Development and performance of LED metal package with an integrated reflector/heat slug structure

This paper reports on the development of new design of Light Emitting Diode (LED) metal package and its thermal and optical performance. The new package exhibits a reflector integrated with a heat slug as one body. Thermal and optical performance of the package was evaluated and compared with that of commercial plastic LED package for reference. The new metal package showed excellent thermal performance compared with the plastic package (R
_{th, j-a}
of 27 K/W vs. 49 K/W and T
_j
of 57°C vs. 86°C at a driving current of 350 mA). Unexpected from the much better thermal performance, optical power from the metal package was not noticeably higher than that from the plastic package when measured by an integration sphere. Comparison of optical simulation results from 50 cm radius far field and near field receiver indicated a significant optical loss at the reflector surface of the metal package. It was demonstrated that the external optical power of the metal package be significantly improved by the change of reflector design. The external optical power was improved from 145.29 mW to 170.15mW by optimizing the two reflectors' angles (from 80° and 80° to 55° and 50°, for the 1st and 2nd reflector, respectively).