[tinwhiskers] Re: Re-balling SAC BGAs
- From: Steve Smith <steve@xxxxxxxxxxxxxxxxxxxxxx>
- To: ab3a@xxxxxxxxxxx
- Date: Sun, 1 Aug 2010 08:56:47 -0700
Hello, Jake (and Bob)
I have a patent-pending on a process that in theory will eliminate or
at least mitigate whiskering propensity of pure-tin finishes by one
to three orders of magnitude, at an estimate. I filed the patent to
document some technology, but it is not a practical thing if one
really wishes to defend against failures due to short circuits from
tin whiskers.
These things may take years to grow, and may have latencies of ten
years or more.
How long must one test something to have a confidence that it solves
that problem?
For whiskers that grow relatively promptly, it takes 3-5 years to have
some confidence that the 3-5 year growth is not being seen.
It takes *forever* to prove that something **will not** happen.
FOREVER.
One cannot do competent engineering with a problem that requires one
wait an indefinite length of time to see something not happening.
The only certain way to deal with the tin-whisker-risk TODAY and in
the months and years to come is a physical barrier, and most
preferably the barrier of an elastomeric conformal coating that
contains the tin whiskers and buckles them when they grow tall enough
to collapse, the tented elastomer causing axial compressive stress
[Euler Buckling], and then containing the still-growing "whisker-ball"
in a dielectric tent, thus preventing short-circuit failures from tin
whiskers.
Over the last five years, I have developed a conformal coating that
does just that, based on the mathematical physics of elastomers. No
other conformal coating in existence is based on the physics of doing
this. In the next 12 months and beyond, it will be undergoing formal
qualification tests. Eventually, Qualified Applicators will be
licensed to apply it.
It is a simple mechanical solution to a simple mechanical problem, and
whether or not it works will be verifiable in any accelerated-aging test
one might care to make.
It is based on the premise that we don't need to wait for whiskers to
grow to see if they don't. Rather, *we don't care* if they grow or
not, since we have an effective containment for those that do,
whenever they might.
Steve Smith
Whisker-Tough Development
acn> Bob, if and when you do, please give me notice of the process.
acn> I'd like to be able to dangle a patent in front of all these
acn> process automation firms AND Cisco to ensure that the processes
acn> we use on large plants and chemical processing facilities have some
reliability.
acn> We get upset when something fails after "only" a year in service
acn> 24/7. I have seen software notices for things that will fail
acn> after 450 days in service. A three year life span for things made
acn> with RoHS technology is a farce to operations like a waste-water
acn> treatment plant, where we expect the damned product to work for decades.
acn> I need something to point to for our OEM suppliers to get clues
acn> from. If people know of other processes, patented or otherwise,
acn> I'd love to hear about who is doing what...
acn> Jake Brodsky
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--
Best regards,
Steve mailto:steve@xxxxxxxxxxxxxxxxxxxxxx
www.consultingscientist.us
http://www.pickensplan.com/
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