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
>>
>
>
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