Development of Thinned Aluminum Flat Heat Pipe Through Inclined Wall and Press Process

Abstract

Heat pipes, commonly used for heat dissipation and thermal management in small electronic and communication devices, are regarded as an excellent solution. Heat pipes must be in surface rather than line contact to be applied to the module and system-level heat dissipation package. As such, a round copper heat pipe is transformed into a plate-like shape through a secondary press process. In this study, an extrusion structure is designed to be sloped to solve the difficulty of making it relatively thin compared with the large area of the plate structure. Specifically, substantial partitions separating the working fluid flow space in the plate-type heat pipe are designed to be inclined at 45 deg, and the extruded envelope is developed to obtain the desired total thickness through the secondary press process. The capillary structure is inserted and positioned within the envelope prior to the secondary press process. In this study, an aluminum flat heat pipe (AFHP) with 0.95 mm total thickness, 150 mm total length, and a capillary structure with braided or carbon wire bundles added thereto was designed and manufactured. Performance test results indicated that the heat transfer performance of the AFHP with inclined wall did not show any deterioration characteristic compared with the AFHP with a normal vertical wall. The isothermal characteristics and heat transfer rate of the AFHP with Cu braid wick were superior to those of AFHP with a simple rectangular groove wick. By contrast, when the carbon wire bundle is added in the Cu braid, the isothermal characteristic was enhanced twice, and the heat transfer rate was 15.5 W by improving approximately 42% under the conditions that inclination angle is −90 deg and the evaporator temperature does not exceed 110 °C.