-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Lou Hart
Sent: Friday, May 19, 2000 8:46 AM
To: [log in to unmask]
Subject: [TN] ASSY: soldering of standoff to PC board


TechNetters,

I'm looking at a what seems to me like a good sized piece of 303 stainless
steel, plated with nickel-tin, a standoff about 7 mm in diameter, 6 mm long,
with a wall thickness of about 1 mm.  Using a metcal iron, our folks are
having trouble soldering this to a PC board.  One of the quality inspectors
says there has not been a problem in the past, with this part, using the
metcal iron.  The standoffs have been in stock for 1 year after nickel-tin
plating.

Here are two questions I think of:

(1)  Is 1 year beyond the shelf life of nickel-tin plating?  Operators think
there is a "coating" on the standoffs that inhibits soldering.

>Intermettalic Growth occurs on any tin - xxx plating, maximum shelf life
should be six months, I have had a interesting learning experience with
intermettalic growth and soldering
For further information take a look at the amp connectors site and search
the technical papers section for intermetallic growth

(2)  Any ideas about a preferred soldering technique for a part like this?



Thanks for any feedback.  All production supervisors are out for the day, so
QA is trying to handle this one...Lou Hart  Compunetix

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