Morning All! Well, I'm starting work on Monday! WOO-HOO! (broken toe and all) Actually, my toe feels fine. It's been a few days now since I broke it, and the blood from the break has had a chance to migrate up to the surface of the skin and it looks worse now than when I first broke it. I won't post any pictures though, don't want to make anybody cringe ;^) I do have some cross-section photos that clearly illustrate what Dwight was talking about. It's obvious that he's been there, done that, and got his t-shirt... http://stevezeva.homestead.com/files/uVia_Bubble.jpg http://stevezeva.homestead.com/files/Uvia_Bubble_2.jpg Steve ----- Original Message ----- From: "Dwight Mattix" <[log in to unmask]> To: <[log in to unmask]> Sent: Thursday, August 27, 2009 1:18 PM Subject: Re: [TN] Via-in-pad blowing bubbles > As described by others plating defects can cause the solder void. However > a more common problem we see is failure of the uVia to wet out. I've got > pics of both conditions going back years now. > > This due to a final shape of an otherwise well formed and plated uVia. The > via needs to wet out. If it doesn't wet, the air will be held in by the > surface tension of the liquidus solder. The temp will finally rise enough > for the air pressure to overcome the surface tension. That's when the > solder ball expands and forms a bridge to an adjacent ball. > > In order to wet out consistently, the uVia final shape should be a bit > more open at the top than at the bottom. If the via sidewalls are too > near vertical or if the plating has a cornice where plating closed down > narrower at the knee of the via it will cause voiding. The liquid solder > forms a meniscus that hangs up on the knee of plating. > > Simple fix? Specify solder copper filled uVias in outerlayers. Tougher > fix? Agree on an acceptability spec with your suppliers for final uVia > shape. Many of the top tier high volume offshore uVia fabs already have a > uVia shape standard that's been applied to them by a large OEM or two > (:-)) who've gone before you. > > > At 06:34 PM 8/26/2009, Chris Mahanna wrote: >>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 > ----------------------------------------------------- --------------------------------------------------- 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 -----------------------------------------------------