The aim of the present work is to study the thermal performance of a hybrid heat sink used for cooling management of protruding substrate-mounted electronic chips. The power generated in electronic chips is dissipated in phase change material (PCM) (n-eicosane with melting temperature ) that filled a rectangular enclosure. The advantage of using this cooling strategy is that the PCMs are able to absorb a high amount of heat generated by electronic component (EC) without acting the fan, during the charging process (melting of the PCM). A two-dimensional mathematical model was developed in order to analyze and optimize a heat sink. The governing equations for masse, momentum, and energy transport were developed and discretized by using the volume control approach. The resulting algebraic equations were next solved iteratively by using tri diagonal matrix algorithm. A series of numerical investigations were conducted in order to examine the effects of the heat generation based Rayleigh number, Ra, and the position of the bottom electronic component, , on the thermal behavior of the proposed cooling system. Results are obtained for velocity and temperature distributions, maximum temperature heat sources, percentage contribution of plate (substrate) heat conduction on the heat removal from electronic components, temperature profile within finite conductive plate and local heat flux density at the plate—modules/PCM interface. The effect of these two key parameters on the electronic component working time (time required by electronic components to reach a critical temperature, ) was analyzed.