Processing procedures for the realization of fine structured channel arrays and bridging elements by LTCC-Technology

This report deals with technological procedures to provide channel partition walls of minimum width inside of Low Temperature Co-fired Ceramics (LTCC) micro fluidic devices demonstrated by means of the fabrication of parallel closely-spaced channels which may act as a specific functional part of a fluidic heat exchanger. Furthermore, the realization of single layer bridging elements inside of channels is discussed. Such an element may be introduced as a delicate sensor substrate providing adequate thermal insulation and low thermal mass as well. The technological processing steps under consideration start with laser micromachining of green ceramic tapes using Nd-YAG-laser equipment and are followed by a modified low-pressure lamination step comprising the application of appropriate adhesives and the incorporation of polymer sacrificial volume materials (SVMs). Consequently, the increased fraction of involved organics requires an adequate adaptation of the firing process to provide a residue-free burnout. Great attention is paid to the prevention of channel cross-section distortion and to the integrity of structures, verified by optical inspection of microsectioned samples. The optimized processing procedures enable the fabrication of channel arrays with a partition wall thickness as small as 100 μm, while single layer bridging elements may span a channel width of 4 mm.