если на него электрически не выведены никакие цепи изнутри, то цеплять его можно и на питалово. В ДШ на драйвер AD8139, например, написано следующее: "The SOIC-8 and LFCSP packages have an exposed paddle on the underside of its body. In order to achieve the specified thermal resistance, it must have a good thermal connection to one of the PCB planes. The exposed paddle must be soldered to a pad on top of the board that is connected to an inner plane with several thermal vias."