In-line Capability Research Articles

Using Magnetic Field Analysis for Localizing Defects of Fuel Cell & Electrolyzer Components

Production capacities of electrolysis and fuel cell technologies are expected to increase significantly in the upcoming years, reducing costs of stack components through numbering-up. To ensure reliability and durability and reduce costs along the manufacturing process, developing suitable in-line non-destructive diagnostic methods for quality control becomes essential for their industrialization.In both fuel cell and electrolyzer stacks, the main components' electrical resistance and current density distribution greatly influence stack efficiency and longevity. Here, the flowing electric current generates a magnetic field depending on its strength and direction. Potential defects caused by the manufacturing process, including cracks, defective welding spots, coating adhesion issues, delamination, and contamination, influence the components' electric conductivity and current density distribution and hence the magnetic field distribution.This work investigates non-destructive diagnostic methods using magnetic field analysis (MFA) to identify changes in the magnetic field distribution and, thus, local electrical resistance and current density distributions of fuel cell and electrolyzer components. The methods used are magnetic field imaging (MFI) and Eddy Current Testing (ECT). MFI analyzes the magnetic field distribution in all three spatial directions to trace electrical currents and identify electrical defects, creating a magnetic field signature that can potentially distinguish between functional and non-functional components along the manufacturing process. ECT measures variations in local conductivity by inducing eddy currents in the sample through an alternating magnetic field generated by a sender coil. These eddy currents create a detectable magnetic field in a receiver and are affected by defects and changes in electrical conductivity. Therefore, the method can characterize sheet resistance and material homogeneity through electrical anisotropy in electrically conductive components.In initial experiments, ECT measurements on coated and uncoated hollow embossed stainless steel bipolar half plates showed systematic differences depending on quality characteristics resulting in unique patterns and inhomogeneities which require further investigation. Furthermore, experiments with both methods on other stack components will be presented and discussed. In addition, their in-line capability will be assessed and evaluated. However, these first promising results imply that MFA is potentially useful as an in-line, non-destructive diagnostic method for quality control.

In-Operando Detection Method for Lithium Metal Deposition during Fast Charging of Lithium-Ion Batteries Derived from Impedance Modeling

Lithium-ion batteries play a key role in the electrification of the transport sector. However, to replace combustion engines with battery-powered electric drive trains, the fast charging capability is essential. Therefore, it is necessary to identify the optimum operating window for lithium-ion cells. A strict criterion for optimization is to prevent lithium metal deposition at the anode, as this undesired side reaction can pose serious safety risks. An efficient technique to optimize charging strategies while tracking lithium plating is needed, as existing approaches have limitations such as a lack of in-line capability, low time precision, or complex experimental setups. In this study, a simple lithium metal deposition detection method is derived from a three-electrode setup. This in-operando method is applied during fast charging using dynamic electrochemical impedance spectroscopy. To model the acquired impedance spectra, a novel equivalent circuit is developed. The model is used to elucidate characteristic impedance features of anodes with deposited lithium metal. These observed characteristic features are then applied to a simplified measurement method in full cells using a single-frequency signal. The precision and high temporal resolution of both methods are demonstrated through validation. Furthermore, the simplified method can be applied in in-operando applications, making it suitable for diverse research and industrial contexts.

Current-voltage characteristics of silicon solar cells: Determination of base doping concentration and hysteresis correction

The measurement of the current-voltage ( IV ) characteristics is the most important step for quality control and optimization of the fabrication process in research and industrial production of silicon solar cells. The occurrence of transient errors and hysteresis effects in IV -measurements can hamper the direct analysis of the IV -data of high-capacitance silicon solar cells. We propose a novel procedure to reconstruct a quasi-steady-state (qss) IV -characteristics from hysteretic measurements by aligning the generalized current density of forward and backward sweeps. In the process, the base doping concentration N B and the cell thickness d are used as optimization parameters and calculated alongside the qss- IV -curve. We summarize the theory behind the method, describe the experimental implementation and verify the applicability of the approach by comparing the extracted doping concentration to multiple alternative methods. For a test set of more than 100 silicon heterojunction solar cells with doping concentrations between 3 and 7∙10 15 cm -3 a RMSD <3.4∙10 14 cm -3 is achieved. Basic parameter extraction from the qss- IV -curve closely match reference values with a RMSD <0.1 % abs in efficiency and fill factor. • Procedure for hysteresis correction proposed and analyzed. • Successful alignment of hysteretic forward and backward IV -curves. • Base doping concentration, resistivity and cell thickness extracted from hysteresis. • Inline capability at high accuracy without additional hardware demonstrated. • Procedure retroactively applicable to existing data to correct transient errors.

Tilt- and warpage measurement as inline quality assessment tool

The tilt of semiconductor dies is a common issue during assembly in power electronics as, e.g. die bonding during silver sintering caused by inhomogeneous thicknesses of applied die-attach material, problems with a homogeneous force application, uneven substrates etc. This tilt usually leads to reliability problems later during testing or operation in the field. A weakly sintered layer will be formed with voids larger than 1–2 μm in major numbers and more importantly will lead to insignificantly developed interfaces. None of them can be detected by SoA failure analytical techniques like scanning acoustic microscopy (SAM) or pulsed infrared thermography (PIRT), since both will still provide a sufficient phonon coupling, indistinguishable to well sintered layers. However, the undetected weak interfaces will lead to severe reliability problems and can only be detected indirectly by thickness measurement without a cross section. In this work, we present a scanning system based on confocal polychromatic distance sensors, which can scan a fully loaded tray of bonded dies on the substrate for industry-grade inline integration. We demonstrate the novel system on different bonded power dies on active metal braze substrate (AMB) under industrial production conditions. We achieve this in the required accuracy of about 2–3 μm in an environment with strong vibration influence. The in-line capability has been proven by using a setup, which is independent of mechanical vibrations and uses only optical fibers to transfer measuring signals within future smart production environments.

Results of a Multicenter Feasibility Study of an Automated Bedside Glucose Monitoring System in the Burn Intensive Care Setting.

Intensive blood glucose regimens required for tight glycemic control in critically ill burn patients carry risk of hypoglycemia and are ultimately limited by the frequency of which serum glucose measurements can be feasibly monitored. Continuous inline glucose monitoring has the potential to significantly increase the frequency of serum glucose measurement. The objective of this study was to assess the accuracy of a continuous glucose monitor with inline capability (Optiscanner) in the burn intensive care setting. A multicenter, observational study was conducted at two academic burn centers. One hundred and six paired blood samples were collected from 10 patients and measured on the Optiscanner and the Yellow Springs Instrument. Values were plotted on a Clarke Error Grid and mean absolute relative difference calculated. Treatment was guided by existing hospital protocols using separately obtained values. 97.2% of results obtained from Optiscanner were within 25% of corresponding Yellow Springs Instrument values and 100% were within 30%. Mean absolute relative difference was calculated at 9.6%. Our findings suggest that a continuous glucose monitor with inline capability provides accurate blood glucose measurements among critically ill burn patients.

Design Considerations to Realize Differential Absorption-Based Optofluidic Sensors for Determination of Ionic Content in Water

Integrated optofluidic absorption spectroscopy has the potential to be used in the real-time identification and quantification of ionic content in drinking water. Such an approach requires single mode operation in combination with low propagation and bend losses. The design criteria for the realization of an integrated near-infrared sensor platform fabricated using silicon waveguide-based technology is presented. The cross section of TriPleX waveguides was optimized for a spectral region between 940 and 1040 nm. The waveguide structure provides single mode operation, high sensitivity combined with reasonable tolerance for fabrication deviations, and $500~\mu \text{m}$ . The optimum sensing length on chip was determined for propagation losses of 0.1, 0.5, and 1.5 dB/cm. Furthermore, a $\Xi $ coupler was designed for the spectral region of interest (0.94– $1.04~\mu \text{m}$ ). Multiple integrated photonic circuit layouts varying in functionality and complexity are reviewed. These optofluidic absorption sensors offer in situ and in-line capabilities, potentially low cost, remote signal data processing, and mechanical and thermal stability. This paper provides a roadmap for maximizing the sensitivity of broadband spectroscopy using differential absorbance.

Recent Advances and Applications of External Cavity-QCLs towards Hyperspectral Imaging for Standoff Detection and Real-Time Spectroscopic Sensing of Chemicals

External-cavity quantum cascade lasers (EC-QCL) are now established as versatile wavelength-tunable light sources for analytical spectroscopy in the mid-infrared (MIR) spectral range. We report on the realization of rapid broadband spectral tuning with kHz scan rates by combining a QCL chip with a broad gain spectrum and a resonantly driven micro-opto-electro-mechanical (MOEMS) scanner with an integrated diffraction grating in Littrow configuration. The capability for real-time spectroscopic sensing based on MOEMS EC-QCLs is demonstrated by transmission measurements performed on polystyrene reference absorber sheets, as well as on hazardous substances, such as explosives. Furthermore, different applications for the EC-QCL technology in spectroscopic sensing are presented. These include the fields of process analysis with on- or even inline capability and imaging backscattering spectroscopy for contactless identification of solid and liquid contaminations on surfaces. Recent progress in trace detection of explosives and related precursors in relevant environments as well as advances in food quality monitoring by discriminating fresh and mold contaminated peanuts based on their MIR backscattering spectrum is shown.

Automated and Cycle Time Optimized Path Planning for Robot-Based Inspection Systems

Robot-based inspection systems, consisting of a standard industrial robot and an optical 3D sensor, increasingly gain importance within production in order to quantify the quality of products. These systems show advantages in terms of costs, flexibility and in-line capability. Based on the inspection plan of a product, the robot path for the inspection system is currently planned manually which is a very time consuming process. Consequently, an automated path planning algorithm generating a time optimized and collision-free path would improve the flexibility of robot-based inspection systems. The presented approach shows an automated and cycle time optimized path planning algorithm for robot-based inspection systems. This is realized by the probabilistic roadmap method applied on all measurement poses in combination with the A* search algorithm for the determination of weighted paths. Finally, the optimization of the path is reduced to a traveling salesman problem which is solved by the Christofides heuristic.

Techniques for Measuring Warpage of Chip Packages, PWBs, and PWB Assemblies

One of the crucial factors for the thermo-mechanical reliability of electronic packages is warpage that occurs during the printed wiring board (PWB) fabrication, solder masking and solder reflow processes. As the quality and reliability requirements of electronic components (packages) become higher, warpage control becomes a more crucial process during the PWB fabrication (manufacturing) and package assembly processes. The warpage of PWBs, PWB assemblies and electronic packages are measured by various techniques. Each technique has both its advantages and disadvantages; therefore the choice of a particular technique depends on whether one wants to measure the warpage of a PWB, PWB assembly or chip package. This paper reviews the pros and cons, such as resolution, speed, costs, accuracy, in-line capability, flexibility, and robustness, of different techniques used for measuring the warpage of chip packages, PWBs and PWB assemblies.

Particle characterisation in highly concentrated dispersions using ultrasonic backscattering method

Determining particle size and concentration in highly concentrated suspensions and emulsions is challenging, especially under process conditions. In general, ultrasound therefore can be used for particle characterisation due to the ability of sound waves to pass opaque dispersions, whereas optical detection principles mostly are limited to low particulate contents. An established acoustic method, the ultrasonic attenuation spectroscopy, uses a transmission setup for measuring the attenuation of a dispersion. A major drawback of this measurement method is caused by the fact, that the measuring gap tends to plug, which again limits the inline capability. To overcome this limitation, an ultrasonic reflection setup is used for gathering the sound waves, which are reflected, respectively backscattered by the dispersion. Statistically analysing the corresponding backscattering signal yields the sound attenuation as well as a scattering intensity equivalent. Both measurement parameters can be shown to be sensitive against particle size and concentration. Based on a single scattering theory, a semi-empirical approach is presented for interpretation of measurement results with respect to particle size and concentration. Measurements, performed on a glass beads in water dispersion, show good agreement with theory for dimensionless wave number 0.1<ka⩽1, even for concentrations up to 30vol.%.

Guided wave approach for inline photovoltaic module component inspection

Reliability of photovoltaic modules is one key factor for being financially attractive for customers all over the world. The further reduction in manufacturing costs lead to increased demands on module components and their materials to maintain acceptable mechanical yields and module reliability. Thus fast, economic and preferably non-destructive component characterization and manufacturing process control methods come more and more into focus. In the present work lamb wave based approaches for material characterization of plate-like photovoltaic module components were evaluated with respect to their precision and inline capabilities. The second-order elastic constants (Young’s modulus and Poisson’s ratio) were determined by automated numeric fitting of the Rayleigh-Lamb dispersion model on experimental data. Furthermore, the influence of mechanical stress on the ultrasound transport properties was investigated. Therefore the components were systematically loaded by mechanical and thermal stress. The resu...

A resonating rheometer using two polymer membranes for measuring liquid viscosity and mass density

A resonating sensor for mechanical liquid properties facilitating measurements at two different modes of operation is presented. One mode is more sensitive to liquid viscosity the other to mass density. A sample liquid is subjected to time-harmonic shear stress induced by two opposed vibrating polymer membranes. These membranes, placed in an external static magnetic field, carry two conductive paths each. The first path is used to actuate the membranes by means of Lorentz forces while the second acts as a pick-up coil providing an induced voltage representing the movement of the membrane. From the resulting frequency response the liquid's viscosity and mass density can be deduced. This double membrane based setup allows examining the test liquid at adjustable frequencies in the low kilohertz range from 500Hz to 20kHz by varying the gap between both membranes. The sensor is suitable, e.g., for low cost handheld devices with inline capabilities and disposable sensor elements for measuring Newtonian liquids such as, e.g., oils and aqueous solutions.

A double membrane sensor for liquid viscosity facilitating measurements in a large frequency range

In this contribution a resonating sensor for viscosity and mass density facilitating measurements at different frequencies is presented. A sample liquid is subjected to time harmonic shear stress induced by two opposed vibrating polymer membranes. These membranes, placed in an external static magnetic field, carry two conductive paths each. The first path is used to actuate the membranes by means of Lorentz forces while the second acts as a pick-up coil providing an induced voltage representing the movement of the membrane. From the resulting frequency response the liquid’s viscosity and mass density can be obtained. This double membrane based setup allows to examine the test liquid at adjustable frequencies in the low kilohertz range from 500 Hz to 20 kHz. This novel sensor design is suitable, e.g., for low cost handheld devices with inline capabilities and disposable sensor elements.

Optical monitoring of thin film properties using in-situ measurement of transmittance and reflectance

Having a good reproducibility and uniformity of the coating properties is a mutual challenge for all coating processes. To face this challenge adequately, it is not only necessary to have accurate control of the coating process but also to have the capability to monitor the optical properties of the coating layers during or directly after deposition. Especially in sensitive multi-layer products produced by large area coating technology, small uniformity variations may give rise to a variation in the visual appearance or other deviations from the product requirements. It becomes necessary to monitor the individual layer thicknesses, requiring sensitive and accurate optical measurement techniques that offer nanoscale precision over large areas. This demand for sensitivity and accuracy puts a strain on the limits of existing in-line measurement capability. The objective of this paper is to discuss some of the measurement problems and give practical solutions to improve accuracy and repeatability of in-situ transmittance and reflectance measurements for optical monitoring of thin film properties.

Fluid flow studies associated with a new electromagnetic flowmeter

The development and commercial introduction of the AquaMaster ® range of electromagnetic flowmeters offers much potential benefit for large scale water flow management. In order to satisfy projected demand figures for this design, the calibration capabilities had to be improved and a multi inline capability introduced. This flowmeter’s development programme included detailed research into all aspects of the flow upstream, downstream and within the body of individual flowmeters, as well as between various combinations of inline meters.

Sputter metallization of plastic parts in a just-in-time coater

The coating of plastic parts such as car head lamps, reflectors for lighting systems and decorative parts with a highly reflective metal layer nowadays is mostly done in big batch coaters using an evaporation technique. We introduce a new just-in-time coater in which only one piece is coated per cycle time. Typical cycle times of 33–56 s have been realized for coating reflector parts with an aluminium layer of 80 nm thickness. The deposition is done by magnetron sputtering. The advantages of this concept are small footprint of the coater, no need for big storage space for substrates, only a small number of substrate fixtures needed, in-line capability, ability to coat substrates of complex shape, deposition of materials with high melting point (e.g. Cr) and deposition of alloys (e.g. CuAl) and sintered material mixtures. For high productivity a new interpole target magnetron sputter cathode has been developed with extremely high target width, high deposition rate and high target lifetime of up to 50 000 coating cycles. The coater concept, the sputter magnetron, thickness distribution and throughput are discussed.

A total reflection X-ray fluorescence spectrometer with monochromatic excitation

A total reflection X-ray fluorescence spectrometer with monochromatic excitation for traceelement analysis on semiconductor wafers is presented. Using a multilayer monochromator intense monochromatic and tunable excitation is provided. The monochromatic excitation brings about a clear background reduction and produces an excitation spectrum of inherent spectral purity. Even with a low power Mo fine-focus tube, detection limits of 10 10 atoms cm 2 are attainable. The tunability of the excitation conditions allows selective excitation, which is especially advantageous for light elements. The in-line capability of the method lends itself to process control in semiconductor fabrication.