Agenda (TBC)

Copper is the preferred material for future electronics: high thermal and electric conductivity, durable and ductile, widely available on the global marked and fully recyclable. Therefore, it is the material of choice for electrical wiring and printed electronics. In addition, all copper electrical interconnects are presently in the research focus due to the advantages of single-component metal systems, i.e. copper is used for connecting components onto copper pads. With the progress of additive manufacturing copper pastes and inks have a high potential. The pastes contain copper in three different states, i.e. ball milled copper flakes, copper nanoparticles and copper salts. Very often the pastes are hybrid, i.e. they contain copper flakes and nanoparticles or copper flakes and salts or even all three copper sources. In the presentation, an overview of the materials will be presented. Afterwards, the focus will be on the copper particle free inks, which are fully based on metal salt. The dominating salt for copper particle free inks is Cu-format (CuF). By different complexing agents, e.g. Amino-2-Propanol, 2-Amino-2-Methyl-1-Propanol or Hexylamine, the decomposition temperature can be reduced to low temperature as 100°C. By the decomposition Cu atoms are released and nanoparticles form which sinter and form the conducting traces. High conductivity can be reached – 50% of bulk copper is reported in literature – and thin fine structured layers are realized. However, the key is to control the nanoparticle formation before the sintering. This is achieved by additives which hinder the growth of the particles when they are formed, realizing homogeneous sized small nano-particles and the speed of the subsequent sinter process, i.e. the heat up rate. The mechanisms of nanoparticle formation and the sinter process itself are discussed, i.e. low temperature sintering in an oven versus laser sintering. Results are presented which show that the particle free ink and the sinter process is ready to be transferred to industrial applications. In addition, first results are presented using the ink for bonding components onto substrates.

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The author describes the process of scaling up coating and drying technologies for the indirect or direct coating of platin catalyst on the membrane or to the gas diffusion layer. A state-of-the-art coating tech like slot die is being explained and the next tech development for digital fabrication of PEM fuel cells using a LIFT technology and laser drying are being explained. As a summary, the author shows how important standardization and inline quality controls are for further development stages of PEM fuel cells.

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The metallization of solar cells with the finest printed lines is one of the most demanding disciplines in the field of printed electronics. Finest lines which are smaller than a quarter of a human hair have to be printed on fragile silicon wafers with high throughput and without interruptions. The aim is to shade as little of the active cell surface as possible and at the same time to ensure high conductivity. Various printing processes can be used for fine-line metallization. In this article, the challenges of solar cell metallization as well as various innovative processes and current results are presented. A special highlight is the metallization of ultra-fine line contacts with a width of only 14 μm.

Copper ink and electrically conductive adhesives for future PV production Achieving net-zero emissions by 2050 will require a significant expansion of PV production capacities, accompanied by a drastic reduction of Ag consumption in solar cell metallization compared to today's standards. We demonstrate the application of new mentalization concepts for high-efficiency c-Si solar cells (TopCon and IBC) based on screen-printed Cu inks and investigate their performance and reliability. This screen-printed approach can serve as a drop-in replacement for Ag inks and drastically reduce Ag consumption and production costs for PV manufacturing. In order to realize lead-free solar cell connections and to facilitate the production of PV modules with temperature-sensitive cell concepts such as silicon perovskite tandems, we are also introducing ECA based cell-cell connections that use minimal amounts of Ag-filled materials.

Solar cells, crucial for reducing global CO2 emissions, must reach a capacity of 70 TW by 2050 for a swift transition to renewables. Sili-con technologies dominate, boasting well established supply chains, processes, and markets. However, enhancing power conversion efficiency (PCE) while maintaining cost effectiveness remains challenging. Tandem solar cells, combining two cells to capture different parts of the sunlight spectrum, offer promise. Silicon-perovskite tandems, particularly, show potential for efficiency gains. Perovskite-based materials could disrupt efficiency while aligning with current manufacturing methods, offering a rapid solution to climate change.This review examines fabrication routes for perovskite-based photovoltaics' industrial integration, focusing on non-concentrated tandem designs. Challenges include processing decisions, but slot die coating emerges as a scalable and efficient solution. Its potential for rapid processing on non-flat substrates makes it strategic for advancing the field.

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Smartization of existing or new products is a trend that is linked to Industry 4.0 and Internet-of-Things. There are several ways to integrate electronics into or onto 3D products. The combination of printed electronics for circuit layers and the assembly of rigid electronic components onto those circuit layers is one of the solutions that is getting a lot of attention nowadays. However, hybrid electronics (as the combination of both printed and rigid electronics) or structural electronics (as products aim to be 3D), needs adapted materials and processes to achieve functional conductive traces and interconnects. In this presentation we present the process of screen printing of conductive Ag-based inks on different 2D foils and the subsequent thermoforming of the same to achieve 3D circuit layers on which, afterwards, rigid electronics can be placed via the use of pick-and-place and conductive adhesives. Besides the description of the process, the different foils and different inks are discussed in this work and the properties of their combination for functional 3D products is discussed.

Electronics are the dispensable element in the current modern society and new era of industrial 4.0, Internet of things (IoT), smart homes, wearable electronics as well as modern health solutions. However, the current electrical circuits manufacturing such as printed circuit boards (PCB) are mainly relying on the complex factories with a series of expensive instruments, consuming large amounts of etching chemicals and producing toxic wastewaters [1,2]. Moreover, the electronics are also limited to 2D rigid FR4 boards, which highly hinder it for individualized smart systems. Printed electronics offers high potential in integrating sustainable electronics on flexible and large area surfaces. It has advantages of high resource efficiency, miniaturized usage of energy in both fabrication and utilization, reduce the usage of the hazardous chemicals, higher potential in recyclability and usage of the biodegradable materials. However, it still faces some critical challenges: a) usage of chemicals and solvents; b) required of post-treatment; c) expensive particle-based ink d) high restriction on 3D printing In this talk, we introduce a hybrid printing system where the polymer/dielectric substrates can be directly printed from FFF technology. The StarJet technology is directly integrated into the 3D printing system as the 2nd extruder which prints the bulk metal (e.g. SAC305 solder) through digital and non-contact deposition of the molten metal droplets or Jet. Compared to current printed electronic technologies, the StarJet technology provides advantages of bulk electrical conductivity, conform printing, no pre- and post-treatment, high compatibility on flexible substrates due to solvent-free printing. Furthermore, when the bulk solder (e.g. Tin silver copper alloy) is used for the molten metal printing, the SMD components can be directly soldered and bonded onto the large-area flexible substrates. It eliminates the troublesome solder reflow process and simplifies the fabrication process. In the contrary to the high temperature of the StarJet printhead (e.g. 320 °C for soldering printing), the printed molten metal structure has high adhesion, high flexibility and no damage to the temperature sensitive polymer foils, textiles, and 3D-printed plastics. The high flexibility has been also shown on foldable polymer foils, where the printed circuits can be folded into a small part and stay fully functional after unfolded. A highly simplified workflow is also introduced where non-experts can make electrical designs and generate hybrid 3D electronic models. Then the hybrid 3D printing system will take care of the rest of printing. With this hybrid-printing platform, it provides high potential to direct prototype 3D electronics and integration of smart sensors with highly conductive traces, direct soldering, and without any post-processing (e.g drying, sintering).

Additive manufacturing of electronics is experiencing increasing demand. Since neither molds nor printing forms are required, the integration of functional electronic components onto 3D objects by means of digital printing technologies such as inkjet, extrusion, aerosol and electrohydrodynamic printing facilitate mass customization. Due to a constant jet width over a large range, aerosol jet printing has the advantage to allow printing onto 3D surfaces without adaptation of the distance between the printhead and the object. However, existing aerosol jet printing systems require the printheads to be orientated in the direction of gravity, operate only continuously and thus need a shutter system to realize discontinuous structures. We develop a novel Aerosol-on-Demand (AoD) jet-printing system that solves the major challenges of digital printing technologies. The core of the patented AoD technology is a new method for aerosol generation from a point-like source within the printhead directly in a sheath gas flow, which hydrodynamically focuses the generated aerosol by means of the inner contour of the attached nozzle. Based on the results obtained by first experiments we implement a CFD model of the printhead. CFD simulations show the feasibility of the hydrodynamic focusing of the locally generated aerosol as well as the existence of stable operating points. Furthermore, the simulations lead to the design of a test setup. Experiments with the test setup verify that aerosol generation can be controlled on demand and thus printing of discontinuous microstructures is possible without ink loss and need for a shutter. There are no aerosol-conducting parts other than the nozzle, i.e. there is no dead volume and no material waste. The minimum ink volume and the cleaning effort are extremely reduced; ink degradation occuring in common atomizers is eliminated. In addition,after a short initial run-in period for the sheath gas no further run-in period is required for the aerosol jet. The aerosol mass flow can be controlled inline to provide a constant ink transfer rate over a wide range of printing speeds. Finally, the printhead can be freely rotated in space during the printing process. Thus, it is also possible to print on stationary components of complex 3D-shape. In conclusion, the novel AoD jet-printing principle shows great potential for applications in functional printing of 2D & 3D electronics

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