The issue of long term storage of parts or boards is not a new one. The military, faced with REALLY long lifetimes (e.g. 50 years for a MX missile) and decreaseing market clout, has had to deal with lifetime buys for a long time. In my mind, there are two possibilities: (1) preserve the original solderability for as long as possible, or (2) plan on restoring the solderability at some point in the future when the part is needed. In the first case, you will have to setup some fairly elaborate storage conditions where oxygen and moisture are excluded. Dry nitrogen is most common, but alternatives could include dessicated conditions or coverage with a heavy noble gas like argon. You will have to setup incoming and outgoing logs that tightly control the inventory, and you have to have floor space for the storage for the life span of the part. In the second case, you restore the solderable surface. Some people do this using aggressive fluxes and re-tinning, with limited success. An alternative to this is to use an electrochemical reduction process called ROSA to change the surface oxides to the base metal, restoring solderability. ROSA can be done on many parts at the same time, it is electroless, and is not too capital intensive. Dave Hillman of Rockwell is the master of ROSA and has published a number of papers on the topic. He would probably answer more fully but he is currently putting the finishing touches on his Master's thesis and so won't stick his head out of his cubicle for another few days. And when he does, if he sees his shadow, there will be 5 more months of winter (in Iowa, that's a safe bet). Where was I? The advantage of the ROSA approach is that it does not matter all that much what the solderability condition was when the part was received, and the storage conditions do not have to be draconian. As the commercial goes, you can pay me now or pay me later..... Doug Pauls Rockwell Collins --------------------------------------------------------------------------------- Technet Mail List provided as a free service by IPC using LISTSERV 1.8d To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt delivery of Technet send the following message: SET Technet NOMAIL Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ---------------------------------------------------------------------------------