agree on tin, provide you have a good barrier layer of Ni or Ni-P at
UBM... rather safe than sorry... not just the solderability issue.  (not
mention what inside the package... )...jk ;-0
> 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
>> >>
>> >
>> >
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