MSD Moisture Sensitive Device
This is of most concern for lead-free builds, but may also be of concern for standard leaded assembly. Basically, what happens is that these parts will gradually absorb moisture over time. If they are then sent into a reflow oven at 260 degrees C, the moisture inside works a lot like the moisture inside of a popcorn kernel, but not as tasty. It rapidly expands and can crack and destroy the part.
If you are dealing with a $600.00 BGA, it's no laughing matter. The worst part is that you can't always catch the damage with a visual inspection. Sometimes it's pretty obvious, but sometimes the damage is just internal to the part or under the part. Then you have expensive debug time in addition to the rework.
What this means for you is that if your parts come with a warning label similar to the graphic here in this post, you need to read the handling precautions carefully. Ideally, you would send us the parts still sealed inside the moisture vapor barrier package. If the package has been opened, we may need to bake the part for 24 or 48 hours prior to assembly.
If you have any components labeled as moisture sensitive, please note them as such in the special instructions when you place the order and make sure we receive the warning label with the part, even if the bag has been opened. If we have to bake the parts, then our turn-times (24 hour, 48 hour, etc.) will start when the components are finished baking.
You can read more in this PDF from the JDEC organization and this article from SMT Magazine. [the SMT article is no longer available]
Dry MSD is good