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PublicationForced Motion Activated Self-Alignment of Micro-CPV Solar Cells( 2024)
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PublicationLaboratory X-ray Microscopy of 3D Nanostructures in the Hard X-ray Regime Enabled by a Combination of Multilayer X-ray Optics( 2024)High-resolution imaging of buried metal interconnect structures in advanced microelectronic products with full-field X-ray microscopy is demonstrated in the hard X-ray regime, i.e., at photon energies > 10 keV. The combination of two multilayer optics—a side-by-side Montel (or nested Kirkpatrick–Baez) condenser optic and a high aspect-ratio multilayer Laue lens—results in an asymmetric optical path in the transmission X-ray microscope. This optics arrangement allows the imaging of 3D nanostructures in opaque objects at a photon energy of 24.2 keV (In-Kα X-ray line). Using a Siemens star test pattern with a minimal feature size of 150 nm, it was proven that features < 150 nm can be resolved. In-Kα radiation is generated from a Ga-In alloy target using a laboratory X-ray source that employs the liquid-metal-jet technology. Since the penetration depth of X-rays into the samples is significantly larger compared to 8 keV photons used in state-of-the-art laboratory X-ray microscopes (Cu-Kα radiation), 3D-nanopattered materials and structures can be imaged nondestructively in mm to cm thick samples. This means that destructive de-processing, thinning or cross-sectioning of the samples are not needed for the visualization of interconnect structures in microelectronic products manufactured using advanced packaging technologies. The application of laboratory transmission X-ray microscopy in the hard X-ray regime is demonstrated for Cu/Cu6Sn5/Cu microbump interconnects fabricated using solid–liquid interdiffusion (SLID) bonding.
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PublicationSensor Systems for Extremely Harsh Environments( 2023-10-31)Sensors are key elements for capturing environmental properties and are today indispensable in the industry for monitoring and control of industrial processes. Many applications are demanding for highly integrated intelligent sensors to meet the requirements on safety, clean and energy efficient operation or to gain process information in the context of industry 4.0. While in many everyday objects highly integrated sensor systems are already state of the art, the situation in an industrial environment is clearly different. Frequently the use of sensor systems is impossible, due to the fact that the extreme ambient conditions of industrial processes like high operating temperatures or strong mechanical loads do not allow a reliable operation of sensitive electronic components. Eight Fraunhofer Institutes have bundled their competencies and have run the Fraunhofer Lighthouse Project ‘eHarsh’ to overcome this situation. The project goal was to realize sensor systems for extremely harsh environments, whereby sensor systems are not only pure sensor elements, rather containing one or multiple sensor elements and integrated readout electronics. Various technologies which are necessary for the realization of such sensor systems have been identified, developed and finally bundled in a technology platform. These technologies are e. g. MEMS and ceramic based sensors, SOI-CMOS based integrated electronics, board assembly and laser based joining technologies. All these developments have been accompanied by comprehensive tests, material characterization and reliability simulations. Based on the platform a pressure sensor for turbine applications has been realized to prove the performance of the eHarsh technology platform.
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PublicationUse of Rotary Ultrasonic Plastic Welding as a Continuous Interconnection Technology for Large-Area e-Textiles( 2023-01-28)For textile-based electronic systems with multiple contacts distributed over a large area, it is very complex to create reliable electrical and mechanical interconnections. In this work, we report for the first time on the use of rotating ultrasonic polymer welding for the continuous integration and interconnection of highly conductive ribbons with textile-integrated conductive tracks. For this purpose, the conductive ribbons are prelaminated on the bottom side with a thermoplastic film, which serves as an adhesion agent to the textile carrier, and another thermoplastic film is laminated on the top side, which serves as an electrical insulation layer. Experimental tests are used to investigate the optimum welding process parameters for each material combination. The interconnects are initially electrically measured and then tested by thermal cycling, moisture aging, buckling and washing tests, followed by electrical and optical analyses. The interconnects obtained are very low ohmic across the materials tested, with resulting contact resistances between 1 and 5 mOhm. Material-dependent results were observed in the reliability tests, with climatic and mechanical tests performing better than the wash tests for all materials. In addition, the development of a heated functional prototype demonstrates a first industrial application.
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PublicationA Direct Real-Time Observation of Anion Intercalation in Graphite Process and Its Fully Reversibility by SAXS/WAXS Techniques( 2023)The process of anion intercalation in graphite and its reversibility plays a crucial role in the next generation energy-storage devices. Herein the reaction mechanism of the aluminum graphite dual ion cell by operando X-ray scattering from small angles to wide angles is investigated. The staging behavior of the graphite intercalation compound (GIC) formation, its phase transitions, and its reversible process are observed for the first time by directly measuring the repeated intercalation distance, along with the microporosity of the cathode graphite. The investigation demonstrates complete reversibility of the electrochemical intercalation process, alongside nano- and micro-structural reorganization of natural graphite induced by intercalation. This work represents a new insight into thermodynamic aspects taking place during intermediate phase transitions in the GIC formation.
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PublicationMechanical properties of structured copper and printed silver hybrid stretchable electronic systems( 2023)Stretchable electronics can be realized using different manufacturing methods and hybrids thereof. An example of the latter is the combination of stretchable circuit boards with screen-printing, which will be discussed in this work. The hybrid stretchable electronics structures are based on photolithographically structured and rigid copper islands and screen-printed silver ink interconnections. This enables the assembly of components with a high number of contacts onto the copper islands and deformable silver ink lines between islands. The transition area between islands and lines is critical due to local stress concentration. The effect and potential mitigations were studied by measuring the electrical resistance of test interconnections under mechanical loading. The first set of samples was elongated up to 30% in tensile tests. The second set of samples was elongated 10%, 20%, and 30% in cyclic tests up to 10 000 cycles. After the tests, extensive failure analysis, e.g. scanning electron microscope, and finite element analysis were conducted. In tensile tests at maximum load, the interconnections either snap apart or their resistance increases by 640% in the transition area. Adding protective structures around the transition area, the resistance increase can be reduced to 12%. Stress concentration in the transition area can be controlled with the layout of the structures, as shown in the cyclic tests. Depending on a layout, the structures protect interconnections in the transition area (resistance <4 Ω at 10% and 20% throughout 10 000 cycles, and up to 5000 cycles at 30% elongation), or with particular designs, cause fatal damage of the circuitry and fail early. The identified failure mechanism is typically fatigue damage caused by the repeated bending of the protective structure. The observed resistance increase at the interface was closely related to the crack propagation phase in the protective structures.
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PublicationLithium-Ion Batteries: Nomenclature of Interphases with Liquid or Solid-State Electrolytes( 2023)Although lithium-ion batteries are playing a paramount role in everyday life around the world, from portable electronics to electric vehicles, there seems to be no international organization governing its development since the commercialization began in 1991. As a consequence, there is no clearly defined nomenclature for certain aspects of lithium-ion batteries. For instance, no international consensus has been reached on the nomenclature of the interphases that play a very crucial role in the operation of lithium-ion batteries. Unfortunately, this absence of proper nomenclature for interphases has been trending for far too long and it is confusing for emerging scientists, especially as it is being dragged to emerging technologies such as solid-state batteries and post-lithium chemistries. Here, the nomenclature problem of the interphases in lithium-ion batteries is critically addressed.
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PublicationQuantifying total lifetimes of consumer products: Stochastic modelling accounting for second-hand use and establishing an open-collaborative database( 2023)Data on the total product lifetimes, which is much needed in the fields of sustainability and circularity assessment, is currently sparse and challenging to measure. To meet such data and methodological needs, the first information system of its kind has been developed as part of this research. While an online portal collects and stores consumer reports on use and disposal patterns for various electronics owned and used, the harvested survey data was automatically fed into a novel stochastic model that allowed estimating the total lifetimes and durability of the different products considering the impacts of second-hand use. This was done without reliance on auxiliary market statistics and costly facility-based analysis while preserving a satisfactory degree of accuracy. Additionally, the structure of the collected data allows for measuring the effects of the different circular practices (repair, reuse, recycling, etc.) on product longevity which is of specific interest to researchers and policymakers.
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PublicationA forecast on future raw material demand and recycling potential of lithium-ion batteries in electric vehiclesThe market for electromobility has grown constantly in the last years. To ensure a future supply of raw materials for the production of new batteries for electric vehicles, it is essential to estimate the future demand for battery metals. This study focuses on the future demand for electric vehicle battery cathode raw materials lithium, cobalt, nickel, and manganese by considering different technology and growth scenarios. The results show that in 2040 the future material demand for lithium, cobalt, and nickel for Lithium-Ion Batteries in electric vehicles exceeds current raw material production. Depending on the growth and technology scenario, the future demand for lithium and cobalt exceeds today's production by up to 8 times in 2040. Nickel exceeds today's production in one scenario. For manganese, future demand in 2040 remains far below today's production. The recycling potential for lithium and nickel is more than half the raw material demand for Lithium-Ion Batteries in 2040. For cobalt, the recycling potential even exceeds the raw material demand in 2040. In conclusion, it remains a challenge for the industry to massively scale up resource production and focus on the recycling of battery metals in the future to meet the increasing consumption of electromobility.
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PublicationMMIC-to-Dielectric Waveguide Transitions for Glass Packages Above 150 GHz( 2023)In this work, novel concepts of an electromagnetically coupled transition and a galvanically coupled transition in glass technology are presented. This enables efficient coupling of signals above 150 GHz into a dielectric waveguide (DWG). Laser-induced deep etching (LIDE) technology provides fabrication of glass holes, cavities, and cutouts with a precision suitable for use in highly integrated mm-wave modules. Based on the package concept presented by Galler et al. (2022), this article introduces an ultracompact galvanically isolated transition from monolithic microwave integrated circuit (MMIC) to a mechanically flexible DWG, offering a minimum insertion loss of 2.95 dB. The simple fabrication provides a cost-effective variant for modern system-in-package solutions. In addition, a galvanic through-plating of the glass cover with through-glass vias (TGVs) and a ring slot structure for the excitation of a DWG are presented. Thereby, the integration density and performance can be further increased. A minimum insertion loss of 2.62 dB within a large 1-dB bandwidth of 18 GHz around the operating frequency of 166 GHz is verified by measurement. Both the transitions cover a high integration density, hermetic sealing, and modular use suitable for requirements of today's modern radar and communication packages.
