If multiple MOSFETs are required to dissipate the total power, then care must be taken not to assume the load will be shared evenly. During normal operation the load will most likely be shared across all MOSFETs. However, on power up the load may be shared unevenly due to the slightly differing Vgsth of the MOSFETs. This is why each MOSFET must be capable of tolerating the maximum load individually. When the MOSFET is a surface mount component, is may be desirable to transfer some of the heat from the MOSFET to a metal area on the other side of the PCB. This can be done with a via array which will provide a thermally conductive path through the PCB to the other side. This however will not be very efficient.