Study On Aluminum Core Printed Circuit Board Applying In High Power LED Packaging

LED lighting is a hot in technological research nowadays. With continuous improvement of LED luminous efficiency and LED drive current increasing substantially, thermal management has become the biggest obstacle to the commercialization of high power LED. This paper chose the high power LED package as research direction to reach the target of industrial applications and studied on several key technical problems on aluminum core printed circuit board applying in high power LED packaging. The main results of this dissertation are listed as follows:1. Putting forward a new method that prepares alumina insulating layer directly on aluminum substrate, and then sputters conductive film on the insulating layer to prepare a new kind of metal core printed circuit board (MCPCB) with high-thermal conductivity. By reducing the thermal conductivity of insulation layer and decreasing the number of heat sink in internal substrate, this method leads the thermal resistance to a minimum. ANSYS finite element simulation and calculation have been carried out to analyse heat dissipation of this MCPCB. According to the experimental results, the thermal resistance of this high power LED package can be reduced from more than 300 K/W of the traditional FR-4 epoxy copper clad laminate to around 10 K/W; compared to the MCPCB used in recent years, when single 3W LED chip is concerned, the temperature of its equivalent position can be reduced by about 3℃, indicating that this new structure of package can improve the heat dissipation effectively. The structure and method have been applied for national invention patents, and are in the stage of publicity with patent application No.200910097241.1, No. 200910097243.0 and No.200910097242.6.2. Studying the anodic oxidation process in terms of both theories and experiments. By anodic oxidation on aluminum substrate, alumina insulating layer with good performance has been prepared at low cost. A systematic analysis has focused on the reasons for short circuit and poor adhesion of conductive layer during the formation of aluminum insulating layer after anodic oxidation, suggesting that the insulation cracking and precipitation of metal impurities in the alloy are mainly responsible for short circuit. Adopting the 5 Series aluminum alloys as substrate and proper control the thickness of oxide film can improve the short circuit. At the same time, increasing the roughness of the substrate surface and improvement of the sealing effect are better ways to enhance the adhesion. Consequently, a preparation plan with guiding significance has been raised to the large-scale production of alumina insulating layer by means of anodic oxidation.3. Designing the multi-layer conductive structure "transition layer & barrier layer & weld layer" and researching on magnetron sputtering to prepare the film of conductive layer. Meanwhile, manufacturing process of usage of the conductive layer to prepare circuit has been studied in a detail. By comparing the 3 process programs, which are mask method, positive inks-etching method and negative ink method, the last was recommended for industrial application.4. Participating in the design of continuous production metal equipment with a large throughput of magnetron sputtering and the establishment of sputtering technology, debugging the production preparation, and carrying out experiments on industrialization tests. The samples in industrialization have been tested. As a result, the pull-off strength of the prepared conductive layer film reaches more than 1.5 MPa, and the insulation resistance is greater than 20 MΩand can withstand the dissolution of 450℃lead-free solder, which meets the process requirements of lead-free SMD soldering and manual welding.5. Making proposal to use A1N as insulating layer in MCPCB and applying for a national invention patent with patent application No.201010505050.7.