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- aluminum heavy wire bonding (1)
- anode (1)
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- dog bone effect (1)
- effective refractive index (1)
- electrochemical (1)
- fresnel reflection (1)
- heel crack (1)
- infrared fiber (1)
- infrared imaging (1)
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- loop forming process (1)
- mechanical accelerated lifetime testing method (1)
- micro-galvanic corrosion (1)
- quantum cascade semiconductor laser (1)
- refractive index (1)
- sub microstructure (1)
- wrinkling (1)
Das Photoscanning-Verfahren dient der zerstörungsfreien Detektion von Defekten in Solarzellen. Die Daten ermöglichen Rückschlüsse auf grundlegende physikalische Parameter der Zelle, wie zum Beispiel den Wirkungsgrad, bzw. mechanische Störungen. Es erlaubt eine umfassende Charakterisierung einer Vielzahl von unterschiedlichen Solarzellentypen. Innerhalb des Projektes werden diese Einsatzmöglichkeiten des Photoscanning-Verfahren verifiziert. Seit 2011 wurde die Weiterentwicklung des Verfahrens innerhalb einer Kooperation mit der Firma SENTECH als Projektträger, der Physikalisch Technischen Bundesanstalt und der TH Wildau als Projektbeteiligte fortgesetzt.
Um eine gute Produktqualität in der Galvanik zu erreichen, müssen Störgrößen wie zum Beispiel der "Hundeknochen"-Effekt vermieden werden. In dieser Arbeit wurde dieser Ansatz genutzt, um eine Methode zur Kennzeichnung als Produktschutz zu entwickeln. Mit definiertem Aufbau und optimalen Parametern ist es möglich, auf geeigneten Substraten, unikale visuell nicht differenzierbare Schichten abzuscheiden. Die abgeschiedenen Schichten und deren lokale Verteilung wurden mit Hilfe konfokaler Lasermikroskopie, Röntgenfluores-zenzanalyse und Laserinterferenzmessungen charakterisiert und qualitativ als auch quantitativ analysiert. Interessenten stellt es damit ein im Grunde traditionelles Verfahren zur Verfügung, das mit dem gewählten Ansatz zu neuen Innovationen führen kann.
Heavy wire bonding is one of the most common interconnection technologies in manufacturing of high-power electronics. For industrial applications, the long-term reliability of these connections is crucial. Besides the selection of the wire material and the loop geometry itself, the loop forming process parameters also have an influence on the reliability of the wire bond. In this work, the influence of the backward bond head movement during wire bonding process on the quality of wire bond connections was systematically investigated and qualified by cyclic mechanical lifetime tests, surface roughness measurements of the heel area by laser confocal microscopy and static pull tests. The wire bond loops were fabricated with 300 μm aluminum H11 and H14CR wires with different hardness values. The lifetime at low frequency cycle and high frequency cycle regime was determined by means of two different mechanical cyclic test methods operating at 5 Hz and at 60 kHz respectively. The results have shown, that the surface topology of the heel region caused by the initial plastic deformation during the loop forming process has a significant effect on the wire bond failure due to heel cracking. The number of loading cycles to failure shows an inverse correlation with the degree of surface roughness in a so called wrinkling analysis in the low and high frequency cycle regime. The soft wire exhibits different lifetimes compared to the hard ones depending on the testing conditions, while a significant decrease of the lifetime is observed with >30 % reverse movement during bonding in all cases.
Additive manufacturing, also known as 3D printing, has gained tremendous importance in recent years. One of the areas where additive manufacturing is particularly useful is in the fabrication of electrodes. Electrodes are an important component of a wide range of applications, including electrochemistry, biomedical engineering, energy storage, analytics, electronics as well as life sciences. Traditionally, electrodes have been manufactured through costly processes such as etching, electroplating or cutting and milling. Additive manufacturing offers a new way to fabricate electrodes by depositing materials layer by layer (Yap et al., 2015). This opens up new possibilities for designing electrodes with complex geometries and structures that would not be possible using conventional methods. As a result, 3D printed electrodes are gaining interest in fields such as electromobility, water disinfection, manufacturing, and life sciences, which will be presented in this paper.
The concept of this thesis is to optimize the manufacturing process of injection moulding tools by using additive manufacturing and thus contribute to environmental protection. For this purpose, the individual steps of the traditional manufacturing process are identified and analysed to determine which steps can be replaced by additive manufacturing. The first step is to clarify which mould components can benefit from additive manufacturing. In particular, the capabilities and limitations of additive manufacturing technologies must be considered.
Furthermore, another focus is on how to optimize the cooling and temperature control of the tools. Potential savings through the use of lightweight or insulating surfaces will be examined. In addition to the technical feasibility, the cost-effectiveness of the concept will also be considered. Finally, the contribution of the concept to the reduction of the environmental impact will be evaluated. In particular, energy savings and the reduction of CO2 emissions are taken into account.
The potential to optimize the injection mould manufacturing process and reduce environmental impact is significant. Using additive manufacturing can be an economic and environmental advantage.
Polycrystalline infrared (PIR) fibers are used for numerous applications, one of those being power delivery for CO2 lasers. However, the fiber tip surface's transmittance cannot be increased with conventional antireflection coatings due to the surface unevenness. Antireflection microstructures (ARMs) offer an alternative way of increasing transmittance. In this work, ARMs were fabricated on the fiber tip surface of an AgClBr fiber by single-pulse femtosecond laser ablation. A single-surface transmittance of 92.8% at 10.6 μm, a CO2 laser operation wavelength, was achieved. The proposed method can help significantly improve the systems' efficiency, where power delivery for CO2 lasers or sources operating in the wide wavelength range is required.
In modern electrochemical coating technology, it is common practice to create uniform layers. However, this study focuses on the deposition of non-uniform layers achieved through a deliberate arrangement of micro structured electrodes on the anode side. The "dog bone effect” was employed as the primary approach [1]. When electroplating on an otherwise uniform surface, this effect selectively processes an area influenced by the geometric edge effect (figure 1 left). The coating within this area is intended to be (i) unevenly distributed and (ii) non-reproducible. Process data was obtained through electrochemical simulations and subsequently applied to a specially designed micro-galvanic setup. This enabled the production of suitable micro structured anodes, validation of coating parameters, and the deposition of visually imperceptible structured areas with inhomogeneous properties using "adhesive gold" on appropriate substrates such as silver and nickel. The layers and their local topography were characterized and analyzed using confocal laser microscopy, X-Ray fluorescence analysis (XRF), as well as a self-designed and constructed laser interference device. As a result, this specific galvanic process technology successfully produced metallic layers that (i) cannot be visually confirmed by the naked eye, (ii) exhibit varied microstructural anode geometries, (iii) display unique differences in layer thickness, (iv) possess non-reproducible and chaotic topographies, and (v) can be detected and identified using conventional analysis techniques or a simple interference setup.
Silver halide polycrystalline infrared fibers (PIR) have unique properties such as excellent transmittance in the spectral range from 3 to 17 µm, while also being highly flexible, non-toxic, and non-hygroscopic. They are used in industry and medicine for CO2-laser power delivery, flexible infrared imaging, and remote process spectroscopy. While PIR fibers possess a quite low attenuation (0.1-0.5 dB/m) in the 8-12 µm range, their total transmittance is limited by significant Fresnel reflections at the fiber end faces due to the high refractive index of silver halide (>2.1). Functionalization of these surfaces with specially designed Anti-Reflective Microstructures (ARMs) enables a striking enhancement of fiber transmittance. In this work, direct imprinting (or embossing) of microstructures to fiber ends and their profiling with a microstructured knife was applied to fabricate such ARMs. The resulting two-dimensional Moth-eye microstructures and one-dimensional microgrooves at the PIR-fiber ends enable to an increase of fiber transmittance in a broadband range of (5-17 µm) as well as to reach up to 20% improvement for PIR-fiber laser cables used for power delivery of CO2-lasers at 10.6 µm.