Active Cooling Using Fluid Channels in a Silicon-Ceramic Composite Substrate

The silicon-ceramic composite substrate (SiCer) allows the combination of MEMS and LTCC technologies in one wafer substrate. The expansion coefficient of the specially developed LTCC is adapted to that of the silicon over a wide temperature range, allowing cofiring of silicon and LTCC for achieving a strong bond interface. The combined very different substrate properties greatly increase the technological potential for the design of new sensor applications. In addition to the implementation of micromechanical components in the silicon layer with simultaneous wiring and electronic integration in the LTCC layer, it is also possible to realize fluid channels in both layers and connect them to each other. The bond connection between silicon and LTCC is considered hermetic above a certain bond frame width. In the first part of this paper, the technology for the generation of channels in the SiCer substrate is presented and a measurement method for determining the gas tightness or the leak rate of the bond connection is shown. In the second part, the technology for the setup of an active fluidic cooling system (water based) in a SiCer substrate is presented. The test module is fluidically and electrically connected in a special test bench. The silicon area in the middle of the module, exposed by DRIE (deep reactive ion etching), contains the cooling channels as well as a mounted thermal test die simulating a lossy component and to measure the temperature on the silicon die.