Papers by Author: Chang Hyun Lim

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Authors: Sung Jun Lee, Ji Hyun Park, Chang Hyun Lim, Won Kyu Jeong, Seog Moon Choi, Yong Soo Oh
Abstract: By the development of high power LED for solid states lighting, the requirement for driving current has increased critically, thereby increasing power dissipation. Heat flux corresponds to power dissipation is mainly generated in p-n junction of LED, so the effective removal of heat is the key factor for long lifetime of LED chip. In this study, we newly proposed the silicon package for high power LED using MEMS technology and estimated its heat dissipation characteristic. Our silicon package structure is composed of base and reflector cup. The role of base is that settle LED chip at desired position and supply electrical interconnection for LED operation, and finally transfer the heat from junction region to outside. For improved heat transfer, we introduced the heat conductive metal plated trench structure at the opposite side of LED attached side. The depth and the diameter of trench were 150 and 100um, respectively. Copper with high thermal conductivity than silicon was filled in trench by electroplating and the thickness of copper was about 100um. Reflector cup was formed by anisotropic wet etching and then, silicon package platform could be fabricated by eutectic bonding between base and reflector cup. The thermal resistance of silicon package was about 6 to 7K/W from junction to case, and also, thermal resistance reduction of 0.64K/W was done by metal plated trench. This result could be comparable to that of other high power LED package. Our silicon package platform is easy to be expanded into array and wafer level package. So, it is suitable for future high efficiency and low cost package.
Authors: Won Kyu Jeung, Chang Hyun Lim, Tae Hoon Kim, Seog Moon Choi
Abstract: A novel rectangular shape microlens array having high sag for solid-state lighting is presented. The rectangular shape of proposed microlens can maximize the fill factor of silicon based light-emitting-diode (LED) packaging and minimize the optical loss through the reduction of unnecessary reflection at the same time. Microlens, which has high sag, over 3 75 μm and large diameter, over 3 mm can enormously enhance output optical extraction eff iciency. Moreover wafer level packaging technology is adopted to improve the aligning accu racy and mass production of LED packaging. This wafer level microlens array can be direc tly fabricated on LED packaging using replication method. It has many advantages in optica l properties, low cost, high aligning accuracy, and mass production.
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