Should this pad be attached to the PCB ground or left floating? The datasheet
does not mention this.
There is an exposed "paddle" on the under side of the package. This paddle is
actually electrically and thermally connected directly to the substrate of the
die. Generally we recommend that the exposed paddle is soldered to a ground
plane in order to provide a thermal path and reduce thermal resistance.
However, some users cannot or do not wish to make this connection for
manufacturing reasons or perhaps during prototype. Hence we provide thermal
resistance for both options.
You can find out more about working with the LFCSP package from our packaging
Application note from Amkor on surface mount assembly of LFCSP packages: