27 August 2020

Introduction

LED lights emitting diode (LED) is a solid-state semiconductor device that can directly convert electrical energy into light. The heart of the LED is a semiconductor chip. One side of the chip is connected to the bracket, one end is the negative electrode, and the other side is connected to the positive electrode of the power supply. The entire chip is encapsulated by epoxy resin. The semiconductor chip is composed of two parts, one is a P-type semiconductor, in which the holes dominate, and the other is an N-type semiconductor, which is mainly an electronic device. When two semiconductors are connected, a PN junction is formed between them. When a current acts on the chip through a wire, the electronic device will be pushed to the P region, in which the electronic device recombines with the hole, and then emits energy in the form of photons. This is the principle of LED.

The LED chip is the core component of the LED and refers to the PN junction. Its main function is to convert electrical energy into light, and the main material is single crystal.

 

How Do They Work?

LED lights generate lighting in semiconductor materials by electroluminescence. Electroluminescence is a phenomenon in which a material emits light when a current or an electric field passes through it-this phenomenon occurs when an electron passes through the material and fills an electron hole. There are electron holes in which atoms lack electrons (negatively charged) and therefore have a positive charge. Semiconductor materials like germanium or silicon can be “doped” to create and control the number of electron holes. Doping is the addition of other elements to a semiconductor material to change its properties. By doping a semiconductor, you can make two different types of semiconductors in the same crystal. The boundary between the two types is called a pn junction. Junctions only allow current to pass through them in one way, which is why they are used as diodes. The LED is made using a pn junction. When electrons pass from one crystal to another, they are filled with electron holes. They emit photons (lights). This is how a semiconductor laser works.

 

What is COB LED?

For the LED market, COB LEDs have many advantages over standard LEDs. COB LED is basically a manufacturer that directly connects multiple LED chips (usually 9 or more) to the substrate to form a single module. Because the single LED used in the COB is a chip rather than a traditional packaging method, the chip can be mounted so that it takes up less space, and the maximum potential of the LED chip can be obtained. When the COB LED assembly is powered on, it looks more like a lighting panel than multiple individual lamps, just like using several SMD LEDs mounted closely together.

 

Advantages of COB LED Chip

Due to the multi-chip package, the light-emitting area of the COB LED can contain more light sources in the same area as the standard LED, thereby greatly improving the lumen output per square inch.

The COB LED uses a circuit with only two contacts to power the multiple diode chips contained therein. This allows each LED chip to work properly with fewer components. In addition, reducing components and eliminating traditional LED chip structure packaging can reduce the heat generated by each LED chip. When coupled with an external heat sink, the ceramic / aluminum substrate of the COB LED can also be used as a more efficient heat transfer medium, thereby further reducing the overall operating temperature of the component. When installing COB on the radiator, you must pay attention to choose a radiator that can dissipate heat, so that COB can fully realize its potential. In the long run, proper heat dissipation can increase efficiency and reduce failure rates.

Another aspect of the COB LED that reduces the failure rate is that, because each chip is directly mounted on the substrate, there is no need to spot solder a single LED chip. The smaller the number of welding points, the lower the failure rate.

When using COB LEDs, since lenses and other traditional LED package components are no longer in place, the optical loss is significantly reduced and the viewing angle is increased.

 

Application of COB LED lighting

COB LED chip has a wide range of applications. Although these devices can be used for higher output conventional lighting, the main purpose of COB LEDs is to replace solid state lighting (SSL) metal halide lamps for high pitch lighting, street lights, high output track lights and downlights.

 

 

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