At present, the LED packaging method can be roughly divided into a lens type (Lens-type) and a reflector type (Reflector-type), wherein the lens can be formed by molding or lens bonding; and the reflective cup chip is more. It has been formed by mixing, dispensing and packaging. In recent years, epitaxial, solid crystal and package design have gradually matured. The chip size and structure of LEDs have been miniaturized year by year. The power of high-power single chip is 1~3W, even more than 3W. LED power continues to increase, and the heat dissipation and heat resistance requirements for LED chip- mounted and system circuit boards are becoming increasingly stringent.
In view of the comprehensive considerations of insulation, pressure resistance, heat dissipation and heat resistance, ceramic substrates have become one of the important materials for chip adhesion technology. The technology can be divided into a thick film process (Thick film), a low temperature co-firing process (LTCC) and a thin film process (DPC). However, the thick film process and the low-temperature co-firing process use screen printing technology and high-temperature process sintering, which is prone to rough lines, inaccurate alignment, and shrinkage ratio problems, if the high-power LED products are increasingly finer for the line, or In the case of LED products that require accurate eutectic or flip chip processes, thick-film and low-temperature co-fired ceramic substrates are gradually in use.
To this end, the high heat dissipation coefficient thin film ceramic heat sink substrate is made of sputtering, electric/chemical deposition, and yellow light lithography. It has the characteristics of precise metal lines and stable material system. It is suitable for high power, small size and high brightness LEDs. The development trend has solved the stringent requirements for the resolution and accuracy of the metal substrate of the ceramic substrate in the eutectic/over-chip packaging process. When the LED chip uses ceramic as the carrier board, the heat dissipation bottleneck of the LED module is transferred to the system circuit board, and the heat energy is transmitted from the LED chip to the heat dissipation fin and the atmosphere, and as the function of the LED chip is gradually improved, the material is also improved. Gradually changed from FR4 to metal core printed circuit board (MCPCB), but with the development of high-power LEDs, the thermal coefficient of MCPCB material (2~4W/mk) cannot be used for higher power products. For this reason, ceramic circuits The demand for ceramic circuit boards has gradually become popular. In order to ensure material stability and light decay stability of LED products under high power operation, the trend of using ceramics as heat dissipation and metal wiring substrates has become increasingly clear. Ceramic materials currently cost more than MCPCB. Therefore, how to use the high heat dissipation coefficient of ceramics to save material use area to reduce production costs has become one of the important indicators for the development of ceramic LEDs. Therefore, in recent years, the integration of polycrystalline packages and system lines with ceramic material COB design has gradually attracted the attention of various packaging and system manufacturers.
COB is not a new technology in the electronics manufacturing industry. It means that the bare epitaxial wafer is directly attached to the circuit board, and the wire/solder wire is directly soldered to the gold-plated line of the PCB. (Wire bonding), through the sealing technology, effectively transfer the packaging steps in the IC manufacturing process to the board for direct assembly. In the LED industry, as modern technology products become more and more lightweight and high-capacity, in addition, in order to save the system board space problem of multiple LED chip design, in the demand of high-power LED system, it is developed to directly stick the chip. COB technology attached to the system board.
The advantages of COB are: high cost efficiency, simple circuit design, saving system board space, etc., but there are also technical thresholds for chip integration brightness, color temperature adjustment and system integration. Taking a 25W LED as an example, a traditional high-power 25W LED light source must be packaged into 25 LED components using 25 1W LED chips, while the COB package is to package 25 1W LED chips in a single chip. The secondary optical lens will be reduced from 25 to 1 piece, which will help to reduce the light source area, reduce material, and system cost, thereby simplifying the secondary optical design of the light source and saving assembly labor costs. In addition, the high-power COB package requires only a single high-power LED to replace multiple LED packages of 1 watt or more, which makes the product thinner and lighter.
It is understood that the current COB package bulbs have occupied about 40% of the LED bulb market, many companies in Japan and China have begun to take the COB package mode. Industry insiders predict that COB packaging will become an inevitable trend in the future.
Although the COB package is very loud and the signs of warming are obvious, the outlook seems to be unclear. "In two or three years, COB packaging technology can not become mainstream." Dr. Zou Jun from the R&D department of Zhejiang Yimi Optoelectronics Technology Co., Ltd. He added that since most domestic enterprises still adopt traditional packaging methods, it takes time for foreign technology to be introduced and popularized under various conditions of technology and cost. COB packaging technology can not quickly occupy the general trend, but it is undeniable. The COB packaging technology is currently a strong development direction.
An embarrassing situation is that there is currently little demand for COB integrated packaging by application companies. Due to the failure of the previous round of investment, many lighting application companies dare not use this packaging method easily. It is understood that the bottleneck of COB packaging technology is how to improve the reliability of the light source and the trial degree of its environment. However, there are not many packaging companies that produce COB light sources on the market at present, and most of them use aluminum substrates as materials. The aluminum substrate COB is prone to light decay and dead light due to its high thermal resistance and low reliability. Although ceramic base is one of the ideal materials for COB, due to its high cost, the cost is higher when the power is less than 2W, which is difficult to be accepted by customers.
"Compared with traditional LED packaging technology, COB panel light source is very soft and has a very large market, which is a future development direction," said Wang Ruixun, chairman of Riming Technology.
"The market is still on the sidelines for COB light sources, the demand is not high. Small chips are used more, and the COB package of large chips still has many problems such as thermal resistance and light efficiency," said a packaging technology engineer in Taiwan. In this regard, netizens on the Internet also have their own words, most of them have doubts about COB packaging, it is not clear whether it is suitable for mass production.
However, companies that can make high-reliability COB light sources, including Taiwanese manufacturers, are rare. Therefore, in order to enhance market demand, many companies implement COB packaging and application integration to solve the problem of inconsistent product standards.
Metal Film resistor is Film resistor (Film Resistors) of a kind.It is the high temperature vacuum coating technology will be closely attached to the porcelain nickel chromium alloy or similar bar surface skin membrane, after debugging cutting resistance, in order to achieve the final requirements precision resistance, then add appropriate joint cutting, and on its surface coated with epoxy resin sealing protection.As it is a lead resistance, it is convenient for manual installation and maintenance, and is used in most household appliances, communications, instruments and instruments.
Metal Film Resistors,2W Metal Film Resistors,3W Metal Film Resistor,5W Metal Film Resistor
YANGZHOU POSITIONING TECH CO., LTD. , https://www.cnfudatech.com