China SSL 2012

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November 5, 2012

Designing and Delivering Quality in SSL

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


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

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


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


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%


Time (hours)

% L

FPhosphor Degradation (Generic, all types)

• Phosphors are chemically very stable over time also

50,000

100%

90%

80%

70%


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


Time (hours)

% L

FEncapsulant Degradation (Generic, all types)

• Rapid initial degradation (first 5k hrs), stable long term

50,000

100%

90%

80%

70%


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…


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


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…


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


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


Time (hours)

% L

FCombined: Plastic/Metal LF, Substrate

50,000

100%

90%

80%

70%

LED ChipPhosphorEncapsulantMetal (Al, Ag)PlasticCombined


5 Sources


Time (hours)

% L

FCombined: “High Bright” LEDs

50,000

100%

90%

80%

70%

LED ChipPhosphorEncapsulantPlasticCombined


4 Sources


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


Light Degradation at the Application Level

Time zero 1000 hours

Brightness

Color


☼ Brightness

This may be OK for some consumer

applications


☼ Brightness


☼ Brightness


☼ Brightness

We don’t typically have this kind of

control on our lights…


☼ Hue


☼ Hue


☼ Hue


☼ Hue

No remote control for this either…


Is it OK for this Application??

Probably for some

markets, probably NOT

for others


Very Application Dependent

As Installed

3 Months Later

You don’t want to be that guy…


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

Documents

China SSL 2012