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TCI6630K2L: Moisture issue after post-reflow washing

Francois Charlot
Mastermind 28287 points
Part Number: TCI6630K2L

Hello,

My customer is making a post-reflow washing which is mandatory in their manufacturing process. This washing involves some chemicals that remain trapped within the metal lid cavity. They observed that our FC-BGA package has a single vent opening in the lid which prevents all chemical traces to be removed. See the picture below.

I have seen that our FC-BGA reference guide recommends a no-clean soldering process, but that is not an option for my customer.

They ask if there is a reason why our package has a single vent opening, and whether we have a version with 2 or more openings. If we only have a package with a single opening, what is our recommendation to avoid chemical or moisture residuals after a cleaning process?


Thank you.

Best regards,
François.

  • 0
    TI__Genius 9065 points

    François,

    I am sorry for the delay. I am trying to get some help from a packaging engineer to help on this thread.

    best regards,

    David Zhou

  • 0 in reply to dzhou
    TI__Genius 9065 points
    Hello François,

    TCI6630K2L uses standard lidded FCBGA package configuration to control warpage and lid adhesion. The current lid attach process serves to provide a vent and ensure good lid integrity. Adding additional vents would compromise the lid adhesion.

    It will be important to understand the chemical used in the post reflow washing process because it may affect package integrity.

    You should bake the part after the wash. Baking temperature will depend on boiling point of the chemical and must not damage the package.

    Hopefully this helps.

    best regards,
    David Zhou
  • 0 in reply to dzhou
    TI__Genius 9065 points
    Hello François,,

    I have more to add now:

    The vent in the Lid of the BGA is for out-gassing during customer SMT reflow. To avoid water, moisture and chemical getting into the Lid through the vent, the best way is to apply Kapton tape over the vent. The tape can be removed after the drying of the washing process.

    Some customers prefer using an epoxy to seal off the vent then removed after the washing process. The selection of epoxy have to careful to make sure it doesn’t have any side effect to chemical being used.

    Our recommendation is to use no clean paste so that we can avoid the washing process. For customers who have to wash their boards after reflow, we suggest to them to seal off the vent to avoid water or chemical to get inside the lid.

    So you have to choose the method that would best fit to your process. Kapton tape and epoxy are the most common methods.

    best regards,
    David Zhou