Shape memory alloy wire actuators are becoming increasingly important due to their outstanding actuator and sensory functionalities, especially in demanding lightweight applications in aerospace technology. However, integration into actuator systems is still challenging. At LAT, a process for form-fit connection using melting spheres was developed in a cooperation project with Ingpuls GmbH funded by the Federal Ministry of Economics and Climate Protection as part of the Central Innovation Programme for Small and Medium-Sized Enterprises (ZIM). A current ZIM project is investigating bonding techniques specifically for printed circuit boards.
Laser micro joining of copper is suitable to create joints which are mechanically much more robust and have a higher electrical as well as thermal conductivity than soldered or brazed joints. Therefore, the process is particularly interesting for the electrical connection of components, e.g. on printed circuit boards.
However, the low reproducibility of the joining result when using near-infrared lasers remains a challenge. The reason for this is mainly the temperature dependency of absorptivity and heat conductivity, in particular the step at the melting temperature.
The reasons for the low reproducibility were recently studied in the frame of a project funded by the German Research Foundation (DFG). The results form the starting point for an ongoing follow-up project, in which different approaches to improve the quality are being investigated.
Within the ForMikro project FlexTMDSense, funded by the German Federal Ministry of Education and Research, an innovative, monolayer accurate deposition and ablation technology at low temperatures for Transition Metal Dichalcogenides (TMD) is developed. This will be used to fabricate low-cost, flexible, ultrasensitive, electronic gas and pH-sensors that will subsequently be manufactured on an industrial scale in an 8-inch cluster facility.
A process for thin film (monolayer) modification using ultrashort pulse (UKP) lasers is being developed at LAT. Due to the minimal thermal disturbance of the short laser pulses, post-treatments of the layer (annealing, phase transformation) can be performed directly on a temperature-sensitive and flexible substrate. Raman spectroscopy is used to investigate and evaluate the quality of the coatings after deposition and post-treatment.
Organic thin films are becoming increasingly important for use in optoelectronic devices. They can be coated from the liquid phase, allowing cost-effective production processes.
Further processing steps are necessary to achieve the desired functionality, for example thermal post-treatment or structuring for serial interconnection. In a cooperation project LAT carries out research in laser-based processes for thermal post-treatment and selective structuring of the generated thin-films for organic photovoltaic modules. In a current follow-up project, these results are to be transferred to a roll-to-roll system at the Fraunhofer Institute for Laser Technology ILT for near-industrial production. These projects are funded by the program EFRE.NRW. Figure: Copyright Fraunhofer ILT, Aachen / Volker Lannert
Spatial Light Modulators (SLMs) are used to shape laser beams dynamically and flexibly. In a ZIM project, an optics module is being realised in which an SLM is used to generate multispots for laser microdrilling. For this purpose, a beam splitter hologram is displayed on the SLM. The split beam is transformed into a Bessel beam via an axicon. This exhibits a long focal length, which is important for achieving a high aspect ratio of the microholes. Using this setup, holes with diameters in the range of a few µm can be flexibly drilled on components at high frequency.
The use of hydrogen as a regenerative energy source is becoming increasingly relevant. A common way of producing hydrogen is the use of so-called electrolysis cells, which are powered by electrical energy. In order to increase the climate efficiency and lower the costs of the hydrogen production the efficiency of these cells has to be increased. In collaboration with The Hydrogen and Fuel Cell Center (ZBT) in Duisburg an enhanced porous transport layer (PTL) is being developed, which is made of a thin titanium foil. A novel method of manufacturing at LAT is being used for production. This method takes advantage of the unique characteristics of femtosecond lasers and allows an arbitrary arrangement of drilled holes on the foil. By drilling holes with a diameter of just a few micrometers a high porosity and different unique features can be achieved.