Integrated micro-heat-pipe fabrication technology

This paper presents the design and fabrication of an integrated micro-heat-pipe system consisting of a heater, an array of heat pipes, temperature and capacitive sensors. Taking advantage of the large difference between the dielectric constants of liquid and vapor, the integrated capacitor can be used for void-fraction measurements in two-phase flows. Both CMOS-compatible and glass-based fabrication technologies are reported. In the CMOS-compatible technology, the heat pipes are capped by a thin nitride layer utilizing wafer bonding and etch back technique. In the glass-based technology, the heat pipes are covered by a glass substrate using die-by-die anodic bonding to allow visualization of the two-phase flow patterns. This approach also results in a significant reduction of the parasitic capacitance, thus enhancing the sensitivity of the capacitance sensor. A few particular problems related to this technology are discussed and proper solutions are proposed.