@inproceedings{DoehlerBoehmeHofmannetal.2022, author = {D{\"o}hler, Torsten and B{\"o}hme, Andrea and Hofmann, Mandy and Neumann, Jens and Bochem, Reinhard and Foitzik, Andreas and Geißler, Ute}, title = {Mikrogalvanische Kennzeichnung als Kopierschutz}, series = {Open Conference Proceedings}, volume = {2}, booktitle = {Open Conference Proceedings}, publisher = {TIB Open Publishing}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-17624}, pages = {157 -- 161}, year = {2022}, abstract = {In order to achieve good product quality in electroplating, disturbance variables such as the "dog bone" effect must be avoided. In this work, this approach was used to develop a method for marking as product protection. With a defined structure and optimal parameters, it is possible to deposit unique visually non-differentiable layers on suitable substrates. The deposited layers and their local distribution were characterized by confocal laser microscopy, X-ray fluorescence analysis and laser interference measurements and analyzed qualitatively as well as quantitatively. It thus provides interested parties with an essentially traditional process that can lead to new innovations with the chosen approach.}, language = {de} } @article{FelkeGrothHempeletal.2024, author = {Felke, Florens and Groth, Anne and Hempel, Martin and Czerny, Bernhard and Khatibi, Golta and D{\"o}hler, Torsten and Geißler, Ute}, title = {Effect of the loop forming process on the lifetime of aluminum heavy wire bonds under accelerated mechanical testing}, series = {Microelectronics Reliability}, volume = {154}, journal = {Microelectronics Reliability}, publisher = {Elsevier}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-18631}, year = {2024}, abstract = {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.}, language = {en} } @article{TarabrinBushunovTeslenkoetal.2021, author = {Tarabrin, Mikhail K. and Bushunov, Andrey A. and Teslenko, Andrei A. and Sakharova, Tatiana and Hinkel, Jonas and Usenov, Iskander and D{\"o}hler, Torsten and Geißler, Ute and Artyushenko, Viacheslav and Lazarev, Vladimir A.}, title = {Fabrication of an antireflection microstructure on AgClBr polycrystalline fiber by single pulse femtosecond laser ablation}, series = {Optical Materials Express}, volume = {11}, journal = {Optical Materials Express}, number = {2}, publisher = {Optical Society of America}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-15384}, pages = {487 -- 496}, year = {2021}, abstract = {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.}, language = {en} } @article{BoehmeDoehlerHofmannetal.2023, author = {B{\"o}hme, Andrea and D{\"o}hler, Torsten and Hofmann, Mandy and Neumann, Jens and Bochem, Reinhard and Geißler, Ute and Foitzik, Andreas}, title = {Electrolytical Coating of Inhomogeneous Structures Distributed on Metallic Surfaces}, series = {Materials Science Forum}, volume = {1106}, journal = {Materials Science Forum}, publisher = {Trans Tech Publications}, issn = {0255-5476}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-18825}, pages = {75 -- 80}, year = {2023}, abstract = {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.}, language = {en} } @article{AdomavičiũtėGrabusovėHinkelUsenovetal.2022, author = {Adomavičiũtė-Grabusovė, Sonata and Hinkel, Jonas and Usenov, Iskander and Novikov, Alexander S. and Sakharova, Tatiana and D{\"o}hler, Torsten and Geißler, Ute and Feliksberger, Elena and Artyushenko, Viacheslav}, title = {Microstructuring of the end-surface for silver halide polycrystalline fibers to suppress Fresnel reflection}, series = {Optical Materials Express}, volume = {12}, journal = {Optical Materials Express}, number = {1}, publisher = {Optica Publishing Group}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-15549}, pages = {34 -- 48}, year = {2022}, abstract = {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.}, language = {en} }