The undercutting of the mask is typically cosmetic in nature unless of course it violates IPC spacing etc. A problem that will eventually occur is the mask that is no longer bonded to the surface of the copper or base material (under cut) can and more than likely will flake off at some time. If it happens after assembly and solder doesn't adhere to the copper under the under cut mask there will be exposed copper. Another thing to question is are there mask dams between surface mount pads you need? If the undercut is bad enough mask dams will come off base material leaving potential for solder shorting. This is where consideration on your end needs to taken. We don't ship out peeling (undercut ) mask when it happens. Dan Skweres Engineering Manager Bartlett Manufacturing Phone:847-639-2102 Ext.#230 Fax:847-639-8838 >>> Kevin Glidden <[log in to unmask]> 09/26/06 11:26AM >>> Question for the PCB fabricators... One of our PCB suppliers is asking us to accept PCBs with a "minor" issue. The problem is described as this: The panels were under-developed and some residual solder mask was left over. To eliminate this, the panels were put through a second pass to ensure all residual solder mask was removed. The result is some overdevelopment of the solder mask. Then, this apparently resulted in an "undercut" along the demarcation lines. They say during a tape test, very small traces of mask from the undercuts comes off. The mask is still present between all features and is adhered to the PCB. But, it is over-developed and has undercuts. They say that while it does not pass the tape adhesion test, it is of no detriment to the PCB quality or performance. My question is if over-developed soldermask maintains the same properties as normally developed soldermask? When I asked about this, they said the properties of the mask are determined by the initial (pre-developing) cure and the final (post-developing cure), and the over-development does not affect the properties. True? In case "it depends", these PCBs are used in avionics power supplies. Thanks in advance! Kevin --------------------------------------------------- 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 -----------------------------------------------------