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LM1086: Soldering impact

Jenny Lu69
Expert 1810 points
Part Number: LM1086

Hi engineers,

I have a customer who had inquiry as below:

"We are using TI regulator Part number 'LM1086ISX-ADJ/NOPB'.

Recently we have observed after re-flow soldering done, IC appearance get changed from silver to copper color.

Please let us know, why IC appearance gets changed..? What is the root cause..? What effect it is and if this is acceptable without affecting IC's performance..? Please note we have been using this IC since long but just this time such observation is there. We suspect re-flow profile but it is still under control as we see IC temperature not exceeding 245c as per datasheet and recommendation for this package.

We have kept production on hold, please suggest next action soon. Just for trail we checked reducing re-flow temperature and then found it to be OK. But want to know, if yellowish appearance all OK?" The images as illustrated.

.

Please give us some help and advice. Thanks.

Best Regards,

  • 0
    TI__Expert 6895 points
    Hi Jenny,

    This is caused by excess heat that is causing the device to oxidize. I do not think it will cause a problem as long as the solder is making a good electrical connection to the board. If you lower the solder temperature do you still end up with the same discoloration? Would you be able to share where you found the solder profile for this package?

    Best Regards,
    Mark
  • 0 in reply to Mark Sellers
    Prodigy 120 points

    Hello Mark,

    Thanks for your attention.

    Once we reduced the profile temperature it is no problem then. See attached profile now we are running where no appearance change problem now. Here can see from profile, peak temperature goes up to ~238 C.

    Earlier temperature was some high but peak temperature was ~248 C. 245 C I referred from LM1086 datasheet as well as IC packaging. I hope functionality and performance is intact even if appearance has changed from some lot and we can use those boards.

    Thanks,

    Jatin.

  • 0 in reply to Mark Sellers
    Expert 1810 points

    Hi Mark,

    Jatin is my customer, he will give direct descriptions about the questions. Thanks for your support again.

    Best Regards,