All of our moisture sensitive components are shipped to us in vacuum sealed, desiccated bags with a moisture indicator. When the parts are removed from the bag (this is done at either SMT setup, or in the stockroom) the indicator is checked. If it is within spec than the parts are processed, if it is not the parts are either returned to the vendor, or baked. In either case, the vendor is notified of the shortfall. After the bags are opened the parts are stored along with the indicator in either a dry box, of a new vacuum sealed, desiccated bag.
Here at Sanders a majority of our parts are of the non-moisture sensitive military style ceramic type, however we have a growing number of commercial type plastic parts. It is my understanding that moisture enters the component through the lead seals, and not the body itself. I am not an expert on package design, however I would expect that most plastic bodied parts would be "moisture sensitive" candidates.
As for a solution to your moisture sensitive dilemma, I recommend working with your suppliers to receive properly sealed, desiccated, and indicated parts. Process the parts assuming they are moisture sensitive, and view the baking as a rework procedure. If you are doing a lot of baking, than there is a shortfall in your handling/stocking process.
Chris Fontaine Manufacturing Engineer, Circuit Card Assembly Sanders, a Lockheed Martin Co.
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