Any via within the BGA pad? Via filled? You can generate your own data by perform sequential thermal shock, drop, vib etc. If it passes, no sweat. If it fails, you need to do risk assessment. As you said mission critical, you must have redundancy in the design. You have to assess based on the life time usage. For example, for a ignition once only, if you have triple redundancy, with your own rel test of 10% fall out probability, you might be OK. (PM must sign off and you must convince your customer there is a minimum risk. Of course, in the system as above example, you have a fall back loop for second ignition mechanism or abort mission all together).
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Sent using BlackBerry
----- Original Message -----
From: Lum Wee Mei [mailto:[log in to unmask]]
Sent: Tuesday, January 03, 2012 08:16 PM
To: [log in to unmask] <[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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