Albert,

The Alternate Final Finishes section of the IPC Assembly and Joining
Committee is trying to correlate time, temperature, and humidity during
storage with solderability, as measured by wetting balance.  We have the
following finishes in test - bare copper, reflowed tin/lead plate, OSP,
electroless nickel/immersion gold, immersion silver, and immersion tin.
Various combinations of aging are being tested in a designed experiment to
see if we can develop mathematical relationships for combinations.  The final
data is now being taken, and a preliminary report will be given at IPC Apex,
and a full report should be done by IPC Expo.

Hopefully, the data can be used by the IPC J-003 Solderability Committee to
do exactly what you want and project solderability of aged surface finishes.
"Steam aging"  really should be called "prediction of solderability under
high heat and extreme humidity, not necessarily representative of long term
storage of tin lead finishes".  However, suffice it to say, steam aging is a
better predictor than most any test we have come up with for TIN/LEAD
coatings only.

Dennis Fritz
MacDermid, Inc
Chairman - Alternate Final Finishes Task Group.

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