Research On Preparation And Performance Of Thermal Grease For High-power LED Heat Dissipation

As an excellent semiconductor optoelectronic device, LED(Light Emitting Diode) have advantages such as small size, low electricity consuming, long lifetime, and environmental protecting, it will hopefully become a new generation of ideal solid-state light sourse in the coming ten to twenty years.With the development towards to high lumens and high power, the problem of LED heat dissipation becomes more and more important.Heat dissipation effects the light output character of LED and its lifetime, it is a critical problem in the packaging of the high power LED.In This article,LED heat dissipation problem has been studied by preparing the thermal grease applied to LED. The mechanism of thermal grease and the influence of surface treatment to thermal conductivity have been studied, and under the guidance of this theory, prepared kinds of thermal grease, such as Al and AlN thermal grease under stearic acid surface treatment, different materials grease thermal (including Graphite, SiC, Cu, Al, Al), different filler sizes of thermal grease and the binary mixture filled thermal grease. By analyzing the influences on thermal conductivity of surface treatment technology, filling ratio, filler materials, filler sizes in the one-component grease thermal and the main filler, reinforcing filler features of thermal grease on the binary mixture thermal grease, the following conclusions:①The surface treatment technology is benefit for Al, AlN grease as an organic coating layer formed in the surface of filler in the course of treatment, and it can improve the thermal conductivity of thermal grease; On the contrary, this technology is not suitable for surface treatment of Graphite, SiC, Cu particles;②The filling ratio should be controlled at 0.55-0.60 for preparation of thermal grease with high thermal conductivity. Particularly, the surface treatmented Al, AlN thermal grease reach to 6.44W/ (m?K) and 3.80W/(m?K), respectively;③Filler sizes impact on the thermal conductivity obviously, the highest thermal conductivity obtained when the particle size is 20μm;④In the binary mixture thermal grease, Ag particles are sutable for reinforcing filler and it is easy to get higher thermal conductivity. Especially, in Ag / AlN mixed filler, the thermal conductivity reaches to 5.49W/(m?K), while nanoparticles is not suitable for preparation of thermal grease because it is too small to increase the thermal conductivity; ⑤The kinds of thermal grease are used for heat dissipating in 1W, 3W, 5W LEDs and 8W LED street lamp. It is found that the thermal grease self-prepared is better than the market products.⑥The LED temperature field simulation is discussed with the help of multi-physics simulation software, the simulation results consistent with the experimental measured junction temperature, substrate temperature, the basic compliance, reflecting the multi-physics simulation in the thermal simulation of LED practicality.