Part 1: What is an LED?

1. What is a Light Emitting Diode (LED)? A Light Emitting Diode (LED) is a new type of solid-state light source that emerged in the 1960s. In 1923, Lossen.o.w discovered light emission in P-N junctions with impurities while studying the semiconductor SiC, leading to the invention of the LED. Initially, this discovery was not given much attention. With the rapid development of the electronics industry and display technology in the 1960s, LEDs gradually gained recognition.

2. How Do LEDs Emit Light? LEDs are made from III-V compound semiconductors such as GaAs (Gallium Arsenide), GaP (Gallium Phosphide), and GaAsP (Gallium Arsenide Phosphide). The core is an active layer composed of a double heterostructure in the middle of the PN junction. When a forward voltage is applied and a small current flows through the terminals, electrons and holes combine to release the excess energy in the form of light and heat. The characteristics of LEDs include forward conduction, reverse cutoff, and breakdown properties, along with light and heat emission.

Part 2: What Are the Advantages of LEDs?

  1. Long Lifespan: Exceeds 100,000 hours.
  2. Low Driving Voltage: Operates between 1.8 to 4.5V.
  3. Low Power Consumption: Energy-efficient, consuming between 40 to 100mW.
  4. Relatively Cool Light Source: Generates minimal heat.
  5. Fast Response Time: Lights up quickly.
  6. Compact Size: Small and suitable for various applications.
  7. Multiple Colors: Available in various colors.
  8. Excellent Vibration Resistance: Solid-state encapsulation makes it durable.
  9. Good Monochromaticity: Stable wavelength ensures pure color.
  10. Environmentally Friendly: Contains no pollutants.

Part 3: How Are LEDs Structured and Classified?

A. Through-Hole LED (LAMP)

  • By Shape: 3mm, 5mm, 8mm, 10mm, etc.
  • By Emission Color: Red, Green, Blue, Yellow, Orange, Yellow-Green, White, Purple, Infrared, Ultraviolet, etc.
  • By Colloid Color: Colorless transparent, colored transparent, colored scattering, colorless scattering (adjustable depth based on ratio).
  • Color Classification: Single color, dual color, full color (tri-color).

B. Surface-Mounted Diode (SMD)

  • By Shape: 0603, 1206, 2810, 3020, 3528, 5050, etc.
  • By Color: Red, Green, Blue, Yellow, Amber, Yellow-Green, White, Purple, Infrared, etc.
  • By Emission Surface: Top-emitting, side-emitting.
  • By Encapsulation Process: Dot encapsulation, MoDing.
  • Color Classification: Single color, dual color, full color (tri-color).

C. Flux LED (Piranha LED)

  • By Top Bead: Φ3mm, Φ5mm, flat head products.
  • By Emission Color: Red, Green, Blue, Yellow, Orange, Yellow-Green, White, Purple, Infrared, Ultraviolet, etc.
  • By Colloid Color: Colorless transparent, colored transparent, colored scattering, colorless scattering (adjustable depth based on ratio).
  • Color Classification: Single color, dual color, full color (tri-color).

D. High-Power LED (Power LED)

  • Types: 1W, 3W, 5W, 10W, etc.
  • By Shape: Imitation luminous, ceramic substrate SMD style, COB module and integrated module.
  • By Encapsulation Process: Dot encapsulation, MoDing.

E. Digital Tube LED (Display)

  • Types: Single-digit, dual-digit, three-digit, four-digit, multi-digit.

F. Dot Matrix Display

  • Shape: Different from digital tubes but with similar specifications.

Part 4: How is the LED Industry Divided?


The LED industry can be divided into upstream wafer production, chip production, midstream packaging, and downstream applications. The specific process flows are as follows:

1. Epitaxial Wafer Process:

  • Substrate
  • Structure design
  • Buffer layer growth
  • N-type GaN layer growth
  • Multi-quantum well light-emitting layer growth
  • P-type GaN layer growth
  • Annealing
  • Inspection (photoluminescence, X-ray)
  • Epitaxial wafer

2. Chip Process:

  • Epitaxial wafer
  • Design and process mask
  • Photolithography
  • Ion etching
  • N-type electrode (plating, annealing, etching)
  • P-type electrode (plating, annealing, etching)
  • Scribing
  • Chip sorting and grading
  • Packaging

3. Packaging Process:

  • Crystal expansion
  • Silver paste application (insulating paste)
  • Die bonding
  • Baking
  • Plasma cleaning
  • Wire bonding
  • Encapsulation
  • Long and short baking
  • Appearance inspection
  • Stripping
  • Sorting
  • Taping
  • Packaging

Part 5: What is the LED Packaging Production Process?

The LED packaging production process includes:

  • Die bonding
  • Wire bonding
  • Encapsulation
  • Baking
  • Plasma cleaning
  • Wire bonding
  • Encapsulation
  • Appearance inspection
  • Stripping
  • Sorting
  • Taping
  • Packaging

Part 6: What Are the LED Optoelectronic Parameters and Characteristics?

ParameterDescriptionUnit
Wavelength (λ)Determines the color of light, ranges from 380nm (violet) to 780nm (red)nm
Forward Voltage (VF)Voltage drop when specified forward current flowsV
Reverse Current (IR)Current when specified reverse voltage is appliedμA
Luminous Flux (Φv)Total light output perceived by the human eyeLM
Luminous Intensity (Iv)Light emitted in a specific direction per unit solid angleCD
Color TemperatureTemperature of an ideal black-body radiator with comparable hueK
Color Rendering (Ra)Ability to render colors accurately compared to natural light-

1. Wavelength Light is an electromagnetic wave, and the wavelength determines the color of light. The visible light spectrum ranges from violet (about 380nm) to red (780nm). Non-visible wavelengths include infrared (greater than 780nm) and ultraviolet (less than 380nm).

2. Forward Voltage (VF) The voltage drop across the LED when a specified forward current flows through it.

3. Reverse Current (IR) The current that flows through the LED when a specified reverse voltage is applied across it.

4. Luminous Flux (Φv) The total amount of light emitted by the LED per unit of time, perceived by the human eye. Measured in lumens (LM).

5. Luminous (or Radiant) Intensity (Iv) The amount of light emitted by the LED in a specific direction per unit solid angle. Measured in candelas (CD).

6. Color Temperature (K) The temperature of an ideal black-body radiator that radiates light of comparable hue to that of the light source. Higher temperatures correspond to bluer light, while lower temperatures correspond to redder light. Common classifications:

  • 2000-4000K: Warm White
  • 4000-5000K: Yellowish White
  • 5000-8000K: Pure White
  • 8000-10000K: Cool White

7. Color Rendering (Ra) The ability of a light source to accurately render the colors of objects compared to a natural light source. The Ra value ranges from 0 to 100, with higher values indicating better color rendering.

Part 7: What Are Some Examples and Tests of LED Mounting?

Single BIN Production: Products are produced with uniform brightness and color zones according to work order requirements.

Mixed BIN Production: Different BIN LEDs are combined according to work order requirements, with BIN1 for odd positions and BIN2 for even positions.