Always important to provide the complete story If you try the oil test on a sample with and without via plug that should show you. If you search the archives you will find the procedure and video links I have posted in the passed on normal plated through holes. The images in the database show small vias but not via in pad. The image of a BGA shows via in pad Although solder mask does absorb moisture and solvent it very unusual to outgas for a long period of time. Many thanks Bob Willis 2 Fourth Ave, Chelmsford, Essex, CM1 4HA England Tel: (44) 1245 351502 Fax: (44) 1245 496123 Mobile: 07860 775858 www.ASKbobwillis.com www.SolderingStandards.com New Package on Package Workshops 24th November www.ASKbobwillis.com/PoPWorkshops.pdf PCB Design for Manufacture & Assembly Workshop 15th October www.ASKbobwillis.com PCB Inspection & Quality Control Workshop 3rd November www.ASKbobwillis.com/faworkshops.pdf Book Bob's "Step by Step Failure Analysis Workshop" 4th November www.ASKbobwillis.com/faworkshops.pdf -----Original Message----- From: Chris Mahanna [mailto:[log in to unmask]] Sent: 27 August 2009 15:47 To: Bob Willis; TechNet E-Mail Forum Subject: RE: [TN] Via-in-pad blowing bubbles Bob et al, Sorry we don't have blinds outgassing. If we see some I'll send a sample to you. Obviously I forgot to mention the via type. They are through vias with single sided solder mask plug. The plug is very deep (>75%), and maybe a separate mask process. Different mask? I doubt that the board is outgassing through the via because we've got ~1.8 mil of uniform plating. How about incomplete plug cure? I think that I may have some evidence of that. Chris -----Original Message----- From: Bob Willis [mailto:[log in to unmask]] Sent: Thursday, August 27, 2009 7:23 AM To: 'TechNet E-Mail Forum'; Chris Mahanna Subject: RE: [TN] Via-in-pad blowing bubbles If you have via in a pad and its solder coated or reflowed with paste what you describe can happen. If there is still volatile material either in the hole, a void below the level of the solder or thin copper plating outgassing through the copper plating can happen. Not however on gold over nickel boards. The eruption and outgassing will be random depending on what is there, speed of heating and how long the solder remains molten. Just like any gassing from a plated through hole you can see a nice ball, a balloon blow out or a sunken joint and this can be all associated with outgassing. The classic problem with through vias is when engineers try to fill small vias on side one reflow, then spend hours cleaning balloons off side two before printing again. If you simply find a sample board with the problem you describe and place it under a microscope, fill the view with a group of pads in question. Take a micro soldering iron and touch sample pads and wash what happens. You can use the old oil outgassing test I have used for years to see the outgassing from the vias on a bare board Unfortunately I don't have a via example to show you but if you look at http://defectsdatabase.npl.co.uk and do a search for via outgassing you will see some a video and gif animation and images. If someone has some good examples of blind vias that are outgassing, send me a board and I will test it and share the video on TechNet. I have tested vias in the is way before for customers but never videoed the results. Many thanks Many thanks Bob Willis 2 Fourth Ave, Chelmsford, Essex, CM1 4HA England Tel: (44) 1245 351502 Fax: (44) 1245 496123 Mobile: 07860 775858 www.ASKbobwillis.com www.SolderingStandards.com New Package on Package Workshops 24th November www.ASKbobwillis.com/PoPWorkshops.pdf PCB Design for Manufacture & Assembly Workshop 15th October www.ASKbobwillis.com PCB Inspection & Quality Control Workshop 3rd November www.ASKbobwillis.com/faworkshops.pdf Book Bob's "Step by Step Failure Analysis Workshop" 4th November www.ASKbobwillis.com/faworkshops.pdf -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Chris Mahanna Sent: 27 August 2009 02:34 To: [log in to unmask] Subject: [TN] Via-in-pad blowing bubbles Hello netters- Have we a term for vias-in-pad blowing solder ball bubbles to the point of bridging? Regardless, is there a unique cure for the problem? I wonder because- how does one get just enough pressure to blow the large bubble, but not blow-out? Bad luck? Or is it not that unusual, and just usually gets screened before it gets to me? Chris --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 15.0 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 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 15.0 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 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 -----------------------------------------------------