Invertier air conditioners are being widely used in the air conditioning sector for energy saving pirposes. These air conditioners use an inverter of a variable frequency dirive(VFD) to control the compressor operating speed based on cooling or heating load fluctuations. If the heat generated by the electronic components of the VFD is not dissipated properly, it can lead to failure of the VFD. In general, a heat sink is used for dissipating the heat gererated by the electronic components of the VFD. The heat sink can be either air cooled of liquid cooled. Using computational fluid dynamics(CFD), the present paper deals with optimization of the thermal performance of an air cooled plate fin heat sink with rectangular fins used in a residential split inverter air conditioner. Commercially availavle CFD tool has been used for simulations. It has been observed that enhancing fluid flow around heat sink and inproving heat transfer area of the fins significantly improce the thermal performance of the heat sink. By using heat sink with rectagular fins having a stepped profile, it has been possible to improve the heat transfer from the baseline case by 27%. Whereas, by using hollow fins, heat transfer improvement of 20% has been achieved.