A new heat spreader that operates on a principle similar to heat pipes has been developed in Low Temperature Cofired Ceramic (LTCC) substrate. The heat spreader use sintered metal powder as the wick structure and water as the working fluid. Key topics related to the fabrication of embedded heat spreaders in LTCC substrate were studied. The conventional LTCC procedure has been improved to suit the requirement of heat spreader. A novel sintered porous silver powder has been developed to provide high capillary pressure and permeability for the wick structure. The maximum mass transport rate of the wick was about 0.692 (g/min) at wick height of 4.5cm. The thermal performance test demonstrated that the prototype heat spreader could work properly at power density of more than 70 W/cm2 without any sign of dry out occur. The successful fabrication of the prototype integrated heat spreader provides concept validation of using advanced two-phase heat management system to greatly improve the effective thermal conductivity of LTCC substrate
