Coating resistor coatings

Figure 9. FTIR spectra of contamination layer on E-beam aperture, and IPA extract of new resistor coating.

Miscellaneous. Ruthenium dioxide-based thick-film resistors have been used as secondary thermometers below I K (92). Ruthenium dioxide-coated anodes ate the most widely used anode for chlorine production (93). Ruthenium(IV) oxide and other compounds ate used in the electronics industry as resistor material in apphcations where thick-film technology is used to print electrical circuits (94) (see Electronic materials). Ruthenium electroplate has similar properties to those of rhodium, but is much less expensive. Electrolytes used for mthenium electroplating (95) include [Ru2Clg(OH2)2N] Na2[Ru(N02)4(N0)0H] [13859-66-0] and (NH 2P uds(NO)] [13820-58-1], Several photocatalytic cycles that generate... 

Electrically Functional. Refractory coatings are used in semiconductor devices, capacitors, resistors, magnetic tape, disk memories, superconductors, solar ceUs, and diffusion barriers to impurity contamination from the substrate to the active layer. 

Fig. 20-3 Heating pipe (HE) in a boiler with a high-resistance coating with electrical separation from the boiler and from the ground by insulating units and a balancing resistor.

Applications Although a wide range of metals can be sputtered, the method is often commercially restricted by the low rate of deposition. Applications include the coating of insulating surfaces, e.g. of crystal vibrators, to render them electrically conducting, and the manufacture of some selenium rectifiers. The micro-electronics industry now makes considerable use of sputtering in the production of thin-film resistors and capacitors . ... 

The largest uses of platinum group metals in electronics are ruthenium for resistors and palladium for multilayer capacitors, both applied by thick film techniques . Most anodes for brine electrolysis are coated with mixed ruthenium and titanium oxide by thermal decomposition . Chemical vapour deposition of ruthenium was patented for use on cutting tools . 

Ruthenium nowadays finds many uses in the electronics industry, particularly for making resistor tracks. It is used as an ingredient in various catalysts and, importantly, in electrode materials, e.g. Ru02-coated titanium elements in the chloralkali industry. Osmium tetroxide is a very useful organic oxidant and, classically, is used as a tissue stain. Both elements are employed in making certain platinum alloys. 

The deposition temperature range is 300-500°C, the partial pressure of the alkyl is 0.5-2.5 Torr, and that of THF is 20-80 Torr. ZnO has found applications in piezoelectric devices, transducers, coatings for photoconductive devices, and non-linear resistors (varistors), and overvoltage protectors. 

There are three major classes of palladium-based hydrogen sensors [4], The most popular class of palladium-based sensors is based on palladium resistors. A thin film of palladium deposited between two metal contacts shows a change in conductivity on exposure to hydrogen due to the phase transition in palladium. The palladium field-effect transistors (FETs) or capacitors constitute the second class, wherein the sensor architecture is in a transistor mode or capacitor configuration. The third class of palladium sensors includes optical sensors consisting of a layer of palladium coated on an optically active material that transforms the hydrogen concentration to an optical signal. 

The sensor element constitutes a palladium-nickel alloy resistor with a temperature sensor and a proprietary coating. The sensor has a broad operating temperature range and a sophisticated temperature control loop that includes a heater and a temperature sensor, which controls the die temperature within 0.1°C. 

Nevertheless the heat capacity of a carbon resistor was not so low as that of crystalline materials used later. More important, carbon resistors had an excess noise which limited the bolometer performance. In 1961, Low [61] proposed a bolometer which used a heavily doped Ge thermometer with much improved characteristics. This type of bolometer was rapidly applied to infrared astronomy as well also to laboratory spectroscopy. A further step in the development of bolometers came with improvements in the absorber. In the early superconducting bolometer built by Andrews et al. (1942) [62], the absorber was a blackened metal foil glued to the 7A thermometer. Low s original bolometer [61] was coated with black paint and Coron et al. [63] used a metal foil as substrate for the black-painted absorber. A definite improvement is due to J. Clarke, G. I. Hoffer, P. L. Richards [64] who used a thin low heat capacity dielectric substrate for the metal foil and used a bismuth film absorber instead of the black paint. 

Manufacture of Printed Wiring Boards. Printed wiring boards, or printed circuit boards, are usually thin flat panels than contain one or multiple layers of thin copper patterns that interconnect the various electronic components (e.g. integrated circuit chips, connectors, resistors) that are attached to the boards. These panels are present in almost every consumer electronic product and automobile sold today. The various photopolymer products used to manufacture the printed wiring boards include film resists, electroless plating resists (23), liquid resists, electrodeposited resists (24), solder masks (25), laser exposed photoresists (26), flexible photoimageable permanent coatings (27) and polyimide interlayer insulator films (28). Another new use of photopolymer chemistry is the selective formation of conductive patterns in polymers (29). 

Using nitrile oxides, various compounds and materials possessing valuable properties have been prepared. Among them are thin-film resistors useful for a thermal head and comprising a nitrile oxide, ruthenium and oxygen, a method for manufacturing the resistor by coating or deposition (529), isoxazole and/or isoxazoline polyheterocyclic systems like 458, which are useful for development of a new class of ionophores (530). 

The cells shown in Figs. 28 and 29 all operate according to the same principles, which have been developed by Arup. The interior of the cell acts as the anode chamber, and a metal oxide cathode placed inside the cell in an alkaline electrolyte acts as the counter electrode. The hydrogen flux across the integrated membrane (coated with palladium on the internal surface) can be measured as the potential drop across a resistor placed between the membrane and the counter electrode. 

First chemical test measurements have been conducted with the array chip. Figure 6.19 shows the results that have been obtained simultaneously from three microhotplates coated with different tin-dioxide-based materials at operation temperatures of 280 °C and 330 °C in humidified air (40% relative humidity at 22 °C). The first microhotplate (pHPl) is covered with a Pd-doped Sn02 layer (0.2wt% Pd), which is optimized for CO-detection, whereas the sensitive layer on microhotplate 3 contains 3 wt% Pd, which renders this material more responsive to CH4. The material on microhotplate 2 is pure tin oxide, which is known to be sensitive to NO2. Therefore, the electrodes on microhotplate 2 do not measure any significant response upon exposure to CO or methane. The digital register values can be converted to resistance values by taking into account the resistor bias currents [147,148]. The calculated baseline resistance of microhotplate 1 is approximately 47 kQ, that of hotplate 2 is 370 kQ and the material on hotplate 3 features a rather large resistance of nearly 1MQ. 

It is of interest primarily for very uniform ultra-thin films and coatings (0.002-5 mils) in applications such as electrical resistors, thermistors, thermocouples, stator cores, connectors, fast-sensing probes, photo cells, memory units, dropwise steam condensers for recovery of sea water, pellicles for beam splitters in optical instruments, windows for nuclear radiation counters, panels for micrometeorite detection, dielectric supports for planar capacitors, encapsulation of reactive powders, and supports in x-ray and optical work. Any significant growth would depend upon a major breakthrough in process techniques and a consequent lowering in price. 

A very useful application of the circuit of Figure 8.3b is produced if we replace the feedback resistor Ru with a resistive transducer such as a coated semiconductor thermistor. The commercial availability of small, rapid-response, chemically inert thermistors that have conveniently measurable resistances at temperatures of 200-600 K makes them an excellent choice as the transducer in chemical applications that require the rapid and accurate measurement of temperature. Unfortunately, a continuous current in Ru may produce undesirable... 

The resolution of potentiometric transducers is dependent upon the construction of the resistance element. In the case of a wire-wound resistance, in order to obtain a high resistance in a small space, the resistance wire is wound on to a mandrel or card which is straight or formed into a circle or helix depending upon the motion of the contact. This limits the resolution of the transducer as the wiper moves from one wire to the next on the mandrel. The best resolution that can be obtained is about 0.01 per cent (see Section 6.10.1). Typical wire-wound potentiometers have strokes of between 0.0025 m and 0.5 m and rotational versions from about 10° of arc to 50 turns. An alternative often employed is the conductive plastic film element. This provides a continuous resistance element and thus, a zero resolution, but such elements suffer from a higher temperature coefficient of resistance. A more recent development is a combination of earlier types in which a conductive plastic coating is sprayed on to a wire-wound resistor. 

---