Terms Of Processing Temperature Research Articles

그라비어 인쇄기술을 이용한 페로브스카이트 태양전지 Roll-to-Roll 제작 공정

Perovskite solar cells (PSCs) are attracting attention as a next-generation thin-film solar cell based on their high efficiency. Technologies to commercialize PSCs for power generation and special purposes have been being developed. Since the PSCs are manufactured using a solution process, the development of a roll-to-roll (R2R) process to mass-produce flexible solar cells at low cost can be a stepping stone for commercialization. In order to manufacture high-quality perovskite solar cells through the R2R process, the perovskite material and charge transport materials must be formed in a roll-based continuous and scalable method. Gravure printing has the advantage of being able to directly form patterns on a substrate. The R2R process has limitations that were not considered in the existing sheet-to-sheet process to fabricate unit cells in terms of process temperature, process time, and environmental management. In this paper, we share the current status of R2R gravure printing process development for perovskite solar cells and discuss issues to be considered and problems to be solved during R2R process design.

3D Printing of Functional Metal and Dielectric Composite Meta-Atoms.

In this report, a novel fabrication method, based on casting Field's metal inside dielectric molds made via fused deposition modeling, is presented. Fused deposition modeling (FDM) has become one of the most common rapid prototyping methods. Whilst it generally produces good quality mechanical structures in thermoplastics, few reliable methods have been demonstrated that produce good quality 3D electrically conductive structures. By using Field's metal to transform dielectric molds into conductive structures, nearly any continuous metal geometry buried within the polymer can be created, allowing for the realization of complex 3D architectures. A wide range of thermoplastic materials used in fused deposition modeling have been investigated, to identify the best candidates in terms of processing temperature, relative permittivity, and loss tangent. Experimental measurements and X-ray computer tomography scans are used to determine the quality of structures fabricated using this method. Based on these findings, functional metamaterials devices operating at 600-700 MHz with high Q-factors have been produced. This method shows potential to be incorporated into standard FDM setups and could be utilized for the fabrication of curved and 3Dgeometries.

The Effect of Strain Rate and Initial Grain Size on Deformation Behavior of OFHC Copper at Elevated Temperatures

Understanding of plastic deformation mechanisms and/or microstructural changes of metals and alloys at elevated temperatures makes possible to control their hot working behavior and final mechanical properties. The aim of the present work is to optimize the conditions to achieve maximum ductility in terms of initial grain size, process temperature and deformation rate. In this study, the OFHC (oxygen-free high conductivity) copper samples of different initial grain sizes (25, 50, 100 and 150 μm) were subjected to tensile tests at temperatures 300, 405, 500 and 700 °C (0.42 - 0.75 Tm) and cross-head speeds of 1, 2, 5, 10, 20 and 50 mm/min (strain rates of 5.6x10-4 - 2.8x10-2 s-1). Experimental results indicated that particular conditions (initial grain size of 50 µm; 700 °C of working temperature and 5.6x10-3 s-1 of strain rate) should be provided in terms of process temperature and deformation rate depending upon initial grain size for dynamic recrystallization and also maximum ductility.

Electrochemical conversion of oxide spinels into high-entropy alloy

Single-phase equiatomic CoCrFeNi high-entropy alloy has been synthesised by direct electrochemical reduction from oxide precursors according to the concept of the FFC-Cambridge process. Metal oxide mixtures were heat treated in air to provide a blend of spinels, which was then employed as the cathode in the electro-deoxidation process. Melts of eutectic CaCl2-NaCl and pure CaCl2 were used as the electrolytes. Varying the experimental conditions in terms of processing temperature and time yielded CoCrFeNi alloys of diverse morphologies, ranging from fine dispersed powders to solid three-dimensional objects, as they are of relevance for additive manufacturing and near-net-shape fabrication. Notably, all solid alloy samples exhibited a higher hardness than calculated by the rule of mixture, despite the presence of significant residual porosity. The results highlight the versatility of the FFC-Cambridge process for alloy preparation and suggest the possibility of economically viable large-scale manufacture of steel-type high-entropy alloys.

Design and fabrication of MEMS-type compliant overhang flip-chip interconnect for RF applications

With the increase of I/O density and scaling of interconnects, conventional solder ball interconnects are required to be made smaller. As a result, the reliability of the conventional solder ball flip-chip interconnects worsens. One method to mitigate this issue is by using underfill. However, underfill undermines the reworkability of the solder joints and is challenging to apply when the gap between chip and substrate is small. Another approach to enhance the reliability is to use taller solder ball interconnects, which is however usually more costly. Instead of using conventional solder ball interconnects, compliant interconnects have also been researched in the past few decades to mitigate the reliability issue. The use of compliant structures can compensate for the coefficient of thermal expansion (CTE) mismatch between a Si chip and an organic substrate. In this work, we present the design and fabrication of MEMS-type compliant overhang flip-chip interconnects. The structures are placed at the end of a coplanar waveguide (CPW) as interconnects between CPWs to research their performance at radio frequency (RF). A micro-fabrication process was adopted to build the interconnects. The CPWs are fabricated using conventional e-beam deposition followed by photolithography and then copper electroplating. The compliant overhangs were fabricated on top of a dome of reflowed photoresist on the CPWs to form a curved shape. The reflow and hard bake of the photoresist requires a process temperature of above 220 °C, which is similar to the reflow temperature of a Sn-Ag-Cu (SAC) solder. Therefore we believe our process is compatible with SAC solder processing infrastructures in terms of process temperature. The fabricated structures show high yield and uniformity. Due to the use of a micro-fabrication based process, the structures have the potential to be scaled and be compatible to wafer level packaging. The CPWs were then flip-chip bonded with the compliant interconnect as transitions. The RF performance of the interconnects up to 50 GHz will be presented.

Silicon Migration from High‐barrier Coated Multilayer Polymeric Films to Selected Food Simulants after Microwave Processing Treatments

The use of microwave (MW) technology for in‐package food sterilization and pasteurization has the potential for widespread use in the food industry. Because the use of MW technology requires that food be processed inside its packaging, the interaction between food and its packaging during processing must be studied to ensure package integrity as well as consumer safety. In this study, two commercially available multilayer films developed for retort sterilization were evaluated for their suitability to MW processing. Film A was composed of oriented nylon//coated polyethylene terephthalate//cast polypropylene (CPP); film B consisted of oriented nylon//coated nylon//CPP with overall oxygen transmission rates <0.2 cc/m2. day. Silicon (Si) was a major component in the coated polyethylene terephthalate layer and food‐contact CPP layer. This study evaluated the influence of MW processing on Si migration from films into selected food‐simulating liquids (FSLs; water and 3% acetic acid) using inductively coupled plasma‐mass spectroscopy, as compared with conventional thermal processing. This study also assessed migration of Si into FSL in terms of process temperature (70–123 °C) and time (18–34 min). A Fourier transform infrared spectrometer was used to evaluate the stability of the silicon–oxygen (Si–O) bonds in the metal‐oxide coated and food‐contact layer of the packaging film. Overall, there were no significant differences (p > 0.05) between the level of Si migration from films to FSL and the stability of Si–O–Si bonds during MW processing as compared with the conventional thermal processing. However, we found that the final processing temperature and time had a significant (p < 0.05) impact on Si migration into the FSL. Copyright © 2013 John Wiley & Sons, Ltd.

CMOS: compatible wafer bonding for MEMS and wafer-level 3D integration

Wafer bonding became during past decade an important technology for MEMS manufacturing and wafer-level 3D integration applications. The increased complexity of the MEMS devices brings new challenges to the processing techniques. In MEMS manufacturing wafer bonding can be used for integration of the electronic components (e.g. CMOS circuitries) with the mechanical (e.g. resonators) or optical components (e.g. waveguides, mirrors) in a single, wafer-level process step. However, wafer bonding with CMOS wafers brings additional challenges due to very strict requirements in terms of process temperature and contamination. These challenges were identified and wafer bonding process solutions will be presented illustrated with examples.

Henry Granjon Prize Competition 2009 Winner Category A: “Joining and Fabrication Technology” Friction Riveting: development and analysis of a new joining technique for polymer-metal multi-material structures

The Friction Riveting (FricRiveting) technique is a new alternative spot joining process developed for polymer-metal multi-materials structures. In the technique, a cylindrical metallic rivet is used to join one or more thermoplastic-metal components by means of plasticizing and deforming the tip of the rotating rivet through frictional heating. Advantages of this new technique are short joining cycles, minimal sample preparation and absence of environmental emissions. Friction riveted joints have enhanced mechanical performance. This study demonstrates the feasibility of FricRiveting by analyzing a case-study joint on polyetherimide/aluminium alloys. Sound joints on polyetherimide/aluminium 2024-T351 with elevated mechanical strength (up to 93% of the rivet strength) were successfully produced and characterized in terms of process temperature, microhardness and microstructure.

Optimized rapid thermal process for high efficiency silicon solar cells

Rapid thermal processing is opening new possibilities for a low-cost and environmentally safe silicon solar cell production, keeping the process time at high temperature in the order of 1 min, due to enhanced diffusion and oxidation mechanisms. Controlling the surface concentration of the junction is one of the major parameters, in order to obtain suitable front surface recombination velocities. Simultaneous diffusion of phosphorus and aluminum is used to realize emitter and back surface field in a single high-temperature step, with optimized gettering effect. Controlling the mentioned parameters on industrial 1 Ω cm Cz material lead in 17.5% efficient solar cells on a surface of 25 cm 2. All results are discussed in terms of process temperature, dopant source concentration and effective process time, below 1 min including high heating and cooling rates.

Competition between gas phase and surface oxidation of TiCl 4 during synthesis of TiO 2 particles

The effect of TiCl 4 surface reaction on the size of product TiO 2 particles is quantitatively investigated over a wide range of process conditions (temperature and reactant concentration) that are typically employed in industrial and research facilities. A model for titania aerosol dynamics is developed accounting for the simultaneous gas phase and particle phase (surface) oxidation rate of TiCl 4. Using this model, the implications of these two chemical pathways on the size of product titania particles are elucidated. It is shown, for the first time, that TiCl 4 oxidation on the surface of freshly formed titania particles is most important at high TiCl 4 concentrations. A design diagram is presented mapping the significance of surface and gas-phase oxidation of TiCl 4 in terms of process temperature and initial TiCl 4 mole fraction. The model predictions are compared with experimental results and conflicting interpretations of the mechanism of titania formation by TiCl 4 oxidation in the literature are reconciled. This model can be used to investigate the significance of surface growth in gas-phase synthesis of fumed silica as well as other ceramic and metallic particles.

Plasma-assisted chemical vapour deposition of tin oxide coatings

A feasibility study was performed to assess the potential of plasma-assisted chemical vapour deposition as a method for the coating of carbon fibre bundles. Rayon-based carbon filaments, in 2000-filament tows, were coated with SnO2. Direct-current and hollow-cathode discharges generated in an SnCl4-O2 medium helped to deposit the SnO2 coatings on fibres that were heated to approximately 800°C, by plasma bombardment, and kept in the plasma for 15 min. Both routes were shown to produce uniform and well adhered coatings, and also to offer advantages in terms of processing temperature and the possibility of continuous processing.