Introduction to the main parameters and structure of LED light-emitting diodes

Introduction to the main parameters and structure of LED light-emitting diodes
We know that the main function of the LED chip is: it can directly convert electricity into light, which can be said to be the heart of the LED. This article briefly introduces the basic knowledge of LED chips, namely: the classification, structure, characteristics and important parameters of LED chips. The LED chip is the core component of the semiconductor light-emitting device LED (LED lamp), and the principle of LED light emission mainly lies in the PN junction of the LED chip. Generally speaking, semiconductor wafer is made up of two parts, and a part is P-type semiconductor, and hole occupies an leading position in it, and the other end is N-type semiconductor, and here mainly is electron. But when these two kinds of semiconductors are connected, a PN junction is formed between them. When the current acts on the chip through the wire, the electrons will be pushed to the P region, where the electrons and holes recombine, and then energy will be emitted in the form of photons, and the wavelength of light is also the color of light. Determined by the material forming the PN junction (LED display).
LED chips are mainly composed of arsenic (AS), aluminum (AL), gallium (Ga), indium (IN), phosphorus, nitrogen (N), and strontium (Si). crystalline silicon.

Classification of LED chips
Use: According to the use, it is divided into two types: high-power LED chips and low-power LED chips;
Color: Mainly divided into three types: red, green, blue (raw materials for making white light);
Shape: Generally divided into square chips , two types of wafers;
size: low-power chips are generally divided into 8mil, 9mil, 12mil, 14mil and other LED chip structures
.
It is composed of doped epitaxial semiconductor material and transparent metal electrode.
Features of LED chips
1. Quaternary chips are prepared by MOVPE technology, and the brightness is brighter than conventional chips.
2. Excellent reliability.
3. Wide application.
4. High security.
5. Long life.
Important parameters of LED chips
1. Forward working current If:
It refers to the forward current value when the light-emitting diode emits light normally. In actual use, the IF should be selected below 0.6 · IFm according to the needs.
2. Forward working voltage VF:
The working voltage given in the parameter table is obtained under a given forward current. It is generally measured when IF=20mA. The forward working voltage VF of the light-emitting diode is 1.4-3V. As the outside temperature rises, VF will drop.
3. VI characteristics:
the relationship between the voltage and current of the light-emitting diode. When the forward voltage is less than a certain value (called the threshold), the current is extremely small and no light is emitted. When the voltage exceeds a certain value, the forward current increases rapidly with the voltage and emits light.
4. Luminous intensity IV:
The luminous intensity of a light-emitting diode usually refers to the luminous intensity in the direction of the normal (for a cylindrical luminous tube, its axis). If the radiation intensity in this direction is (1/683) W/sr, then 1 candela (symbol is cd) is emitted. Since the light-emitting diodes of general LEDs have low intensity, the luminous intensity is often used as a unit of candlepower (candela, mcd).
5. Lighting angle of LED: -90°-+90°
6. Spectral half-width Δλ:
It represents the spectral purity of the luminescent tube.
7. Half-value angle θ1/2 and viewing angle:
θ1/2 refers to the angle between the direction where the luminous intensity value is half of the axial intensity value and the luminous axis (normal direction).
8. Full shape:
The angle calculated according to the LED luminous solid angle is also called the plane angle.
9. Angle of view:
refers to the maximum angle of LED light emission. Depending on the angle of view, the application is also different, also called the angle of light intensity.
10. Half shape:
The angle between the normal 0° and the maximum luminous intensity value/2. Strictly speaking, it is the angle corresponding to the maximum luminous intensity value and the maximum luminous intensity value/2. The packaging technology of the LED causes the maximum luminous angle to not be the light intensity value of the normal 0°, and the introduction of the deviation angle refers to the angle between the angle corresponding to the maximum luminous intensity and the normal 0°.
11. Maximum forward direct current IFm:
The maximum forward direct current allowed to be added. Exceeding this value can damage the diode.
12. Maximum reverse voltage VRm:
The maximum reverse voltage allowed is the breakdown voltage. Above this value, the light-emitting diode may be damaged by breakdown.
13. Working environment topm:
the ambient temperature range in which light-emitting diodes can work normally. Below or above this temperature range, the light-emitting diode will not work properly, and the efficiency will be greatly reduced.
14. Allowable power consumption Pm:
The maximum value of the product of the forward DC voltage applied to both ends of the LED and the current flowing through it is allowed. Exceeding this value, LED heat, damage.