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

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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


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The hot side of the light

Presenter: Pier Angelo Favarolo 18th March 2014

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The zumtobel group

Our companies Annual revenues: 1,243.6 million €

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The zumtobel group

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

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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.

Thermal management

Why?

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  • Anode

Junction Cathode PCB

Light Emitting Diodes

Light generation

The recombination of electrons and holes generate photons

Electrodes

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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

  • rder of some Megawatts per square meters.
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Light Emitting Diodes

Phosphor conversion InGaN emission

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Light Emitting Diodes

Heat sources Die Phosphor Board

Heat ~ 70% Light ~ 30% of the electrical power

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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?

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  • 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
  • rder 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.

Light absorption on the glob-top

Purpose of the investigation Foreign particle

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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
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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 simulation model

Phosphor conversion (Stokes‘ shift) losses The discrete ordinates radiation model (DORM) is adopted in order to take into account the volumetric absorption of the radiation

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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

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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.

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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

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The simulation model

Temperature distribution of the glob-top Simulation IR-Camera image

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The simulation model

Temperature distribution

Ø 250 µm Ø 250 µm Ø 1000 µm Ø 500 µm

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Thank you for your attention