| With the development of semiconductor lighting, better thermal management inhigh-power and small-sized LED devices are needed. This paper has analyzed differentthermal conducting substrates and introduces a substrate called direct plated copper (DPC)substrate, which is quite suitable for high power LED packaging.DPC is a novel ceramic substrate and it makes full use of perfect material properties ofceramic, such as high mechanical strength, high thermal conductivity, excellent insulatingproperties and the proper coefficient of thermal expansion (CTE). Compared withconventional substrates, thin film technology has been applied to DPC process which has theability to reach10~50μm width line, and the substrate could form vertical interconnects by viaplating. So DPC could meet integration requirements for high precise LED packages. DPCcould be fabricated in low temperature while used in high temperature, which could not onlyimprove substrate’s property by decreasing the thermal stress and warpage but the cost ofproduction.This research focuses on DPC fabrication, testing, and a novel substrate with theapplication of self-alignment. The main research contents are as follows:At first, fabricate DPC substrate by optimizing the processes. By choosing a proper kind ofmaterial and thickness for adhesion layer, the optimized adhesion system has been established,the adhesion strength between the metal layer and ceramic layer has been greatly enhancedand the strength test reveals that failure occurs on the solder pad. Features of different platingstructures and plating abilities as well as the applied occasions of various copper platingsolutions have been compared. An optimized copper plating solution system has beenfounded in DPC process. By comparing quality of plating surface, adhesion strength andsolderability of DPC substrate’s gold surface which is deposited through physical method and electroplating respectively, the better deposition method is determined.Then, test performances of DPC substrate. Tests for Basic properties and thermal shockexperiments have been applied to DPC substrate. According to LED packaging applications,thermal resistance test has been carried out by comparing LED packages with a conventionalMCPCB substrate and direct bonded copper (DBC) substrate. Results show that DPC hasobvious advantages over MCPCB in thermal conduction, and the similar ability as DBC.At last, propose a novel structure for DPC substrate. The structure could achieveself-alignment of LED chip in SMD process which effectively improves the chips’ alignmentprecision. The experiment results have shown that angular deflection error of the chip couldbe controlled within0.14°, and the original displacement error could be decreased to be below30μm, which means the new structure could improves LED chip’s alignment accuracy. |
