Speaking of LED, I think a lot of friends thought of LED heat, especially high-power LED. If the heat treatment is not done, LED brightness and life will drop quickly, for the LED, how to achieve effective reliability and heat conduction, is very important. So we in the design of LED products must be taken into account when the heat treatment. LED heat treatment program a lot, mainly from the structure and performance of the two major improvements, we are here on the commonly used LED heat treatment program summarized as follows:
First: low-power epoxy resin cooling method:
The traditional low-power LED heat treatment program is in the package with a small amount of epoxy resin, this way is relatively simple, we are no longer detailed study here. Mainly in the packaging when the choice of good epoxy resin on the line.
Second: flexible metal substrate (aluminum plate)
Epoxy resin heat resistance is relatively poor, there may be the situation is that the life of the LED chip itself is not reached before the epoxy resin has been discolored, therefore, to improve heat dissipation is an important key. In addition, not only because the heat phenomenon will change the epoxy resin, and even short wavelengths will also cause problems for epoxy resin, which is because the white LED light spectrum, also contains short wavelength light, while the epoxy resin is quite Vulnerable to white light in the LED short-wavelength light damage, even low-power white LED, has been able to epoxy resin
Destruction of the phenomenon intensified, not to mention high-power white LED issued by the short wavelength of light more, worse natural than the low-power style more quickly, and even some products in the continuous lit after the service life of only 5,000 hours, or even shorter The Therefore, with its constant to overcome the old packaging materials, "Epoxy" to bring color problems, it is better to seek a new generation of packaging materials efforts.
So in recent years gradually switch to high thermal conductivity ceramic, or metal resin package structure, is to solve the heat, and strengthen the original characteristics of the effort. LED chip high-power commonly used methods are: large-scale chip to improve the luminous efficiency, the use of high light efficiency of the package, and large current. This type of practice although the amount of current will increase the proportion of luminous, but the heat will rise.
For high-power LED packaging technology, due to heat problems caused by a certain degree of trouble, in this context with a cost-effective metal substrate technology, has become a high efficiency LED after another concerned about the new Development of the past because the LED output power is small, so the use of traditional FR4 glass epoxy packaging substrate, and will not cause too much heat problems, but used in lighting with high power LED, the luminous efficiency of about 20% to 30 %, Although the chip area is very small, the overall consumer power is not high, but the unit area of heat is very large. In general, the resin substrate cooling, can only support 0.5W below the LED, more than 0.5W or more LED, and more use metal high heat dissipation substrate for packaging, the main reason is that the substrate heat dissipation directly affect the LED life and performance, So the packaging substrate has become the focus of the development of high-brightness LED products.
On the LED packaging substrate cooling design, the current can be roughly divided into, LED chip to the package of heat conduction, and the package to the external heat to convey the two major parts. When using high heat conduction material, the temperature difference inside the package will become smaller, then the heat flow will not be localized, LED chip as a whole heat flow, radial flow to the inside of the package, so the use of high thermal conductivity material, Thermal diffusibility. In the case of improved heat transfer, it is almost entirely dependent on material lifting to solve the problem. Most people believe that, with the LED chip large-scale, high current, high-power development, will accelerate the metal package to replace the traditional resin packaging. On the current metal high heat dissipation substrate material, can be divided into two kinds of hard and flexible substrate, the structure, the hard substrate is a traditional metal materials, metal LED packaging substrate aluminum and copper materials, insulation part, mostly mining Filled with high thermal conductivity of inorganic fillers, with high thermal conductivity, processing, electromagnetic shielding, thermal shock resistance and other metal properties, the thickness is usually greater than 1mm, most of which are widely used in LED lighting module, and lighting modules, Is the same with the aluminum substrate with high thermal conductivity, high heat requirements, the ability to serve as high-power LED packaging materials.