Hi Jorge! Silver/Platinum finishes will oxidize/sulfidize over time and
become very nonsolderable. A very aggressive flux (ANSIJ-STD-004 type H) is
typically used when this oxidized/sulfidized condition exists. It is my
opinion that you would be better off utilizing a tin/nickel finish - it
will oxidize over time also but you will not need an aggressive flux to
remove the oxide and make a metallurgically sound solder joint. Good Luck.

Dave Hillman
Rockwell Collins
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Jorge A Rodriguez <[log in to unmask]> on 09/14/99 03:22:14 PM

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Subject:  [TN] Multilayer SMT Voltage Suppressor




               I am having a hard time soldering a chip component. This
0603
chip is a multilayer surface mount transient voltage surge suppressor from
Harris (Part Number V5.5MLA0603H). I am suspecting from the termination
finish
which it's Silver/Platinum. I already checked the profile and it's OK. I
even
tried two different solder pastes (no clean and water wash) and I had the
same
result: dewetting and poor soldering, actually the solder paste seems to
reflow
without forming a fillet. I taught that maybe the component was
contaminated but
I discarded that when I learned we had a similar problem with another
product
using a component with similar termination finish (Silver/Platinum). I am
really
suspecting that the termination finish is the problem, I would rather have
the
nickel/tin finish, but according to the vendor they said they've never seen
the
problem we have with another costumer, it seems we are the only ones.
Another
thing is that when I made my tests (the two different solder pastes),
everything
on the board looked OK except those components. Is there anyone who has had
problems with Silver/Platinum termination finish?, Is this termination
plating
more difficult than others?, what are the benefits if we change it to
Nickel/Tin?



               Any advice will be appreciated.

               Thanks

Jorge A. Rodriguez
Conexant Systems, Inc.
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