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The light from white LED lamps and LED strip lights is usually provided by industry standard surface-mounted device LEDs (SMD LEDs). [2] Non-SMD types of LED lighting also exist, such as COB (chip on board) and MCOB (multi-COB). Surface-mounted device LED modules are described by the dimensions of the LED package. A single multicolor module may ...
LED power dissipation is modeled as a current source; thermal resistance is modeled as a resistor; and the ambient temperature is modeled as a voltage source. High power light-emitting diodes (LEDs) can use 350 milliwatts or more in a single LED. Most of the electricity in an LED becomes heat rather than light – about 70% heat and 30% light. [1]
Surface-mount technology (SMT), originally called planar mounting, [1] is a method in which the electrical components are mounted directly onto the surface of a printed circuit board (PCB). [2] An electrical component mounted in this manner is referred to as a surface-mount device ( SMD ).
Many circuits operate LEDs at less than the specified maximum current to save power, or to reduce brightness, or to use a common resistor value. For indoor use, tiny surface mount high-efficiency LEDs can easily light up with 1 mA (0.001 A) or more current, which most digital logic outputs can easily source or sink.
Solder paste is used in the manufacture of printed circuit boards to connect surface mount components to pads on the board. It is also possible to solder through-hole pin in paste components by printing solder paste in and over the holes. The sticky paste temporarily holds components in place; the board is then heated, melting the paste and ...
Soldering and brazing are thought to have originated very early in the history of metal-working, probably before 4000 BC. [2] Sumerian swords from c. 3000 BC were assembled using hard soldering. Soldering was historically used to make jewelry, cookware and cooking tools, assembling stained glass, as well as other uses.
The circuit board is passed over a pan of molten solder in which a pump produces an upwelling of solder that looks like a standing wave. As the circuit board makes contact with this wave, the components become soldered to the board. Wave soldering is used for both through-hole printed circuit assemblies, and surface mount.
Although tetrachromatic white LEDs have excellent color rendering capability, they often have poor luminous efficacy. Trichromatic white LEDs are in between, having both good luminous efficacy (>70 lm/W) and fair color rendering capability. [29] One of the challenges is the development of more efficient green LEDs.