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Substrates
The Materials employed tor insulating substrates of thin-film circuits are commonly glasses, ceramics and glass ceramics. Glazed alumina is most popular. Substrates are usually rectangular or square in shape. The thickness of substrates is 0.6, 1.0 and 1.6 mm. The substrate of an 10 must have a high mechanical strength, low electrical conductivity, and good thermal conductivity. The substrate surface must be mirror-like. The degree of surface finish determines the thickness of deposited films. The process of fabrication of substrates includes several stages: blank cutting, lapping, polishing, cleaning, washing, etching, drying, and last, ion bombardment using a glow descharge. She treatment gives the desired surface finish and thus ensures a good adhesion of films to the substrate. Minute crystal defects cause appreciable changes in the properties of thin-film elements. XI. Прочитайте текст Д и задайте 10 вопросов по содержанию текста. Conductors and Contact Pads Conducting films serve as interconnections, inductors, and capacitor plates. The conductivity of a metal film depends on the film thickness. A film conducts well at a thickness of 0.1 The materials for metallized current-carrying stripes interconnecting circuit elements and contact pads must fill the following requirements. 1.High adhesion to a substrate. Contact pads are subject to thermal shocks during soldering or welding and 2. High conductance. The circuit designer usually specifies a lower level of connection pattern conducance 3. Chemical stability. The factors affecting the quality of films are corrosion, structural changes leading to 4. Good solderability to enable adequate circuit assembly. Contact pads serve to connect the circuit to input, 5. The parameters of contact pads are a contact resistance, current-voltage characteristic, and noise 6. The materials for thin-film conductors are commonly gold and aluminum vaporized in a vacuum.
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