Hi Mei,

You should check the location of the solder balls, if at the center of the
balls or at the pads interfaces.
Do you have less voids by changing process parameters?
Can you perform HASS test to the PCBs
Reuven

On Wed, Jan 4, 2012 at 3:16 AM, Lum Wee Mei <[log in to unmask]> wrote:

> 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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