I've purchased three WM8804 MSL 3 chips, which came in a sealed moisture-sensitive package with instructions to mount the chips on the board within 168 hours of the bag being opened. However, it is not possible for me to mount all three of them within that time (I'm doing prototyping right now, not production).
Basically, I know that the first chip will be fine (I'll mount it right after I open the bag). However, the other chips will not necessarilly be mounted 168 hours after opening (there may be problems, I might need to order new boards, etc.).
I don't have the equipment necessary to "bake" the chips, and I'm not doing reflow (just hand soldering). Are there any ways I can prolong the 168 hours (storage techniques, etc.) in order to prevent moisture damage to the unmounted chips? Or is it fine to simply reseal the bag after use?
Best Answer
Open the bag, take one IC out, place a teaspoon or two of white rice into the bag, and make sure to reseal airtight. The rice will take up most of the mosture that you've introduced with the atmosphere exchange when opening the bag. If you want to do it professionally, use moisture absorbing silica gel, but rice works perfectly (Don't cook rice or silica gel afterwards).
I've had a part which said it should be soldered within four weeks after unpacking, lying around for about a year in the open, and successfully put it to operation (hand soldering). Nothing popped off or cracked. So it can't be too critical, and maybe relevant only for reflow or wave soldering.
By the way: Why can't you bake the devices? An oven in the kitchen will probably do just fine.