Ceramic modules for micro solid-oxide fuel cells

Micro solid-oxide fuel cells (μ-SOFCs) based on microfabrication processes are a promising alternative to batteries for supplying portable electronics, as very high energy densities may be achieved. However, a complete μ-SOFC module is a quite intricate structure, comprising 1) a gas-processing unit (GPU) to process a convenient energy source such as lighter gas into a more usable form, 2) the energy-generating cells proper, and 3) a post-combustor. The mechanical integration of these elements and their fluidic and electrical interconnection into a single module is a very challenging task for micro-scale integration. Therefore, a modular low-temperature co-fired ceramic (LTCC) package is proposed, allowing individual testing and subsequent full integration of the different cell elements. The package functions as a hotplate, a mechanical support for the hot zone and as an electrical / fluidic interconnect, applying a slender-bridge design to minimise thermal conduction losses and stresses, thus allowing convenient low-temperature electrical connections and fluidic ports. For applications requiring a better thermal expansion match to silicon and borosilicate glass, a silicon / borosilicate glass-sealed variant was also developed. Preliminary thermal characterisation of these packages is shown, and concepts for integrating the GPU and post-combustor into the LTCC structure are presented.