Hi Bev, I certainly can understand after drop testing as well as field returns (also dropped?!), but all I have seen are right after reflow. Werner -----Original Message----- From: Bev Christian <[log in to unmask]> To: [log in to unmask] Sent: Fri, 12 Jun 2009 1:35 pm Subject: Re: [TN] Corner ball pad cratering Chris, We do extensive cross-sectioning to qualify any new reflow process and all new Blackberry models. I have never, ever seen a pad cratering event at this juncture - only after dropping during testing or from field returns. Bev -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Chris Mahanna Sent: Friday, June 12, 2009 1:26 PM To: [log in to unmask] Subject: Re: [TN] Corner ball pad cratering Genny and Bev, Out of curiosity- are you sure that the cratering was not: induced thermally (during reflow cool down), but did not manifest itself as a problem until other mechanics came into play? It just seems like that would be more common. Chris Chris Mahanna Robisan Laboratory -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Genny Gibbard Sent: Friday, June 12, 2009 12:12 PM To: [log in to unmask] Subject: Re: [TN] Corner ball pad cratering As always, Steve, you are a wealth of information. That article is perfect, thank you. This seems to mirror what Amol said about doing a 1/4 of the length. This article said to do an L shaped bead 2-6 balls along each corner side. Here are some photos to post. Would you oblige? BGA is 40mm per side. PCB is ~1 ft sq. A little bigger than what is found in the typical blackberry, I think... Ball pitch is 1.27mm. We believe the cause is mechanical, not thermal. Thanks everyone. Genny -----Original Message----- From: Steve Gregory [mailto:[log in to unmask]] Sent: June 12, 2009 6:35 AM To: TechNet E-Mail Forum; Genny Gibbard Subject: RE: [TN] Corner ball pad cratering Morning Genny, Since you said you were going to look at corner bonding, here is a really good article (if you haven't seen it already) that Michael Kochanowski from Intel and Brian Toleno from Henkel did about it: http://www.trafalgar2.com/documents/Technical_Articles/6.09-kochanowski. pdf Steve -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Genny Gibbard Sent: Thursday, June 11, 2009 3:10 PM To: [log in to unmask] Subject: [TN] Corner ball pad cratering Hello all, If you have identified a BGA with corner ball pad cratering, what would be your suggestions to correct this condition? Our thoughts: 1. We plan to evaluate our handling processes to reduce/remove excessive flex/strain occurring around this part 2. We plan to evaluate corner bonding or underfilling for the BGA. Which do you feel would be the best direction to go? Do you have other suggestions? Thanks in advance for all your help Genny --------------------------------------------------- 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 ----------------------------------------------------- --------------------------------------------------------------------- This transmission (including any attachments) may contain confidential information, privileged material (including material protected by the solicitor-client or other applicable privileges), or constitute non-public information. 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