Hello TechNet:
We performed some experiments on Immersion White Tin boards and found the
following . . . .  First, we had no problems with solder paste application.
Second, no problems with vision systems, etc., and part placement.  Third,
solder joints looked pretty good . . i.e. . no problems.  Here is the
kicker.  The mounting holes on the top side were white tin.  The mounting
holes need to be very flat for good contact so we do not apply solder paste
to these holes.  The white tin, after exposure to humidity of the
environmental chambers looked very oxidized and a flaky white powdery like
substance was observed.  Also under some RF type connectors, the white
powdery like substance was observed.  The powdery like flaky substance did
not show up under any other components only the gold RF connectors.

What experience have any of you had with the immersion white tin process?
Any ideas, thoughts, etc., on the powdery white substance??? We are going to
have our "product assurance forensic lab" analyze it and see what they come
up with, but we also thought it a good idea to tap the intelligence of the
TechNet World as well.

Ron Hollandsworth
ITT


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