Thermal and optical investigations of high power LEDs with metal embedded printed circuit boards

Abstract

To improve the thermal and optical performances for high power LEDs, a metal embedded printed circuit board (MEPCB), with a columnar copper slug inside the low cost FR4 material, was introduced in this paper. This novel structure makes it possible to connect the LED component directly to the outside environment. The thermal performances, including thermal resistances and temperature distributions of the MEPCB were evaluated by employing the finite element analysis method (FEA) and transient thermal measurement. The luminous and chromatic characteristics were also measured and analyzed at transient state and steady state. Results showed that the maximum reductions in the total thermal resistance and junction temperature were 65.60% and 56.25% by using the MEPCB compared with the conventional metal core printed circuit board (MCPCB). Benefiting from the excellent thermal performance of the MEPCB, up to 24.14% increase in steady state luminous flux was obtained compared with the MCPCB. Moreover, the correlated color temperature (CCT) shift value between 150mA and 900mA could be controlled within 93K. This work demonstrates that the MEPCB is more suitable for LEDs working at wide current ranges.