Pretty well concur with Dave and Joyce, my version:
The least bad for soldering is matte tin.

Immersion tin goes on very thin, as the reaction which forms it is self
limiting and so gives very short term protection - say 3 months or so. It
then becomes as solderable as wood due to formation of CuSn intermetallic.
It can also be very variable, both from supplier to supplier and batch to
batch. I have even seen within a batch. Possibly its only merit is that it
can form the CuSn before it whiskers.
Electroplated tin can be thicker and less porous so therefore offers the
possibility of longer protection. Thicker with Sn means greater tendency to
whisker.
As a general rule anything "bright and shiny" means trouble for soldering.
In the case of electroplates the organics that give that polished finish and
look so pretty are not solderable, just interfere with wetting and can
outgas. Bright Sn whiskers sooner and worse than matte.
Of course Sn plating is soluble (and fusible) in solder and therefore the
actual solderability is dependent on the copper underneath.

Mike

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Guy Ramsey
Sent: Friday, March 06, 2015 1:51 AM
To: [log in to unmask]
Subject: [TN] bright electroplated tin, versus immersion matte tin

Can anyone give me a nutshell difference between immersion tin for a solder
finish and electroplated tin? 
Advantages, disadvantages as a surface finish more than the chemical and
plating process differences. 
Thanks,
Guy





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