螺絲

LED device cooling challenges
Compared with other light sources, high power LED have a serious cooling problem, mainly because of LED does not heat through infrared radiation.

According to U.S. Department of Energy study showed that the power used to drive LED 75% ~ 85% of the final conversion into heat and must be a way through the heat conduction from the MR16 chip into the lower part of printed circuit boards, radiator, enclosure, or light structural elements and so on. U.S. Department of Energy energy efficiency and renewable energy sector reached a called "Thermal Managementof WhiteLEDs" report. In short, the excessive heat will reduce the LED's light output and produce color cast.
In addition, the thermal management of the pros and cons will have some long-term effects, such as the reduction in light output will lead to shortened life. U.S. Department of Energy, said: Manufacturers usually fixed at 25 ℃ under the LED junction temperature test. However, under normal circumstances junction temperature of 60 ℃ or higher, in these cases the output of LED lights may only be rated 10% or less.

For the tungsten light bulb, the heat is through the way of heat radiation, heat directly from the filament into the surrounding environment. The main heat dissipation LED device chip to the system by means of thermal shell.

LED device manufacturers to provide a package-level thermal management. For manufacturers, the most concerned about is how to reduce the thermal resistance of the chip to the external package. Usually installed in some small LED lights on the plate there are many leads, these leads form the main thermal path, and for the LED, its chip-to-lead thermal resistance is critical. Package design based on LED manufacturers and types of changes, but the concept is very similar to packaging.

In this example, LED chips are usually used bonding layer (bondlayer) is assigned to a metal paste link layer (metalinter connectlayer), and this layer has been affixed to the metal connections assigned to a ceramic base (Ceramic Substrate) and an electrical insulation thermal pad (ThermalPad). The whole package is designed to maximize the optical output and the back to remove the heat from the LED chip.
Hechfellner said: Even the most efficient Led lighting devices are also required to design the cooling system. Because the traditional light source is conducted through the heat radiation, so they will not have such heat. Many LED manufacturers in the electrical and structural aspects of the specific heat has more experience. Engineers need to change their philosophy, and should be considered after the first consider thermal power. For the LED system manufacturers, the current design of 90% challenge caused by the heat, and electrical and structural problems caused by only accounted for 10%.

Hechfellner added: system-level manufacturers are facing the biggest problem is to develop a high efficiency heat lamp, LED device can be easily inserted into the holder, and the heat can be quickly imported into the environment. To my knowledge, the current market has no such system. Improve the thermal cross-section of materials and design tools for research and development of such systems is necessary. We are committed to creating a good development platform, such as the help of simulation tools for accurate simulation of LED, so as to facilitate our customers better thermal design.
LED LED package is the essence of efficiency even increased, but the heat dissipation problem is still there. Because the light output decreases with increasing temperature, a greater proportion of electric power into heat will further enhance the LED temperature. Over time, LED light output will decrease, and its heat will accelerate the aging of the LED.

A commonly used indicator is the attenuation of the white LED luminous yellow phosphor, which may be caused due to heat or environmental triggers, but that does not mean that the low efficiency of the chip to work or have more heat generated. Need to meet the thermal management of the program cycle in the LED can be used to remove the entire heat requirements.