china ssl 2012
DESCRIPTION
Technical discussion of the mechanisms, rates, and causes of color shift and light depreciation in LED LampsTRANSCRIPT
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Copyright © 2012 Cree, Inc. pg. 3
SSL Quality Begins with the LED Lamp
• LED lamp types, construction• Sources of light degradation• Applications impact• Right LED lamp for the application
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Copyright © 2012 Cree, Inc. pg. 4
An LED Lamp is a Complex System
LED Chip:– Determines raw
brightness and efficacy
Phosphor system:– Determines color point,
color quality and color point stability
Package:– Protects the chip and
phosphor– Helps with light and heat
extraction– Primary in determining
LED lifetime
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pg. 5Copyright © 2012 Cree, Inc.
Different LED Lamp Architectures
Molded Plastic Package, Silver Lead
Frame
Large COB array, Al, Ag Substrate
Ceramic Substrate, Silicone Dome
“High Bright” LEDs designed for consumer
applications
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pg. 6Copyright © 2012 Cree, Inc.
1. Chip Degradation
3. Silicone Encapsulant Degradation
2. Phosphor Degradation
Different Sources of Light Degradation
3 Sources
4. Al, Ag Substrate Degradation
5. Plastic Degradation1. Chip Degradation
3. Silicone Encapsulant Degradation2. Phosphor Degradation
5 Sources
4 Sources
1. Chip Degradation
3. Silicone Encapsulant Degradation
2. Phosphor Degradation
4. Plastic Degradation
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pg. 7Copyright © 2012 Cree, Inc.
Time (hours)
% L
FLED Chip Degradation (Generic, all types)
• LED chips actually get brighter over the first 10-20k hours of operation
• Real LED chip degradation is very, very slow…
50,000
100%
90%
80%
70%
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pg. 8Copyright © 2012 Cree, Inc.
Time (hours)
% L
FPhosphor Degradation (Generic, all types)
• Phosphors are chemically very stable over time also
50,000
100%
90%
80%
70%
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pg. 9Copyright © 2012 Cree, Inc.
Phosphor can peel at the edges, let less blue light through to be converted – color shift, loss of light
Possible Sources of Phosphor Degradation
Phosphor coating is put on chip, generally does not degrade
Micro-delaminations can occur over time, thermal stress –further loss of light, potential for color shift
LED Chip
Phosphor
Illuminated Object
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pg. 10Copyright © 2012 Cree, Inc.
Time (hours)
% L
FEncapsulant Degradation (Generic, all types)
• Rapid initial degradation (first 5k hrs), stable long term
50,000
100%
90%
80%
70%
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pg. 11Copyright © 2012 Cree, Inc.
Encapsulant Degradation Source
Siloxane (R2SiO)n
OSi OSi OSi OSi
R R R R
R R R R
• Silicone encapsulants theoretically cross-link like this:
• Silicone encapsulants actually cross-link like this:
OSi OSi OSi OSi
R R R R
R R R R
OSi OSi OSi OSi
R Si R R
R O
OSi OSi OSi OSi
R Si R R
R O
OSi OSi OSi OSi
R Si R R
R O
CO
CO2
CH3
COCO2
CH3
CH3
• …and a lot of *stuff* comes off them…• Weight loss can slightly reduce RI, long
stranded polymer chains can turn brown/absorb light…
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pg. 12Copyright © 2012 Cree, Inc.
Time (hours)
% L
FPlastic & Metal Substrate Degradation
• Similar degradation profiles, plastic degradation is typically a bit more pronounced
50,000
100%
90%
80%
70% Metal (Al, Ag)Plastic
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pg. 13Copyright © 2012 Cree, Inc.
Plastic & Metal Degradation Mechanism
• This LED lamp architecture depends on metal substrate and plastic sidewall reflectivity
• Plastic can degrade under photon bombardment and thermal stress
• Metal can tarnish due to application environmental conditions (moisture, sulfur, etc.)
• Both can reduce LED lamp light output…
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pg. 14Copyright © 2012 Cree, Inc.
Time (hours)
% L
FPlastic Degradation in Low Cost Packaging
• Plastic degrades quickly and blocks light in this package architecture
• No metal to reflect the light
50,000
100%
90%
80%
70%
Plastic
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pg. 15Copyright © 2012 Cree, Inc.
Time (hours)
% L
FCombined: Ceramic/Silicone Dome
• Typical LM-80 performance at 85°C, med-high current density (chip size dependent)
50,000
100%
90%
80%
70%
LED ChipPhosphorEncapsulantCombined
3 Sources
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pg. 16Copyright © 2012 Cree, Inc.
Time (hours)
% L
FCombined: Plastic/Metal LF, Substrate
50,000
100%
90%
80%
70%
LED ChipPhosphorEncapsulantMetal (Al, Ag)PlasticCombined
• Typical LM-80 performance at 85°C, med-high current density (chip size dependent)
5 Sources
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pg. 17Copyright © 2012 Cree, Inc.
Time (hours)
% L
FCombined: “High Bright” LEDs
50,000
100%
90%
80%
70%
LED ChipPhosphorEncapsulantPlasticCombined
• Typical LM-80 performance at 85°C, med-high current density (chip size dependent)
4 Sources
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pg. 18Copyright © 2012 Cree, Inc.
Time (hours)
% L
FTypical LM-80 Performance by Lamp Type
• Ceramic/Si Dome LED lamp architecture generally have superior Lumen Maintenance vs. Plastic/Metal architectures
• Both can be Lighting-class, always demand the LM-80 report
• HB LED Lamps – demand the LM-80 report
• 5mm lamps – LM-80 is NOT defined
50,000
100%
90%
80%
70%
Ceramic/Silicone Dome
Plastic, Leadframe / COB
5mm LEDs“High Brightness” LEDs
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Copyright © 2012 Cree, Inc. pg. 19
Light Degradation at the Application Level
Time zero 1000 hours
Brightness
Color
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Copyright © 2012 Cree, Inc. pg. 20
☼ Brightness
This may be OK for some consumer
applications
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Copyright © 2012 Cree, Inc. pg. 21
☼ Brightness
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Copyright © 2012 Cree, Inc. pg. 22
☼ Brightness
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Copyright © 2012 Cree, Inc. pg. 23
☼ Brightness
We don’t typically have this kind of
control on our lights…
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pg. 24Copyright © 2012 Cree, Inc.
☼ Hue
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pg. 25Copyright © 2012 Cree, Inc.
☼ Hue
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pg. 26Copyright © 2012 Cree, Inc.
☼ Hue
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pg. 27Copyright © 2012 Cree, Inc.
☼ Hue
No remote control for this either…
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Copyright © 2012 Cree, Inc. pg. 28
Is it OK for this Application??
Probably for some
markets, probably NOT
for others
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Copyright © 2012 Cree, Inc. pg. 29
Very Application Dependent
As Installed
3 Months Later
You don’t want to be that guy…
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Copyright © 2012 Cree, Inc. pg. 30
Select the Right LED For Right SSL Application
• LED lamps are complex systems with different parts that degrade at different rates
• Quality and reliability in SSL applications can be very dependent on the LED lamp architecture
• High Bright and 5mm LEDs should not be used for most Lighting Applications
XLamp XP-E
XLamp MC-E
XLamp XP-G
XLamp MP-L
XLamp XP-C
XLamp MX-6
XLamp ML-E/C/B
XLamp MT-G
XLamp CXA2011
XLamp XB-D
XLamp XT-E
XLamp MT-G2
XLamp XP-G2
XLamp XPE-HEW
XLamp XM-L
XLamp XTE-HV
XLamp XML-HV
XLamp CXA1507/12
XLamp CXA2520/30
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