Technical points: 0.1W, 0.3W, 0.5W, 1W, 3W, 5W, 10W, 20W, 30W, 50W, 100W heat sink price
With the continuous evolution of LED materials and heat dissipation packaging technology, the brightness of LED products has been continuously improved, and LED applications have become more and more extensive. The use of LEDs as the backlight of displays has become a hot topic recently. The main reason is that different types of LED backlight technologies have advantages over traditional cold cathode tubes (CCFL) in terms of color, brightness, lifetime, power consumption, and environmental protection requirements, which attract industry players to actively invest.
The power of the original single-chip LED is not high, the heat generation is limited, and the heat problem is not big, so its packaging method is relatively simple. However, with the continuous breakthrough of LED material technology in recent years, LED packaging technology has also changed, from the early single-chip shell-type packaging to the flat, large-area multi-chip packaging module;
Its working current has progressed from the early low-power LEDs of about 20mA 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.
Since the thermal problems derived from high-brightness and high-power LED systems will be the key to the product function, to quickly discharge the heat of the LED components to the surrounding environment, first of all, we must start with the thermal management of the package level (L1 & L2). The current industry practice is to connect the LED chip to a heat spreader with solder or thermal paste, and the heat spreader reduces the thermal resistance of the package module. This is also the most common LED package module on the market. The main sources are Lumileds, OSRAM, Cree and Nicha and other internationally renowned LED manufacturers.
Many terminal applications, 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 alone are obviously not enough. Moving towards multi-chip LED packaging and direct bonding of 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. Using ceramics or heat pipes is an effective way to prevent overheating, but thermal management solutions increase the cost of materials. The purpose of high-power LED heat dissipation management design is to effectively reduce the thermal resistance between the chip heat dissipation and the final product. R juncTIon-to-case is one of the solutions using materials, providing low thermal resistance but high conductivity. The heat is directly transferred from the chip to the outside of the package shell through chip attachment or hot metal methods.
Of course, the heat dissipation components of the LED are similar to the heat dissipation 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 heat countermeasures. In terms of the most popular large-size LED TV backlight modules, the input power of 40-inch and 46-inch LED backlights are 470W and 550W, respectively. Considering that 80% of it is converted into heat, the required heat dissipation is about 360W and 440W.
So how to take away these heat? At present, the industry has water cooling method for cooling, but there are doubts about high unit price and reliability; There are also heat pipes with heat sinks and fans for cooling. For example, a 46-inch LED backlight LCD TV from the Japanese manufacturer SONY, but the 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.
Cooling method
Generally speaking, according to the way the heat is taken away from the heat sink, the heat sink can be divided into active heat dissipation and passive heat dissipation. The so-called passive heat dissipation means that the heat of the heat source LED light source is naturally radiated into the air through the heat sink. The heat dissipation effect is proportional to the size of the heat sink, but because it naturally emits heat, the effect is of course greatly reduced. It is often used in equipment that does not require space, or to dissipate heat for components that do not generate much heat. For example, some popular motherboards also adopt passive cooling on the north bridge, and most of them adopt active cooling. Active cooling is to forcefully take away the heat emitted by the heat sink through cooling devices such as fans. It is characterized by high heat dissipation efficiency and small size of the equipment.
Active heat dissipation, subdivided in terms of heat dissipation, can be divided into air cooling, liquid cooling, heat pipe cooling, semiconductor cooling, chemical cooling, and so on.
