Tenison - the problem is the protection of one surface from the other
process. If you run carbon first then it will require a dryfilm to protect
it from plating up with the silver. When you remove the dryfilm there is a
chance of staining the Ag surface and thus impacting solderability. If you
run Ag first, then the thermal exposure for curing the Carbon and the
outgassing of the ink may also impact solderability.
The best method I have tried to date is to use a peelable mask over the
carbon but the cost/labor involved is prohibitive to the point that
supplying ENIG in its place is an actual cost saving.
Another option is to use the Ag as a switch pad. The 4553 document covering
I Ag has data to 1 million cycles for membrane type switch pads, recommended
for class 1 and class 2 applications only.


Regards

Gerard O'Brien
Photocircuits Corporation
Co-Chairman 4-14 plating committee.


-----Original Message-----
From: Stone, Tenison (MN10) [mailto:[log in to unmask]]
Sent: Friday, January 21, 2005 9:04 AM
To: [log in to unmask]
Subject: [TN] IAg and carbon pads

I would be curious to hear answers to this question asked yesterday:

Question for anyone: Has anyone used IAg as a board finish with carbon ink
over any desired areas?  Seems like it might work for a keypad with parts on
one side and contacts on the other...


Looking at lead free - can we replace HASL with IAg and have carbon pads on
the opposite side?  What should be tested to prove a design using IAg and
carbon pads?

Tenison Stone
Sr. Process Engineer
Honeywell, International
1985 Douglas Dr. N
MN10-2471
Golden Valley, MN  55422
Tel: 763-954-4925   Fax: 763-954-4447
[log in to unmask]

---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 1.8e
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to
[log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to
[log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16
for additional information, or contact Keach Sasamori at [log in to unmask] or
847-615-7100 ext.2815
-----------------------------------------------------

---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 1.8e
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815
-----------------------------------------------------