Scientific Publications "Production Technologies"

The fabrication of microstructured polymer optics enables a multitude of new options in the design of technical optics. However, challenges arise along the varying process chains of mold insert fabrication, integration into molding tools, replication by means of injection compression molding and metrology. In order to study the effects, diffractive optical elements (DOE) and microlens arrays (MLA) are fabricated using two different process chains. DOEs are fabricated using a laser direct writing (LDW) based mold insert fabrication. The MLA mold insert is produced using ultra-precision milling (UPmilling). Both optical parts are replicated using injection compression molding. The occurring effects are discussed and the results show, that with complete process control high quality microstructured polymer optical parts can be produced and characterized.

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In this work, a new process chain for the fabrication of curved micro-structured optical elements by injection compression molding is investigated. The fabrication is demonstrated for the example of a curved diffractive optical element (DOE). In a first process step a master substrate is fabricated using laser direct writing on a curved glass substrate. Blazed diffractive micro-structures with lateral feature sizes down to 5 μm and height of 1.6 μm are created. A subsequent electroplating process is applied to create a nickel stamper to be used as a tool insert for the molding process. During electroplating, a 3 mm nickel layer is formed, transferring the diffractive structures from the master substrate into a solid mold insert. The nickel stamper shows an accurate reproduction of the micro-structures. The mold insert is integrated into an injection compression molding tool to replicate the optical elements. Results show that the blazed diffractive structures are replicated with a high quality. Tests of the components within a chromatic-confocal measurement setup confirm that they can potentially replace expensive conventional elements.

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Polymer optics have gained increasing importance in recent years. With advancing requirements for the optical components, the fabrication process remains a challenge. In particular, the fabrication of the mold inserts for the replication process is crucial for obtaining high-quality optical components. This review focuses on fabrication technologies for optical mold inserts. Thereby, two main types of technologies can be distinguished: fabrication methods to create mold inserts with optical surface quality and methods to create optical microstructures. Since optical mold inserts usually require outstanding form accuracies and surface qualities, a focus is placed on these factors. This review aims to give an overview of available methods as well as support the selection process when a fabrication technology is needed for a defined application. Furthermore, references are given to detailed descriptions of each technology if a deeper understanding of the processes is required.

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This paper presents a simple approach for high accuracy assembly of multiple ultra-thin chips on flexible foil substrates. The chips are placed initially in cavities on a chip carrier substrate and transferred onto a thermally releasable adhesive tape. After application of epoxy-based adhesive onto the chip surface the chips are transferred onto the foil substrate. Finally, the epoxy adhesive is cured and the adhesive tape is removed. It was found that a wafer dicing tape with releasing temperature of 90 °C as thermally releasable adhesive tape and a two-component epoxy adhesive with a curing temperature of 65 °C is suitable for the process.  High placement accuracy of the chips of less than 30  µm in x- and y- orientation as well as rotational misalignment lower than 0.2° was obtained. The process is demonstrated on polyimide foil with a resulting chip flatness of ± 5 µm.

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Faster product lifecycles make long-term investments in machines for micro assembly riskier. Therefore, reconfigurable manufacturing systems gain more and more attention. But most companies are uncertain if a reconfigurable manufacturing system can fulfill their needs and justify the initial investment. New and improved techniques for product development have the potential to foster the utilization and decrease the investment risk for such systems. In this paper, four different methods for product development are reviewed. A set of criteria regarding micro assembly on reconfigurable manufacturing systems RMS is established. Based on those criteria and the assessment, a novel approach for a product development method is provided, which tries to combine the strengths of the beforehand presented approaches. It focuses on the conceptual design phase to overcome the customers’ uncertainty in the development process. For this, an abstract representation of a micro-assembly product idea as well as a decision tree for joining processes are established and validated by real product ideas using expert interviews. The validation shows that the conceptual design phase can be used as a useful tool in the product development process in the field of micro assembly.
 

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Several European projects on Digital Innovation Hubs (DIHs) have developed their own platforms or marketplaces, offering solutions for companies to improve their production processes, products or business models with digital technologies.

These marketplaces have a high potential to make a real difference for companies, but how to make the most out of them?

The aim of the meeting is to bring together Digital Innovation Hubs representatives, who are part of the European Catalogue of DIHs and who are part of the Working Group on Digital Innovation Hubs, to explore:

• What marketplaces and platforms exist and how could they be grouped together?
• How regions could benefit from them for their own companies?
• How Digital Innovation Hubs could be the main distributors of the portfolio of tools developed by EU-funded Innovation Actions at regional level?