4 Trends Of White LED Package

1.       The development of new type phosphors

YAG: Ce3 + is a phosphor which was widely used in the earliest white LED technology, but because of its low red component in the emission spectrum, it is difficult to obtain a high color rendering index and low color temperature white LED. On the other hand, the continued development of semiconductor lighting makes people to develop a higher conversion efficiency phosphor. Recently, the engineer of the industry has developed an excellent thermal stability and chemical stability red phosphor which can completely replace the alkaline earth metal sulfides to achieve high color rendering index, low color temperature white LED,

Currently, countries like United States, Japan, is mature in the LED phosphors aspect technology, and hold most important patent. They dominated LED market by the occupation of the phosphor patented.

2.       White LED optical model and development

Phosphors used for white LED, must according to specific needs, such as phosphor particle size, etc. The study of the phosphor focused on the optical properties affect to white led package performance. For example, the light extraction efficiency, color and spatial distribution of light and color quality. In these studies, Using Monte Carlo ray tracing method and optical software simulation of the optical properties of the LED package structure, the phosphor layer is treated as Mie scattering material, Thus, can obtained excitation and emission characteristics of white LED through the optical simulations. However, the phosphor specific scattering properties does not take into consider in simulated, lack of experimental verification.

3.       New phosphor coating methods

The traditional way is use point powder mode as coating method, filled with a mixture of colloidal phosphor in the chip support cup bowl, then heat curing. It is difficult to control the amount of phosphor with this coating method, and because the entire excitation light vary, prone to occur macular or blue spots and other uneven light color to white LED. A famous company proposed conformal coating phosphor coating methods, They flip LED chip surface covered phosphor layer of uniform thickness, improve the stability of the white LED light color. Some companies use a layer of phosphor deposited on the surface of the chip to achieve excitation. These coating methods are applied to the chip in contact with the phosphor. H.Luo and other researchers optical simulation results show that, this method increased back-scattering loss of the excitation light, reducing the light extraction efficiency of the device. With white LED optical simulation depth, phosphor far-field excitation scheme shows more advantages.

4.       Bulk current injection and thermal structure

In order to meet the demand for general lighting high luminous flux, people increased driving power of single chip. Previously 1W high power chip is injected into 3W, 5W, or even higher. This makes the white LED thermal problem getting worse, People use various cooling techniques, such as heat pipes, micro heat pipe, water, air and other methods implemented on the LED heat dissipation.