Dear Mr. Engelmaier,

Thanks for your reply. The PBGA under modeling is 1.0mm pitch, 25-mil
balls. ATC is 0-100C, 2 cycles/hr. In one case study, the package size is
27x27mm, die size 21x21mm, die thickness is 12mil, full array with ball
count of 672. The predicted CMF when using 15-mil and 24-mil thick BT
substrate is 839 and 6653 cycles respectively. The adopted approach is
substructure and micro-model approach. First, the whole package
was meshed and treated as a substructure except the solder joint of
interest (under the corner of die); then a substructure analysis was done
to generate stiffness matrix; In micro model, the solder joint of interest
was modeled in detail and creep analysis was done. I use ANSYS 5.4.

Please let me know if you need more information.

Regards,

Yuan Li

On Sat, 29 May 1999, Werner  Engelmaier wrote:

> Hi Yuan,
> This increase is possible only if the thickness increase substantially
> reduces the warpage of the PBGA or substantially decouples the influence of
> the die on the global expansion mismatch. It still sounds too large, though.
> To say something more, I need the full details of your analysis and some of
> the result details.
>
> Werner Engelmaier
>
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