Thermal characteristics and fabrication of silicon sub-mount based LED package

a r t i c l e i n f o Keywords: COB package Silicon sub-mount LED package Thermal resistance In this paper, the cost of a light emitting diode (LED) package is lowered by using a silicon substrate as the base attached to the chip, in contrast to the conventional chip-on-board (COB) package. In addition we proposed an LED package with a new structure to promote reliability and lifespan by maximizing heat dissipation from the chip. We designed an LED package combining the advantages of COB based on conventional metal printed circuit board (PCB) and the merits of a silicon sub-mount as a substrate. When an input current 500–1000 mA was applied, the fabricated LED exhibited the light output of approximately 112 lm/W at 29 W. We also measured and compared the thermal resistance of the sub-mount package and conventional COB package. The measured thermal resistance of the sub-mount package with a reflective film of Ag and the COB package were 0.625 K/W and 1.352 K/W, respectively. The demand for high-output light emitting diode (LED) packages has increased with growing demand for LED lighting and diversified fields of application. Increasing the package light output has the advantage of enhancing light conversion efficiency [1–3]. At the same time, energy other than light, which is mostly released as heat, now accounts for 75–85% of the total energy applied. As detailed in numerous, recent studies on LED light output, this means that the visible light conversion efficiency of incandescent light bulbs has been exceeded. By securing the highest visible light energy conversion efficiency, LED lighting is expected to be widely utilized in the lighting markets of the near future. However, the greatest disadvantage of the LED is that 75–85% of the total energy applied is still expelled as heat. Thus, for further advancement , the first obstacle to overcome is heat transfer [4–6]. The structure of conventional LED lighting has seven complex thermal nodes, including the LED package thermal node and the metal printed circuit board (PCB) thermal node. Heat transfer generated from the chip during LED operation is difficult for this structure. Due to the complex manufacturing process of conventional LED modules and the structurally complex thermal node, in order to improve the heat dissipation characteristics , chip-on-board (COB) packages are being developed [7–11]. Many research studies have been done on the thermal characteristics of the high-power multi-chip LED packages [8,9]. …