Study On Preparation And Performance Of High Power LED Silicon Substrate

With the increasing popularity of high power LED,the heat problem has become a major factor affecting the life and the reliability of LED.So exploring the low thermal resistance of the LED packaging structure and packaging materials is essential for the development of high power LED.In this paper,the high power LED silicon substrate was studied.The structure,preparation process and performance test of the silicon substrate were studied.Specific work and conclusions are as follows:Firstly,the structure of the silicon substrate,the SiO₂ insulation layer and the structure of the multilayer film were designed.The Cr/Cu/Ni gradient structure is used as the conductive layer.The heat dissipation performance of the traditional packaging based aluminum was compared with the packaging based silicon by the thermal resistance theory analysis and finite element simulation.The results show that the heat conduction of flip chip package based silicon is better.ANSYS simulation software was used to simulate and optimize the thickness of silicon wafer,the thickness of insulation layer and the array spacing of LED chip.The optimal parameters are as follows:the thickness of the silicon wafer is 0.7⁰.9mm,the thickness of the insulation layer is less than 30?m,and the chip array spacing is 2.0mm.Then,three kinds of preparation process of the silicon substrate,namely plus method,minus method,and the mixed addition and subtraction method,were designed.The advantages and disadvantages of three kinds of preparation process were analyzed and compared.Finally modified mixture preparation process was chosen as process for preparing silicon substrate.The key technologies involved in the preparation of silicon substrate were studied and optimized.The chemical vapor deposition process parameters were optimized to solve the problem of uneven thickness of SiO₂ on the surface of silicon wafer.The plating parameters were optimized,which solved the problem that the current density is too large or too small.The parameters of electroless plating were optimized to solve the problem of insufficient plating or uneven plating due to the lack of pretreatment.The problem of the decomposition of the plating solution caused by the high temperature of the plating solution was solved.At last,the silicon substrate and its LED packaging module were tested in some aspects,such as insulation voltage,bonding strength and thermal conductivity.The bulk resistance of the silicon substrate reaches 1.3×10¹⁶?·cm³.2×10¹⁶?·cm,and the withstand voltage is up to 3kV.The bonding strength of the adhesive layer on the surface of silicon is much higher than that of the non adhesive layer.The thermal resistance of 4W packaging based aluminum is 9.33?/W,while the thermal resistance of the 4W packaging based silicon is 3.57?/W.The results show that the thermal conductivity of packaging based silicon is better than that of packaging based aluminum.