We are using the MPM3570E on our boards, and we noticed that some units did not generate proper output voltage. Upon further inspection, after removing the metal can from one unit, we discovered moisture inside. After drying the part, the faulty units started operating normally. The moisture was most likely the washing liquid left over after assembly.
Do you have any instruction for the part assembly and drying in order to mitigate this? It might be better if you could tape the hole after packaging. Drying the part after assembly might remove the water, but some corrosive material can still stay trapped inside and cause additional issues down the road if the part is operating in humid environment.
The hole is in the case for thermal expansion relief seen during relow process. The MPM3570E needs to be baked to remove the moisture during a board wash.
Please read the Moisture Sensitivity Technical Note for more information.
As a follow-up comment regarding the Moisture Sensitivity Note – we have also seen issues with post-assembly wash causing issues with the MPM3550E parts. The parts were handled as per the note, but were subjected to a post-assembly liquid wash cleaning cycle.
The technical note addresses handling before and during assembly to reduce “popcorn effect” but does not explicitly cover post-assembly moisture exposure - or soaking. It might be a good idea to add something to the note about these post-assembly cleaning processes also requiring a follow-up dry-out/bake cycle to ensure that any liquid is removed from the internals of the module. It was not clear to our assembly vendor that these modules could retain liquid within the outer “can” cover, but it can definitely cause problems.