It's possible, depending on how adhered the mask is. My thought was not so much on the undercut entrapping anything; however, once the adhered mask began to separate from the glass of copper (at whatever stage), then it would allow for entrapped 'stuff' at this newly formed pocket or space. This of course could happen during assembly (from pre-clean to post-clean) and while in use (environmental conditions, humidity, dust, dirt, etc). Franklin -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Kevin Glidden Sent: Tuesday, September 26, 2006 12:52 PM To: [log in to unmask] Subject: Re: [TN] Over-developed Soldermask Franklin, The concern of the undercut trapping residues or contaminants is an interesting point and one that I had not considered. Would that not also be a concern during the initial soldering / cleaning steps that the flux residues could get trapped in the undercuts? Thanks! --------------------------------------------------- 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 -----------------------------------------------------