The app. note in the link below suggests suggests that "The minimum pad size for Freescale’s products is 3 mm by 3 mm when using thin film overlays to about 0.5 mm thickness of acrylic or ABS plastic".
In a proximity sensing application, assuming the area of the object to be sensed is >= 9mm sq. and the profile of the object is planar to the sensing electrode pad on a PCB, is it accurate to interpret the 3mm x 3mm recommendation, as a 9mm sq. minimum electrode pad area for Freescale's touch sensing products?