Heat dissipation design prolongs the service life of LED

Date:05-08-2019

As a substitute for halogen lamp, incandescent lamp and […]

As a substitute for halogen lamp, incandescent lamp and fluorescent lamp lighting system, the development of LED lighting market will be considerable. The growth of LED is attributed to its superiority in adaptability, lifetime and efficiency over traditional lighting forms. LED has more design freedom, provides a very long service life, and is also quite efficient, can convert most of the energy into light, thereby minimizing the amount of heat emitted.

Generating heat
However, the LED still generates significant heat at the semiconductor junction. This heat can adversely affect the LED, so heat dissipation must be carried out to ensure the real advantage of solid-state lighting (SSL). LED is usually classified by color temperature. There are many variations of different colors on the market.
If the working temperature of the LED changes, its color temperature will also change. For example, the temperature rise of white light can cause the LED to emit warmer CT. In addition, if there is a chip temperature change on the same array of LED, it may emit a certain range of color temperature, thus affecting the quality and appearance of terminal lighting products.

Maintaining the correct chip temperature of the LED can not only prolong the service life, but also produce more light; therefore, only a small number of LED can achieve the desired effect. The increase of working temperature may have a negative impact on the performance of LED, but this effect can be recovered. However, if the junction temperature exceeds the junction temperature, especially the maximum operating temperature of the LED (120-150 C), irreversible effects may occur, leading to complete failure.

In fact, the working temperature is directly related to the lifetime of the LED; the higher the temperature, the shorter the lifetime of the LED.

The same is true of LED drivers, whose lifetime is determined by the lifetime of electrolytic capacitors. By calculating, it can be determined that the life of capacitor doubles with the decrease of working temperature of 10 C. Therefore, ensuring effective heat dissipation management can provide uniform quality, appearance and service life for LED arrays, thus opening up opportunities for further application in the growing industry.

There are many ways to improve the heat dissipation management of LED products. It is necessary to select the right type of thermal conductive materials to ensure the desired heat dissipation effect. In the field of materials, products range from heat-conductive packaging resins that provide heat dissipation and environmental protection to heat-conductive interface materials used to improve thermal conductivity efficiency.
The thermal conductive interface material is a compound designed to fill the gap between the device and the radiator, thereby reducing the thermal resistance at the boundary between the two. This material will accelerate the heat loss and reduce the working temperature of the equipment. Cured products can also be used as adhesives. Examples include siloxane RTV (room temperature vulcanization) or epoxy compounds. Material selection usually depends on the required bonding strength or operating temperature range.
Another option for thermal conductivity is to use thermal conductive packaging resins. These products are designed to provide protection for the equipment, while also allowing the heat generated in the equipment to radiate into the surrounding environment. In this case, the packaging resin becomes a radiator and transfers heat from the device. These products can be used in LED devices, and can also help extract light from the cell according to the selected color.
Packaging resins also include the use of thermal conductive fillers; however, the use of base resins, hardeners and other additives can be changed to provide a wide range of options, including epoxy resins, polyurethanes and silicone resin chemicals. Different chemicals will provide a range of attributes, each of which should take into account the final application requirements.

Packaging material options
For example, polyurethane materials provide excellent flexibility, especially at low temperatures, which is a major advantage over epoxy resins. Organosilicon resins can also provide this flexibility at low temperatures and provide excellent high-temperature properties that are superior to other existing chemical compositions. Organosilicon products are often more expensive.
Epoxy resins are very strong and provide excellent protection in all kinds of harsh environments. They are rigid materials with low thermal expansion coefficients, and in some cases can be added to the product with a certain degree of flexibility. The addition of packaging resins can produce a large number of customized products for various applications; therefore, it is recommended to discuss applications in detail with relevant material suppliers.

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