Well, I hate to be a heretic but...  I do know of one instance where 
BGAs that were over 7 years old were installed on boards quite 
successfully, no heroic storage measures had been taken and the only 
precaution was baking the parts prior to installation.  In this case the 
company that had made the parts went bankrupt shortly after the parts 
were designed in and the decision was made to do a lifetime buy of parts 
from distributors.  Arguably not the best decision and clearly not one 
made on technical merit, but in this case there were no adverse effects.

regards,

Graham Collins
Senior Process Engineer
Sunsel Systems
(902) 444-7867 ext 2211

On 4/8/2015 9:22 AM, Mike Fenner wrote:
> 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]
> ______________________________________________________________________
>



______________________________________________________________________
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] 
______________________________________________________________________