Study on conformal phosphor coating for phosphor converted white LEDs through ionic wind patterning

The morphology of phosphor layer in white phosphor converted white LEDs is very important since it plays a vital role in optical performance such as correlated color temperature (CCT) and angle color uniformity (ACU). Owing to its outstanding optical performance, conformal phosphor coating process has attracted plenty of attention since it was proposed. In this article, a new method through ionic wind patterning for realizing conformal phosphor coating was proposed. The principle of such a patterning method was based on the interaction between ionic wind and liquid encapsulation. Masks were applied to control the ion flow for obtaining the desired patterning. As a result, compact and uniform phosphor encapsulation layer was successfully fabricated, its geometry was presented and its optical performance enhancement was demonstrated by experiments. Compared with the traditional dispensing coating process, the angular CCT deviation of the proposed structure is reduced from 1630K to 366K, when the averaged CCT is ~5400K.