The two-phase spreading is described extensively in this study and represents key issue in many application fields such as space satellites and launchers, aeronautics, railways as well as in computer world. Considering constant increase of surface heat fluxes to dissipate in electronic field, the thermal management is a key challenge to be addressed. Effective spreading of the heat offers an elegant and performant way to reduce electronic equipment temperatures or increase their waste heat power. The conductive technologies are analyzed showing performances and reliability limitations. To solve the problem, Euro Heat Pipes proposes a two-phase spreading technology. Main design guidelines and boundary condition influences are extensively described to take full advantages of the two-phase technology in the spreading issue. An innovative solution is proposed to enhance the thermal performances of the device over a wide range of temperatures with the implementation of a reservoir inside the device that will enhance hydraulic and thermal performances over a wide operating temperatures range. This patented concept is described and benefits are exposed. The proposed two-phase concept is applied on an aeronautic representative application to perform the full thermal characterization. The thermal performance is notably stable on the entire tested temperatures range and validates thermal resistance gain over 50%. Such an electronic temperature reduction enables a significant reliability increase or the raise of heat power to transport.