The hot side of the light Presenter: Pier Angelo Favarolo 18th - PowerPoint PPT Presentation

The hot side of the light Presenter: Pier Angelo Favarolo 18th March 2014 1

The zumtobel group Our companies Annual revenues: 1,243.6 million € 27.03.2014 2 2

The zumtobel group Production plants 7162 employees in 18 production plants in four continents with one common denominator: The passion for light! 27.03.2014 3 3

Thermal management Why? Modern luminaires contain electronic devices (e.g. drivers) and semiconductors (LEDs, OLED). Their performances and reliability strongly depend on their temperatures: the lower, the better . CFD is a powerful tool to investigate the underlying physics of the problem and hence make suitable design changes. 27.03.2014 4 4

Light Emitting Diodes Light generation The recombination of electrons + + + and holes generate photons + + + + Anode + + + + - + - - + Junction - - - - - Cathode - - - - - PCB Electrodes 27.03.2014 5

Light Emitting Diodes Dice In a typical COB (Chip-On-Board) module the dice have a surface of almost 0.5 mm² and the generated heat and radiant fluxes are of the order of some Megawatts per square meters . 27.03.2014 6 6

Light Emitting Diodes Phosphor conversion InGaN emission 27.03.2014 7 7

Light Emitting Diodes Heat sources Light ~ 30% of the electrical power Phosphor Die Board Heat ~ 70% 27.03.2014 8 8

Light Emitting Diodes Heat sources The Silicon-Phosphor compound has a poor thermal conductivity . What happens if some accidentally trapped foreign particle is absorbing the light on the glob-top? 27.03.2014 9 9

Light absorption on the glob-top Purpose of the investigation Foreign particle Analysis of the thermal behavior of the - glob-top due to the presence of an accidental light absorption. Control of the glob-top temperatures in - order to avoid alterations of the physical and optical properties of the Silicon- Phosphor compound. Impact of several parameters like the - position and the dimension of the absorbing particles. 27.03.2014 10 10

The simulation model Physical phenomena Physical phenomena to be simulated  Light generated by the dice  Conversion losses in the phosphor  Light absorption on the glob-top  Heat conduction  Buoyancy-driven convection  Heat radiation 27.03.2014 11 11

The simulation model Phosphor conversion (Stokes‘ shift) losses Glob-top model  The glob-top is a compound of Silicon and Phosphor The whole glob- top volume is involved in the Stokes‘  shift The discrete ordinates radiation model (DORM) is adopted in order to take into account the volumetric absorption of the radiation 27.03.2014 12 12

The simulation model Modelling the light  The multi-band model is used in order to separate the luminous radiation from the thermal one.  The spectrum is divided into two bands: one for the visible and the other one for the IR part of the spectrum 27.03.2014 13 13

The simulation model Modelling the light source  The dice are modelled as gray bodies  The radiant temperature and the emissivity are chosen in order to radiate the desired amount of energy in the visible part of the spectrum. 27.03.2014 14 14

The simulation model Modelling the light source  The light source has a high temperature used to generate the radiant flux.  As this temperature is not realistic, it is necessary to isolate thermally, the light source from the rest of the model → Non-conductive baffles 27.03.2014 15 15

The simulation model Temperature distribution of the glob-top Simulation IR-Camera image 27.03.2014 16 16

The simulation model Temperature distribution Ø 250 µm Ø 250 µm Ø 500 µm Ø 1000 µm 27.03.2014 17 17

Thank you for your attention 27.03.2014 18