Void-free underfill encapsulation for flip chip high voltage LED packaging

High voltage LED (HVLED) is a LED chip configuration that comprises multiple LED units in series, and offers higher luminous output than that of conventional LED chip configurations. Due to the high luminous output and, accordingly, an elevated junction temperature, the thermal performance of HVLED must be enhanced by the flip chip assembly with high-thermal conductivity underfill. To maximize the ability of the underfill to dissipate heat, a void-free, uniform underfill must be achieved. A method to achieve a void-free underfill is introduced and discussed.