As the LED technology progress, LED applications are increasingly diversified, from the early power indicator, progress to a power, long life, high visibility LED lighting products. However, because the high power LED input power is only 15 to 20% converted to light, the remaining 80 to 85% is converted to heat, if the heat is not timely to the outside, then the LED grain interface temperature will be too high and affect the light Efficiency and luminous life.
LED development heat is the key
With the LED materials and packaging technology continues to evolve, LED products continue to improve the brightness, LED applications more and more widely, and for the LED industry to provide a stable growth of the market map. LED as a display of the backlight, it is a recent hot topic, from the small size of the display backlight gradually developed to large size LCD TV backlight, quite gradually replace the CCFL backlight posture. Mainly in the color of the LED, brightness, life expectancy, power consumption and environmental protection requirements are more than the traditional cold cathode tube (CCFL) more advantages, and thus attract the industry to actively invest.
Early single-chip LE D power is not high, heat is limited, the problem is not hot, so its packaging is relatively simple. But in recent years, with the LED material technology breakthrough, LED packaging technology also will change from the early single-chip shell-type package gradually developed into a flat, large-scale multi-chip packaging module; its current from about 20mA Of the low-power LED, progress to the current 1/3 to 1A or so high-power LED, single LED input power up to 1W or more, or even to 3W, 5W.
The package is more evolutionary
As the high-brightness high-power LED system will be derived from the thermal problems will affect the product function key, to LED components of the heat quickly discharged to the surrounding environment, first of all must be from the package level (L1 & L2) thermal management to proceed; It is the most common LED packaging module on the market today. The main sources are Lumileds, OSRAM, CREE, and Cumens, which are the most common LED package modules on the market. Nicha and other well-known international LED manufacturers.
These LED modules can be assembled in a single row of linear light sources, or made in an array or circular arrangement, and then joined in a heat dissipation substrate as a surface light source. But for many terminal applications, such as mini-projector, automotive and lighting with light source, in a specific area required for the amount of lumens need more than lumens or tens of thousands of lumens, single crystal package module is clearly inadequate To cope with, to multi-chip LED package, and the chip directly to the substrate is the future development trend.
In LED real product applications, whether for the display backlight, light or general lighting, usually as needed, a number of LED assembly on a circuit board. On the one hand, the circuit board plays the role of carrying the LED module. Taking into account the structural strength and cooling needs.
Need to worry about material costs
Traditional LED power is not large, the heat problem is not serious, as long as the use of general electronic copper foil printed circuit board that is sufficient to meet, but with the high prevalence of high-power LED, this board is not enough to meet the cooling needs, The printed circuit board is attached to a metal plate, the so-called Metal Core PCB, to improve its heat transfer path.
In addition there is a practice directly in the aluminum substrate surface directly as an insulating layer or dielectric layer, and then in the dielectric layer surface as a circuit layer, so LED module can be directly on the wire in the circuit layer. At the same time in order to avoid the thermal conductivity of the dielectric layer and increase the thermal resistance, and sometimes take the way to perforate the LED module at the bottom of the soaking film directly into the metal substrate, the so-called direct adhesion of the chip.
In addition to the metal substrate, in order to cope with the development of high-power LED packaging and direct bonding of the substrate substrate, in addition to considering the heat dissipation, the thermal expansion coefficient of the chip must be considered in order to avoid thermal deformation caused by thermal stress and Reliability problems, so at home and abroad are also developing ceramic substrate and metal composite substrate. These newly developed substrate materials not only have good heat dissipation, while the thermal expansion coefficient (between 4 ~ 8ppm / K) and LED chips are matched, the only drawback is the price than the average metal substrate expensive.
Focus on fanless heat dissipation
In fact, LED cooling components and CPU cooling is similar, are from the heat sink, heat pipe, fan and thermal interface material composed of air-cooled module, of course, water is one of the thermal countermeasures.
To the current most popular large-size LED TV backlight module, 40-inch and 46-inch LED backlight input power of 470W and 550W, respectively, 80% of which turn into heat, the required heat dissipation of about 360W And about 440W. (Such as SONY 46 "LED TV), but the fan power and noise, etc., but also with the heat pipe with the heat sink and fan to cool (such as SONY 46" LED TV), but the fan power and noise, etc. Therefore, how to design a fanless way of cooling is to determine the future who can win the important key.