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Thick-film Technology
Published in Lionel M. Levinson, Electronic Ceramics, 2020
René E Coté, Robert J. Bouchard
Thick-film resistors are also widely used to produce trimmers and precision potentiometers, as discrete components and as part of certain thick-film circuits. In contrast to wire-wound elements, the thick-film resistors provide advantages in stepless resistance resolution, a wide range of resistance values, and adaptability to miniaturization. Recent advances in materials technology have led to TCR of ±50 ppm/°C and significant improvements in surface smoothness and uniformity. This has been a consequence of new glass chemistry and control of particle morphology to provide an optimum trade-off in surface and bulk characteristics. For example, even very high resistivity fired films, which usually contain a high volume percentage of glass, have a sufficient surface density of functional phase such that a single 125 μm wide wiper finger will make positive contact with conductive areas in traversing the potentiometer track. Thus, with simple five-finger metallic wipers, contact resistance variations (CRV) of ±1% can be achieved over a range of.1.5 Ω/square to 1 MΩ/square.
Overview of Ceramic Interconnect Technolgy
Published in Fred D. Barlow, Aicha Elshabini, Ceramic Interconnect Technology Handbook, 2018
Aicha Elshabini, Gangqiang Wang, Dan Amey
Ceramic substrates provide the base onto which all thick-film circuits are fabricated. Ceramic materials are used in substrate applications primarily because of their high mechanical strength, high electrical resistivity over a broad temperature range, and chemical inertness relative to a variety of processing conditions. Because ceramic substrates can withstand temperatures in excess of 1000°C, thick-film materials are often fired at temperatures of about 1000°C and lower. Thick-film technology comprises specially formulated pastes applied using screen printing, fired onto a ceramic substrate in a definite pattern, and sequenced to produce electrical components, interconnections, and a complete functional circuit. These pastes possess an organic binder to make them thixotropic in nature with dual viscosity: viscous at rest and flowing with motion [22]. These pastes possess essentially a functional phase to produce a film with desired electrical properties. Depositing successive layers result in multilayer interconnection formation containing integrated passive components, added active chips, and integrated circuits (see Figure 1.2).
Introduction to Thin Films and Coatings
Published in Fredrick Madaraka Mwema, Tien-Chien Jen, Lin Zhu, Thin Film Coatings, 2022
Fredrick Madaraka Mwema, Tien-Chien Jen, Lin Zhu
Thin film has a thickness in the order of 0.1 μm or smaller, while thick film is thousands of times thicker. The most important difference between these two classes of material is methods of creating them. Thin film materials are usually manufactured using sophisticated and vacuum-based methods, whereas thick films are produced through cheaper and simple methods. For example, thin film metal resistors are usually produced by atomic-based processes such as sputtering, whereas thick film metal resistors are manufactured using stencil and screen-printing methods. In terms of properties, thin films exhibit attractive active/functional properties, whereas thick films exhibit better surface protection properties.
Application of extension rings in thermography for electronic circuits imaging
Published in Quantitative InfraRed Thermography Journal, 2022
For each ring combination, the camera was used to measure the temperature of a blackbody, for three different temperature setpoint values: ambient (24.1°C), 50°C and 75°C. A Fluke 4181 IR calibrator was used as the blackbody. For each temperature and ring configuration, a horizontal temperature profile across the entire thermogram was recorded, the spatial resolution per pixel was calculated and the camera focusing distance was measured. Because the uniform surface of the blackbody made it difficult to focus the camera, as no reference points were visible, a custom-made thick-film test resistor network on alumina was used for correct focusing (Figure 4). For spatial resolution measurements, a microscope reticle calibration slide ruler was used. The ruler was placed in a holder, in front of the camera, and next, it was illuminated with a small halogen lamp. The metallic overprint on the glass substrate provided the required thermal contrast. The resolution was calculated as the quotient of the horizontal distance seen by the camera and the number of pixels. A perfect lens without any aberrations was assumed and, at first, the limits imposed by diffraction phenomena were not taken into account. The pictures of the thick-film resistor and the ruler are shown in Figure 4.
A study of thickness dependent microstructure of poly (3-hexylthiophene) thin films using grazing incidence x-ray diffraction
Published in Soft Materials, 2022
Manoj Kumar, Srihari Velaga, Amarjeet Singh
We investigated thin films of P3HT with grazing incidence x-ray diffraction technique using synchrotron x-ray radiation. Thin films of P3HT of two different thicknesses, 32 nm and 61 nm, were prepared using spin coating technique at two different spinning speeds 1000 rpm and 500 rpm respectively. Combining high-resolution vertical scan (1D-GID) with 2D diffraction intensity maps (2D-GID), we analyzed the microstructure of the films in terms of degree of crystallization (DOC), texture and coherence length of crystallites. A comparative analysis of thick film and thin film elucidated the role of substrate interaction in determining the microstructure. A comparison of non-annealed and annealed films (110°C) illustrated that the solution-frozen morphology and relaxed microstructure were widely different. Thermal treatment had widely different effect on thick and thin films. For thick film, the crystalline density (DOC) in vertical direction increased strongly (~10 times). Both factors – reorientation of crystallites and fresh crystallization contributed to strong increase in DOC. Crystalline coherence length improved only marginally in this case. On the contrary, the relaxed microstructure of the thin film possessed very low crystalline density (DOC), stronger texture and higher coherence length. The crystalline coherence length was substantially increased from ~12 to ~16 nm on thermal treatment. The change of thickness only from 61 nm to 32 nm brought very drastic modification in the microstructure of the films.
A numerical investigation of convective condensation in micro-fin tubes of different geometries
Published in Numerical Heat Transfer, Part A: Applications, 2020
Weiyu Tang, Wei Li, W. J. Minkowycz
Compared to the extensive experimental investigations, there is still little numerical work about condensing flows in micro-fin tubes. The velocity, phase, and temperature fields of the fluid zones can be easily visualized through numerical approaches, which may greatly help understand the heat transfer enhancement of micro-fin tubes. Wang et al. [8] proposed a laminar film evaporation model for annular flow regime to predict the heat transfer coefficient. It was assumed that the thin film formed on the surface is drained by the surface tension and interfacial shear stress, while the thick film is driven by the shear force. A good agreement has been found between the developed annular model and the experimental results for high heat flux and high mass flux. Zhang et al. [9] compared the heat transfer performance of two micro-fin tubes, and validate their numerical model with experimental data points and empirical correlations. As a result, a more promising heat transfer enhancement was reported for the helical micro-fin tube at high mass flux and vapor quality compared to the straight micro-fin tube.