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Original question:

ADS1118: IRUG - issue : IC on the bottom side of the board is nonfunctional

ADS1118: IRUG - issue : IC on the bottom side of the board is nonfunctional

Cyril Metzger
Prodigy 70 points
Part Number: ADS1118


Hello,

Sorry for the delay since my last update on the subject but it was summer vacation for everyone.

I got news from my manufacturers, their expert thinks that maybe this casing should be considered MSL-3 (not MSL-1 as stated in the datasheet) and so we should try to bake the components before assembly (the components were purchased on digikey.com).
So it may be several weeks until you hear from me again as we ordered new PCBs and a new manufacturing (with baking of the components), and then we will perform tests on this new batch.

Cyril.

  • 0
    TI__Guru* 98195 points

    Cyril,


    Thanks for the post.

    I'll wait for your new results, but I must comment that we do tests for the qualification for our devices and I'm confident in the MSL-1 rating for the RUG package for the ADS1118. Based on the device's small size, I would imagine that the package is good for moisture sensitivity because the low plastic content wouldn't absorb much moisture.

    I did get an email from one of the packaging experts here, and he thought that if the bottom device may have shifted or become mis-aligned during a second reflow (if the reflow is done twice for different sides of the board). I had shown him your e2e post from:

    https://e2e.ti.com/support/data-converters/f/73/t/923592

    If this is potentially the problem, they could perform an x-ray of the failed board while it is still mount to check for the positioning.

    Did the expert mention anything about the voiding in the solder? That is still the thing that I quickly see in image from the previous post.

    Joseph Wu

  • 0 in reply to Joseph Wu
    Prodigy 70 points

    Hello,

    On the previous boards the aligment seems fine.

    The expert did not mention the voiding but according to our manufacturer it's not an issue as there is always small voids like these ones, and also on the other components and they work fine.

    I received the new batch of equipped circuits (10 boards) with the ADS1118 baked before assembly and they all work fine.

    So for now this solution seems to work but there is still a chance that we just got lucky for this batch.

    In conclusion I think that we will systematically bake the ADS1118 before assembly and we will know for sure when we manufacture several hundreds of circuits. This is not yet scheduled for now so I will keep you informed, it may take several months ...

    Best regards,
    Cyril.

  • 0 in reply to Cyril Metzger
    TI__Guru** 113765 points

    Hi Cyril,

    Thanks for the update.  We will close this post for now, but if you have any further questions please feel free to create a new thread/post.

    Best regards,

    Bob B