All of this may be true, but I suspect, and we are seeing it proven at
various different places, that the differences between different pads can be
made virtually zero, IF the pads are cleaned of all mask residues.   A
microetch and/or acid cleaner does not seem to be enough, by itself, an
alkaline cleaner seems to be required.   Yes, it is possible to alkaline
clean LPI soldermask, without any attack.  I can give you more information if
you contact me directly.

Rudy Sedlak
RD Chemical Company


In a message dated 97-10-16 10:10:40 EDT, you write:

>The copper surface has a given plating potential. If features are connected
>together, the TOTAL surface drives the plating potential. Hence, smaller
>surfaces have lower plating potential and are harder to plate. A floating
>feature, not connected to any plane, is harder to plate. When one feature
>does
>not plate, others connected to it do not plate. This phenomenon is sometimes
>called the galvanic effect. Other variants of this phenomenon are also
>encountered when using electroless processes.
>
>
>Jacques Coderre
>e-mail:[log in to unmask]
>
>
>---------------------- Forwarded by Jacques A Coderre/Bromont/IBM on
10/16/97
>09:49 AM ---------------------------
>
>
>[log in to unmask] on 10/15/97 04:14:55 PM
>Please respond to [log in to unmask] @ internet
>
>To: [log in to unmask] @ internet
>cc:
>Subject: [TECHNET] Exposed copper pads/Immersion NiAu
>
>PWB manufacturers:
>Has anyone seen the phenomonen of exposed copper SMT pads after
>immersion NiAu. To further complicate this issue, any pad (via or SMT)
>that is tied to this pad in a net also does not get plated. This condition
>does not occur on every panel within the rack. One panel will have it,
>while the adjacent panel does not.
>Are we looking at a static charge on the panel that keeps certain nets
>from plating?
>Any ideas on what's causing this would be appreciated.
>
>Thank you
>Ron Hayashi

##############################################################
TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c
##############################################################
To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body:
To subscribe:   SUBSCRIBE TECHNET <your full name>
To unsubscribe:   SIGNOFF TECHNET
##############################################################
Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information.
For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700 ext.311
##############################################################