Until a couple of years ago, on .5mm pitch, the smallest solder mask web allowed was always spec'd at .005", since any narrower then that and flaking was almost guaranteed. I have just addressed this issue with two of our board vendors, who were resistant, since I wanted wide pads AND solder mask on our .5mm pitch parts....but they were able to obtain compliance when I relaxed my spec to..."....minimum solder mask web of .004" with adhesion of web (i.e., no flaking). Also, solder mask can be allowed to go up to the pad, but NOT encroach onto the pad". Most suppliers can hold this process, and the "newer" solder masks are capable of good adhesion if processed properly. Hope this helps Jeff Hempton, Sr. SMD Mfg. Engineer United Technology Electronic Controls e-mail: [log in to unmask] ______________________________ Forward Header __________________________________ Subject: Re: [TN] Fab: Mask dams between fine pitch smt pads Author: Mike Bailey <[log in to unmask]> at Internet Date: 10/13/1999 6:41 AM .0035 - .004 is within the capabilities of most shops, even on .5mm pitch devices. Occasionally, this is an issue when small via holes in high aspect ratio boards must remain open after developing. It requires a slightly overdeveloped condition to clear all mask residue from the holes. Otherwise it is consistently achievable. -----Original Message----- From: Ed Cosper [mailto:[log in to unmask]] Sent: Wednesday, October 13, 1999 5:16 AM To: [log in to unmask] Subject: [TN] Fab: Mask dams between fine pitch smt pads Hi all, Just a quick industry capability questions. Are board manufactures still having trouble holding mask dams between fine pitch (19mil) SMT pads. As recent as a year or so ago I was under the impression that board shops would ask the remove these small dams when they got them on the Gerber data. Is this still common. I am interested in what most people think is feasible regarding mask dams that are 4 mils wide and smaller. All responses are appreciated. Ed Cosper ABC ############################################################## 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. If you need assistance - contact Gayatri Sardeshpande at [log in to unmask] or 847-509-9700 ext.5365 ############################################################## ############################################################## 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. If you need assistance - contact Gayatri Sardeshpande at [log in to unmask] or 847-509-9700 ext.5365 ##############################################################