Hi Rudy and all:
Just a thought; could this shelf life stipulation be based on tin plating
that was an immersion tin plate? Is it possible that the shelf life call out
is a remnant of the past when immersion tin coatings based on stannous
chloride and thiourea were used? Remember Shipley LT-26 (and the smell)?
These were not the new generation immersion tins with solderability
preservatives built in.
With a couple of millionths of Sn over Cu, they lasted about as long as it
would take you to get the part out of the final rinse, dry it and run down
the hall to solder it into the board.



Regards

Michael Barmuta

Staff Engineer

Fluke Corp.

Everett WA

425-446-6076

-----Original Message-----
From: Rudy Sedlak [mailto:[log in to unmask]]
Sent: Thursday, July 24, 2003 3:51 PM
To: [log in to unmask]
Subject: Re: [TN] Short Solderability Time Limits


Bev:
On electroplated Tin, clearly one of the questions needing answering is how
they define solderability...or putting it another way, when you test
solderability, what flux you using?

..another aspect of this, as many have pointed out, is that this is a
self-serving limitation, as you now have lost your "right to
complain/object" if the
parts are out of the bag any significant time.

Another interesting question is "Is the tin, bright, or matte:?"  That will
have an effect, with bright Tin having greater shelf life.

I would turn this back to purchasing, and suggest that you want minimum 30
day guarantee, and so start by asking for 90 days...

Good luck.

Rudy

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