Zhongke Core Source Ye Shanghui: LED professional lighting gives priority to light distribution design / high reliability / cost performance

LEDs never lack new opportunities or new markets. At the 2016 High-tech LED Annual Meeting, the "Next Technology Battle of Packaging" special event by Hyun Shuo Optoelectronics, Ye Shanghui, executive deputy general manager of Zhongke Core Source, brought "K-COB ultra-high power COB application to the guests." The theme of the trend.

Ye Shanghui, Executive Deputy General Manager of Zhongke Core Sources

LEDs enter the professional lighting field, first of all to improve light output and light stability.

In some special large-space lighting fields, it is also necessary to put forward higher requirements for light distribution, and to achieve higher requirements for long-distance projection. In some industrial lighting environments, higher requirements are also placed on the reliability of the luminaire.

For example, some of the lights at the ceiling station of Guangzhou South Railway Station are not lit, and higher requirements are placed on LEDs in places where large space is difficult to maintain. In the case of traditional explosion-proof lamps, more power and better protection are also needed.

From the replacement of 150 watts, 400 watts of power, higher power LED replacement encountered some difficulties. In the field of large space professional lighting, the metal halide lamp power exceeds 1KW. In these applications, due to the long distance of space, it is also the demand for directional lighting. It is required to provide output with small angle and high light intensity.

This requires higher brightness and better reliability of LEDs. When we are doing high-power LEDs, taking into account reliability management and optical design, we are faced with some problems and may have some contradictions.

Heat distribution of COB

The appearance of the COB package structure has been around for 20 years. In the early days of low-power applications, its performance focused on chip temperature control.

When it comes to a certain power, when the COB field is more than 100 watts from tens of watts, the industry has a lot of professional analysis. The chip temperature control itself can achieve a better range, but after the power increases and the density increases, it Part of the fluorescence of the fluorescence conversion can not be ignored.

If the power is too large, more than 200 watts, its temperature may exceed 300 degrees, and its heat source is not in the chip.

Material temperature characteristics

The most common is yellowing, vitrification, and cracking. The presence of blue light indicates that there is no problem with the chip, and the fluorescence conversion lacks the yellow portion, so blue light appears.

Fluorescent material properties

Why does yellow light fail? When it exceeds a certain temperature, the fluorescence efficiency drops sharply. The phosphor is attenuated from 200 to 250 degrees, and it is impossible to return to the original state.

For the 150 watt light source, from the structural simulation to the actual finished product test, the temperature is concentrated in the center, and the heat at the center point is difficult to be exported, which is limited by the thermal conductivity of the silicone.

Thermal structure analysis of COB light source

Fluorescent ceramic is a ceramic crystal. A technology converted from laser ceramics matches the visible yellow light part and maintains the characteristics of the original ceramic. It has good thermal conductivity and good temperature resistance.

We have designed a package structure that allows the heat of the fluorescent part to be equalized on the fluorescent ceramic and is guided to the heat sink by the design of the structure.

The effect of our practical application is that, under the condition of 600 watts, the extraction point at 105 degrees can also control the center temperature of the phosphor ceramic to about 120 degrees.

Optical advantage

Solving the short board of the package structure is a key to COB's improvement of light efficiency. After the density increases, the pitch of COB is reduced. Generally, we are now making high-density COB. The pitch of the chip is less than 1 mm, and its thermal performance is particularly obvious.

By improving this structure, the entire light source can be operated at a relatively low temperature level. From the viewpoint of fluorescence conversion characteristics, the fluorescent ceramic can maintain a fluorescence conversion rate of 95-98 or more in the range of 120-150 degrees.

At the same time, the design of the fluorescent ceramic can be well matched with the spectrum of the blue chip, without causing the fluorescence and the spectrum to be too wide, and the repeated excitation affects the efficiency. The ceramics can be designed to increase the output of light through the microstructure of the surface. In the end, we can reach 160 seconds / watt.

Low thermal resistance package

It is still necessary to consider the chip junction temperature control. The chip junction temperature control is determined by the package thermal resistance, and the package structure can improve the package thermal resistance. We can now do the same, and the thermal resistance can be reduced by half.

At the same time, the more high-power light source needs the support of heat dissipation, it needs a strong match to the center heat release. Through the design of the radiator, the temperature difference between the center end and the end is controlled at 5 degrees, and the temperature difference between the upper and lower sides and the center point is controlled within 2 degrees.

The final effect is that under the condition of 300 watts, the extraction point is at 66 degrees, and the highest temperature of the surface of the light source is about 120 degrees.

Industrialization path

Through technology transfer, we have developed a crystal matching of fluorescent ceramics in the infrared band of LEDs, positioned in high-power, ultra-high-power COB light sources.

The first generation of light source is 630 days of daily temperature aging as of January 4, 2017, and the aging cycle exceeds 15120 hours. At the same time, the 85-degree aging test was proposed. Two sets of samples were made: 300 watts of samples and 500 watts of samples. At present, it has exceeded 7500 hours, and we are aging under the conditions of +2.1 times of current.

We did the LM-80 test. The result of the 80 certification may be 2018, and it may take more than 10,000 hours. At the same time, the light source has not stopped, and a steady state output of 1000 watts has been achieved.

From material research and development, to white light patents, to patents without package structure, we have achieved a series of results, and at the same time obtained 5 international PCT international patent applications, we have a complete patent structure.

Ultra-high power COB applications have very obvious advantages in sports applications. Sports require precise backlighting and small light decay. The domestic level of environmentally friendly lamps has stopped at 120 watts, which limits the size of the light source. In the small size, it is more than 200 watts. It is also a relatively blank field.

In road lighting, it is hoped that the life of the light source lamp will reach more than 8 years. At present, there are many plans to do it. One is the separation of the light source and the power source, which can reduce the maintenance cost.

Our direction, when the maintenance cost is higher than the cost of the lamp, it must impose strict requirements on the reliability of the LED lamp.

Professional lighting prioritizes light distribution design: small size, high power; priority is high reliability: long life, low light decay; priority cost performance: high quality, maintenance free.

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