Basic Knowledge Of LED

What LED? What are the characteristics of led?

A piece of electroluminescent semiconductor material is placed on a shelf with leads, and then sealed with epoxy resin around it to protect the inner core wire, so the LED has good shock resistance. The core part of the light-emitting diode is a wafer composed of a p-type semiconductor and an n-type semiconductor. There is a transition layer between the p-type semiconductor and the n-type semiconductor, which is called a p-n junction. In the PN junction of some semiconductor materials, when the injected minority carriers and majority carriers recombine, the excess energy is released in the form of light, thereby directly converting electrical energy into light energy. With reverse voltage applied to the PN junction, it is difficult to inject minority carriers, so it does not emit light. This kind of diodes made by the principle of injection electroluminescence are called light-emitting diodes, commonly known as LEDs.

Light Emitting Diode, or Light Emitting Diode, is a semiconductor solid light emitting device. It uses solid semiconductor chips as light emitting materials. When a forward voltage is applied to both ends, the carriers in the semiconductor recombine to cause photon emission to generate light. LED can directly emit red, yellow, blue, green, cyan, orange, purple, and white light.

Low working voltage, good impact resistance, fast response speed, high brightness, energy saving, long life, no flicker, no ultraviolet rays, no mercury pollution.

2. What fields can LED products be applied to?

LED displays, traffic lights, signal displays of electronic equipment, switches, telephones, home improvement lighting, outdoor plazas, street lighting, and lighting.

3. What is the light effect unit? lm/w lumens per watt

4. What is the brightness unit? Candela/square meter (cd/m2) or nits

5. What is the illuminance unit? lux lux

6. What is the color temperature unit? K Kelvin

7. What is the color rendering index unit? CRI Ra, the color rendering index of daylight and incandescent lamps is 100.

8. Why is the same color temperature produced by different manufacturers different from the naked eye?

There will be errors in production, and there will be chromatic aberrations, generally the nominal range is, such as 3500-4500K

9. What is the luminous efficiency of the incandescent lamp? What is the color rendering index?

About 10-15lm/w color rendering index 100.

10. What color rendering index range can LED do? What kind of color rendering index is commonly used in our company? Range 70-95, our company commonly used Ra70, 80

11. What is the use of color rendering index?

Restore the true color level of the item. The higher the color rendering index, the more true the reflected color

12. What kind of lighting products can LED do, please give examples?

Bulbs, tubes, downlights, panel lights, light bars, spotlights, high bay lights, floodlights

13. What are the structural components of conventional LED lights? What are the uses of each?

The lamp bead is the light source,

led drive power supply, provide stable DC voltage,

Aluminum radiator, dissipates the heat generated by the lamp beads and the power supply

Lamp housing, waterproof and dustproof

Support

circuit board

14. How to distinguish between good and bad LED lamp beads?

15. What is the structure of the LED lamp beads?

Bracket, chip, glue, phosphor, wire 17. What kinds of materials are available for the wires in the LED lamp beads?

Basically, the wire is made of 0.999 pure gold wire, the diameter is divided into: 0.8mil, 1.0mil. There are also some manufacturers pursuing low prices with copper-doped alloy wires. 18. What kinds of materials are currently available for the LED lamp bead bracket?

The led bracket is generally made of copper (there are also iron, aluminum, ceramics, etc.). Because copper has good conductivity, there will be leads inside it to connect the electrodes inside the LED lamp bead. After the LED lamp bead is packaged, the lamp The beads can be removed from the bracket, and the copper feet at both ends of the lamp beads become the positive and negative electrodes of the lamp beads, which are used for welding to LED lamps or other LED products. 19. Which manufacturers of LED chips currently have? Please give examples of first-tier and second-tier brands?

It is used to shine. Common chips in the market are: the United States: CREE, Bridgelux; Japan: Nichia, Toyoda Gosei; Osram, Germany; Taiwan: Epistar, Kellett (a subsidiary of Chi Mei Group), Guangzhou Jia, Taigou, Guanghong, New Century, Everlight, Baihong, Guanglei; Mainland China: Xiamen San'an, Shanghai Blu-ray, Silan Mingxin, Dalian Lumei…………. (Mainland China now mainly uses Taiwanese chips)

16. Which manufacturers of LED lamp beads currently have? Please give examples of first-tier and second-tier brands?

United States: CREE, Bridgelux; Japan: Nichia, Toyoda Gosei; Osram, Germany; Taiwan: Epistar, Kellett

17. What does LED light distribution mean? What methods can be used to achieve the required light distribution effect? The angle and area where the light is emitted from the luminaire can reflect the cover, PC lens 22. What is the unit of the protection level? What does the content of the text represent?

The 18 protection level is usually expressed by two numbers followed by IP, and the numbers are used to clarify the protection level.

The first number indicates the range of equipment resistance to dust, or the degree to which people are protected from hazards in a sealed environment. I represents the level of preventing solid foreign objects from entering, and the highest level is 6;

The second number indicates how waterproof the device is. P represents the level of preventing water ingress, and the highest level is 8.

For example, the protection class of the motor is IP65, the protection class is IP55, etc.

The level of protection against contact with electrical equipment and foreign objects (the first number) The level of protection against water-proof of electrical equipment (the second number)

IP rating, IP (INGRESS PROTECTION) protection grade system IPXX

According to the classification of waterproof and dustproof, such as IP 65, it refers to dustproof grade 6 (completely dustproof), waterproof grade 5 (to prevent the entry of water droplets), and waterproof grade 8. Not leaking.

19. What does COB mean?

COB surface light source is chip-on-board packaging, which is one of the bare chip mounting technologies

Integrated LED, chips on board. Many LED chips are loaded on a chip board and then packaged.

20. What does smd mean?

Surface mount devices, SMD LED lamp beads,

21. How many kinds of LED lamp bead packages can be divided into structural points? What are the characteristics?

1. Why should LED be packaged?

The function of the LED package is to connect the outer lead to the electrode of the LED chip, which not only protects the LED chip, but also improves the luminous efficiency. Therefore, LED packaging not only completes the output of electrical signals, but also protects the normal operation of the die and outputs visible light. It can be seen that the LED package has both electrical parameters and optical parameter design and technical requirements, which is not a simple task.

2. LED packaging equipment

Due to the high requirements for LED packaging, whether it is a direct-plug or SMD LED, a high-precision die bonding machine must be used, because the precise position of the LED die into the package will directly affect the light emission of the entire packaged device efficient. If the position of the die in the reflecting cup is deviated, the light cannot be completely reflected, which directly affects the brightness of the LED. However, with an advanced PR System (Pre-Image Recognition System) die bonder, regardless of the quality of the lead frame, the LED die can still be accurately welded to the predetermined position.

3. LED package form

According to different applications, different dimensions, heat dissipation schemes and luminous effects. There are many types of LED packaging. At present, LEDs are classified according to the packaging form, mainly Lamp-LED, TOP-LED, Side-LED, SMD-LED, High-Power-LED, Flip Chip-LED, etc. Lamp-LED (vertical LED)

The early emergence of Lamp-LED is the in-line LED, and its package adopts the form of potting. The potting process is to first inject liquid epoxy resin into the LED molding cavity, then insert the pressure-welded LED bracket, put it in an oven to allow the epoxy resin to cure, and then detach the LED from the cavity and form it. Due to the relatively simple manufacturing process and low cost, it has a high market share.

SMD-LED (Surface Mount LED)

The SMD LED is attached to the surface of the circuit board, suitable for SMT processing, and can be reflow soldered. It solves the problems of brightness, viewing angle, flatness, reliability, consistency, etc., and uses lighter PCB board and reflective layer materials. After the improvement, the heavy carbon steel material pins of the in-line LED are removed, so that the display reflective layer needs to be filled with less epoxy resin, and the purpose is to reduce the size and reduce the weight. In this way, surface mount LEDs can easily reduce the weight of the product by half, and ultimately make the application more perfect. Side-LED

At present, another focus of LED packaging is side-emitting packaging. If you want to use LED as the backlight light source of LCD (liquid crystal display), then the side light emission of the LED must be the same as the surface light emission to make the LCD backlight light evenly. Although the design of the lead frame can also achieve the purpose of side light emission, the heat dissipation effect is not good. However, Lumileds company invented the design of the reflector, using the principle of the reflector to emit the side light of the surface-emitting LED, and successfully applied the high-power LED to the large-size LCD backlight module.

TOP-LED (top emitting LED)

Top-emitting LEDs are more common SMD light-emitting diodes. Mainly used in backlight and status indicator lights in multi-functional ultra-thin mobile phones and PDAs. High-Power-LED (High-Power LED)

In order to obtain high-power and high-brightness LED light sources, manufacturers are developing toward high-power in LED chip and package design. At present, LED packages that can withstand several watts of power have appeared. For example, the package structure of the Norlux series high-power LED is a multi-chip combination with a hexagonal aluminum plate as a base (to make it non-conductive). The base has a diameter of 31.75mm, and the light-emitting area is located at the center of it, with a diameter of about (0.375×25.4) mm. It can hold 40 LED dies, and the aluminum plate serves as a heat sink at the same time. This package uses conventional die high-density combination packaging

It is equipped with high luminous efficiency, low thermal resistance, and high light output power under high current. It is also a promising LED solid light source.

It can be seen that the thermal characteristics of power LEDs directly affect the operating temperature, luminous efficiency, luminous wavelength, and service life of the LED. Therefore, the packaging design and manufacturing technology of power LED chips are more important. Flip Chip-LED (Flip Chip LED)

The LED flip-chip package structure is basically made with a plurality of perforations on the PCB. Each perforation on one side of the substrate is provided with two different areas of conductive material that are open to each other, and the conductive material is laid flat on the substrate On the surface, there are a plurality of unpackaged LED chips placed at each perforation on the side with conductive material. The positive and negative contacts of a single LED chip are connected to the conductive material on the surface of the substrate by solder balls, and The surface of the side of the plurality of LED chips facing the perforation is dotted with a sealant made of a transparent material, and the sealant is in the shape of a hemisphere at each perforation. It belongs to light-emitting diodes with flip-chip welding structure. Plug-in type, patch type, integrated type.

22. How many kinds of LED lamp beads can be divided in terms of power? What are the specific powers? For example, more than 8 kinds

Low power, high power, COB, 0.06w,0.1w,0.2w,0.5w,1w,2w,3w,5w,8w,10w,20w,40w

23. What is the theoretical life of LED? 100,000 hours

24. What are the reasons that affect the quality of LEDs?

Whether the selected raw materials are good or bad, whether the packaging process is perfect (there is no dust, the components fit perfectly), and the heat dissipation copper pad material.

25. What is the use of the circuit board? What are the characteristics of each? What materials of circuit boards are available?

Multiple LED lamp beads can be connected. FPC, soft and small in size, can be bent at will, PCB has good heat dissipation, can carry power, and is easy to assemble

26. What is the light-emitting angle of conventional LEDs? SMD lamp beads half intensity 120°

27. Why do countries in the world ban incandescent lamps? Energy is scarce in the world, incandescent lighting has low efficiency and high energy consumption.

28. What is the light emitting principle of LED?

A piece of electroluminescent semiconductor material is placed on a shelf with leads, and then sealed with epoxy resin around it to protect the inner core wire, so the LED has good shock resistance. The core part of the light-emitting diode is a wafer composed of a p-type semiconductor and an n-type semiconductor. There is a transition layer between the p-type semiconductor and the n-type semiconductor, which is called a p-n junction. In the PN junction of some semiconductor materials, when the injected minority carriers and majority carriers recombine, the excess energy is released in the form of light, thereby directly converting electrical energy into light energy. With reverse voltage applied to the PN junction, it is difficult to inject minority carriers, so it does not emit light. This kind of diodes made by the principle of injection electroluminescence are called light-emitting diodes, commonly known as LEDs.

The solid semiconductor chip is used as a luminescent material. When a forward voltage is applied to both ends, the carriers in the semiconductor recombine and cause photon emission to generate light.

29. What types of light sources are currently circulating on the market? Like a tungsten lamp! What are the characteristics of each? Incandescent lamp, fluorescent lamp, induction lamp, high pressure sodium lamp, mercury lamp, LED lamp

30. Where does the LED lamp bead pad refer to and what is its use?

On the aluminum substrate board, it is used to fix the LED lamp beads through soldering, provide current and dissipate heat

31. On what basis are the LED lamp bead models classified? For example, there are no less than 10 models!

High power, according to the brand creep XP-G luxeon M/rebel/ F3, F5.

More part is based on external dimensions, 3014, 3020.3528, 2835, 3535, 5050.3214.3222.4014.5630.5730

32. What does light decay mean? As the light source is used, the emitted light will slowly attenuate and the light efficiency will decrease

LED light decay refers to the fact that after a period of time when the LED is lit, its light intensity will be lower than the original light intensity, and the lower part is

The light decay of LED.

33. According to international practice, how much light decay can be considered as invalid? 30%

34. The calculation formula of power? P=UI=Voltage times current 43. What does AC DC stand for? What are the characteristics of each?

Alternating current is a periodical change in size and direction over time, while direct current is a current with a constant direction.

The AC voltage is high, can be transformed, and the transmission loss is small, so the long-distance transmission after the alternating current is transformed

Low DC voltage, large transmission loss and stability

35. What colors can LED do? Red, yellow, green, blue and white, others can be adjusted

36. What is the relationship between color temperature and color? The color temperature is low and the color is reddish-yellow, the higher the color temperature is, the color is bluish

37. What is the most commonly used implementation method for white LEDs?

Most of the white LEDs currently produced are made by covering a layer of light yellow phosphor coating on the blue LED (near-UV, wavelength 450nm to 470nm). This yellow phosphor is usually made by adding cerium-doped yttrium Aluminum garnet (Ce3+:YAG) crystal

The body is ground into a powder and mixed in a dense adhesive. When the LED chip emits blue light, part of the blue light will be efficiently converted by this crystal into a mainly yellow light with a wider spectrum (the center of the spectrum is about 580nm).

38. What is the band unit of light? Wavelength: Nano

39. Many LED products have aluminum and copper materials. What is the use?

Aluminum: mainly use housing, radiator, aluminum substrate,

Copper: As a conductor wire, aluminum substrate heat dissipation pad. Thermal pad for heat pipe and flexible light bar.

40. The difference and characteristics of constant voltage and constant current?

Constant voltage means that no matter how the load changes, the output voltage of the power supply will not change. The constant current means that no matter how the load changes, the output current of the power supply will not change.

41. What are the voltages of our conventional products? What voltage products can be produced through customization? AC 100-265V, DC 12V DC 24V

42. What is the voltage of a single LED usually? Will there be a difference in the voltage of LEDs of different colors?

A single LED power supply is usually 2.7-3.5V,

Yellow-red is generally 1.8-2.2V, blue-white-green is 2.8-4V

43. How many LEDs for 12V and 24V lamps are in one group?

12V is a group of 3, 24V is a group of 6

44. What are the corresponding certifications in the United States, the European Union, Japan, and South Korea?

UL, CE, PSE, KC

45. What is the meaning of series and parallel? Can draw pictures!

46. What is the power supply? What's the use?

ED power drive is a voltage converter that converts the power supply into a specific voltage and current to drive the LED to emit light.

LED drive power, transformer, convert the high-voltage AC of the mains power into low-voltage DC required by LED lamp beads

The efficiency of the conversion of high-voltage AC from mains power into low-voltage DC required for LED lamp beads, the higher the efficiency, the lower the loss.

The heat dissipation pad can be connected on the entire PCB as a whole, and the limited heat dissipation area can be used to the limit.

47. What is the purpose of our PC with PC mask?

Protect the lamp beads and prevent dazzling,

48. How many color changes can RGBled lamp beads achieve?

Generally red, yellow and green

Red (R bright), yellow (RG bright), green (G bright), cyan (GB bright), blue (B bright), purple (BR bright), white (RGB

49. Why is there a price difference for products that look similar in appearance? There may be a big price difference. What factors cause the price difference? There are no fewer than 5 examples!

The use of LED chips is good or bad, the driving power efficiency and the height of the power factor, the heat dissipation aluminum and the shell are good or bad, the PC material is good or bad, the thickness of the conductive wire and the degree of insulation are good or bad.

50. The led tube is currently the most conventional product, the cheapest is only a few yuan, how do they achieve this

What kind of price?

The plant environment is poor, the use of non-strictly trained workers, the use of inferior chips, inferior non-isolated power supplies, inferior aluminum materials, inferior PC lenses, and inferior wires

51. Our main products: street lights, flood lights, tunnel lights, petrol station lights, solar street lights, high bay lights

52. Our commonly used power supply brands: Taiwan Mingwei power supply, Shenzhen Songsheng power supply, Lizhuo power supply, Zhuhai classic power supply

53. The light-emitting angle of the lamp: Normally 120-140°, the angle of the double lens can be selected from 5/15/30/45/60/90/120 degrees

54. The color temperature of Cree COB<5000K

55. Color temperature distinction: 2700-7500K

2700-3500K warm white 4000-4500K natural white 5500-6500K positive white 7000-7500K positive white