Graeme
There was a similar study performed by Alison Winlow at ISL in the early
90s. She found a similar result. If anyone is in contact with Alison they
might ask her to comment.
Best regards
LeeJ. Lee Parker, Ph.D.
JLP Consultants LLC
804 779 3389
----- Original Message -----
From: "Graeme Stewart" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Tuesday, August 22, 2006 4:25 AM
Subject: Re: [LF] Immersion Silver and Conductive Carbon Ink
I only have a hard copy of the paper, it was written for SMTA International
conference in Sept 2001 but you can get a copy at
http://www.smta.org/knowledge/proceedings_abstract.cfm?PROC_ID=790
They tested Imm Ag for keypad applications using a contact resistance test.
There conclusion was that for keypad applications in portable products the
finish was a viable alternative to ENIG with prolonged exposure to a
corrosive atmosphere being the exception.
Regards,
Graeme.
-----Original Message-----
From: Leadfree [mailto:[log in to unmask]] On Behalf Of John Burke
Sent: 18 August 2006 18:21
To: [log in to unmask]
Subject: Re: [LF] Immersion Silver and Conductive Carbon Ink
Oh OK,
I think though that they actually put the carbon ink on at the board
vendors, so the problem they are experiencing is the carbon
lifting/peeling/chipping off right Douglas?
John
-----Original Message-----
From: Leadfree [mailto:[log in to unmask]] On Behalf Of Creswick, Steven
Sent: Friday, August 18, 2006 10:10 AM
To: [log in to unmask]
Subject: Re: [LF] Immersion Silver and Conductive Carbon Ink
John,
I was thinking of 'cleaning' after the reflow process had been done, and
immediately before the carbon ink step. ... whatever the 'cleaning' step
might be. :-)
Steve
-----Original Message-----
From: John Burke [mailto:[log in to unmask]]
Sent: Friday, August 18, 2006 1:06 PM
To: '(Leadfree Electronics Assembly Forum)'; Creswick, Steven
Subject: RE: [LF] Immersion Silver and Conductive Carbon Ink
A word of warning, any attempt to "clean" a silver board in process to make
the carbon ink "stick" will probably render it useless by the time it gets
to being soldered at the assembly stage. There is indeed a co-deposited
material to prevent tarnish with most of those chemistries.
John
-----Original Message-----
From: Leadfree [mailto:[log in to unmask]] On Behalf Of Creswick, Steven
Sent: Friday, August 18, 2006 9:26 AM
To: [log in to unmask]
Subject: Re: [LF] Immersion Silver and Conductive Carbon Ink
Scott,
Along Lester's line of thought, are there preservatives / anti-tarnish
constituents, etc. still on the surface? Do they have the same problem with
virgin boards [before you reflow components on them, etc.]? Or is it worse
in the virgin state?
Can they argon plasma clean [as a test], or maybe a solvent wipe of some
nature ... Solvent as best suggested by potential platers out there.
Steve
-----Original Message-----
From: Leadfree [mailto:[log in to unmask]] On Behalf Of Lester Subrattee
Sent: Friday, August 18, 2006 11:07 AM
To: [log in to unmask]
Subject: Re: [LF] Immersion Silver and Conductive Carbon Ink
Hi Scott,
I don't have a solution for your problem except to say that you're
depositing on metal and should have no issues if it is clean. Unless the
silver is actually lifting off. I think it could be a surface prep issue or
contamination from either the PCB house or your fabricator in handling.
Get
the surface analyzed and cleaned, then retry.
That being said, there have been studies by some OEMs that indicate
capability of Immersion Silver as a contactable surface in lieu of gold.
That is one of the reasons Immersion Silver's popularity has increased.
Unfortunately, I don't have the details and reports but someone on the Forum
might.
Good Luck,
LS
-----Original Message-----
From: Douglas, Scott [mailto:[log in to unmask]]
Sent: Friday, August 18, 2006 10:41 AM
To: [log in to unmask]
Subject: Immersion Silver and Conductive Carbon Ink
Fellow list persons,
=20
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?
=20
As always, thank you in advance for your comments.
Scott Douglas, NCE=20
Staff Technical Specialist
Harman Specialty Group=20
3 Oak Park Drive=20
Bedford, MA 01730=20
Phone: (781) 280-0406=20
Email: [log in to unmask]
Web: www.harmanspecialtygroup.com=20
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