Hi Dave - I think the ANSIJ-STD-002/003 committees need to do a another
"report" on the use of conditioning treatments and the correlation of such
treatments to prediction of storage conditions! There is a common
misconception in the electronics industry that steam aging equals some
magical amount of storage life. The JSTD 002/003 specifications spelled out
how steam aging should be interpreted as based on the 002/003 committees
testing:

"6.8  Accelerated Steam Aging Limitations  The accelerated steam aging of
solderable coatings has been, and continues to be, the subject of intense
investigation (see IPC-TR-464). Compared to other aging methods, steam
aging satisfactorily accelerates the degradation of tin and tin/lead
surfaces in a manner similar to natural aging. The degradation mechanisms
of surface oxidation and Cu/Sn intermetallic growth are both enhanced by
the heat and humidity of steam. Properly applied tin and tin/lead coatings
can withstand the steam aging environment well beyond the 8 hours specified
and may survive natural aging well beyond 12 months. Due to the combined
effects of specific geometry, storage environment, and material systems, it
is not possible to accurately predict storage life. "

Note that the committees said".... steam aging satisfactorily accelerates
the degradation of tin and tin/lead surfaces in a manner similar to natural
aging...." and "Due to the combined effects of specific geometry, storage
environment, and material systems, it is not possible to accurately predict
storage life".

Steam aging (maybe we should have said steam conditioning) is just a method
of degrading a component or pwb surface finish to assess the robustness of
that finish. The Alternative Finishes Task group is going to be looking at
the subject of conditioning as its next task in the upcoming year.
Information from those efforts will be used in the 002/003 specifications.
Give me an email if I can furnish further explanation.


Dave Hillman
ANSIJ-STD-002/003 CoChairman
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[log in to unmask] on 10/24/97 01:31:54 PM

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Subject:  [TN] steam age




  As most board shops do, we regularly test boards for solderability. This
is done after accelerated aging in a steam chamber for 8hrs. I believe this
test is supposed to simulate one year of aging but cannot find any
information that confirms this assumption. Does anyone know if this is
true? If not, what time frame does it simulate?
David Arivett
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