There were no published standards for storage and moisture protection for PCBs until 2010, but nonetheless problems with moisture damage were common. Lead free processing further increased the need for controls because saturated vapor pressure is commonly 3X that encountered in SnPb reflow.
Baking at elevated (90-120C) temperatures was traditionally the “solution” but warpage, de-lamination, oxidation and inter-metallics are all undesirable by products.
Published in the latter part of 2010 IPC 1601 ‘Printed Board Handling and Storage Guidelines’ recognized these problems. It states that, “Baking not only increases cost and cycle time, it can also degrade solderability of the printed board which requires extra handling and increases the likelihood of handling damage or contamination.”
The document also states “Baking is NOT recommended for OSP coatings, as it deteriorates the OSP finish. If baking is deemed necessary, the use of the lowest possible temperature and dwell time is suggested as a starting point.”
“In general, both the printed board fabricator and the user should strive to avoid baking by practicing effective handling, packaging, storage, and process controls…”
ITM also offers some useful insight into this issue