In a message dated 10/28/99 7:42:49 PM Central Daylight Time,
[log in to unmask] writes:

> Guys,
>
>  What stencil thicknesses are typically being used for MicroBGA's?
>
>  What kind of solder paste height is considered to be enough for these
>  packages?
>
>  Thanks
>
>
>  John Harris
>
>  AEMS Pty Ltd
>

Hi John!

At my past employer we had a 146-ball DSP micro-bga and I used a 4-mil
stencil and had all the bigger stuff (50-mil) "solder paste compensated"...
which means that the pads are actually overprinted a bit, this is to give you
the volume back that you took away reducing the stencil thickness to print
the micro-BGA good...it'll all wick back to the joints during reflow. Didn't
have a way to measure the solder paste height, but it seemed to work good for
me. Every board we built fired-up, and we didn't have a RMA...take it for
what it's worth. Good starting point anyway...

-Steve Gregory-

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