presenter: pier angelo favarolo 18th march...
TRANSCRIPT
1
The hot side of the light Presenter: Pier Angelo Favarolo
18th March 2014
2
27.03.2014 2
The zumtobel group Our companies
Annual revenues: 1,243.6 million €
3
27.03.2014 3
The zumtobel group Production plants
7162 employees in 18 production plants in four continents with one common denominator:
The passion for light!
4
27.03.2014 4
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?
5
27.03.2014
+
+
+ +
+ + +
- -
- -
- - -
+
-
-
+ +
-
+
-
-
+ +
-
Anode
Junction
Cathode
PCB
Light Emitting Diodes Light generation
The recombination of electrons
and holes generate photons
Electrodes
6
27.03.2014 6
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.
7
27.03.2014 7
Light Emitting Diodes Phosphor conversion
InGaN emission
8
27.03.2014 8
Light Emitting Diodes Heat sources
Die
Phosphor
Board
Heat ~ 70%
Light ~ 30% of the electrical power
9
27.03.2014 9
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?
10
27.03.2014 10
- 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.
Light absorption on the glob-top Purpose of the investigation
Foreign particle
11
27.03.2014 11
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
12
27.03.2014 12
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
13
27.03.2014 13
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
14
27.03.2014 14
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.
15
27.03.2014 15
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
16
27.03.2014 16
The simulation model Temperature distribution of the glob-top
Simulation IR-Camera image
17
27.03.2014 17
The simulation model Temperature distribution
Ø 250 µm Ø 250 µm
Ø 1000 µm Ø 500 µm
18
27.03.2014
Thank you for your attention