04 Fakultät Energie-, Verfahrens- und Biotechnik
Permanent URI for this collectionhttps://elib.uni-stuttgart.de/handle/11682/5
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Item Open Access Automatic joining of electrical components to smart textiles by ultrasonic soldering(2021) Micus, Sebastian; Haupt, Michael; Gresser, Götz T.A suitable connection method to automatically produce E-textiles does not exist. Ultrasonic soldering could be a good solution for that since it works with flux-free solder, which avoids embrittlement of the textile integrated wires. This article describes the detailed process of robot-assisted ultrasonic soldering of e-textiles to printed circuit boards (PCB). The aim is to understand the influencing factors affecting the connection and to determine the corresponding solder parameters. Various test methods are used to evaluate the samples, such as direct optical observation of the microstructure, a peeling tensile test, and a contact resistance measurement. The contact strength increases by reducing the operating temperature and the ultrasonic time. The lower operating temperature and the reduced ultrasonic time cause a more homogeneous metal structure with less defects improving the mechanical strength of the samples.Item Open Access Design and analysis of methods to connect microelectronics to smart textiles(2022) Micus, Sebastian; Gresser, Götz Theodor (Prof. Dr.-Ing.)The smart textiles market shows a high growth potential during the next ten years. However, the integration of conventional electronics in textiles requires a lot of manual work. As a result, the products tend to have very high prices, which inhibits the success. During the production processes, the joining step offers the greatest potential to reduce manual manufacturing, but a suitable connection method for the automated production of E-textiles does not exist, yet. For this reason, this thesis analyses different connection methods for joining electronic components to textile integrated litz wires. The selected processes show a high potential for automation. The chosen methods are thermode soldering, insulation displacement connections (IDCs), anisotropic conductive adhesives (ACA), laser soldering, ultrasonic soldering and ultrasonic welding. Various test methods were developed and used to evaluate the samples in order to ensure the reliability of the joinings, such as direct optical observation of the microstructure, a peeling tensile test, and a four-wire contact resistance measurement. The thesis consists of four peer reviewed paper. Each paper focuses on one or more connection methods. In the first paper, hot bar soldering, IDCs and ACA was investigated. The second paper focuses on the ultrasonic soldering. The third paper presents the development on laser soldering and the final paper shows the results of ultrasonic welding. Hot bar soldering initially showed great results. However, solder was drawn into the strands, which was not possible to prevent. Drawn-in solder has a clear negative effect on the textile properties close to the contact point. IDCs have good preconditions for an automated smart textiles production. The strands can slip into the IDCs even under a certain deviation in position. However, thin wires are important to ensure the textile properties of the smart textile, but the available connectors were not suitable to connect AWG 32 or thinner strand. At the current stage of development, anisotropic conductive bonding methods are only conditionally suitable for the usage in automated production. The bonding process has weaknesses due to inadequate contacting and process time. Ultrasonic soldering works with flux-free solder, which avoids embrittlement of the textile integrated wires trough drawn in solder. The influencing factors of the connection and the corresponding solder parameters were determined. The contact strength increases by reducing the operating temperature and the ultrasonic time. A lower operating temperature and a reduced ultrasonic time cause a more homogeneous metal structure with less defects, resulting in an improved mechanical strength of the samples. Contactless laser soldering is considered to be a good contacting method to reduce the joining zone on the textile. An ytterbium-doped fibre laser (1064 nm) was used and different sets of parameters were investigated by means of different designs of experiment. The copper strands in the textile tape were stripped by the laser and soldered to the printed circuit board (PCB) without any transport. Unfortunately, some conductors were poorly wetted by solder. The connection between flexible textiles and stiff electronic components has always been a structural weakness and a limiting factor to establish smart textiles in our everyday life. Therefore, the next chapter focuses on reliable connections between conductive textiles and conventional litz wires by ultrasonic welding. It shows a promising approach. The electrical and mechanical performance of the samples were investigated after both 15 and 30 wash and dry cycles in a laundry machine. The resistance of the joints increased by more than 300 %, because the silver coated wires suffered under the laundry cycles. While the mechanical strength during the peeling test decreased only about 20 % after 15 cycles and remained the same after 30 cycles. Ultrasonic welding showed good results for connecting conductive textiles to litz wires, which enables the production of smart textiles with textile sensors.Item Open Access Integrating electronics to textiles by ultrasonic welding for cable-driven applications for smart textiles(2021) Micus, Sebastian; Rostami, Sahar Golmohammadi; Haupt, Michael; Gresser, Götz T.; Meghrazi, Milad Alizadeh; Eskandarian, LadanThe connection between flexible textiles and stiff electronic components has always been structurally weak and a limiting factor in the establishment of smart textiles in our everyday life. This paper focuses on the formation of reliable connections between conductive textiles and conventional litz wires using ultrasonic welding. The paper offers a promising approach to solving this problem. The electrical and mechanical performance of the samples were investigated after 15 and 30 wash-and-dry cycles in a laundry machine. Here the contact resistances and their peeling strength were measured. Furthermore, their connection properties were analysed in microsections. The resistance of the joints increased more than 300%, because the silver-coated wires suffered under the laundry cycles. Meanwhile, the mechanical strength during the peeling test decreased by only about 20% after 15 cycles and remained the same after 30 cycles. The good results obtained in this study suggest that ultrasonic welding offers a useful approach to the connection of textile electronics to conductive wires and to the manufacture of smart textiles.Item Open Access Textile-based coils for inductive wireless power transmission(2021) Micus, Sebastian; Padani, Laura; Haupt, Michael; Gresser, Götz T.We developed and evaluated different textile-based inductive coils for near-field wireless power transmission. The technology uses electromagnetic induction for the contactless transfer of electrical energy. Therefore, we investigated various methods for the attachment of conductive materials on a textile-based material and the production of textile-based coils based on QI standard. Afterwards, the textile-based coils were examined and evaluated due to their specific quality characteristics. This happens by calculating the transmission quality and the maximum efficiency of the system which enables comparison of different coil systems and indicates the transmission efficiency of the systems.