Konferenzbeiträge

Compliant mechanisms are becoming increasingly important, especially in force measurement and weighing technology, due to their zero backlash, wear resistance, and zero friction. Their deformation under external forces can be analyzed well with analytical calculations and FEM simulations. Analytically, only mechanisms with symmetrical and longitudinally symmetrical hinges are described. This paper presents a method that allows transversally symmetric hinges to be described analytically. The model must be computed numerically due to the built neutral fiber and the nonlinearities in the used calculation method. The developed method is then compared with FEM calculations in a parameter study and considered to be validated. Finally, outlooks are formulated on how the created method can for instance be used to develop load cells for later calculations. Moreover, it is shown to what extent it is possible to implement this method for general calculations of compliant mechanisms.

The combination of low temperature cofired ceramic multilayer technology with thin film deposition methods enables new functional principles by expanding the available portfolio of materials. Low-stress integration of micromechanical chips can be achieved, for example, by using reactive multilayers as local heat sources, which can be deposited directly onto the ceramics. Shadow masks are ideal for structuring these multilayers. The technology has the advantage that the layers are patterned without the use of etching chemicals and no residues of masking layers or photoresist remain on the non-coated areas. Flexible polyimide used to cover the non-coated areas can adapt to the surface unevenness of the ceramic. The polymer has excellent temperature stability and is compatible with vacuum coating processes. It is available in various thickness gradations and can be easily structured by laser cutting. The accuracy of the mask fabrication by means of laser cut is studied in this work. Structures with a line width of 30 μm can be precisely cut into 75 μm thick polyimide foils. Mask and chip are mechanically aligned, thus a positioning accuracy of 70 μm and better when using the outer edge of mask and chip for alignment is achievable. Major influences of the laser process on the precision of the mask and the resulting transfer fidelity to the ceramic surface are discussed. The method is suitable for reliably reproducing layers with structure sizes from 30 μm with a pitch of 150 μm.

This paper discusses the application of reactive bonding for the area of L ow Temperature Cofired Ceramics (LTCC) assemblies. The goal is to reduce the thermal-mechanical stresses during soldering by transferring heat only locally to the solder joints without heating the entire component. Such a reactive multilayer system (R MS) consists of alternating nanolayers (10 - 300 nm) of at least two metal components which produce an exothermal reaction after ignition. Although the deposition of an RMS is established on silicon substrates for the use in micro-electromechanical systems (MEMS), it is very challenging to create them on LTCC substrates. One of the main obstacles is to over come all issues connected with the significant roughness, because it is not an optimum territory to deposit nanolayers. In this paper, different methods like chemical mechanical polishing (CMP) and laser ablation, to modify the surface morphology, are presented. A direct relation between the morphology and the exothermal reaction can be observed. In addition, 3-D Computational Fluid Dynamics (CFD) simulations were conducted to analyze the process in more detail. These simulations make use of a shoebox model with different layers and an adjustable user-defined function for the heat release of the RMS to adapt the reaction front velocity and the combustion temperature to the experimental values.