What Is a Rectangular LED?
Rectangular Light Emitting Diodes (LEDs) are a type of package for LED elements.
Rectangular LEDs are a type of through-hole LEDs.
Typically, through-hole LEDs are known as bullet-type LEDs, featuring a hemispherical cylindrical top.
Rectangular LEDs can be considered a variation of bullet-type LEDs.
Applications of Rectangular LEDs
Rectangular LEDs are characterized by even light emission to the front and sides and are mainly used for illuminating a wide area, such as indicators, car room lamps, operation check lamps for various devices, illumination, and light art. Because they are bright and inexpensive, they are also often used for general craft purposes.
Rectangular LEDs used to be popular because their wide angle and even emission of light are very suitable for LCD panel backlighting. However, surface-mount LEDs are now the mainstream in this field, and rectangular LEDs are no longer used.
Characteristics of Rectangular LEDs
The LED element is a junction of a P-type semiconductor and an N-type semiconductor.
When a positive potential is applied to the P side and a negative potential to the N side, holes move to the negative side in the P-type semiconductor and electrons move to the positive side in the N-type semiconductor. The holes and electrons meet at the P-N junction surface and recombine, resulting in a transition to a lower energy level state.
At this time, light is emitted with a wavelength corresponding to the difference in energy levels before and after recombination. This difference in energy level (band gap) is a value specific to the semiconductor material, and the emission color of the LED is determined by the semiconductor material.
Rectangular LEDs consist of the above LED elements fixed on a lead frame, with the anode (positive) terminal connected to the LED element using bonding wire, and then encapsulated in a rectangular shape using encapsulating resin. The cathode (negative) terminal comes directly from the lead frame.
Rectangular LEDs are two-terminal elements with anode and cathode terminals. To identify the terminals, the anode terminal is slightly longer than the cathode terminal. The anode side is connected to the positive side of the power supply and the cathode side to the negative side. When connected in reverse, it will not light up.