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November 2004

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Subject:
From:
Happy Holden <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, [log in to unmask]
Date:
Wed, 24 Nov 2004 13:58:50 -0500
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Scott,
I'm surprised at their answer. We have been making immersion silver boards
for 6 years now and it has proved to be far superior to ENIG.  It is very
easy to run and the conveyorized line is the least costly to buy.  We do
not charge for it unlike ENIG that carries a quite large price adder.
Shelf life for ImAg has been 6-12 months if left in the sealed-sulfur free
bags that we ship the boards in.  Solderability has been excellent AS LONG
AS THE ASSEMBLER REALIZES THAT THIS IS NOT HASL OR ENIG ! ! We have had
problems with assemblers taking them out of our bags and stacking them on
shelves exposed to humidity and picking them up without gloves.  Once the
assembler is educated that you can't mishandle these boards like HASL or
ENIG, the problems go away.  It also has been the best finish for
lead-free assembly processes.
This PCB Fabricator may not have the money to buy a new line for Immersion
Silver and so he want you to stay with ENIG.  But ENIG corrosion problems
go up with increase heat cycles and smaller pitches-so best to make the
transition to some other finish NOW.

Happy Holden
Westwood Associates




Scott Lefebvre <[log in to unmask]>
Sent by: TechNet <[log in to unmask]>
11/24/2004 01:42 PM
Please respond to
TechNet E-Mail Forum <[log in to unmask]>; Please respond to
Scott Lefebvre <[log in to unmask]>


To
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Subject
[TN] Immersion Silver






I just got off the phone with one of our PCB FAB shops and was surprised
on his response to Immersion Silver as a solder finish.
He suggested that we do not use it as a replacement for HASL and to use
gold instead.  All the things I've read and did research on IAg in
contraction to he said.   The shop said shelf life is less than 6 months
and tarnish was a big issue.  It was more expensive than ENIG and not that
many shops do it in-house.

My understanding is the shelf life is 6-12 months if stored and handled
properly.  They silver used today has an anti-tarnishing agents to prevent
tarnishing.  I was also under the impression that IAg is less costly than
ENIG.

Your opinion in this matter would be greatly appreciated.

Thank you,

Scott

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