Bruno Balluch

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.

Optimization of cavity fabrication for micro-fluidic systems

Processing parameters for an optimized fabrication of micro structures with dimensions ranging from 20 mum to 4 mm channel width and up to 2 mm height providing height/width aspect ratios of 10/1 have been investigated for 3 different LTCC-tapes (low temperature co-fired ceramics). The fabrication process is based on an optimized NdYAG-laser machining process and an adapted isostatic single step lamination method where a remarkable reduction of recommended lamination pressure is conducted successfully, in order to minimize distortions of channel geometry but still providing tightness of laminated LTCC-layers. Different procedures have been tested to improve channel geometry. Consequently different tape-compatible SVM (sacrificial volume materials) have been employed, including liquids working as fillers and adhesives, respectively. The preprocessed structures have been fired in accordance with TGA-optimized (thermo gravimetric analysis) firing profiles which provide a residue-free burnout. This paper summarizes the influence of processing parameters on the final dimensions of various test channel devices.

Material characteristics of the LTCC base material CeramTape GC

This paper provides new material property measurement results of the ceramic film material CERAMTAPE GC (manufactured by CERAMTEC GMBH), a commercially available LTCC (Low Temperature Co-fired Ceramics) tape for electronic and microfluidic applications in harsh environment. Following material properties are presented: x-y-z-shrinkage dependent on the lamination pressure, density, weight loss, surface parameters of the green and co-fired tape, thermal properties, Youngs modulus, permittivity, chemical composition, and bio-compatibility.

Set-up of a biological monitoring module realized in LTCC technology

Low temperature co-fired ceramic (LTCC) technology was originally developed for the realization of multilayer circuits of high reliability. It was recognized that LTCC technology is a valuable development in thick film technology, which launches new application areas as it becomes evident that complex three-dimensional structures can easily be realized. When considered for biological applications ceramic tape material must be proved with regard to its biocompatibility. A selection of appropriate commercially available ceramic tapes has been characterized in respect to the influence on proliferation, viability and adherence of cells. Aspects of realization of a complex biological monitoring module comprising a three-dimensional network of channels and cavities will be demonstrated.

A Ceramic Microfluidic Device for Monitoring Complex Biochemical Reactive Systems

A 3-dimensional mesofluidic biological monitoring module has been successfully designed and fabricated using a low-temperature co-fired ceramic (LTCC) technology. This mesofluidic device consists of a network of micro-channels, a spherical mixing cavity and measuring ports. A selection of appropriate commercially available ceramic tapes has been chosen with regard to their biocompatibility performance. Specific processing procedures required for the realization of such a complex structure are demonstrated. Three dimensional numerical flow simulations have been conducted to characterize the concentration profiles of liquids at a specific measuring port and verified by experiment.

Die LTCC-Technologie als Plattform für die Herstellung von Fluidik-Mikrostrukturen für biologische Applikationen

SummaryLow temperature co-fired ceramic (LTCC) technology was originally developed for the realization of multilayer circuits of high reliability. LTCC-technology is now considered as a valuable further development in thick film technology, which launches new application areas as it becomes evident that complex three-dimensional structures can easily be realized. Aspects of realization of a complex biological monitoring module comprising a three-dimensional network of channels and cavities will be demonstrated. Based on mixing and reaction experiments the functionality of the device is demonstrated.ZusammenfassungDie LTCC (Low Temperature Co-fired Ceramic)-Technologie, die ursprünglich für den Aufbau von hoch zuverlässigen Mehrlagenschaltungen entwickelt wurde, eröffnet die Möglichkeit, auch komplexe dreidimensionale Strukturen in einfacher Weise aufzubauen. Am Beispiel eines Monitoring-Moduls zur Erfassung von biologischen Reaktionen wird die Herstellung einer komplexen Mikrofluidik-Applikation vorgestellt. Anhand eines definierten Mischprozesses sowie eines Reaktionsprozesses, welche sich auf numerische Simulationen abstützen, wird die Funktionalität des Systems aufgezeigt.

Modified wetting balance set-up for the evaluation of lead-free solder / flux / metallization systems

This paper presents experimental investigations of wettability on lead-free solder/flux/solid metallization combinations obtained under nitrogen atmosphere. An adapted testing method is applied where fluxed samples are preheated. A commonly performed wetting balance testing method is explained in principle and the measurement system modifications as well as the adapted experimental procedures being performed are discussed in detail. Lead-free tin-silver alloy Sn96 Ag and a copper doped Sn96Ag3.5Cu solder have been considered for testing in combination with five different widely employed FR4-metallization finishes and three Ag-based thick film conductor pastes. Selected solder bath temperatures cover the range from 240degC up to 260degC. One conventional RMA-type flux and two low solid no-clean fluxes have been provided for promoting the wetting tests. The effect of sample preheating varying within the range from 85degC to 115degC is investigated. Results are compared to conventional lead bearing material systems