Wolfgang,

Thanks for the reply. I don't know the background yet. The original
request came from apps.  My guess is same as yours.

It is a full array 1.0mm pitch 27mm BGA. The only way I can think of is to
x-section across the diagonal of the package. Howeverit  is not preferred.


Yuan
>Yuan: The customers may have encountered problems with this device due
to
> coplanarity issues and wants to know what the guaranteed coplanarity
> actually is to see if he can live with that or not, or if he has to adjust
> his processes to that, or to have this measure for the future to reject all
> parts that are not in spec.
> I personally would think about using a 5mil stencil if the part is discribed
> with 150µm for coplanarity.
>
> What´s the background of this?
>
> Wolfgang
>
> -----Ursprüngliche Nachricht-----
> Von: LI YUAN [mailto:[log in to unmask]]
> Gesendet am: Mittwoch, 15. August 2001 00:37
> An: [log in to unmask]
> Betreff: [TN] Interesting Coplanarity ?
>
> I had a customer asking this question:
> The customer has the devices already soldered on the board and want to know
> what is the coplanarity. Is is a valid question? If so, how?
>
> Thanks,
>
> YL
>
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