LED lighting fixtures have more or less problems in the process of manufacturing or in the application process. The following is a collection of 98 common problems in the LED industry. I am familiar with these 98 LED lighting problems, let alone claiming martial arts, but At least on the LED rivers and lakes is also a class of people.
First, what is LED?
The LED is an English Light Emitting Diode, which is a semiconductor solid-state light-emitting device. It uses a solid semiconductor chip as a light-emitting material. When a forward voltage is applied to both ends, carriers in the semiconductor recombine to cause photon emission. The light produced by the LED can directly emit red, yellow, blue, green, cyan, orange, purple, white light. The first commercial diode was produced in 1960. Its basic structure is an electroluminescent semiconductor material. On a leaded shelf, and then sealed with epoxy resin around, to protect the internal core wire, so the LED's seismic performance is good.
Second, why is LED the fourth generation light source (green lighting)?
Answer: According to the illuminating mechanism of electric light source: the first generation light source: resistance illuminating such as incandescent lamp. Second generation light source: arc and gas illuminating such as sodium lamp. Third generation light source: phosphor illuminating like fluorescent lamp. Fourth generation light source: solid state The chip emits light like an LED.
Third, LED lighting mechanism and working principle?
A: Light-emitting diodes are made of III-IV compounds, such as GaAs (gallium arsenide), GaP (gallium phosphide), GaAsP (phosphorus gallium arsenide) and other semiconductors. The core is PN junction. Therefore, it has general The IN characteristic of the PN junction, that is, forward conduction, reverse cutoff, and breakdown characteristics. In addition, under certain conditions, it also has luminescence characteristics. Under forward voltage, electrons are injected into the P region from the N region, and the holes are P. The area is injected into the N zone. A part of the minority carriers (small children) entering the other area is combined with the majority carriers (multiple sub-) to emit light.
Fourth, what optical characteristics of LED?
Answer: 1. The light emitted by the LED is neither monochromatic nor broadband, but the balance between the two. 2. The LED light source is like a point source and not a point source. 3. The color of the LED emits light varies with the space direction. However, the junction temperature of the LED under constant current operation strongly influences the forward voltage VF.
5. What are the ways to construct LEDs?
Answer: LEDs have different chemical compositions because of their different colors: red: aluminum-indium-gallium-phosphide; green and blue: indium-gallium-nitride; white and other colors are appropriately selected with RGB three primary colors. The ratio of LEDs is similar to that of semiconductors, but the processing accuracy is not as good as that of semiconductors, and the cost is still high.
What is the luminous wavelength of each color?
Answer: At present, the spectral wavelength distribution of super bright LEDs commonly used in domestic colors is 460 ~ 636nm, and the wavelengths are blue, green, yellow green, yellow, yellow orange, red in order from short to long. Common color LEDs Typical peak wavelengths are: blue - 470 nm, cyan - 505 nm, green - 525 nm, yellow - 590 nm, orange - 615 nm, red - 625 nm.
7. What kinds of packaging methods does LED have?
A: Packing method: 1. Lead type LED package , 2. Surface mount (SMT-LED) package, 3. Chip-on-board (COB) LED package, 4. System package (SiP) LED package 5. Wafer bonding and chip bonding.
8. What are the classification methods for LEDs?
1. According to the luminous color of the luminous tube. According to the color of the light-emitting tube, it can be divided into red, orange, green (subdivided into yellow-green, standard green and pure green), blue light, etc. In addition, some light-emitting diodes contain chips of two or three colors. The light-emitting diodes of the above various colors can be classified into four types of colored transparent, colorless transparent, colored scattering and colorless scattering according to whether the light-emitting diode is doped with or without a scattering agent, colored or colorless. Scatter-type LEDs are used for indicator lights.
2. According to the characteristics of the light-emitting surface of the light-emitting tube. According to the characteristics of the light-emitting surface of the light-emitting tube, the round lamp, the square lamp, the rectangular, the surface light-emitting tube, the lateral tube, the surface-mounted micro tube, and the like. The circular lamp is divided into φ2mm, φ4.4mm, φ5mm, φ8mm, φ10mm and φ20mm according to the diameter. In foreign countries, the φ3mm LED is generally recorded as T-1; the φ5mm is recorded as T-1 (3/4); φ 4.4 mm is written as T-1 (1/4).
From the half-value angle size, the angular distribution of the circular luminous intensity can be estimated. There are three types from the angular distribution of luminous intensity:
(1) High directivity. Generally, it is a pointed epoxy package or a metal reflective cavity package without a scattering agent. The half-value angle is 5°-20° or less, has high directivity, can be used as a local illumination source, or combined with a light detector to form an automatic detection system.
(2) Standard type. Usually used as indicator light, its half value angle is 20 ° ~ 45 °.
(3) Scattering type. This is an indicator light with a large viewing angle, the half value angle is 45° to 90° or more, and the amount of the scattering agent is large.
3, according to the structure of the LED
According to the structure of the light-emitting diode, there are structures such as a full epoxy encapsulation, a metal base epoxy package, a ceramic base epoxy package, and a glass package.
4, according to luminous intensity and working current
LEDs with ordinary brightness according to luminous intensity and working current (lighting intensity <10mcd); ultra-high brightness LEDs (lighting intensity >100mcd); high-intensity light-emitting diodes with luminous intensity between 10 and 100mcd. General LED work The current is between ten mA and tens of mA, while the low current LED has an operating current below 2 mA (the brightness is the same as that of a normal LED).
In addition to the above classification methods, there are methods for classifying by chip material and classifying by function.
9. What are the production process steps of LED?
1. Process:
a) cleaning: ultrasonic cleaning PCB or LED bracket, and drying;
b) Mounting: After the silver electrode is placed on the bottom electrode of the LED die (large wafer), the expansion is performed, and the expanded die (large wafer) is placed on the thorn crystal table, and the die is punched under the microscope with a stylus. One by one mounted on the corresponding pad of the PCB or LED holder, and then sintered to cure the silver paste;
c) Pressure welding: The electrode is connected to the LED die by an aluminum wire or gold wire welder for current injection. The LED is directly mounted on the PCB, generally using an aluminum wire welding machine. (The production of white TOP-LED requires a gold wire welding machine);
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