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What Is a Chip Diode?

Diodes are components used in electronic circuits. They come in various packages, such as shapes and casings, depending on their purpose. Older diodes, called through-board diodes, have wires, or leads, that go through holes in a printed circuit board and are soldered to metal tracks on the reverse. Modern diode designs, called chip diodes, are surface-mounted: small rectangular packages that are soldered to the surface of the board.

Diodes
- Diodes are typically made of semiconducting material such as silicon. A chip of the semiconductor is "doped" -- meaning it has added impurities -- such that one side has more negatively charged electrons and the other has more positively charged "holes." A diode works like a valve, allowing current to flow in one direction only. Many common diode packages consist of a small cylinder with a lead at either end. Some high-power diodes become very hot; these have a metal casing that can be bolted onto a heatsink.
Surface-Mount Technology
- In through-hole construction, holes are drilled in a printed circuit board; the components are placed on the opposite side of the board from the metal tracks that carry the current, with their leads passing through the holes. The leads are soldered to "pads," circular areas of metal surrounding the holes. Surface-mount technology, or SMT, is an alternative circuit construction method in which components such as diodes rest on the side of the board with the metal tracks, and are soldered in place without the need for holes. SMT construction can save a considerable amount of space, and often allows for faster assembly. Resistors, transistors and capacitors are all available in SMT form, as are diodes.
Chip Diodes
- SMT diodes are sometimes called chip diodes. These typically lack leads; instead, a layer of metal is bonded to the outside of the package at each terminal, allowing the chip diodes to be soldered to the surface of the printed circuit. This leadless design saves space on the board, and may also make for a flatter circuit, allowing slimmer electronic devices to be constructed.
Considerations
- At the prototyping stage, leadless chip diodes can be problematic as they can't be plugged directly into a conventional breadboard. Like other SMT components, chip diodes can potentially increase manufacturing setup costs compared to through-hole diode packages. The type of package that a diode is housed in can affect the diode's operating characteristics -- although chip diodes can be produced with a wide range of characteristics, they can't fulfill every possible role and may not be appropriate for some applications.

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