LED application trends and packaging technology trends

The development and application trend of LED brightness

Figure 1 and Figure 2 as the LED unit brightness increases, so the application field of LED is more and more broad, but the pursuit of LED brightness at the same time, the LED chromaticity requirements gradually become a general consensus, in other words the pursuit of color similar to the sun's LED has become the common goal of downstream application industry.

The application of LED in various commodities facing problems of heat, power consumption, nothing more than the color rendering, color uneven and so on, but with different solutions industry has unique and significant differences (Figure 3), such as lighting and automobile industry in order to improve the beam, using LED a mobile phone number is hundreds of times the backlight board, relative to the drive current increase, making the cooling strategy has become the primary problem urgent. The most commonly used method is to encapsulate the LED chip directly on the substrate with high thermal conductivity. In contrast with the mobile phone camera with flash, power consumption based on the consideration of no use of high current density to increase the brightness, so how to effectively use LED light and uniform irradiation to the illuminated body, far more attention than how to improve the cooling effect. The usual method is to use the lens and reflector (mirror), the LED light will converge to the camera angle. In addition the LED color rendering although there are still some areas and LED manufacturers are closely related, but in fact most of the downstream application vendors have begun to use the method of groping white LED, that is to say the initiative LED CRI has been transferred to the downstream application industry.

Figure 3 LED commodity applications

96 years after the advent of white LED lighting equipment, many automobile manufacturers try to make all kinds of related products using white LED, the white LED chip output per watt of Hui has been from the past lumen (LM) increased to tens or even hundreds of lumens, for example, in order to obtain the 40W and fluorescent light beam phase, using LED module the number of chips from the past nearly one thousand dropped to dozens, the cost and size of more practical. However, results in a substantial increase in brightness, but the heat problem become the biggest obstacle to commercialization, in addition the emission spectrum of the high brightness white LED in the red component of low color temperature and color rendering, resulting in less sunlight and fluorescent lamp, the utility of white LED has again been questioned. LED heat dissipation and packaging

The heat problem, such as the current density of LED lighting applications up to 100mA, if not for the heat treatment (thermal impedance) 10 ~ 20 LED module temperature which exceeds the ambient temperature, too high as module temperature, and if the thermal impedance for comparison, LED light output about 20% lower. Figure 4 is a commonly used strategy, basically it is the LED chip is directly packaged in a high thermal conductivity of the substrate, the substrate will quickly eliminate the heat LED.

Figure 4 LED cooling strategy

Figure 5 is the LED application manufacturer Matsushita blue emitting white light LED module will be directly packaged in the machine, the machine body as cooling media, according to the test results show that even if the current is increased by three times, about half of the thermal impedance module only traditional epoxy resin encapsulation; star and motor is red and green, blue (RGB) three LED color chips are packaged in metal substrate formed white LED module, basically white LED module structure and its Matsushita Electric, is the use of metal substrate as cooling medium. Panasonic in order to improve the heat dissipation of the LED chip, so the use of multilayer substrate metal material and metal composite material made of 64, 20 x 20mm blue LED chip is directly packaged in multilayer substrate, and a white LED module with yellow phosphor, light at room temperature for 120lm is the highest level in the industry. In addition, the blue LED chips can be directly encapsulated in the sapphire substrate, because the heat emitting layer close to the substrate, thus obtaining a good cooling effect, its thermal resistance, is the traditional package mode about 1/200.

As shown in Figure 6 SHARP simulation analysis, decided to improve the heat dissipation of the terminal thickness and area, and then according to the results of simulation analysis to improve the LED chip module terminal.

OMRON is set to two radiating dedicated terminal in the LED chip, LED chip and increase the current density increase light output, and use Reflector to LED chip to produce light in front of injection (Figure 7), so the structure of the external quantum efficiency by the traditional 30 to 50% to 80%, while the LED module of OMRON is a blue chip, but as long as the collocation can be transformed into a yellow phosphor for white light emitting LED. In addition, the company is developing RGB three kinds of LED chip technology in the single module, the white light-emitting LED module with the point of light can be converted into the advantages of light, so that the light can be evenly distributed in the irradiated body.

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