1 Article to Introduce What is the LED Basically?

LED (Light Emitting Diode) is a semiconductor light source that produces light through the direct electroluminescent effect when an electric current passes through a semiconductor material. Known for their efficiency, environmental friendliness, and long lifespan, LEDs have found extensive applications in modern society. The development of LED technology continues, and with advancements in new materials and manufacturing techniques, it is expected to demonstrate its unique advantages in more areas in the future.

Principle of LED

An LED consists of a PN junction, which is a combination of a P-type semiconductor (with an excess of holes) and an N-type semiconductor (with an excess of electrons). When current flows from the P-type layer to the N-type layer, electrons and holes combine near the PN junction, releasing energy. This energy is emitted in the form of photons, producing light.

Main LED Packaging Materials

Main LED Packaging Materials Include: Chips, Wires, and Mounts.

• Chips: Available in square and round shapes; red, green, and blue colors, with sizes ranging from 8mil to 45*45mil.
• Wires: Gold, silver, alloy, aluminum, and copper wires.
• Mounts: PPA, PCT, EMC ceramics. EMC mounts have advantages such as high heat resistance, non-yellowing, high current, high power, high density, UV resistance, and small size.

Development History of LED

Since Thomas Edison invented the light bulb in 1879, humanity has entered the era of electric lighting. Today’s lighting solutions have evolved to be primarily LED-based. Before replacing traditional lighting technologies, the development of LED technology has gone through a century of evolution, with the following milestones:

• Early Discovery: In 1907, British engineer H.J. Round discovered the phenomenon of electroluminescence, which was an early concept of LED technology.
• First LED: In 1927, Russian inventor Oleg Losev created the world’s first LED light bulb, but it did not find practical application at the time due to cost and technological limitations.
• Technical Breakthrough: In 1955, physicists at the American Radio Corporation discovered the infrared radiation of gallium arsenide and other semiconductor alloys, laying the foundation for the later development of LEDs.
• Visible Light LED: In 1962, Nick Holonyak Jr. of General Electric successfully created the first visible light-emitting red LED, marking the transition of LED technology towards lighting tools.
• Commercialization and Color Development: By the late 1970s, LEDs of various colors, including red, orange, yellow, green, and cyan, had been developed. However, it was not until 1993 that Shuji Nakamura, a Japanese scientist, invented the blue LED, which was key to bringing LED lighting technology into homes and commercial lighting.
• White Light LED: In 1998, white light was produced by coating blue LED chips with YAG yellow phosphor, marking the official entry of LEDs into the lighting era.
• Nobel Prize: Shuji Nakamura was awarded the Nobel Prize in Physics in 2014 for his contributions to the invention of blue LEDs, recognizing his efforts to create energy-efficient and bright white light sources.
• Popularization in the 21st Century: After entering the 21st century, the cost of LED bulbs has dropped significantly, while maintaining their energy-saving, safe, and high-brightness characteristics, beginning to fully replace traditional lighting technologies.
• Intelligence and Diversity: The ease of controlling LEDs, their small size, and the ability to produce a variety of colors make lighting solutions more intelligent and personalized. Users can control the brightness and color of lighting through wireless devices, making LED lighting technology more diverse.

Features of LED

• High Efficiency: LEDs are more energy-efficient than traditional incandescent and fluorescent lights because they convert more electrical energy into light energy rather than heat.
• Long Lifespan: The lifespan of LEDs far exceeds that of traditional light sources, generally reaching over 50,000 hours.
• Fast Response: The illumination and extinguishing of LEDs can be almost instantaneous, making them very suitable for applications that require rapid switching, such as automotive brake lights.
• Durability: LEDs do not have filaments or gas filling, making them more shock-resistant and durable.
• Compact Size: The small size of LEDs makes them easy to integrate into compact spaces, suitable for the design of modern electronic devices.
• Environmentally Friendly: LEDs do not contain harmful substances such as mercury, and their long lifespan reduces the generation of waste.
• Dimmable: Many LEDs can be easily dimmed, providing more flexible lighting solutions.
• Color Diversity: LEDs can emit various colors of light, including red, green, and blue. By combining different colors of LEDs or using special phosphors, a variety of colors, including white light, can be produced.

Basic Specifications of LED Chips:

Size of LED chip

• 0603: Converted to the metric system is 1608, indicating that the length of the LED component is 1.6mm, and the width is 0.8mm. It is commonly referred to as 1608 in the industry and 0603 in English.
• 0805: Converted to the metric system is 2012, indicating that the length of the LED component is 2.0mm, and the width is 1.2mm. It is commonly referred to as 2012 in the industry and 0805 in English.
• 1210: Converted to the metric system is 3528, indicating that the length of the LED component is 3.5mm, and the width is 2.8mm. It is commonly referred to as 3528 in the industry and 1210 in English.
• 3014: This is the metric designation, indicating that the length of the LED component is 3.0mm, and the width is 1.4mm.
• 3030: This is the metric designation, indicating that the length of the LED component is 3.0mm, and the width is 3.0mm.
• 3528: This is the metric designation, indicating that the length of the LED component is 3.5mm, and the width is 2.8mm. It is commonly referred to as 3528 in the industry (3.551.9).
• 2835: This is the metric designation, indicating that the length of the LED component is 3.5mm, and the width is 2.8mm. It is commonly referred to as 2835 in the industry (3.550.8).
• 5050: This is the metric designation, indicating that the length of the LED component is 5.0mm, and the width is 5.0mm. It is commonly referred to as 5050.

Angle of LED chip

Angle Specifications The light-emitting angle of LED light sources is between 90-160 degrees; there are differences among manufacturers, usually between 115-125 degrees. The angle affects the light-emitting angle and illumination of the finished lamps.

LED Color Temperature (LCT) of LED

Different color temperatures can evoke different emotional responses in people. Warm white 2700K-3300K is stable and warm; Natural white 4000K-5000K is refreshing, natural, and comfortable; Daylight white 5500K-6500K is serious and cool; Cool white above 7000K is cold and elegant, suitable for jewelry. Light sources are generally categorized into three types based on color temperature: 

• Warm white 2700K-3300K

Warm light has a color temperature below 3300K. It is similar to the color of incandescent light, with more red light, giving a warm, healthy, and comfortable feeling. It is suitable for homes, residences, hospitals, hotels, and places with lower temperatures.

• Natural white 4000K-5000K

Its color temperature ranges from 4000K to 5000K. Warm white light is soft and gives a pleasant, comfortable, and peaceful feeling. It is suitable for stores, hospitals, offices, restaurants, waiting rooms, and other places.

• Daylight white(Cool Light) 5500K-6500K

Cool Light Also known as daylight, its color temperature is above 5300K. The light source is close to natural light, giving a bright feeling and helping people concentrate. It is suitable for offices, meeting rooms, classrooms, drafting rooms, design studios, library reading rooms, exhibition windows, and other places.

Color Rendering Index (CRI) of LED

The ability of a light source to reveal the colors of objects is called color rendering, which is compared to the appearance of object colors under the same color temperature reference or standard light sources (incandescent lamps or daylight). The Color Rendering Index (CRI) of a light source that is high can illuminate objects to show more realistic colors. Currently, the CRI is a common method for defining and evaluating the color rendering properties of light sources.

Applicable Ranges for Different Color Rendering Indices (CRI):

• Ra ≥95 Suitable for museums, art galleries, and printing industries and venues.
• Ra ≥90 or 80 Suitable for homes, restaurants, high-end textile crafts, and similar industries.
• Ra ≥70 Suitable for offices, schools, outdoor street lighting.
• Others, Suitable for heavy industrial factories, outdoor street lighting, outdoor road lighting, and some places with lower requirements.

Heat dissipation is a crucial factor for design of LED lights

Above H series LED fixture is a long-last products made by PCcooler, our engineers are good at design of heat-dissipation for LED.

Application field of LED

1. General lighting: home, office, shopping malls, streets and other lighting.
2. Lights: traffic lights, car taillights, etc.
3. Display: LED display is widely used in billboards, information display, etc.
4. Decorative lighting: festival decoration, landscape lighting, stage lighting, etc.
5. Special lighting: plant growth lights, medical lighting, mining lighting, etc.

Future trend of LED