Basic knowledge of LED chips

50 years ago, people already knew the basic knowledge that semiconductor materials can generate light. In 1962, Nick Holonyak Jr. of General Electric developed the first practical visible light emitting diode. LED is the abbreviation of light emitting diode. Its basic structure is a piece of electroluminescent semiconductor material placed on a frame with leads, and then sealed with epoxy resin on all sides, that is, solid packaging, so it can protect the internal core wire, so LED has good shock resistance.

Initially, LEDs were used as indicator light sources for instruments and meters. Later, LEDs of various colors were widely used in traffic lights and large-area display screens, generating good economic and social benefits. Take a 12-inch red traffic light as an example. In the United States, a long-life, low-efficiency 140-watt incandescent lamp was originally used as the light source, which produced 2,000 lumens of white light. After passing through the red filter, 90% of the light was lost, leaving only 200 lumens of red light. In the newly designed lamp, Lumileds used 18 red LED light sources, including circuit losses, with a total power consumption of 14 watts to produce the same light effect. Car signal lights are also an important application area for LED light sources.

2. The principle of LED chip

LED (Light Emitting Diode) is a solid-state semiconductor device that can directly convert electricity into light. The heart of LED is a semiconductor chip. One end of the chip is attached to a bracket, one end is the negative pole, and the other end is connected to the positive pole of the power supply, so that the entire chip is encapsulated by epoxy resin. The semiconductor chip consists of two parts, one part is a P-type semiconductor, in which holes dominate, and the other end is an N-type semiconductor, which is mainly electrons. But when these two semiconductors are connected, a "PN junction" is formed between them. When current acts on the chip through a wire, electrons will be pushed to the P region, where electrons and holes recombine, and then they will emit energy in the form of photons. This is the principle of LED light emission. The wavelength of light, that is, the color of light, is determined by the material that forms the PN junction.

3. Major chip manufacturers

Osram from Germany, Lumen, CREE, AXT from the United States, FPD, TK, AOC, HL, Edison, ED from Taiwan, Seoul from South Korea, Nichia and Toshiba from Japan, Dalian Lumei, Fudi, Sanan, Hangzhou Silan Mingxin, Nichia from mainland China, etc. They are all well-known chip suppliers. They are subdivided according to the place of origin below.

Taiwan LED chip manufacturers: Epistar (ES), (Lianquan, Yuankun, Lianyong, Guolian), Huga, Genesis Photonics, Arima Optoelectronics (AOC), Tekcore, Qili, Juxin, Guanghong, Jingfa, Shichuang, Zhoulei, Liansheng (HPO), Hanguang (HL), Guanglei (ED), Tyntek (TK), Yaofu Zhouji TC, Formosa Epitaxy, Guotong, Lianding, VPEC, etc. Huaxing (Ledtech Electronics), Unity OptoTechnology, ParaLight Electronics, Everlight Electronics, Bright LED Electronics, King bright, Lingsen Precision Industries, Ligitek Electronics, Lite-On Technology, HARVATEK, etc.

Mainland LED chip manufacturers: Sanan Optoelectronics (abbreviated as (S), Shanghai Epilight (E), Silan Mingxin (SL), Dalian Lumei (abbreviated as (LM), Diyuan Optoelectronics, Huacan Optoelectronics, Nanchang Xinlei, Shanghai Jinqiao Dachen, Hebei Lide, Hebei Huineng, Shenzhen Orient, Shenzhen Century Jingyuan, Guangzhou Puguang, Yangzhou Huaxia Integrated, Gansu Xintian Electric Company, Dongguan Fudi Electronic Materials, Qingxin Optoelectronics, Jingneng Optoelectronics, Zhongwei Optoelectronics, Qianzhao Optoelectronics, Jingda Optoelectronics, Shenzhen Fangda, Shandong Huaguang, Shanghai Lanbao, etc.

Foreign LED chip manufacturers: CREE, HP, Nichia, Toyoda Gosei, Taiyo Nippon Sanso, Toshiba, Showa Denko (SDK), Lumileds, Smileds, Genelite, Osram, GeLcore, Seoul Semiconductor, Bridgelux, Epivalley, etc.

4. Classification of LED chips

1. MB chip definition and characteristics

Definition: MetalBonding chip; this chip is a patented product of UEC. Features:

(1) Using Si, a material with a high heat dissipation coefficient, as the substrate makes heat dissipation easy.

Thermal Conductivity

GaAs: 46W/mKGaP: 77W/mK

Si: 125～150W/mK

Cupper: 300~400W/mk

SiC: 490W/mK

(2) The epitaxial layer and the substrate are bonded (wafer bonding) through a metal layer, while reflecting photons to avoid absorption by the substrate.

(3) The conductive Si substrate replaces the GaAs substrate, which has good thermal conductivity (the thermal conductivity coefficient differs by 3 to 4 times) and is more suitable for the field of high drive current.

(4) The metal reflective layer at the bottom is beneficial for improving brightness and dissipating heat.

(5) The size can be enlarged and applied in the high power field, eg: 42milMB.

2.GB chip definition and characteristics

Definition: GlueBonding chip; this chip is a patented product of UEC. Features:

(1) The transparent sapphire substrate replaces the light-absorbing GaAs substrate, and its light output power is more than twice that of the traditional AS (Absorbable structure) chip. The sapphire substrate is similar to the GaP substrate of the TS chip.

(2) The chip emits light on all four sides and has an excellent pattern diagram.

(3) In terms of brightness, its overall brightness has exceeded the level of TS chips (8.6mil).

(4) Dual-electrode structure: Its high current resistance is slightly inferior to that of TS single-electrode chip.

3. TS chip definition and characteristics

Definition: transparent structure chip, which is a patented product of HP. Features:

(1) The chip manufacturing process is complex, much more complex than ASLED.

(2)Excellent reliability.

(3) Transparent GaP substrate, does not absorb light and has high brightness.

(4) Widely used.

4.AS chip definition and characteristics

Definition: Absorbable structure chip; after nearly 40 years of development efforts, Taiwan's LED optoelectronics industry has reached a mature stage in the research and development, production and sales of this type of chip. The research and development levels of major companies in this regard are basically at the same level, with little difference.

The mainland chip manufacturing industry started late, and its brightness and reliability are still a certain distance away from the Taiwan industry. The AS chips we are talking about here refer specifically to UEC's AS chips, eg: 712SOL-VR, 709SOL-VR, 712SYM-VR, 709SYM-VR, etc.

Features:

(1) Quaternary chip, manufactured using MOVPE process, has a brighter brightness than conventional chips.

(2) Excellent reliability.

(3) Widely used.