The story I got from the board house was that the mask actually oozed out thru the via on the other side during topside cure and essentially pooled up forming a bump. We are investigating calling out for a plug and tent on that board to try to resolve this issue. I had a 3 mil max number for height in mind....is that a reasonable number to go with? Amol Kane | Process Engineer Catalyst Manufacturing Services, Inc. 941 Route 38, Owego NY 13827 Phone: (607) 687-7669 Extn 349 | Website: www.catalystems.com -----Original Message----- From: Steve Gregory [mailto:[log in to unmask]] Sent: Friday, October 28, 2011 9:06 AM To: 'TechNet E-Mail Forum'; Amol Kane Subject: RE: [TN] maximum height of artifacts above the soldermask Hi Amol, 7-mils? WOW, that's a lot! If you're trying to print paste and have anything holding the stencil up, especially close to fine pitch devices, then you're going to lose your print definition and print more paste than you intend. How fine is the fine pitch? 20-mils? 25-mils? I was going to suggest something that I have done in the past which is to have the vias half-etched in the bottom of the stencil so that the stencil can sit flush and gasket against the PCB. But if the bump is truly 7-mils you wont be able to do that because the bump height will exceed the stencil thickness (I typically use 4-6 mils). Why are the via tents 7-mils tall? Did they get done twice or something? Steve -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Amol Kane Sent: Friday, October 28, 2011 8:45 AM To: [log in to unmask] Subject: [TN] maximum height of artifacts above the soldermask Dear Technetters, Is there a spec/guidance/industry best practice recommendation on the maximum height of artifacts (like silkscreen, via tents etc.,) above the soldermask surface?. Assuming the stencil foil sits squarely on the soldermask, any height above that will induce a (localized) standoff if any such artifact is near the pad. We have some boards in which the via tents are 7 mils above the rest of the mask surface. Some of these vias are close to fine pitch devices. I am afraid that I won't be able to control the volume of paste during printing leading to shorts. The board house saying I won't have an issue (big surprise there! :)). Is there something I can use as a basis of my push back ? Thanks in advance!! Amol Kane | Process Engineer Catalyst Manufacturing Services, Inc. 941 Route 38, Owego NY 13827 Phone: (607) 687-7669 Extn 349 | Website: www.catalystems.com<http://www.catalystems.com/> ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. For more information please contact helpdesk at x2960 or [log in to unmask] ______________________________________________________________________ --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 16.0 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 For additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 ----------------------------------------------------- ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. For more information please contact helpdesk at x2960 or [log in to unmask] ______________________________________________________________________ --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 16.0 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 For additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 -----------------------------------------------------