Thomas Günther

Zusammenfassung

Nowadays, there is a growing demand for structures in the micrometer and submicrometer regime for electrochemical and optical applications to fabricate circuit paths or optical gratings. Therefore, the aim of this work is to show the applicability of a simple and inexpensive method to manufacture micrometer- and submicrometer structures of ultrathin metal coatings on polymer substrates of cyclic olefin copolymer (COP) as well as on glass using maskless photolithography followed by lift-off. To enhance the adhesion of the photoresist on the polymer substrates surface pretreatments of the polymer substrates, e.g., by glow discharge or atmospheric plasma treatment were executed. The lithography process was carried out using a sprayed negative photoresist on glass and COP substrates exposed to ultraviolet light via a micromirror assay and without a mask. Based on the exposure limit and an initial proof of concept, gratings with a line width of 100 µm and a period of 200 µm were manufactured. After development, no adhesion layers were applied to facilitate fabrication and minimize costs. Thus, the substrates were sputtered with 50 nm gold layers, which were lifted off with acetone. During the processing, the factors influencing the accuracy of the structures, such as prebake, postbake and development parameters, were determined and an optimal parameter setting was derived.

Zusammenfassung

Hard coatings can be applied onto microstructured molds to influence wear, form filling and demolding behaviors in microinjection molding. As an alternative to this conventional manufacturing procedure, “direct processing” of physical-vapor-deposited (PVD) hard coatings was investigated in this study, by fabricating submicron features directly into the coatings for a subsequent replication via molding. Different diamondlike carbon (DLC) and chromium nitride (CrN) PVD coatings were investigated regarding their suitability for focused ion beam (FIB) milling and microinjection molding using microscope imaging and areal roughness measurements. Each coating type was deposited onto high-gloss polished mold inserts. A specific test pattern containing different submicron features was then FIB-milled into the coatings using varied FIB parameters. The milling results were found to be influenced by the coating morphology and grain microstructure. Using injection–compression molding, the submicron structures were molded onto polycarbonate (PC) and cyclic olefin polymer (COP). The molding results revealed contrasting molding performances for the studied coatings and polymers. For CrN and PC, a sufficient replication fidelity based on AFM measurements was achieved. In contrast, only an insufficient molding result could be obtained for the DLC. No abrasive wear or coating delamination could be found after molding.

Zusammenfassung

Die Benetzung von Schmelze-berührenden Maschinenkomponenten sowie die Anhaftung von erstarrtem Kunststoff auf dem Formwerkzeug basiert auf Wechselwirkungen an der Grenzfläche zwischen Kunststoff und Werkzeugmaterial. Ein Ansatz zur Charakterisierung der Benetzbarkeit von Festkörperoberflächen ist die Bestimmung der freien Oberflächenenergie auf Basis von Kontaktwinkelmessungen. Bisherige Studien ermittelten die freie Oberflächenenergie von verschiedenen Hartstoffschichten meist durch Kontaktwinkelmessungen bei Raumtemperatur oder basierend auf einem statischen Messverfahren, welches nahezu keine Reproduzierbarkeit aufweist. Um die Benetzbarkeit von Hartstoffschichten für die Kunststoffverarbeitung zu bewerten, wurden in dieser Studie dynamische Kontaktwinkelmessungen von zwei Prüfflüssigkeiten auf poliertem Stahl sowie einer Titannitrid- (TiN), zwei Chromnitrid- (CrN) und einer amorphen Kohlenstoffbeschichtung (a-C:H:Si) im Entformungstemperaturbereich von 60 °C bis 140 °C durchgeführt. Anschließend wurden die freien Oberflächenenergien der Beschichtungen für den betrachteten Temperaturbereich nach der Methode von Owens, Wendt, Rabel und Kaelble bestimmt. Die Ergebnisse zeigen, dass die CrN-Beschichtungen die geringste freie Oberflächenenergie aufweisen. Im Vergleich zeigte sich für alle Hartstoffschichten eine Abnahme der freien Oberflächenenergie mit sich erhöhender Temperatur. Die chemische Zusammensetzung der Probenoberfläche scheint bei gleichbleibenden Messbedingungen für glatte Oberflächen der bestimmende Faktor für die Höhe der freien Oberflächenenergie zu sein. The wetting of melt-facing surfaces as well as the sticking of solidified plastic on molding tools is related to surface effects between plastic materials and mold material. One approach to quantify the wetting on solid surfaces is the determination of the free surface energy. Several studies determined the free surface energy of hard coatings used in polymer processing based on the drop shape analysis. These measurements were, however, mostly conducted at room temperature, which is not comparable to molding temperatures, or were limited to static contact angle measurements, which are nearly non-reproducible. In this study, the wetting of hard coatings used in polymer processing was investigated by measuring the advancing contact angle of two test fluids on a titanium nitride, two differently deposited chromium nitride and one diamond-like carbon coating at relevant demolding temperatures in the range from 60 °C to 140 °C. The results showed the smallest free surface energy values for the two chromium nitride coatings. The comparison of all investigated coatings revealed a decline of the free surface energy with increasing solid temperature. The chemical composition of the material seems to be a determining factor for smooth surfaces and constant measuring conditions.

Zusammenfassung

The demolding of plastic parts remains a challenging aspect of injection molding. Despite various experimental studies and known solutions to reduce demolding forces, there is still not a complete understanding of the effects that occur. For this reason, laboratory devices and in-process measurement injection molding tools have been developed to measure demolding forces. However, these tools are mostly used to measure either frictional forces or demolding forces for a specific part geometry. Tools that can be used to measure the adhesion components are still the exception. In this study, a novel injection molding tool based on the principle of measuring adhesion-induced tensile forces is presented. With this tool, the measurement of the demolding force is separated from the actual ejection step of the molded part. The functionality of the tool was verified by molding PET specimens at different mold temperatures, mold insert conditions and geometries. It was demonstrated that once a stable thermal state of the molding tool was achieved, the demolding force could be accurately measured with a comparatively low force variance. A built-in camera was found to be an efficient tool for monitoring the contact surface between the specimen and the mold insert. By comparing the adhesion forces of PET molded on polished uncoated, diamond-like carbon and chromium nitride (CrN) coated mold inserts, it was found that a CrN coating reduced the demolding force by 98.5% and could therefore be an efficient solution to significantly improve demolding by reducing adhesive bond strength under tensile loading.

Zusammenfassung

This work is motivated by the rarely available material data for thermosets and a missing inline viscosity measurement method to monitor melt property deviations. A nozzle viscometer is designed for inline viscosity measurement of phenol-formaldehyde compounds. The nozzle viscometer is mounted at the plasticizing unit of an injection molding machine. A fluid coolant circuit allows a dynamic tempering to pause the transient crosslinking reaction. A 2D FDM model is implemented, to calculate the viscous heating within an injection cycle and to compensate the temperature rising effect in the viscosity measurement. The FDM model processes the inline sensor signals in a closed loop correction in real time to determine a corrected reactive viscosity model. The signal-to-noise-ratio quantifies the reliability of the inline viscosity measurement method.

Zusammenfassung

LDS-MIDs (laser direct structured mechatronic integrated devices) are 3D (three-dimensional) circuit carriers that are used in many applications with a focus on antennas. However, thanks to the rising frequencies of HF (high-frequency) systems in 5G and radar applications up to the mmWave (millimeter wave) region, the requirements regarding the geometrical accuracy and minimal wall thicknesses for proper signal propagation in mmWave circuits became more strict. Additionally, interest in combining those with 3D microstructures like trenches or bumps for optimizing transmission lines and subsequent mounting processes is rising. The change from IM (injection molding) to ICM (injection compression molding) could offer a solution for improving the 3D geometries of LDS-MIDs. To enhance the scientific insight into this process variant, this paper reports on the manufacturing of LDS-MIDs for mmWave applications. Measurements of the warpage, homogeneity of local wall thicknesses, and replication accuracy of different trenches and bumps for mounting purposes are presented. Additionally, the effect of a change in the manufacturing process from IM to ICM regarding the dielectric properties of the used thermoplastics is reported as well as the influence of ICM on the properties of LDS metallization—in particular the metallization roughness and adhesion strength. This paper is then concluded by reporting on the HF performance of CPWs (coplanar waveguides) on LDS-MIDs in comparison to an HF-PCB.

Zusammenfassung

Mechatronic Integrated Devices or Molded Interconnect Devices (MID) are three-dimensional (3D) circuit carriers. They are mainly fabricated by laser direct structuring (LDS) and subsequent electroless copper plating of an injection molded 3D substrate. Such LDS-MID are used in many applications today, especially antennas. However, in high frequency (HF) systems in 5G and radar applications, the demand on 3D circuit carriers and antennas increases. Electroless copper, widely used in MID, has significantly lower electrical conductivity compared to pure copper. Its lower conductivity increases electrical loss, especially at higher frequencies, where signal budget is critical. Heat treatment of electroless copper deposits can improve their conductivity and adhesion to the 3D substrates. This paper investigates the effects induced by tempering processes on the metallization of LDS-MID substrates. As a reference, HF Printed Circuit Boards (PCB) substrates are also considered. Adhesion strength and conductivity measurements, as well as permittivity and loss angle measurements up to 1 GHz, were carried out before and after tempering processes. The main influencing factors on the tempering results were found to be tempering temperature, atmosphere, and time. Process parameters like the heating rate or applied surface finishes had only a minor impact on the results. It was found that tempering LDS-MID substrates can improve the copper adhesion and lower their electrical resistance significantly, especially for plastics with a high melting temperature. Both improvements could improve the reliability of LDS-MID, especially in high frequency applications. Firstly, because increased copper adhesion can prevent delamination and, secondly, because the lowered electrical resistance indicates, in accordance with the available literature, a more ductile copper metallization and thus a lower risk of microcracks.

Zusammenfassung

Thermosonic wire bonding is a well-established process. However, when working on advanced substrate materials and the associated required metallization processes to realize innovative applications, multiple factors impede the straightforward utilization of the known process. Most prominently, the surface roughness was investigated regarding bond quality in the past. The practical application of wire bonding on difficult-to-bond substrates showed inhomogeneous results regarding this quality characteristic. This study describes investigations on the correlation among the surface roughness, profile peak density and bonding quality of Au wire bonds on thermoplastic and thermoset-based substrates used for high-frequency (HF) applications and other high-end applications. FR4 PCB (printed circuit board flame resitant class 4) were used as references and compared to HF-PCBs based on thermoset substrates with glass fabric and ceramic filler as well as technical thermoplastic materials qualified for laser direct structuring (LDS), namely LCP (liquid crystal polymer), PEEK (polyether ether ketone) and PTFE (polytetrafluoroethylene). These LDS materials for HF applications were metallized using autocatalytic metal deposition to enable three-dimensional structuring, eventually. For that purpose, bond parameters were investigated on the mentioned test substrates and compared with state-of-the-art wire bonding on FR4 substrates as used for HF applications. Due to the challenges of the limited thermal conductivity and softening of such materials under thermal load, the surface temperatures were matched up by thermography and the adaptation of thermal input. Pull tests were carried out to determine the bond quality with regard to surface roughness. Furthermore, strategies to increase reliability by the stitch-on-ball method were successfully applied.

Zusammenfassung

The use of focused ion and focused electron beam (FIB/FEB) technology permits the fabrication of micro- and nanometer scale geometries. Therefore, FIB/FEB technology is a favorable technique for preparing TEM lamellae, nanocontacts, or nanowires and repairing electronic circuits. This work investigates FIB/FEB technology as a tool for nanotip fabrication and quantum mechanical tunneling applications at a low tunneling voltage. Using a gas injection system (GIS), the Ga-FIB and FEB technology allows both additive and subtractive fabrication of arbitrary structures. Using energy dispersive X-ray spectroscopy (EDX), resistance measurement (RM), and scanning tunneling microscope (STM)/spectroscopy (STS) methods, the tunneling suitability of the utilized metal–organic material–platinum carbon (PtC) is investigated. Thus, to create electrode tips with radii down to 15 nm, a stable and reproducible process has to be developed. The metal–organic microstructure analysis shows suitable FIB parameters for the tunneling effect at high aperture currents (260 pA, 30 kV). These are required to ensure the suitability of the electrodes for the tunneling effect by an increased platinum content (EDX), a low resistivity (RM), and a small band gap (STM). The STM application allows the imaging of highly oriented pyrolytic graphite (HOPG) layers and demonstrates the tunneling suitability of PtC electrodes based on high FIB aperture currents and a low tunneling voltage.

Zusammenfassung

Hard coatings can be applied onto microstructured molds to influence wear, form filling and demolding behaviors in microinjection molding. As an alternative to this conventional manufacturing procedure, “direct processing” of physical-vapor-deposited (PVD) hard coatings was investigated in this study, by fabricating submicron features directly into the coatings for a subsequent replication via molding. Different diamondlike carbon (DLC) and chromium nitride (CrN) PVD coatings were investigated regarding their suitability for focused ion beam (FIB) milling and microinjection molding using microscope imaging and areal roughness measurements. Each coating type was deposited onto high-gloss polished mold inserts. A specific test pattern containing different submicron features was then FIB-milled into the coatings using varied FIB parameters. The milling results were found to be influenced by the coating morphology and grain microstructure. Using injection–compression molding, the submicron structures were molded onto polycarbonate (PC) and cyclic olefin polymer (COP). The molding results revealed contrasting molding performances for the studied coatings and polymers. For CrN and PC, a sufficient replication fidelity based on AFM measurements was achieved. In contrast, only an insufficient molding result could be obtained for the DLC. No abrasive wear or coating delamination could be found after molding.

Zusammenfassung

Microsystems and interconnect devices based on ceramic substrate materials are used in many high temperature and power applications due to their superior thermal properties. With the current state-of-the-art pro-cesses, such as direct-bonded copper or high/low temperature co-fired ceramics, only 2D or multilayer struc-tures can be realized. In this paper, we present a fully digital, selective and additive process chain based on direct laser-induced activation and subsequent autocatalytic metallization of injection molded Al2O3-based substrates to produce 3D-ceramic interconnect devices. In order to laser-activate the Al2O3, it has either to be sintered in H2 atmosphere or doped with Cr2O3. The resulting selective metallization shows an adhesive strength of up to 50 N/mm² and can be connected with common interconnection technologies, such as reflow soldering, wire bonding etc. Thus, the developed process chain offers new possibilities in ceramic circuit carrier design and the integration into complex microsystems.

Zusammenfassung

Todays continuous improvement and advancement in the injection molding process for plastics allow for increasing reliability of the process parameter control, whereas the fluctuations of the material properties still present a great challenge. To compensate for these fluctuations, a nozzle capillary rheometer is developed with the aim to determine the viscosity inline during the injection process in series production applications. An essential part of this work is the signal processing and the definition of a suitable integration boundary to ensure a reliable signal evaluation. In addition, based on mathematical modeling and established correction factors, it is possible to determine the effective viscosity accurately without the need to replace the capillary channel according to the Bagley correction.

Zusammenfassung

Diese Arbeit beschreibt die Entwicklung eines mikro-integrierten multispektralen Bildgebungssystems für die hyper-spektrale Bildgebung (HSI). Ziel ist es, durch den Einsatz von polymeren optischen Komponenten die Integrations-dichte zu erhöhen, das Gewicht zu reduzieren und gleichzeitig die Funktionalität im Vergleich zu klassischen HSI-Ka-merasystemen zu verbessern. Wirtschaftlichen Vorteile einer vereinfachten Montage durch direkte Integration von Be-festigungselementen als auch die Möglichkeit der Massenproduktion von Polymeroptiken werden betrachtet. Eine Stra-tegie zur Integration in ein Kamerasystem wird entwickelt, welche die Anforderungen für die Mikromontage aller Kom-ponenten erfüllt. Es werden Methoden zur Mikromontage eines polymeren Mikrolinsenarrays (MLA) mit 12.000 Mikrolinsen in Bezug auf die Positionierung eines Charge-Coupled Device (CCD) Chips sowie eines Beugungsgitters ange-wendet. Die direkte Integration von Befestigungselementen in das MLA ermöglicht dabei eine ultrakompakte Montage mit einer reduzierten Anzahl von Montagevorgängen. Die Ausrichtung der Spektrallinien auf die CCD-Pixel ermöglicht die Optimierung der Anzahl der auf einem einzigen Chip abgebildeten Spektren. Die Funktionalität des Systems wird demonstriert und stellt eine technologische Verbesserung für eine Vielzahl von Anwendungen dar, die von der Verfüg-barkeit eines solchen Systems in Bezug auf Einfachheit, Kosten, Größe und Gewicht profitieren können. This work describes the development of a micro-integrated multi-spectral imaging system for hyperspectral imaging (HSI). The aim is to employ polymeric optical components to increase integration density and reduce weight while provid-ing improved functionality compared to classical HSI camera systems. Economic advantages of both, simplified assembly by direct integration of mounting features and the ability of mass production of polymer optics are being addressed. An integration strategy into a camera system is developed, providing the required features for micro-assembly of all compo-nents. Methods for micro assembly of a polymeric microlens array (MLA) with 12.000 micro lenses in relation to the positioning of a Charge-Coupled Device (CCD) chip as well as a diffraction grating are applied. The direct integration of mounting features into the MLA allows for ultra-compact assembly with a reduced number of assembly processes. Fur-thermore, it enables the alignment of spectral lines to the CCD pixels, thus optimizing the number of spectra mapped on a single chip. The functionality of system is demonstrated, presenting a technological improvement for a large variety of applications, which may profit from the availability of such a system in terms of simplicity, costs, size and weight.

Zusammenfassung

Most accelerometers today are based on the capacitive principle. However, further miniaturization for micro integration of those sensors leads to a poorer signal-to-noise ratio due to a small total area of the capacitor plates. Thus, other transducer principles should be taken into account to develop smaller sensors. This paper presents the development and realization of a miniaturized accelerometer based on the tunneling effect, whereas its highly sensitive effect regarding the tunneling distance is used to detect small deflections in the range of sub-nm. The spring-mass-system is manufactured by a surface micro-machining foundry process. The area of the shown polysilicon (PolySi) sensor structures has a size smaller than 100 µm × 50 µm (L × W). The tunneling electrodes are placed and patterned by a focused ion beam (FIB) and gas injection system (GIS) with MeCpPtMe3 as a precursor. A dual-beam system enables maximum flexibility for post-processing of the spring-mass-system and patterning of sharp tips with radii in the range of a few nm and initial distances between the electrodes of about 30–300 nm. The use of metal–organic precursor material platinum carbon (PtC) limits the tunneling currents to about 150 pA due to the high inherent resistance. The measuring range is set to 20 g. The sensitivity of the sensor signal, which depends exponentially on the electrode distance due to the tunneling effect, ranges from 0.4 pA/g at 0 g in the sensor operational point up to 20.9 pA/g at 20 g. The acceleration-equivalent thermal noise amplitude is calculated to be 2.4–3.4 mg/Hz. Electrostatic actuators are used to lead the electrodes in distances where direct quantum tunneling occurs.

Zusammenfassung

To realize quantum tunneling applications with movable electrodes, sharp tips with radii down to several tens of nanometers are necessary. The use of a focused ion beam (FIB) and focused electron beam (FEB) with a gas injection system (GIS) allows the integration of geometries in the nanoscale directly into micro and nano systems. However, the implementation of the tunneling effect clearly depends on the material. In this work, a metal-organic precursor is used. The investigation of the prepared tunneling electrodes enables an insight into FIB/FEB parameters for the realization of quantum tunneling applications. For this purpose, a high-resolution transmission electron microscopy (HRTEM) analysis is performed. The results show a dependence of the material nanostructure regarding platinum (Pt) grain size and distribution in an amorphous carbon matrix from the used beam and the FIB currents. The integration of the tips into a polysilicon (PolySi) beam and measuring the current signal by approaching the tips show significant differences in the results. Moreover, the approach of FEB tips shows a non-contact behavior even when the tips are squeezed together. The contact behavior depends on the grain size, proportion of platinum, and the amount of amorphous carbon in the microstructure, especially at the edge area of the tips. This study shows significant differences in the nanostructure between FIB and FEB tips, particularly for the FIB tips: The higher the ion current, the greater the platinum content, the finer the grain size, and the higher the probability of a tunneling current by approaching the tips.

Zusammenfassung

Electronic devices and their associated sensors are exposed to increasing mechanical, thermal and chemical stress in modern applications. In many areas of application, the electronics are completely encapsulated with thermosets in a single process step using injection molding technology, especially with epoxy molding compounds (EMC). The implementation of the connection of complete systems for electrical access through a thermoset encapsulation is of particular importance. In practice, metal pin contacts are used for this purpose, which are encapsulated together with the complete system in a single injection molding process step. However, this procedure contains challenges because the interface between the metallic pins and the plastic represents a weak point for reliability. In order to investigate the reliability of the interface, in this study, metallic pin contacts made of copper-nickel-tin alloy (CuNiSn) and bronze (CuSn6) are encapsulated with standard EMC materials. The metal surfaces made of CuNiSn are further coated with silver (Ag) and tin (Sn). An injection molding tool to produce test specimens is designed and manufactured according to the design rules of EMC processing. The reliability of the metal-plastic interfaces are investigated by means of shear and leak tests. The results of the investigations show that the reliability of the metal-plastic joints can be increased by using different material combinations.

Zusammenfassung

Geräteelektronik und dazugehörige Sensoren sind in modernen Anwendungen steigender mechanischer, thermischer und chemischer Beanspruchung ausgesetzt. Dabei werden die Elektroniken in vielen Anwendungsbereichen mit Duroplasten, im Speziellen mit Epoxidharzformmassen (Epoxy Moulding Compounds, EMC), in einem Prozessschritt mit dem Spritzgussverfahren vollständig verkapselt. Die Umsetzung der Ankontaktierung der Gesamtsysteme für den elektrischen Zugang von außen ins Innere einer Duroplastverkapselung ist von besonderer Bedeutung. In der Praxis kommen hierfür meist metallische Steckerkontakte zum Einsatz, die als Teilbereich eines Gesamtsystems im Spritzgussverfahren mit Kunststoff verkapselt werden. Jedoch bringt diese Vorgehensweise Herausforderungen mit sich, da die Schnittstelle zwischen den metallischen Steckerkontakten und dem Kunststoff eine Schwachstelle für die Zuverlässigkeit darstellt. So wurden im Rahmen der Untersuchungen metallische Steckerkontakte aus Kupfer-Nickel-Zinn-Legierung (CuNiSn) und Bronze (CuSn6) verwendet. Die Steckerkontakte aus CuNiSn wurden weiterführend mit Silber (Ag) und Zinn (Sn) beschichtet. Für die Abmusterung des Metall-Kunststoff-Verbundes wurde ein Spritzgusswerkzeug nach den Designregeln der EMC-Verarbeitung ausgelegt und hergestellt. Die Untersuchungen zur Zuverlässigkeit des Metall-Kunststoff-Verbundes erfolgte mittels Scherversuchen und Dichtheitsprüfung. Die Ergebnisse der Untersuchungen zeigen, dass durch den Einsatz verschiedener Materialkombinationen die Zuverlässigkeit der Metall-Kunststoff-Verbindungen erhöht werden kann.

Zusammenfassung

Molding techniques allow the replication of surface structures to enable improved or novel functions for optics, fluidics and further applications. In general, the molding process can be facilitated by means of antiadhesive-coated molds due to a reduction of demolding forces, wear or prevention of heat dissipation. Consequently, employing coated molds, an improved demolding of features with submicron dimensions and high aspect ratio can be expected. In order to achieve adequate results regarding the replication of nanostructures, accurate mastering techniques to structure the coating are required. One possible technique is focused ion beam (FIB) writing, which was investigated in this study regarding its suitability to mill structured surfaces of submicron dimensions into coated mold inserts. Mold inserts were coated with a thin-film diamond-like carbon (DLC) and chromium nitride (CrN) as well as electroless plated nickel-phosphorus (NiP). The coatings were examined by means of SEM imaging and roughness measurements regarding their applicability for the creation of nanostructures. Subsequently, a test pattern was written into the coatings using a FIB-SEM dual beam system. The test pattern consisted of the USAF test chart target groups 9, 10 and a Siemens star. The lateral dimensions were ≤ 980 nm. During ion beam milling, the beam parameters current and the number of scan repetitions were varied to investigate their influence on the structuring result. Subsequently, SEM measurements were conducted to characterize the milled nanostructures. Different lateral resolutions and depths of the pattern and effects like redeposition or the proximity effect were observed for the nanostructures depending on the coating and processing conditions. Lateral feature sizes down to 60 nm could be realized. In conclusion, the gained results approved FIB writing as a suitable technique to manufacture highly precise nanostructures into surface coatings for molding.

Zusammenfassung

Die Herstellung von dreidimensionalen Schaltungsträgern aus spritzgegossenen Thermoplasten, welche mittels Laserdirektstrukturierung und anschließender außenstromloser selektiver Metallisierung funktionalisiert werden, ist mittlerweile Stand der Technik. Bei erhöhter thermischer und/oder mechanischer Belastung z.B. durch Steigerung der elektrischen Leistungsdichte, stoßen Thermoplaste jedoch an ihre Grenzen. Hier bieten keramische Substratmaterialien klare Vorteile. Die Herstellung von solchen keramischen Schaltungsträgern mittels laserinduzierter Direktmetallisierung wurde erfolgreich realisiert. Hierfür wurden zwei Unterschiedliche Varianten an Al2O3-Keramiken untersucht. In der ersten Variante erfolgte das Sintern der Al2O3-Keramiken in H2-Atmosphäre, in Variante 2 wurden die Al2O3-Keramiken mit Cr2O3 dotiert und an Luft gesintert. Anschließend erfolgte für beide Varianten eine Laserstrukturierung mit darauffolgender außenstromloser Metallisierung. Somit ließen sich 3D-Schaltungsträger mit hoher thermischer Belastbarkeit, einer geringen Wärmeausdehnung und einer guten elektrischen Isolation herstellen. Die abgeschiedenen Metallschichten zeigten vergleichbare und zum Teil bessere Eigenschaften als solche auf klassischen thermoplastischen 3D-Schaltungsträgern. Three-dimensional interconnect devices based on injection molded thermoplastics, which are laser direct structured and subsequently plated via selective electroless metallization are meanwhile the state-of-the-art. With increased thermal and or mechanical load, e.g. at high electric power densities, ceramic materials show superior properties compared to thermoplastic materials. The fabrication of ceramic interconnect devices based on laser-induced metallization has been successfully demonstrated. Therefore, Al2O3 has been used, which was either sintered in H2-atmosphere or doped with Cr2O3 and sintered in air, followed by laser structuring and electroless metallization. Thereby, 3D interconnect devices with high thermal robustness, low thermal expansion and good electric isolation could be manufactured. The metallization on ceramics showed similar or even better properties than on conventional thermoplastic substrates.

Zusammenfassung

Essential quality features of pressure sensors are, among other accuracy-related factors, measurement range, operating temperature, and long-term stability. In this work, these features are optimized for a capacitive pressure sensor with a measurement range of 10 bars. The sensor consists of a metal membrane, which is connected to a PCB and a digital capacitive readout. To optimize the performance, different methods for the joining process are studied. Transient liquid phase bonding (TLP bonding), reactive joining, silver sintering, and electric resistance welding are compared by measurements of the characteristic curves and long-term measurements at maximum pressure. A scanning electron microscope (SEM) with energy-dispersive X-ray spectroscopy (EDX) analysis was used to examine the quality of the joints. The evaluation of the characteristic curves shows the smallest measurement errors for TLP bonding and sintering. For welding and sintering, no statistically significant long-term drift was measured. In terms of equipment costs, reactive joining and sintering are most favorable. With low material costs and short process times, electric resistance welding offers ideal conditions for mass production.

Zusammenfassung

In this paper, a fluidic capacitive inclination sensor is presented and compared to three types of silicon-based microelectromechanical system (MEMS) accelerometers. MEMS accelerometers are commonly used for tilt measurement. They can only be manufactured by large companies with clean-room technology due to the high requirements during assembly. In contrast, the fluidic sensor can be produced by small- and medium-sized enterprises (SMEs) as well, since only surface mount technologies (SMT) are required. Three different variants of the fluidic sensor were investigated. Two variants using stacked printed circuit boards (PCBs) and one variant with 3D-molded interconnect devices (MIDs) to form the sensor element are presented. Allan deviation, non-repeatability, hysteresis, and offset temperature stability were measured to compare the sensors. Within the fluidic sensors, the PCB variant with two sensor cavities performed best regarding all the measurement results except non-repeatability. Regarding bias stability, white noise, which was determined from the Allan deviation, and hysteresis, the fluidic sensors outperformed the MEMS-based sensors. The accelerometer Analog Devices ADXL355 offers slightly better results regarding offset temperature stability and non-repeatability. The MEMS sensors Bosch BMA280 and TDK InvenSense MPU6500 do not match the performance of fluidic sensors in any category. Their advantages are the favorable price and the smaller package. From the investigations, it can be concluded that the fluidic sensor is competitive in the targeted price range, especially for applications with extended requirements regarding bias stability, noise, and hysteresis.

Zusammenfassung

The project “key enabling technologies for clean production” (KET4CP), which is supported by the European Commission, has the aim to connect small and medium-sized enterprises (SME) and Technology Centres (TC) for cleaner, greener and more efficient production. Within this context, SMEs and TCs across Europe work together to establish an open-innovation network and to raise awareness in productivity and environmental performance. This article presents how an open European network of TCs opens its innovation process to support SMEs to become cleaner, greener and more efficient. Furthermore, this article shows how the TCs and SMEs become a part of the open-eco-innovation platform in clean production and how successful the open-eco-innovation process of different European countries is. We revealed that a pan-European open innovation process for eco-innovations with TCs for key enabling technologies (KET TCs) and Enterprise Europe Network partners (EEN) is a successful approach for SMEs that want to produce and develop cleaner products. An application example is mentioned, in which TCs from different European countries have contributed to developing a product of a SME for energy harvesting. The SME, together with the TCs, developed a generator that is installed in city-level water supply pipes and so, it is outstanding in its application. This innovative application is also described in this article.

Zusammenfassung

Thermoset materials offer a multitude of advantageous properties in terms of shrinkage and warpage as well as mechanical, thermal and chemical stability compared to thermoplastic materials. Thanks to these properties, thermosets are commonly used to encapsulate electronic components on a 2nd-level packaging prior to assembly by reflow soldering on printed circuits boards or other substrates. Based on the characteristics of thermosets to develop a distinct skin effect due to segregation during the molding process, the surface properties of injection molded thermoset components resemble optical characteristics. Within this study, molding parameters for thermoset components are analyzed in order to optimize the surface quality of injection molded thermoset components. Perspectively, in combination with a reflective coating by e.g., physical vapor deposition, such elements with micro-integrated reflective optical features can be used as optoelectronic components, which can be processed at medium-ranged temperatures up to 230 °C. The obtained results indicate the general feasibility since Ra values of 60 nm and below can be achieved. The main influencing parameters on surface quality were identified as the composition of filler materials and tool temperature.

Zusammenfassung

Hermeticity of an electronic package defines its effectiveness to seal and protect the encapsulated electronics from the ingress of contaminants, gases, and moisture, as well as helping avoid toxic materials from inside the capsule contacting tissue. Using accelerated testing by methods of leak detection analysis, the theoretical limit of the lifetime due to water ingress of an encapsulated device can be estimated. However, classical methods are not sufficient for microencapsulations and exhibit limitations due to the resolution of the detection mechanisms required for such small cavities. With the availability of cumulative helium leak detection (CHLD), the detection limits can be extended by several magnitudes of resolution. However, limitations due to the physics of leakage apply. This article discusses the limitations concerning the ability for combined gross and fine leak testing in combination with outgassing effects using CHLD for miniaturized implantable medical devices. Practical aspects are evaluated regarding the applicability of CHLD for such microencapsulations at the example of an AuSn-sealed alumina package.

Zusammenfassung

A drastically growing requirement of electronic packages with an increasing level of complexity poses newer challenges for the competitive manufacturing industry. Coupled with harsher operating conditions, these challenges affirm the need for encapsulated board-level (2nd level) packages. To reduce thermo-mechanical loads induced on the electronic components during operating cycles, a conformal type of encapsulation is gaining preference over conventional glob-tops or resin casting types. The availability of technology, the ease of automation, and the uncomplicated storage of raw material intensifies the implementation of thermoset injection molding for the encapsulation process of board-level packages. Reliability case studies of such encapsulated electronic components as a part of board-level packages become, thereupon, necessary. This paper presents the reliability study of exemplary electronic components, surface-mounted on printed circuit boards (PCBs), encapsulated by the means of thermoset injection molding, and subjected to cyclic thermal loading. The characteristic lifetime of the electronic components is statistically calculated after assessing the probability plots and presented consequently. A few points of conclusion are summarized, and the future scope is discussed at the end.

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We demonstrate mass production compatible fabrication of polymer-based micro Fresnel lenses by injection compression molding. The extremely robust titanium-molding tool is structured with high precision by focused ion beam milling. In order to achieve optimal shape accuracy in the titanium we use an iterative design optimization. The inverse Fresnel lens structured into the titanium is transferred to polymers by injection compression molding, enabling rapid mass replication. We show that the optical performance of the molded diffractive Fresnel lenses is in good agreement with simulations, rendering our approach suitable for applications that require compact and high-quality optical elements in large numbers.

Zusammenfassung

An ever-growing market demand for board (second) level packages (e.g., embedded systems, system-on-a-chip, etc.) poses newer challenges for its manufacturing industry in terms of competitive pricing, higher reliability, and overall dimensions. Such packages are encapsulated for various reasons including thermal management, protection from environmental conditions and dust particles, and enhancing the mechanical stability. In the due course of reducing overall sizes and material saving, an encapsulation as thin as possible imposes its own significance. Such a thin-walled conformal encapsulation serves as an added advantage by reducing the thermo-mechanical stresses occurring due to thermal-cyclic loading, compared to block-sized or thicker encapsulations. This paper assesses the encapsulation process of a board-level package by means of thermoset injection molding. Various aspects reviewed in this paper include the conception of a demonstrator, investigation of the flow simulation of the injection molding process, execution of molding trials with different encapsulation thicknesses, and characterization of the packages. The process shows a high dependence on the substrate properties, injection molding process parameters, device mounting tolerances, and device geometry tolerances. Nevertheless, the thermoset injection molding process is suitable for the encapsulation of board-level packages limiting itself only with respect to the thickness of the encapsulation material, which depends on other external aforementioned factors.

Zusammenfassung

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 (UP-milling). 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.

Zusammenfassung

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.

Zusammenfassung

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.

Zusammenfassung

Micro lens arrays (MLA) are broadly used in a multitude of optical applications, whereas increasingly extended areas need to be structured. Furthermore, growing quantities of microoptical components require micro- and nano-replication techniques, such as injection moulding and injection compression moulding. Therefore, ultra-precision milling strategies for manufacturing of mould inserts have been evaluated regarding applicability, surface quality and processing time. Different milling strategies were investigated regarding processing time and resulting surface quality. Single flute diamond milling tools were used to mill the mould cavities in nickel-phosphorus (NiP) coating deposited on tooling steel. The experiments were conducted on a 5-axis ultra-precision milling machine and qualitative results regarding observed effects of the different strategies were evaluated. The achieved surface qualities were analysed and quantified using white light interferometry. Methods of ring, radial or spiral milling strategies showed different failure modes and shortcomings such as stepping, pin residues or long processing times. Using a method, where a specifically designed milling tool was immersed in a single step into the bulk material, best results were achieved and the processing time for each lens was reduced to a minimum. The quality of the MLA could be further increased by immersing the milling tool in a defined angle. It was observed, that the centering and radius of the diamond of the milling tool was a major factor. Conclusively, the results show that high quality tooling in combination with the applied milling strategy enables significant improvements in quality and costs.

Zusammenfassung

In this work, a polymer microlens array (MLA) for a hyperspectral imaging (HSI) system is produced by means of ultraprecision milling (UP-milling) and injection compression molding. Due to the large number of over 12,000 microlenses on less than 2 cm², the fabrication process is challenging and requires full process control. The study evaluates the process chain and optimizes the single process steps to achieve high quality polymer MLAs. Furthermore, design elements like mounting features are included to facilitate the integration into the final HSI system. The mold insert was produced using ultraprecision milling with a diamond cutting tool. The machining time was optimized to avoid temperature drifts and enable high accuracy. Therefore, single immersions of the diamond tool at a defined angle was used to fabricate each microlens. The MLAs were replicated using injection compression molding. For this process, an injection compression molding tool with moveable frame plate was designed and fabricated. The structured mold insert was used to generate the compression movement, resulting in a homogeneous pressure distribution. The characterization of the MLAs showed high form accuracy of the microlenses and the mounting features. The functionality of the molded optical part could be demonstrated in an HIS system by focusing light spectrums onto a CCD image sensor.

Zusammenfassung

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 micro lens 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 ultraprecision milling (UP-milling). 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.

Zusammenfassung

Polymer optics are widely used in various applications, replacing traditional glass lenses. The ability to create free-form and micro-structured optics, as well as fast replication, gives them major advantages over traditional glass lenses. However, the fabrication of complex optical components requires full process control and understanding of influencing factors on the quality of the polymer optical parts. In this work, a curved diffractive optical element (DOE) is fabricated using injection compression molding. Different gate designs were evaluated and the movement of the compression stamper was optimized to obtain good filling behavior. The process stability was analyzed and improved by controlling the melt temperature precisely. Finally, the molding parameters were optimized, focusing on the mold temperature, melt temperature and compression force. Curved diffractive optical elements were replicated with feature sizes of 1.6 μm. The experiments showed that all aspects of the molding process have to be controlled perfectly to produce complex polymer optics. High mold temperatures and compression force are necessary to replicate micro-structured features. The work presents a broad investigation and description of the fabrication process and their influences.

Zusammenfassung

Packaging represents an important part in the microintegration of sensors based on microelectromechanical system (MEMS). Besides miniaturization and integration density, functionality and reliability in combination with flexibility in packaging design at moderate costs and consequently high-mix, low-volume production are the main requirements for future solutions in packaging. This study investigates possibilities employing printed circuit board (PCB-)based assemblies to provide high flexibility for circuit designs together with film-assisted transfer molding (FAM) to package sensors. The feasibility of FAM in combination with PCB and MEMS as a packaging technology for highly sensitive inertia sensors is being demonstrated. The results prove the technology to be a viable method for damage-free packaging of stress- and pressure-sensitive MEMS.

Zusammenfassung

Cost-effective electronic packaging technology plays a vital role in the manufacturing industry with ever increasing demand for microelectronics and microsystems. The application of thermoset encapsulation of electronic parts offers a wide range of advantages with respect to thermal, mechanical and chemical properties. Transfer Molding, mainly available in the Far East, is dominantly used for the manufacturing of such polymeric packages 2. Thermoset injection molding extends a good scope of advantages over transfer molding like availability in Europe and ease of raw material handling. The implementation of thermoset injection molding for encapsulation of electronic components provides the European small and medium-sized enterprises (SMEs) with access to customized packaging solutions. The feasibility of this implementation is defined and tested in this work.

Zusammenfassung

Micro technology deals with the fabrication of structures in the length scale between 0.1 and 1000 µm and can be considered as an important enabler for micro systems such as miniaturized sensors. Recent advances in micro manufacturing will be demonstrated by examples of microfluidic, optical and mechatronic devices. In the area of microfluidics, the fabrication of centrifugal microfluidics for automated analytics and diagnostics via injection compression molding is addressed. Manufacturing of optical components via micro injection molding and precision assembly of those components will be presented with respect to optical sensors. Molded interconnect devices serve as an example for the manufacturing of mechatronic devices. Apart from manufacturing technologies, the application of simulation methods for the assessment of manufacturability and reliability of the devices will be discussed.

Zusammenfassung

Today's printed electronics are mainly focused on producing sensors on thin, flexible, smooth foils, which limits their use on 2D applications. Within this study we report on the design of inkjet printed capacitive touch and humidity sensors on thermoplastic substrates, to fabricate printed functional structures on injection molded 3D components. Both sensors are based on printed differential interdigital capacitors (IDC) made of silver ink and a printed sensitive layer. Reproducible results and low hysteresis were achieved, proving the concept to be able to improve sensitivity and to reduce drift effects due to temperature as well as moisture absorption by the substrate.