Fabrication thick films

Instead of the system silica/silicate also other systems such as titania/titanate, zirconia/zirconate can be used as a reference system [xiv]. The response time of freshly fabricated thick-film sensors based on thin-film /3-alumina is very short (about 15 ms at 650 °C). After several weeks of operating this time increases 10 times (150 ms) [xv]. Solid electrolyte C02 sensors using Ni/carbonate composite as measuring electrode are suited for measuring of C02 in equilibrated water gases [xiv]. Using semiconducting oxides and carbonates like ITO (indium tin oxide) Nasicon-based C02 sensors are able to measure at room temperature [xvi]. 

Although the thickness of spun-coated films may be controlled by the concentration of the polymer in the solution, the spinning rate, and the spin-coating temperature, it is difficult to fabricate thick films and the thickness obviously cannot be monitored during deposition. In addition, no combinatorial fabrication methods have been developed for spun- coated PLEDs (see above). 

PVC plastisol based coating compositions are desirable coating vehicles from the standpoint of fabrication, thick film capability, and have the ability to be formulated with high solids, but generally exhibit poor durability, color retention, chalk resistance and dirt resistance ... 

X-ray exposure of samples to fabricate thick-film resist structures has developed into an important technique for microfahrication of a wide variety of devices. The use of X-rays to expose thick-film resist samples is advantageous for a variety of reasons including ... 

Equally important as tape casting in the fabrication of multilayer ceramics is thick film processing. Thick film technology is widely used in microelectronics for resistor networks, hybrid integrated circuitry, and discrete components, such as capacitors and inductors along with metallization of MLC capacitors and packages as mentioned above. 

Film and sheet are defined as flat unsupported sections of a plastic resia whose thickness is very thin ia relation to its width and length. Films are generally regarded as being 0.25 mm or less, whereas sheet may range from this thickness to several centimeters thick. Film and sheet may be used alone ia their unsupported state or may be combined through lamination, coextmsion, or coating. They may also be used in combination with other materials such as paper, foil, or fabrics. 

Weathering. Articles fabricated from FEP are unaffected by weather, and thek resistance to extreme heat, cold, and uv kradiation suits them for apphcations in radar and other electronic components. For example, after 15 years of solar exposure in Florida, the tensile strength (73) and light transmission (96%) of a 25-p.m thick film was unchanged and the film remained crystal clear. Elongation increased slightly for the first 5 to 7 years of outdoor exposure, probably as a result of stress relaxation. Beyond 10 years, a small decrease was observed. 

Copper Sulfide—Cadmium Sulfide. This thin-film solar cell was used in early aerospace experiments dating back to 1955. The Cu S band gap is ca 1.2 eV. Various methods of fabricating thin-film solar cells from Cu S/CdS materials exist. The most common method is based on a simple process of serially overcoating a metal substrate, eg, copper (16). The substrate first is coated with zinc which serves as an ohmic contact between the copper and a 30-p.m thick, vapor-deposited layer of polycrystaUine CdS. A layer is then formed on the CdS base by dipping the unit into hot cuprous chloride, followed by heat-treating it in air. A heterojunction then exists between the CdS and Cu S layers. 

Polymer thick films also perform conductor, resistor, and dielectric functions, but here the polymeric resias remain an iategral part after cuting. Owiag to the relatively low (120—165°C) processiag temperatures, both plastic and ceramic substrates can be used, lea ding to overall low costs ia materials and fabrication. A common conductive composition for flexible membrane switches ia touch keyboards uses fine silver particles ia a thermoplastic or thermoset polymeric biader. 

Experimental information for polymeric LED is sparse. A key problem for conventional lime-of-flighl studies is that the condition of generating a sheet of carriers whose spatial extension is small compared to the thickness of a = 100 nm film is difficult to meet. On the other hand, thick films fabricated, for instance, by solvent casting rather than by spin coating, may differ regarding their morphology and, concomitantly, the built-in-disorder. On the fundamental side, transport in... 

The tape-casting method makes possible the fabrication of films in the region of several hundred micrometers thick. The mechanical strength allows the use of such a solid electrolyte as the structural element for devices such as the high-temperature solid oxide fuel cell in which zirconia-based solid electrolytes are employed both as electrolyte and as mechanical separator of the electrodes. 

A. Gac, J.K. Atkinson, Z. Zhang, CJ. Sexton, S.M. Lewis, C.P. Please, and R. Sion, Investigation of the fabrication parameters of thick film titanium oxide-PVC pH electrodes using experimental designs. Microelectronics Int. 21, 44—53 (2004). 

M.A. Afromowitz and S.S. Yee, Fabrication of pH-sensitive implantable electrode by thick-film hybrid technology. J. Bioeng. 1, 55-60 (1977). 

Typically items with a thickness of less than about 1 mm can be treated as thermally thin. This constitutes single sheets of paper, fabrics, plastic films, etc. It does not apply to thin coatings or their laminates on noninsulating substances, as the conduction effects of the substrate could make the laminate act as a thick material. The paper covering on fiberglass insulation batting would be thin pages in a closed book would not. 

Figure 1. Smart dust mote and its components Micro-fabricated sensors, optical receiver, signal-processing and control circuitry the power source consists of a solar cell and a thick-film battery. (Derived with permission from ref 16. Copyright 2001 IEEE)...

Metal in gap (MIG) or ferrite heads are produced with a combination of machining, bonding, and thin-film processes. Thin-film inductive heads are manufactured using thin-fihn processes similar those of semiconductor 1C technology (discussed in Chapter 19). The thin-film head production process is rather unusual, as it involves both very thin and very thick films. We choose to present here a detailed summary of the fabrication process of thin-film inductive heads with a single-layer spiral coil. This may serve, once again to, illustrate the centrally important role of electrochemical deposition in connection with modem information technology. 

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