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|A Charging Unit Based on Micro-PEM-Fuel Cells in LTCC-Technology|
|Keywords: LTCC system, micro scaled PEMFC, 3D structuring|
|LTCC is a typical technology for the production of highly integrated ceramic microelectronic packages. Compared to epoxy-based PCB’s LTCC technology offers a higher integration degree, an excellent high frequency behaviour and a higher reliability. Furthermore LTCC offers the possibility to integrate 3-D-structures for e.g. mechanical sensors or the transport of fluid or gaseous substances. The mentioned structures are built up step by step during the LTCC multilayer manufacturing process. With regard to the present need for self-sustaining energy source systems LTCC-technology is suited very well for the assembling of micro-scaled fuel cells. LTCC technology offers the possibility to unite a system with all necessary components for a micro-scale fuel cell on one substrate carrier. Because of the variety in 3D structuring of the LTCC all kinds of geometrical variants of the cell dimensions as well as different flow fields are possible. Furthermore electronic components, which are needed in a self-sustaining fuel cell-system, can be integrated. The paper presents the development of a serial connected 4 cell charging system as self-breathing PEMFC (Polymer Electrolyte Membrane Fuel Cell), which includes a DC/DC converter and a charging circuit for an accumulator. At first a system concept was generated to achieve the requirements (voltage level, electric power, current density). The electrical components (DC/DC transformation, charging controller) should have an efficiency as high as possible to keep the system efficiency high. As an electrical buffer a Li-polymer accumulator was integrated. For the integration of gas channels different structuring technologies (punching, milling, Laser) were checked regarding accuracy and process compatibility. The channels are required to supply the MEA’s (Membrane-Electrode-Assemblies) with hydrogen. The MEA is the electrochemical core of the fuel cell. It consists of different gas distribution layers (GDL), a well dispersed catalyst (Pt) on the surface of the proton conductor (perfluorocarbon chains activated by sulfonic acid groups). In the charging system commercial MEA’s from GORE (Gore Primera Series 56) were used. Finally the fuel cell system was characterized. Different U-I-curves were measured with different operation modes. In maximum power point output the system provides an electrical power of 0.55 W and promises to be a real alternative to battery based charging units.|
Fraunhofer Institut Keramische Technologien und Systeme
Dresden 01259, Germany