY

  • 0
    Guru 58965 points

    Arrhenius equation gives an acceleration factor (AF) for data retention based on a temperature (K) difference. See: http://focus.ti.com/general/docs/litabsmultiplefilelist.tsp?literatureNumber=slaa334a

    But given that you are talking ~30 seconds of soldering at ~650K  vs. >100 years of retention at ~300K, I do not think there is any problem.

    -- OCY

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