We're aware of no industy acceptance standard for max moisture content of a board.
For more on moisture levels, get a copy of: "Removing Moisture from Electronic Components and Assemblies", CS Leech, Jr, Circuits Assembly, May 1994. The article discusses: * Some of the basic physics of water loss in detail - especially the issue of vacuum moisture removal. * Vaporization of water via vacuum may as not be the most effective moisture removal method in all instances [change of physical states (liquid to vapor) can result in the formation of ice (the article describes a neat demonstration of this reaction) which impedes the removal of water from a board].
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