Great question. I have observed voids in fillets on components other than
BGAs as well. We have not studied them. Werner?

> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]]On Behalf Of Jason Gregory
> Sent: Thursday, February 14, 2002 9:06 AM
> To: [log in to unmask]
> Subject: [TN] Vacuolar porosity under leads
>
>
> I have a question regarding vacuolar porosity under leads.
> A potential customer has forwarded me some CAD data and will send
> me some boards for me to inspect using our 5DX X-ray. His
> concerns are that during reflow, the flux attempts to outgas and
> stops just short of total outgassing when the joint solidifies.
> This situation then forms "pockets" in the joint in the lead/pad
> interconnect.
> My question is this - Has anyone done any studies regarding this
> phenomena and if so, does this affect the integrity of the joint?
> My belief has always been that the structure and formation of the
> heel portion of the joint comprises the actual integrity of the
> joint and the toe fillet (or lack thereof) does not play into the
> lifespan (or strength) of the joint. Therefore, the lead/pad
> interconnect would also not be the main point of contention.
> In Alabama, we had some components (QFP48) that had a ground lug
> on the bottom part of the package that was soldered to a pad
> directly beneath. The lug was approximately 1mm by 1mm and the
> pad was approximately 7/10mm by 7/10mm. In this case, the
> porosity dilemma was evident. We would see, through 3D
> laminography, that large voids were formed, causing roughly a 40%
> or so decrease in actual solder interconnect area. Some playing
> around with the reflow profile displayed better results, but
> never resolved the issue.
> Any thoughts/comments would be greatly appreciated.
>
> Thanks,
>
>
> Jason Gregory
> Software Specialist
> Sanmina-SCI - Tech Center Austin
> 15508  Bratton Lane
> Austin, Tx. 78728
> (512)246-5648
> [log in to unmask]
>
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