Hello Dave, Happy new near to you and all the technet folks! Is the paper available in the open domain? Or is there a paid means of obtaining it. We had a similar situation with a BGA not too long ago, but it was a mixed technology process (SnPb paste + SAC305 BGA). I am assuming the voiding limits mentioned in the J-STD are for like technologies, as it can be almost impossible to get rid of voiding in mixed technologies (depending upon component mix and overall thermal mass) due to max temp limitations. Regards, 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: TechNet [mailto:[log in to unmask]] On Behalf Of David D. Hillman Sent: Wednesday, January 04, 2012 9:50 AM To: [log in to unmask] Subject: Re: [TN] Solder voids in BGA balls Hi Wee Mei! We just published our BGA void investigation work at the SMTAI conference in Fort Worth. The title of the paper is " The Last Will and Testament of the BGA Void" which was in paper session AAT8. The current BGA void requirement is "a maximum of 25% of the X-ray image area" per the IPC-JSTD-001. Despite the rumor mill, that requirement was established by the IPC JSTD 001 committee based on several data sets submitted by industry members several years ago. We initiated and completed the recent investigation as component and solderball sizes have changed considerably and we wanted to determine if the requirement was still valid. We have also used our investigation conclusions to form a revised BGA void criteria proposal to the IPC JSTD 001 committee for their assessment/review. You stated that you were considering the voids as "rejectable" on several factors but the industry requirement is 25% maximum so technically you don't have a basis for that rejection. However, there is no reason to have that much void activity in a area array device unless you have a design feature such as a via in pad causing a void influence. The majority of void issues are due to solder paste problems - either the condition of the paste or the reflow parameters. I suggest you pursue two actions - (1) the Process manager needs to investigate/establish why there are so many voids and present that technical detail to you for assessment; (2) Pull a copy of the SMTAI paper and look at the various industry studies that are referenced within it. Those industry studies can be used to fully understand the various details of BGA voids, their formation, and how they may be part of your case. Good Luck. Dave Hillman Rockwell Collins [log in to unmask] Lum Wee Mei <[log in to unmask]> Sent by: TechNet <[log in to unmask]> 01/03/2012 07:16 PM Please respond to TechNet E-Mail Forum <[log in to unmask]>; Please respond to Lum Wee Mei <[log in to unmask]> To <[log in to unmask]> cc Subject [TN] Solder voids in BGA balls Dear TechNet Buddies, My colleague was performing BGA x-ray inspection to 20pcs of the PCBA, each of them has a BGA on the board. She observed that all the BGA solder balls have high number of multiple solder voids of various sizes within each of them. The estimated summation of the solder voids from each ball ranges from 20 - 25%. As the voids are within the acceptable value of 25%, process manager wanted QC to consider the workmanship as process indicator. My colleague approached me for advice and being a QC, I decided to consider them as reject base on : (a) When consulted, Process Manager is not able to determine whether such extensive solder voids will have any impact on the PCBA reliability. (b) Though the solder voids size/summation are within the 25%, this value are observed on every BGA's solder balls, across all the 20 BGAs. (c) The PCBAs are Class 3 and to be used on mission critical application. Before QC decision to reject them was communicated, the process engineer recall 5 of the PCBA to perform another round of reflow. Questions : 1. Should the above solder voids workmanship be considered as "process indicator" or "reject"? 2. Is there disposition for workmanship that is classified as "process indicator" such as rework or replacement? For me, it should not. 3. Since the process engineer recall 5 of them to perform another round of reflow, does it not mean he also concur that the workmanship is not acceptable? I am a self-learned QC, so any sharing on this matter will be greatly appreciated. Thanks and regards, ~wee mei~ ______________________________________________________________________ This email has been scanned by the Symantec Email Security.cloud service. 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