Thermal spreaders have been of interest over the last few decades. Heat pipes, Thermal Pyrolytic Graphite (TPG), and other graphite-based materials have been commonly used for enhancing the thermal performance. This study will start for a discussion of Chemical Vapor Deposition (CVD) of diamond manufacturing to enable high conductivity plates for heat spreading. Later attention will be turned to absolute thermal conductivity measurements. A measurement technique for the thermal conductivity of a thin diamond plate was proposed. Baseline measurements have been established via a similar copper plate with a thermal conductivity of 400 W/m-K. IR thermal images were collected. Heat losses are calculated via analytical and numerical models. We found that one type of thermal management CVD diamond has a thermal conductivity of approximately 820 W/m-K accounting both diamond film and thin Silicon substrate.