Yes, probably 90% of any oxide that forms is there within a few hours. Long term storage is not an area I have studied deeply, but I recall reading somewhere a synopsis of a paper where the author proposed the idea of just buying naked die and packaging them as required. Be interested to hear views on that, I just thought that would open another can of works along the known good die debates of yesteryear, and moved on. -- Best Wishes Mike Hi gang - hate to destroy an industry myth but tin oxidation is pretty much self limiting. The oxidation reaction will hit a plateau around 40 nm and then stop. Most long term solderability loss isn't from oxidation of the external interface but rather the consumption of a tin layer from intermetallic growth over time. Since a BGA typically has a SMD gold over nickel over copper pad (the gold is consumed during ball attach) and the IMC growth of tin/nickel is very slow, once the solderball outer surface hits the 40 nm mark, solderability isn't going to change, especially if MSL/inert gas packaging is used. Dave On Tue, Apr 7, 2015 at 1:52 PM, Stadem, Richard D. <[log in to unmask] > wrote: > Drypak alone won't do any good unless the it is done with nitrogen. The > oxidation will continue unless all Oxygen is purged and the hermetic bag is > sealed. > > -----Original Message----- > From: TechNet [mailto:[log in to unmask]] On Behalf Of Joyce Koo > Sent: Tuesday, April 07, 2015 1:42 PM > To: [log in to unmask] > Subject: Re: [TN] 5 year old BGAs > > low temp storage with hermatic seal package (dry pack)... pack in a way > according to your forecast usage level (once a year for example or every 6 > month). if it is programmable device, make sure you still has computer and > program to run for it... check solderability every year. just in case you > see problems, you have time to final alternative, like re-design-usually > take 3-6 month go through qual (not if you want to, but > 5 years anything can happen)...my 1.6 cents. > jk > > Hi Peter - Sue and Richard gave you the critical parameter = proper > > storage. The two primary processes you want to stop or significantly > > slow > > down: the oxidation of the solderballs and the absorption of water by > > the BGA laminate/molding. If you use the industry MSL bags designed to > > control moisture diffusion, use desiccant, use an inert gas such as > > argon or nitrogen and then store the bags in a controlled environment, > > you will address both issues and should be able to get a 5 year use > > life. Most folks try to cut corners/costs and do things cheaply which > > dooms their potential for success. > > > > Dave Hillman > > Rockwell Collins > > [log in to unmask] > > > > On Tue, Apr 7, 2015 at 8:53 AM, Peter G. Houwen > > <[log in to unmask]> > > wrote: > > > >> We have an FPGA that may not be available to us soon. One of the > >> options available to us to avoid a redesign is to buy 5 years' supply > >> of the BGA. > >> > >> I'm being asked to analyze the risk factors (and we need an answer > >> today of course) > >> > >> We can easily bake parts for moisture, but what about plating > >> degradation on the balls? Any other problems I might expect? > >> > >> I assume that even with baking we should expect some yield reduction, > >> but I can't begin to guess how much. > >> > >> Thanks, > >> > >> Pete > >> > > > > > > ______________________________________________________________________ > > This email has been scanned by the Symantec Email Security.cloud service. > > For more information please contact helpdesk at x2960 or > > [log in to unmask] > > ______________________________________________________________________ > > > > > ______________________________________________________________________ > This email has been scanned by the Symantec Email Security.cloud service. > For more information please contact helpdesk at x2960 or [log in to unmask] > ______________________________________________________________________ > > ______________________________________________________________________ > This email has been scanned by the Symantec Email Security.cloud service. > For more information please contact helpdesk at x2960 or [log in to unmask] > ______________________________________________________________________ > ______________________________________________________________________ This email has been scanned by the Symantec Email Security.cloud service. For more information please contact helpdesk at x2960 or [log in to unmask] ______________________________________________________________________ ______________________________________________________________________ This email has been scanned by the Symantec Email Security.cloud service. For more information please contact helpdesk at x2960 or [log in to unmask] ______________________________________________________________________