S. Lüftl

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.

Developing a Sealing Material: Effect of Epoxy Modification on Specific Physical and Mechanical Properties

To develop a matched sealing material for socket rehabilitation of grey cast iron pipes, an epoxy resin is modified by the addition of different components to improve the flexibility. Three different modifications are made by adding ethylene-propylene diene monomer (EPDM) rubber powder, reactive liquid polymer (ATBN) and epoxidized modifier. In this paper the effect of the modification method as well as the influence of absorption of water on the mechanical and physical properties are analyzed in terms of: tensile strength, modulus of elasticity, adhesion performance, pressure resistance, glass transition temperature and water content. A comparison with neat epoxy shows for all materials that the modulus of elasticity and strength decrease. Unlike other tested modification methods, the modification with rubber powder did not enhance the flexibility. All materials absorb water and a plasticization effect arises with further changes of mechanical and physical properties. The application of the sealant on the grey cast iron leads to a reduction of the strain at break (in comparison to the common tensile test of the pure materials) and has to be evaluated. The main requirement of pressure resistance up to 1 MPa was tested on two chosen materials. Both materials fulfill this requirement.

Characterization and binder burnout studies of ferrite LTCC tapes

This publication provides the results of material characterization and binder burnout studies of the commercially available ferrite LTCC (Low Temperature Co-fired Ceramics) tape ESL 40012 used for integrated passive components in LTCC packages. The investigations comprised surface roughness measurements of the fired tape and chemical analysis of the green tapes as well as tapes fired at different peak temperatures by X-ray powder diffraction (XRD) and energy dispersive X-ray spectroscopy (EDXS) analysis. Furthermore, thermogravimetric analysis (TGA) in air and binder burnout studies of different unlaminated stacking heights and different heating rates were performed.