Design and optimization of heat dissipation and illumination patterns in novel recessed chip-on-board designs for high-power LED lighting applications

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Thermal management is a fundamental limiting factor in solid state lighting applications, affecting the devicereliability and luminous efficacy. In high-power applications, the increased chip density exacerbates the needfor efficient heat dissipation pathways. Chip-on-board (COB) approaches improved the state of the art byremoving the need to individually package LED chips, while yielding better cooling efficiencies by providing amore intimate thermal contact between the chip and heat sink. However, in COB LED products the flat boarddesign limits the heat spreading that can take place at the interface with heat sinks. A recessed heat sinkcarrying the COB is proposed as an approach to improve the heat spread within the heat sink, and therebyimprove the cooling efficiency of the COB assembly. While the idea is attractive, the design trade-offs in termsof cooling capabilities, recess depth & shape and their impact on the luminous intensity spatial distribution areunknown. Additionally, the recessed heat sink material and relative placement of the phosphor may have anadverse effect on the color output of the light fixture. Systematic studies of heat sink-recessed COB designs canyield insights into these trade-offs and optimum operating points. The research can improve the adoption ofhigh-power solid state lighting in industrial applications, with tremendous environmental benefits, as theincrease in light output per watt consumed greatly reduces energy waste and green-house gas emission fromnon-renewable energy sources.