Metal lid on the bottom of the CBGA152 package

07/16/07

What am I supposed to do with the metal lid on the bottom of
the CBGA152 package?

The metal lid on the bottom of the CBGA152 package is physically connected to the die ground. However, it does not have to be
physically connected to a ground pad on the board.

It is only an indication that it is connected to the die ground in
case it happens to be touching any other potential on the PCB...
As concerns thermal dissipation, the percentage of heat you will
be able to remove via this metal lid is negligible compared to
the main thermal path which is at the top of the device.
There is no significant benefit of having a pad for thermal
considerations below the metal lid, considering the
constraints of having it.