Electrothermic Properties And Preliminary Applications Of Freestanding Si-O-C Films For LED Heat Dissipation

LED(Light Emitting Diode)is an excellent semiconductor optoelectronic device which transforms electricity into light.Its luminescent efficiency is only 10%?20%,which means that 80%?90%of electric energy is converted into thermal energy.If the heat could not be transported timely to outside,the junction temperature of LED will be increased,the shortening of service life will be suppressed,and causes the failure of phosphor.With the development of LED towards to high light intensity,high power and small size,the issue of heat dissipation has been increasingly outstanding.The special requirement for the packaging materials of LED is put forward with higher output power of LED,high extraction efficiency,and the large number of heat brought by large dissipated power.The proper substrate is significant for the heat dispersion of LED.Recently,the SiC are currently being explored as an important ceramic coatings because of their low thermal expansion coefficient,high thermal conductivity and low density,which makes them a very attractive candidate material for electronic packaging.The SiC accord with the requirements of substrate for high power LED as follows:high insulating,more stable,the thermal expansion coefficient match to LED chip,uniform and the high mechanical strength.The aim of the present study is to prepare the ceramic substrate suits for the heat dissipation and thermal mismatch of LED base on the research of our laboratory earlier.The preparation process of freestanding Si-O-C films used polycarbosilane(PCS)as precursors were explored and optimized,and the preliminary applications on the package structure of LED has been observed.The main research contents as follows:In this thesis,we prepared freestanding Si-O-C films through the oxidative-induced crosslinking of PCS in air for 3 hours,and the pyrolysis temperature was from 900 to 1200 ?.The change law of thermal and electro properties of freestanding Si-O-C films were charactered and analysised.The results show that the freestanding Si-O-C films were material with excellent thermal conductivity and resistivity.Both of them were reduced with increasing the pyrolysis temperature.And the properties of films sintered at 950 ? were the most excellent of all.LED based on freestanding Si-O-C films were packaged,and its properties such as light,color and electrical were characterized.The results show that the properties of freestanding Si-O-C film LED accord with the description on SJ/T 11401-2009<The spectrum of semiconductor light-emitting diodes product>,which was the electronic industry standard of China,such as correlated color temperature,color rendering index and luminous flux.The results of measurment of the thermal resistance and the junction temperature of LED show that the freestanding Si-O-C films prepared at 950 ? were more excellent than A1 substrate.