Heat management of electronic device is now rapidly upgrading and considered challenging due to the increase of power and decreasing size of the electronic device. Due to the economic cost, system complexity and operating conditions, the traditional cooling methods are quite impossible. That is the reason why using of phase change material (PCMs) in passive cooling system is considered as a great alternative in recent years. Hydrated salt and Paraffin, which are known as organic phase change material (PCMs), has been greatly recommended in energy storage component due to its high latent heat, non-toxicity and very low melting temperature. Using the PCM energy storage and cooling systems lead to a significant volume reduction to store the same amount of energy compared to sensible heat storages. The experiment attempts to illustrate the difference in heat transfer for a heat sink with and without paraffin wax at different power level.