Power Electronics

Resistors and Capacitors: Surface-Mounting Takes Center Stage

Paraphrasing an old saying, “electronic systems cannot exist by semiconductors alone.” Virtually every electronic system requires passive components, primarily resistors, and capacitors. Although passive components do not change as rapidly as their active semiconductor cousins, nevertheless there has been a gradual change in passive components. Probably the biggest recent innovation with resistors and capacitors is their availability with surface-mount interconnections.

Flat thick and thin film chip resistors, cylindrical resistors, resistor networks and power resistors are available in surface-mount types that are available from domestic and foreign manufacturers. Variable resistors, such as trimming potentiometers are also available as surface-mount components.

Capacitors classifications depend in on your point of view. Some capacitors are categorized according to their dielectric material, such as film and ceramic types. Others are classified according to their plate material, such as aluminum, tantalum, and soon niobium. They can also be grouped according to their application, such as trimmer capacitors, motor start and run capacitors. Plus, there are variable capacitors and fixed types categorized as electrolytic, electrostatic and electrochemical. Most are available as surface-mount components.

In its Book, “Electronic Passive Components,” ECA (Electronic Components, Assemblies & Materials Association) that is associated with the EIA (Electronic Industries Association) notes that parts have now been standardized. “The parts are robust and withstand the traditional surface-mount process stresses. When assembly process stresses are excessive, care should taken to ensure the parts selected are able to withstand the stresses. Surface-mount resistors and capacitors have the highest part count on most boards. High speed placement equipment minimize this impact by lower the per piece assembly cost.”

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