Being in aerospace, we have faced this issue, both successfully and unsuccessfully. I remember pulling 5 year old parts off the shelf for a program only to see the welds at the body encased in a white oxidation (on that one, we redesigned and re-qualified the product, ouch). The main issues are oxidation, tin migration and left over acids from manufacture on the die itself. I'm no expert on tin migration, but my understanding is that in tin-lead alloys, even at room temperature, the tin will migrate until at some point, the parts are no longer solderable. We do periodic testing on our 30 year life time buy parts. If they look marginal, we'll have to dip tin them all. Since you are probably dealing with commercial parts, I recommend delidding a representative sample at an appropriate interval (no longer than 1 yr) to see if they are deteriorating inside. If they are, you get to figure out some way to save them or redesign and requalify. Let's move on to oxidation and storage. Humidity indicators, paper labels, plastic carriers, most anything can be a source of contamination that migrates to the leads and accelerates loss of solderability. Here's what we did for 30 year storage: 1. Pretin the parts. 2. Clean them really really well including plastic carriers for DIPS etc - use clean latex gloves for all handling of parts and carriers - final rinse in DI water followed by grain ethyl alcohol O-E-760 (a FED spec for Everclear). 3. Bake out at 150 F for 1 hour min (carriers air dry 1 hour in a clean place) 4. Unit pack in a non-amine based ESD shielded bag - pull all air out and purge w/ nitrogen and heat seal. 5. Slip that bag into a moisture vapor barrier bag - TYVEK/foil/anti-static poly non-amine based bag w/ a clay based desiccant in TYVEK pkg and a humidity indicator card - pull all air out and purge w/ nitrogen and heat seal. 6. Put the vapor barrier bag into a pink poly non-amine based bag with humidity indicator card and heat seal. 7. Finally, all of this goes into 55 gallon steel drums with say 80 units of clay desiccant in TYVEK bags and with humidity indicators installed in the lids. 8. All storage must be temperature controlled. We use 70 F, colder may be better to retard chemical processes internal to the ICs. It seems like overkill 7 times over, but if you don't do enough, the heart break comes when it is too late to do a good enough job. Just remember this, to keep moisture out, metal or glass containers are nearly perfect and all plastics work poorly in comparison - even with the aluminum foil, the moisture barrier bags allow moisture to penetrate. Contact me offline for specific brands that we determined to be acceptable. Good luck. --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 1.8e 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 or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 -----------------------------------------------------