Thermal
As an indication of the importance of keeping the thermal grease layer thin, if the thermal grease layer increases to 0.002 inch thick, the required heatsink thermal resistance changes to 2.4°C/W.
The large heatsink used for the APA100 EVM is required for full output power sine waves over temperature. A smaller heatsink can be used for music, which requires much less average power.
The heatsink should be tight without bending the board or damaging the IC. However, there should be slight dimpling of the boards around the screws. Heatsink screws were tightened with a torque of 1.5 inch−pounds on the APA100 board. A washer and lock−washer can be used to help secure the heatsink, but is not required in most applications.
