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 ##############################################################