As LED technology advances, LED applications are also increasingly diverse, from the early power indicator light, progress to have the advantages of power saving, long life, high visibility LED lighting products. However, since only 15 to 20% of the high-power LED input power is converted into light, the remaining 80 to 85% are converted into heat. If these heats are not discharged to the outside world properly, the temperature of the LED die interface will be too high to affect the light emission Efficiency and luminous life.
LED heat development is the key
With the LED materials and packaging technology continues to evolve, LED products continue to promote the brightness, LED applications more widely, and for the LED industry to provide a stable growth in the market territory. To LED as a display backlight, is a hot topic recently, from the small size monitor backlight gradually developed to large size LCDTV backlight, quite gradually replace the CCFL backlight posture. Mainly in the LED color, brightness, life expectancy, power consumption and environmental protection requirements are more advantages than the traditional cold cathode tube (CCFL), which attracted the industry to actively invest.
Early single-chip LED power is not high, limited heat, heat is not a big problem, so the package is relatively simple. However, with the constant breakthrough of LED material technology in recent years, LED packaging technology has also changed. From the early single-chip shell-type package gradually developed into a flat, large area multi-chip package module; its current from the early 20mA Of the low-power LED, progress to the current 1/3 to 1A high-power LED, single LED input power up to 1W or more, even to 3W, 5W.
Packaging more evolution
Since the heat problems derived from the high brightness and high power LED system will be the key factors influencing the function of the product, to quickly discharge the heat of the LED components to the environment, the thermal management at the package level (L1 & L2) must first be carried out. Is the LED die with solder or thermal paste followed by a heat sink, via the heat sink to reduce the thermal impedance of the package module, which is currently the market's most common LED package module, the main source Lumileds, OSRAM, Cree and Nicha Such as LED world-renowned manufacturers.
In practice, these LED modules can be assembled in a row of linear light source, or arranged in an array or circular array, and then joined to a heat sink substrate as a surface light source. However, for many end applications, such as mini projectors, automotive and lighting sources, the required lumen output in a given area needs to exceed thousands of lumens or tens of thousands of lumens. Obviously, single-die package modules are obviously inadequate To cope with, toward multi-chip LED package, and chip direct substrate adhesion is the future trend.
In LED real product applications, whether it is used for display backlight, indicator light or general lighting, it is usually necessary to assemble a plurality of LEDs on a circuit substrate. On the other hand, with the LED output power getting higher and higher, the substrate must also play the role of heat sink, in order to transfer the heat generated by the LED chip out in the material selection, it must be Take into account the structural strength and cooling needs.
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