With the increasing demand for LED lighting, the heat dissipation problem of high-power LEDs has been paid more and more attention, because too high temperature will cause the LED luminous efficiency to be attenuated; if the waste heat generated by LED operation cannot be effectively dissipated, it will directly affect the life of the LED. This has a fatal impact. Therefore, in recent years, the resolution of high-power LED heat dissipation has become the subject of research and development by many related companies.
For high-power lighting LED cooling technology , each company can be said to be a supernatural power. For example, Taiwan's Guanghai Technology has developed a 'COHS package cooling technology '. Guanghai Technology is using its own carrier board design capability to directly direct LEDs. Packaged on a copper base with high thermal conductivity, the high thermal conductivity of copper is like the role of a heat sink. Together with the circuit design and its own process to overcome the adhesion between the insulating film and the copper material, it develops the so-called COHS technology (Chips On Heat Sink), and has 47 COHS related patents.
COHS cooling technology prospects can be expected
Guanghai Technology said that the company's 'COHS heat dissipation technology' is different from the traditional COB packaging method, eliminating the need for unnecessary thermal resistance between the chip and the pedestal, and using copper with better thermal conductivity than aluminum as the substrate. For the wick module above 60W, the concept of a uniform temperature plate has been added to transmit heat more quickly. Overall, the advantages of this technology include low thermal resistance of the module, easy control of the junction temperature, test points that provide the measured junction temperature, low-cost packaging structure, easy installation, and good heat dissipation. At present, Guanghai Technology's products have been applied to LED street lighting projects in Qingyun County, Shandong Province, LED street lighting projects in Daxing District of Beijing, and various indoor and outdoor lighting .
In the new product test held at the Korea University of Technology, the electrode temperature of the 120W (W) module of Guanghai Technology is about 70 degrees Celsius, and the electrode temperature of other 60 watt modules is as high as 150 degrees Celsius. The power is less than half of the light sea products, but the electrode temperature is much higher, which shows the advantages of the light sea cooling technology. It is understood that in order to enter the Korean market, Guanghai Technology will invest 10 million US dollars to build a production line in Gyeonggi Province, South Korea.
The COHS heat dissipation technology uses a copper substrate. At present, another highly attractive heat dissipation technology uses a ceramic substrate. The cost of the ceramic substrate is quite competitive, and has a thermal expansion coefficient and a high heat resistance similar to that of the semiconductor, and can effectively Solve hot skew and high temperature process problems, therefore. At this stage, many companies have invested in the research and development of ceramic substrate technology, such as Tongxin Electronics.
Ceramic substrate cooling
Liu Huanlin, general manager of Tongxin Electronics, said that the LED ceramic substrate will be the main growth momentum of Tongxin Electronics in the future. The company's products are DPC ceramic substrates. At present, there are four types of ceramic heat-dissipating substrates: HTCC, LTCC, DBC, and DPC. Among them, DPC (Direct Plate Copper) is a process in which a ceramic substrate is coated with a copper layer by vacuum sputtering, and then a developing process is used to manufacture a circuit. Combining materials and thin film process technology, it is the most commonly used ceramic heat sink substrate in recent years.
Basically, LED heat sink substrates are mainly divided into metal and ceramic substrates. The metal substrate is made of aluminum or copper. Due to its mature technology and cost advantages, it is currently used in general LED products . The ceramic substrate has high alignment accuracy, and is recognized as an excellent material for heat conduction and heat dissipation. It is the best solution for high-power LED heat dissipation. Although the cost is higher than that of the metal substrate, the heat dissipation and stability required by the illumination are higher than Electronic products such as notebook computers and TVs, including international companies such as Cree, Osram , Philips and Nichia, use ceramic substrates as the heat dissipation material for LED chips.
Comparing various ceramic heat dissipation technologies, among them, HTCC (High Temperature Co-fired Multilayer Ceramic Substrate) is an early development technology, but its electrode material selection is limited due to its high process temperature (1300 to 1600 Â° C). And the production cost is quite expensive, and it is gradually being replaced by LTCC. In addition, the thermal conductivity of DPC ceramic substrate is better than that of low temperature ceramic co-firing (LTCC) and heat dissipation aluminum substrate. Therefore, DPC ceramic substrate heat dissipation technology has been favored in recent years. Tongxin Electronics said that the company's current ceramic substrate is still in short supply, and the production capacity is sung. The factory has a monthly capacity of 300,000 pieces (4å‹Ã—4å‹ each, 440 to 890 pieces per piece (depending on the design). The Philippines has a monthly capacity of 100,000 pieces and will have 50,000 new capacity added in the near future. Overall, as LEDs replace traditional lighting as a future trend, Tongxin Electronics will benefit from this application for a long time.
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