If my memory serves me right, Mil-HDBK has one page of dissimilar metal
coupling chart, the tin and solder are very close on the chart (allowed
coupling within 0.2V difference).  I don't have the chart with me (bury
under pile of papers on my desk..the pile has life of its own..).
The tin plating normally has some problems due to poor quality of plating,
similar problems can be found for poor plating of solder.  "plated and
fused" tin is not that much different than the "hot solder dipped" pin/leads
in term of corrosion resistance.  we are talking about storage, inside box,
2nd level packaging, with environmental testing listed as ppb contamination
level, such as ESS)... Not exposed to outdoor environment or under the sea
like the Titanic...Fused or dipped normally get rid of the voiding and high
temperature eliminated any organic entrapment (brightener, etc) ...(assume
you clean the leads properly after the fuse/dip process).
....
my UN-exalted opinion...please let me know if my memory is fading..(high
electro-chemical potential on Alzheimer's disease)...
                                  jk
At 09:49 AM 11/5/99 EST, you wrote:
>Dave:
>
>With all due respect to your exalted position in this area....
>
>I have seen many many problems in the fabrications area caused by having pure
>Tin, as compared to having Solder, especially if the it is true solder, i.e.
>that it is the true alloy, which seems to have profoundly better corrosion
>resistance than merely "plated solder", which is nothing other than discrete
>chrystals of Tin and Lead.
>
>(Should I note that we make money and have products which have a life only
>because they solve this issue... in selected situations:-)
>
>And ignoring any ostensibly authoritative EMF tables, which I have found to
>be effective in academia, and few other places (because they are meaningful
>only when the electrolyte is deionized water),  the solder seems to have much
>better resistance to corrosion than pure Tin, and especially plated Tin,
>which seems especially "active".
>
>If what I am saying is true, that Solder is much more passive than pure Tin,
>you have the makings for a seriously pumping galvanic cell, which should need
>only an electrolyte to crank up, and deliver you Tin oxide all over the pure
>Tin plating...
>
>And remember, free advice is often worth what you pay for it...
>
>Regards,
>
>Rudy Sedlak
>RD Chemical Company
>
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