We experienced issues with BGA microvoiding due to the PWB finish being electrolytic hard gold. After extensive and costly failures analysis, the root cause was determined to be a polymer film which is co-deposited during the plating process, which outgases during reflow. There are a couple good industry white papers which talk to this phenomena
Kenneth D. Crandall
Director, Quality Engineering
Thales Communications Inc.
240-864-7488
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Victor Hernandez
Sent: Wednesday, January 04, 2012 7:38 AM
To: [log in to unmask]
Subject: Re: [TN] Solder voids in BGA balls
What type of solder and surface finish?
Victor,
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Lum Wee Mei
Sent: Tuesday, January 03, 2012 7:17 PM
To: [log in to unmask]
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~
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