The processing and application of graphite powder-based sacrificial layer for fabrication of microfluidic structures in LTCC is described. Such layers are produced as pastes, which are screen-printed in LTCC sheets to avoid sagging, by supporting closed, three-dimensional structures such as channels, membranes during firing. The aim of the paper is to highlight the selection of paste materials and the effects of processing conditions on the fabricated micro-fluidic components. It is seen that the complete burnout of graphite powder is the most critical stage as it is in kinetic competition with the open pore-elimination process of LTCC, which occurs at 785°C in our system.