Discussion on the advantages of COB encapsulation in LED lamps

The initial stage of LED lighting is mainly decorated with decorative light sources. Although the power is small and the price is high, the reliability is high, the control is strong, and the volume is small. Therefore, the first emerging market is night light and line lights. With the gradual development of LED lighting fixtures, LED lighting fixtures have gradually replaced some traditional light source products in public places such as lighting engineering auxiliary lighting. In 2009, LED lamps began to enter the mainstream lighting in developed countries. In the commercial applications where electricity costs are high and the use time is long, LED lamps quickly become the new darling of the market. The market has certain recognition and acceptance of LED lighting products. Other features such as environmental protection, small size, and high reliability of LED lamps have gradually emerged.

Overall, with the improvement of LED product quality and cost performance, LED lighting is moving in the direction of replacing all other artificial light sources.

At present, LED indoor lighting fixture design technology is difficult

a) Thermal technology issues

Like traditional light sources, LED light sources generate heat during operation, depending on the overall luminous efficiency. Under the action of external electric energy, the radiation of electrons and holes recombines to produce electroluminescence, and the light radiated near the PN junction needs to pass through the semiconductor medium of the chip itself and the encapsulating medium to reach the outside (air). Comprehensive current injection efficiency, radiation luminescence quantum efficiency, external light extraction efficiency of the chip, etc., finally only 30-40% of the input electrical energy is converted into light energy, and the remaining 60-70% of the energy is mainly caused by non-radiative recombination lattice vibration. Form converts heat.

In general, LED lamps work stably, quality is good, and the heat dissipation of the lamp body itself is very important. The structure of the LED lamp is generally composed of the LED light source connected to the heat dissipation structure, the driver and the lens, so the heat dissipation is also an important part, if the LED cannot Very good heat dissipation, its life will also be affected. The heat dissipation of high-brightness LED lamps on the market often uses natural heat dissipation, and the effect is not ideal.

b) Power drive technology issues

Since the LED is a characteristic sensitive semiconductor device and has a negative temperature characteristic, it needs to be stably operated and protected during the application process, thereby generating a driving concept. LED devices have almost strict requirements for driving power. Unlike ordinary incandescent bulbs, LEDs can be directly connected to 220V AC mains. The LED is a low voltage drive of 2~3 volts. It is necessary to design a complicated conversion circuit. LED lamps for different purposes must be equipped with different power adapters. At present, there are many components in the common driving power supply, many unexpected factors in the use environment, high failure probability, unstable output characteristics, insufficient protection measures for LEDs, and mismatch with LED life (power life <20Kh, LED life>30Kh At the same time, the cost of a good driving power supply is too high, accounting for more than 20-40% of the cost of the lamp.

c) Secondary light distribution technology problem

Generally, in order to make the light emitted by the LED chip output better, to get the maximum use, and to meet the design requirements in the illumination area, it is necessary to design the secondary optical system of the LED light source, and the secondary optical design mainly considers how to put the LED. The light emitted by the light source is concentrated on the desired illumination area, so that the light emitted by the whole system can meet the design requirements. At present, the basic optical components used in the secondary optics mainly include two types of lenses and reflectors, how to improve the brightness of the light exit surface of the lamp. Uniformity, reducing uncomfortable glare and how to achieve a better light distribution curve and improving the utilization efficiency of light in the working surface are the main problems faced by secondary light distribution technology.

d) Lighting standardization issues

At present, due to the lack of unified standards for LED lighting products in China, coupled with the unbalanced development of existing equipment and their respective work bases and technical levels, the LED lighting application products appearing on the market have various types and performances. Different and poorly interchangeable, it poses severe challenges to the development of the entire industry, and at the same time restricts the healthy development of the LED lighting industry to a certain extent.

How to solve these technical difficulties in COB packaging technology

a) Shorten the hot aisle and reduce the thermal resistance

The thermal resistance of the system for traditional packaging applications is: chip-solid glue-solder joint-solder paste-copper foil-insulation-aluminum. The thermal resistance of the COB package system is: chip-solid glue-aluminum. The system thermal resistance of COB package is much lower than that of traditional SMD package, which greatly improves the life of LED.

b) Improve the uniformity of light output

Conventional packaging creates a light source component for LED applications by attaching multiple discrete devices to a PCB, which has problems with spotlight, glare, and ghosting. The COB package is an integrated package, which is a surface light source. The viewing angle is large and easy to adjust, reducing the loss of glare and light refraction, and uniform light emission.

c) enhance color temperature consistency

The integrated package can avoid the chromatic aberration problem between multiple packaged devices of traditional light source, and the chromaticity space distribution is relatively uniform.

d) Light engine design, multi-function integration

The COB light source makes it easier to integrate the power supply and the drive to form a light engine. The LED light source and the LED drive circuit are placed on the same substrate, which can reduce the production cost of the LED lighting module, and the structure is more compact, leaving more design for the lamp design. The large space also avoids the risk of integrating the light source and the power supply chain at the downstream manufacturing end, which can reduce the difficulty of setting the external power supply.

e) Modularization and standardization

The modularization of COB light source can promote the standardization process of light source and luminaire. The modularization of light source can make products mutually replaceable and solve the problem of repeated investment of resources. It is easier to integrate from power integration to optical, mechanical, electrical and thermal functions.

The development direction of integrated light source standardization is from light source module to light engine, and the final light source form must be reflected in the form of module for disassembly and replacement. The light source module is combined with the electronic device to form a light engine module; after the function is modularized, it is an inevitable trend that the standard connection interface is connected to each other and gradually standardized. In addition, there are thousands of specifications of LED packaging products, which are various in variety, different in performance, and poor in interchangeability compatibility. Only the integrated light source form is in line with the development trend of standardization.

The integration and standardization of LED devices, the comprehensive analysis is mainly in addition to reducing the overall cost of the device, and easy to design, easy to form a streamlined design. More important is the uniformity of the form, interface standards, compatibility interchange, and easy to ensure the consistency of device performance.

COB package in LED lighting advantages

In summary, the COB package format has the following advantages for the downstream luminaire field:

1. Shorten the heat channel and reduce the thermal resistance;

2, the entire surface of the light, improve the uniformity of light;

3, integrated package, enhance color temperature consistency;

4. The light source can be integrated with partial drive to reduce the difficulty of designing the external power supply;

5, compact structure, easy to design the lighting;

6, the system reliability is more stable;

7, easier to achieve modular lighting, easy to standardize and promote.

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