Hi Susan: Some PCB fab shops continue to use a "Scotch Brite" style of abrasive wheel or brush as a final surface prep operation prior to soldermask application. They feel it can provide a better surface(more tooth)to bond soldermask to than just a chemical Sn/Pb strip. It can also remove surface residues than could be left behind with a chemical strip. The problem with the brush approach is it can leave broken off fibers from the brush if the process is not properly controlled and rinsed. This is possibly one of the conditions that is showing up, in addition to broken-off overhang from overplating and/or overetching that aggressive brushing can cause. Regards Michael Barmuta Staff Engineer Fluke Corp. Everett WA. 425-446-6076 -----Original Message----- From: Susan Mansilla [mailto:[log in to unmask]] Sent: Sunday, September 12, 2004 3:26 PM To: [log in to unmask] Subject: Re: [TN] PWB Conductive Contamination Under Solder Mask; What Can ... I received the photo - I realize Technet did not. The one surface land does show over hang, but the one on the bottom from another coupon shows NO overhang. The one with overhang also shows severe UNDERCUT of the solder mask next to the land. I am puzzled by the "scotch brite" comment as I can think of no reason for using this in a SMOBC product. Any and all tinlead plating should have been stripped off prior to cleaning and solder mask application, The overhang of copper that was present on the top coupon would not have been removed by an abrasion process. The real proof would be seeing what the sample looked like in the "as plated" tin/lead condition and finding out why an abrasion process was used. The few times I have used an abrasion process only caused the overhang to become splinters that then came loose later on and caused problems. The undercut of the solder mask is also a potential threat for trapping contamination later on during HASL or assembly processing. Susan Mansilla Technical Director Robisan Laboratory, Inc. 6502 E 21st Street Indianapolis, IN 461219 www.robisan.com 317-353-6249 --------------------------------------------------- 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 847-509-9700 ext.5315 ----------------------------------------------------- --------------------------------------------------- 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 847-509-9700 ext.5315 -----------------------------------------------------