Hi, Scott,
Lester and Graeme both bring up good points. While immersion silver has
been found to be wire-bondable, and they even make key pads with it,
those are both mechanical processes that would break through any
immersion silver tarnish.
Conductive epoxy inks and carbon inks are another issue. They may not
bond well to IAg if there is any tarnishing. Perhaps on one board you
could try a rubber erasure followed by alcohol to determine if that
improves the bonding of inks and epoxies. If it works, then you
understand what the root cause of the problem is. The solution could be
derived from that.

-----Original Message-----
From: Leadfree [mailto:[log in to unmask]] On Behalf Of Douglas, Scott
Sent: Friday, August 18, 2006 9:41 AM
To: [log in to unmask]
Subject: [LF] Immersion Silver and Conductive Carbon Ink

Fellow list persons,
 
I have a printed circuit board used in a remote control unit. We changed
the solder plating on the board to immersion silver for RoHS compliance.
Our fabricator is having a problem getting the conductive carbon ink to
stick to the immersion silver. Is anyone aware of this type of problem?
We are trying to figure out if we just have a vendor problem or is there
some issue with the immersion silver and conductive carbon ink
combination. Any suggestions as to changes or corrective actions?
 
As always, thank you in advance for your comments.
Scott Douglas, NCE
Staff Technical Specialist
Harman Specialty Group
3 Oak Park Drive
Bedford, MA 01730
Phone: (781) 280-0406
Email: [log in to unmask]
Web: www.harmanspecialtygroup.com 


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