Prolong the service life of the LED heat radiating design and use the material to choose?

Developers can dissipate heat through the effective management to improve LED efficiency and service life, but JADE BRIDGES explained, carefully selected materials and application methods of critical heat dissipation.

The LED industry is one of the fastest growing technology industry. Although LED has many years of application in many electronic devices, but recently the application of high-power LED more in a variety of lighting and auto (Figure 1), signs and home appliance products, the amount of money. LED lighting is very reliable but based on reliability depends on the thermal design of components around good. This paper will introduce how to carefully select the cooling material and understand how to use these materials.

Figure 1. LED car headlight applications not only require a good heat, and can also protect LED lights.

LED as halogen lamps, incandescent and fluorescent lighting system alternatives, development of the lighting market will be very considerable. The growth of LED due to LED in the aspects of adaptability, life and efficiency is superior to the traditional lighting form. LED has more design freedom, provide a very long service life, and is quite efficient, most of the energy can be converted into light, thereby minimizing the heat.

Heat generation

However, LED is still in the semiconductor junction have obvious heat. This heat can have a negative impact on the LED, so it is necessary to heat, to ensure the realization of solid-state lighting (SSL) the real advantage. LED classification usually by color, there are many variants of different colors on the market.

If the LED temperature change, its color will change. For example, white light temperature, can lead to LED a warmer CCT. In addition, if there are changes in the same chip temperature in the array of LED, may launch a range of color temperature, thus affecting the quality and appearance of terminal lighting products.

As shown in Table 1, the right to keep the LED chip temperature can not only prolong the service life, but also can produce more light; therefore, only the LED can achieve the desired effect. Working temperature may have a negative impact on the performance of LED, but this effect can be restored. However, if more than the junction temperature, especially higher than LED (120-150 C) the maximum working temperature, may influence can not be recovered, resulting in complete failure.

Table 1. CREE XLamp LED the characteristics shown, the performance of LED varies with temperature.

In fact, the temperature and the LED life is directly related; the higher the temperature is, the shorter life of LED, as shown in figure 2. The LED driver is in the same way, the life is decided by the life of the electrolytic capacitor. Through the calculation, the working temperature can be determined, every drop of 10 degrees, the service life of the capacitor is doubled. Therefore, to ensure the effective thermal management can provide a consistent appearance quality, and the service life of the LED array, thus opening up opportunities for further application of the continuous development of the industry.

Figure 2. curves recorded at 350 mA Cree XLamp LED driven by the junction temperature and the life.

Thermal relief

There are many ways to improve the thermal management of LED products, must choose the right type of conductive materials, in order to ensure the cooling effect to achieve the desired. In the field of materials, thermal interface materials from the heat conducting encapsulation resin provides thermal and environmental protection to improve thermal efficiency of the product range.

Thermal interface materials are designed for compound filling 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, reduce the operating temperature of the equipment. The cured product can also be used as adhesive material. Examples include RTV (RTV silicone) or epoxy compounds. Material selection usually depends on the required temperature range or adhesive strength.

Another option is to use thermal conduction resin package. These products are designed to provide protection for the equipment, but also make the equipment to generate heat to the surrounding environment. In this case, a packaging resin radiator, and the heat conduction from the device. These products can be used on the LED device, and also can be selected according to the color of the light extraction from the unit for help.

The package also includes the use of resin filler; however, can be altered by the use of basic resin, curing agent and other additives, to provide a range of options, including epoxy resin, polyurethane resin and silicon chemicals. Different chemicals will provide a series of attributes, each application should take into account the needs of the end of the.

The option of packaging materials

For example, the polyurethane material provides excellent flexibility, especially at low temperatures, compared with epoxy resin is one of the main advantages. Silicone resin can also provide this flexibility at low temperature, and excellent high temperature performance, more than other existing chemical components. Silicone products are usually more expensive.

Epoxy resin is very strong, provide excellent protection in harsh environments. It is a rigid material having a low coefficient of thermal expansion, and can be added to a certain degree in the products in some cases flexible. Resin added can produce a lot of performance with customized products for a variety of applications; therefore, suggestions and related material suppliers in detail application.

apply property

No matter what type of heat in the choice of products, as well as some of the key attributes must be considered. These parameters can be quite simple, such as equipment operation temperature, electrical requirements or other restrictions, such as viscosity, curing time.

The other parameter is more important for equipment, but only one