Hi Graham, Thanks for the reply. I've noticed some resistors we've removed have a sort of Swiss cheese look to the chip bonder remaining on the PWB. It this what you'd expect to see or is this exactly what you are talking about? Thanks, Ken -----Original Message----- From: TechNet [mailto:[log in to unmask]]On Behalf Of Collins Graham Sent: Tuesday, April 27, 2004 10:49 AM To: [log in to unmask] Subject: Re: [TN] Glue Dots (chip bonding) Hi Kenny Based on an issue found at a previous employer, I offer this advice - check a couple of parts where you are seeing the shorts, remove the part and see if there are voids in the glue. Screen printed glue suffers from the possible issue of moisture absorption. As it sits on the screen printer, if the glue is hygroscopic it will absorb moisture. If the glue cure profile is hot enough the moisture can popcorn, resulting in voids in the glue. These voids can trap flux, leading to the sort of symptom you are seeing. regards, Graham Collins Process Engineer, Northrop Grumman Canada Corporation Halifax (902) 873-2000 ext 6215 >>> [log in to unmask] 04/27/04 02:20PM >>> This is one of those questions to resolve a discussion we are having regarding the size of glue dots. We have had several failures in the past due to flux contamination under some 0805 resistors causing a high impedance short. We found some issues with the cleaning process that when corrected, I believe, fixed the problem. We also changed the aperture of the stencils to a smaller oval pattern. My question is, does a glue dot that bridges under a part from pad to pad (no chip bonder on the actual pads) make it any harder to clean than a glue dot that does not bridge from pad to pad? My feeling is that the cleaning process should clean off the flux in either condition. Thanks in advance for your expert opinions. KennyB --------------------------------------------------- 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 ----------------------------------------------------- --------------------------------------------------- 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 -----------------------------------------------------