Mike,
Folks at Nokia Research Center in Irving, Texas did studies on enlarged
corner pads. They were trying to improve PBGA reliability without using
underfill and found that removing the corner solder joints didn't help much.
Their other option was to strengthen the joints by making the balls
oversize. By making the corner pads and balls bigger, they anchor the
package to the carrier and are better able to handle shock inputs. Their
solution was dubbed "anchor pads."

Let me know if you would like more info.

Terri


> ----------
> From:         Yuen, Mike[SMTP:[log in to unmask]]
> Reply To:     TechNet E-Mail Forum.
> Sent:         Wednesday, October 17, 2001 10:59 AM
> To:   [log in to unmask]
> Subject:      [TN] BGA corner pad
>
> Greetings,
>
> I understand BGA reliability is a very complex subject. Folks had been
> doing DOEs for years trying to determine the significant factors
> involved. For most perimeter PBGA, corners joint seem to be the weakest
> link.  I wonder if anyone out there had done  studies on enlarging just
> the corner pads of a BGA to enhance reliability.
>
> Thanks,
> M. Yuen
>
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