The thermal issue of the LED in the backlight

  With the continuous evolution of LED materials and packaging technology, the application of LEDs has become wider and wider, and the use of LEDs as the backlight source of displays has become a hot topic recently.

  The power of the single-chip LED in the early stage is not high, the heat generation is limited, and the heat problem is not big, so its packaging method is relatively simple. However, in recent years, with the continuous breakthrough of LED material technology, LED packaging technology has also changed, from the early single-chip shell-type packaging to a flat, large-area multi-chip packaging module; its working current has changed from the early 20mA The low-power LEDs of the left and right have evolved to the current high-power LEDs of about 1/3 to 1A. The input power of a single LED is as high as 1W or more, and even the 3W and 5W packaging methods have evolved.

  Many terminal application products, such as mini projectors, automotive and lighting sources, require more than thousands of lumens or tens of thousands of lumens in a specific area. Single-chip package modules are obviously not enough to cope with it. , Moving towards multi-chip LED packaging, and directly adhering the chip to the substrate is the future development trend.

  The heat dissipation problem is the main obstacle in the development of LEDs as lighting objects. The use of ceramics or heat pipes is an effective method to prevent overheating, but the heat dissipation management solutions increase the cost of materials, and the purpose of high-power LED heat dissipation management design is to effectively reduce The thermal resistance between chip heat dissipation and product, R junction-to-case is one of the solutions using materials. It provides low thermal resistance but high conductivity. The heat is directly transferred from the chip to the package through chip attachment or hot metal methods. The outside of the enclosure.

  Of course, the heat sink components of the LED are similar to the heat sink of the CPU. They are mainly air-cooled modules composed of heat sinks, heat pipes, fans and thermal interface materials. Of course, water cooling is also one of the thermal countermeasures. With regard to the current popular large-size LED TV backlight modules, the input power of 40-inch and 46-inch LED backlights are 470W and 550W, respectively. When 80% of them are converted into heat, the required heat dissipation is about 360W. And around 440W.

  So how to take away this heat? At present, the industry has liquid cooling method for cooling, but there are doubts about high unit price and reliability; heat pipes are also used for cooling with heat sinks and fans, such as the 46-inch LED backlight of the Japanese manufacturer SONY. Source LCD TV, but problems such as fan power consumption and noise still exist. Therefore, how to design a fanless cooling method may be an important key to determining who will win in the future.