Discussion on the advantages of COB encapsulation in LED lamps
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Discussion on the advantages of COB encapsulation in LED lamps

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Difficulties in LED indoor lighting fixture design technology

Heat dissipation technology problem

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. Formal conversion of 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 It is well cooled and its life is affected. The heat dissipation of high-brightness LED lamps on the market often uses natural heat dissipation, and the effect is not satisfactory.

Power drive technology problem

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.

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, and how to improve the brightness of the light-emitting surface of the lamp. Uniformity, reducing uncomfortable glare and how to achieve a better light distribution curve, improving the utilization efficiency of light in the working surface is the main problem faced by the secondary light distribution technology.

How does COB packaging technology solve these technical difficulties?

  • shorten the heat channel 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.

  • Improve light uniformity

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. Because the COB package is an integrated package, it is a surface light source, with a large viewing angle and easy adjustment, reducing the loss of glare and light refraction, and uniform light emission.

  • Enhanced color temperature consistency

One-piece package can avoid chromatic aberration between multiple packaged devices of traditional light source, and the chromaticity space is evenly distributed.

  • 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.

  • 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 complicated in variety and performance, and the compatibility of interchangeability is poor. 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.

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