Conformal Phosphor Distribution for White Lighting Emitting Diode Packaging by Conventional Dispensing Coating Method With Structure Control

Conformal phosphor distribution is a well known way to improve optical performance for white light emitting diode (LED) packaging. However, it is difficult to be realized by mature and cheap dispensing coating methods. In this paper, with consideration given to the effect of boundary constraint on liquid wetting morphology, a method to achieve phosphor conformal distribution is presented by conventional dispensing coating with controlling the slanting angle of reflector cups. The numerical simulations and experiments on phosphor dispensed into reflector cups with different slanting angles are conducted. The results show that uniform phosphor distribution can be obtained when the slanting angle is the same as the contact angle between the phosphor slurry and the reflector cup side wall. The rule can be used to guide the design of the reflector cup and a simple change of reflector cup can realize phosphor conformal coating for white LEDs by the low cost traditional dispensing coating process.