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]
______________________________________________________________________
|
