A conventional technique for coating a phosphor on an LED, as shown in FIG. 1, includes directly applying a polymer material 20 such as epoxy, etc., into which the phosphor is mixed, onto an LED 10, and then, curing the polymer material 20.
The conventional method of coating a phosphor on an LED has a problem that the polymer material 20 including the phosphor cannot be easily patterned. Therefore, in the conventional phosphor coating method, the phosphor must be applied to the entire surface after completion of wire bonding. In this case, when the LED to which the phosphor is applied cannot have desired performance (for example, in color, uniformity of color, etc.), the LED, which is expensive due to the wire bonding, is wasted, and thus, the overall manufacturing cost increases.
In addition, the conventional method of coating a phosphor on the LED 10 is not appropriate for mass production. More specifically, in the conventional phosphor coating method, since the polymer material 20 including the phosphor must be separately coated onto each LED, the coating is expensive.
Further, the conventional method of coating a phosphor on the LED 10 has a problem in that the thickness of the polymer material 20 including the phosphor cannot be easily adjusted. When the thickness of the polymer material 20 including the phosphor increases, intensity of light having a frequency varied by the phosphor increases, and when the thickness of the polymer material 20 including the phosphor decreases, intensity of light having a frequency varied by the phosphor decreases. Therefore, since the thickness of the polymer material 20 including the phosphor is an important factor for determining colors finally obtained from the LED 10, the thickness must be precisely controlled. In particular, since the light is emitted from side surfaces of the LED 10 as well as an upper surface thereof, the thickness of the polymer material 20 including the phosphor disposed on the side surfaces of the LED 10 as well as the thickness of the polymer material 20 including the phosphor disposed on the upper surface of the LED 10 must be precisely controlled.
Furthermore, since the polymer material 20 including the phosphor is applied onto the LED 10 to a non-uniform thickness in the conventional method of coating a phosphor on the LED 10, uniform colors cannot be obtained. For example, when a white light is obtained by mixing a blue light emitted from a blue LED 10 and a yellow light obtained by a yellow phosphor, the white light with yellow color is transmitted to an observer 1 of FIG. 1 since the thickness of the polymer material 20 including the phosphor is large, and the white light with blue color is transmitted to an observer 2 of FIG. 1 since the thickness of the polymer material 20 including the phosphor is small.