A luminous element is an element which converts electric current into light. Representative examples of luminous element include a light-emitting diode (LED), a semiconductor laser diode (LD), etc.
The LED is a device in which, when current is supplied thereto, electrons and holes meet at a P-N semiconductor junction (a P-N junction) and generate light. In general, the LED is manufactured in a structure of a module having an LED thereon. An LED module is mounted on a printed circuit board (PCB) to generate light when current is supplied to the LED module from an electrode formed on the PCB.
The light-emitting performance and lifespan of such an LED module are directly influenced by heat generated by an LED. When the heat generated by the LED stays longer in the LED, dislocation, mismatch, and the like occur in a crystalline structure of the LED, thereby decreasing the lifespan of the LED.
Thus, many techniques have been introduced to promote dissipation of heat generated by an LED. For example, an LED package in which a ceramic substrate is combined with an LED chip may be mounted on a PCB, or an aluminum oxide (Al2O3) insulation layer may be formed by anodizing an aluminum substrate and an LED chip may be mounted according to a chip-on-board (COB) method.
An aluminum nitride (AlN) which is an expensive nitride-based material may be used for a ceramic substrate applied to an LED package. In order to secure durability, the ceramic substrate should be formed to a thickness of 400 μm or more. Thus, when the ceramic substrate is applied to the LED package, manufacturing costs increase and decreasing thermal resistance in a vertical direction is limited.
In the COB method using an Al2O3 insulation layer, an expensive ceramic substrate may be omitted to decrease manufacturing costs. However, higher thermal resistance and lower withstand voltage characteristics may be exhibited than when the ceramic substrate is applied. Thus, high heat radiation performance is difficult to be achieved and thus the COB method is difficult to be applied to a high-power product, such as a head lamp, which generates a large amount of heat.