Hello Lum Wee,

On top to classic IPC-7095 (B) Design and Assembly Process Implementation
for BGAs, you can find interesting and useful information relating voids in
BGA S-J, by reading the following Standards :

- IEC 61191-6  Printed board assemblies – Part 6: Evaluation criteria for
voids in soldered joints of BGA and LGA and measurement method

- JEDEC STANDARD JESD217  Test Methods to Characterize Voiding in Pre-SMT
Ball Grid Array Packages  


Best Regards

Gabriele


-----Messaggio originale-----
Da: TechNet [mailto:[log in to unmask]] Per conto di Lum Wee Mei
Inviato: mercoledì 4 gennaio 2012 2.17
A: [log in to unmask]
Oggetto: [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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