Clean solder dipped surface is tin rich.  Very similar to the tin fused
surface (surface=150 A - 200 A).  Based on the experiences on
storage/solderability data, it is believed that both fused tin and solder
dipped (or HASL) clean surfaces have very similar shelf life (oxidation).
For second level packaged PWA, 85C/85RH/5V type of tests showed very little
difference between the two surfaces (clean! properly).  If anyone has
different reliability test data, please let me know. By the way, strictly
speaking, the tin plated and fused is 98% tin... Never want to use pure tin
due to you know what... "cat" whiskers should stay as part of the cat, not
as part of the assembly.  ("Oh my fur and whiskers!"--1832-1898)
                                      jk
p.s. are you talking about 100% pure (strictly) tin?
At 09:51 PM 11/7/99 EST, you wrote:
>JK:
>
>Suspect, based strictly on observed phenomenon, that the EMF of fused solder
>could be one of those strange situations that does not follow the rules, and
>may be more passive than would be indicated by strictly looking at the table
>of EMF.  Indeed, if the 63/37 eutectic alloy is an actual compound, this
>would make sense.
>
>Have no data to back this up, simply note that fused solder is REAL passive,
>and has a REAL long shelf life, whereas pure Tin plating almost seems to
>oxidize as you watch it....
>
>Rudy Sedlak
>RD Chemical Company
>
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