Chuck DeMilo Director, Product Marketing

Luminus Devices, Inc. 1100 Technology Park Dr.,

Billerica, MA 01821

LED Performance & Testing

An LED perspective of an outdoor area light

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Lots of lumens = Lots of LEDs Cost & Complexity

LED Street & Area Lights

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Bigger chips (fewer LEDs)

1mm2 2mm2

100+ lm 200+ lm

4mm2

400+ lm

9mm2

900+ lm

Fewer LEDs but with the same fixture lumens and efficacy

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Kilo-lumen LEDs

Current density (A/mm2)

Rel

ativ

e Ef

fica

cy (

LPW

)

80%

90%

100%

110%

120%

130%

140%

150%

0.00 0.25 0.50 0.75 1.00

350mA/mm2 1mm2 = 350mA 2mm2 = 700mA 9mm2 = 3150mA

Bigger chips produce high lumen solutions with high efficacy

1mm2 2mm2

9mm2

100+ lm 200+ lm

900+ lm

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Thermal Flux Density

Spatially separated sources with distributed thermal flux

Single source with higher thermal flux density

Thermal management is critical to ensure reliability of high flux density sources

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Thermal Management

0%

20%

40%

60%

80%

100%

25 50 75 100 125 150Junction Temperature (C)

Rel

ativ

e Lu

min

ous

Flux

(%)

Flux vs. Junction Temp (typical) Life vs. Junction Temp (typical)

0%

20%

40%

60%

80%

100%

75 100 125 150Junction Temperature (C)

Rel

ativ

e Li

fetim

e (L

70/B

50)

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Chip Construction: Thermal Optimization Chip construction

– Vertical chip design – High External Quantum Efficiency – Current (heat) spreading electrodes – Epitaxial layer bonded to metal sub-mount

LED junction

Metal substrate

Current spreading electrodes

Surface extraction

High efficiency back reflector

Sub-mount material Thermal Conductivity (W/mK)

Sapphire 35

Silicon 150

Copper Tungsten 200

Copper 350

LED chip design for high optical & thermal flux density 8

Aluminum Nitride Ceramic

Material Thermal Conductivity (W/mK)

Aluminum Nitride 200

Aluminum Oxide 20

LED package design for high optical & thermal flux density

Package Construction: Thermal Optimization

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Redundant Bond Wires

Redundancies boost reliability

Multiple bond wires in parallel

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Testing

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LM-79, LM-82, LM-80

LM-79: Luminaire

LM-82: Light Engines / LED Lamps LM-80: LED Light Sources

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LM-79 Electrical & Photometric Measurements of

Solid-State Lighting Products

Tests • Voltage & Current • Luminous Flux • Luminous Efficacy • Intensity vs. Angle • Color (CCT & CRI)

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LM-82 Characterization of LED Light Engines & LED Lamps for Electrical and

Photometric Properties as a Function of Temperature

Zhaga: An LED light engine is a combination of an LED module and the associated control gear.

Test at multiple temperatures • Current & Voltage • Luminous Flux • Luminous Efficacy • Intensity vs. Angle • Color (CCT & CRI)

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LM-80 Measurement of Lumen Maintenance of

LED Light Sources

Test at multiple temperatures vs. time • Current & Voltage • Luminous Flux • Chromaticity

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LM-80 Test Requirements • Testing at a NVLAP 17025 accredited laboratory.

– Technical qualifications and competence

• Control parameters – Junction temp – Ambient air temp – Relative humidity

• Duration – Minimum 6,000 hours – Measurement interval of 1,000 hours

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Temperatures & Measurement Points • LM-80 requires 3 case temperatures (Ts) 55°C, 85°C and 3rd temp determined by LED manufacturer

________________________________

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Test Conditions

• Current: 3.2A = 350mA/mm2 • Ambient air temp (TA): TA maintained within 5°C of TS

• Relative Humidity: RH < 65%

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LM-80 Test Data

Increase in light output? • Diffusion of dopants • Relaxation of internal stresses

Short-term artifact, brightness will not continue to increase over time 19

Lumen Maintenance Extrapolation from LM-80 Data

Hard to believe! 20

TM-21 Projecting Long Term Lumen Maintenance of

LED Light Sources

• Max lumen maintenance projected life = 6X test duration.

• Sample size ≥ 20 units per test condition to use the 6X multiplier.

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TM-21 Extrapolation Lamp Lumen Depreciation Calculations Standard Exponential Decay Curve Fit

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LM-80 at 1A/mm2 & TM-21 Extrapolation

LM-80 data at high current density of 1A/mm2

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LEDs Don’t Last Forever!

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Lumen Maintenance Calculation Average Degradation

Understand the performance of the all of the LEDs under test!

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Failure Modes “LM-80 does not attempt to induce any failure modes”

LM-80 is a partial view into overall reliability and anticipated lifetime

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Test Methods: Wafers & Wafer Lots

• LM-80/TM-21 do not specify the number of wafers or wafer lots used for the test. – Testing 20 LEDs from 3 different wafer lots may be more

meaningful than testing 1,000 LEDs from a single wafer lot.

Test data should represent the production distribution

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Lumen Maintenance: B50 & B10

B50 = 50% of population fails at the L70 lifetime B10 = 10% of population fails at the L70 lifetime

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L70(B50) = 68,000 hours at Tj=110C at 9A L70(B10) = 21,000 hours at Tj=110C at 9A

• LED Manufacturer Testing Beyond LM-80 – Full Qualification Testing – Highly Accelerated Testing

• Induce Failure Modes

– Infant Mortality

Additional Reliability Analysis

Lumen Maintenance

Qualification Test Reports Reliability Application Notes

Data Sheets 29

Summary • LM-80 & TM-21 are critically important in

standardizing the lumen maintenance projections for LEDs and driving adoption.

• Luminaire manufacturers and municipalities should: – Dig into the LM-80 test methodology – Understand the distribution of performance (not just the average) – Go beyond LM-80 to fully understand reliability and expected lifetime

A comprehensive examination of all available reliability and lifetime data will lead to the best purchasing and deployment decisions.

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Thank You!

Chuck DeMilo Director, Product Marketing

Luminus Devices, Inc. 1100 Technology Park Dr.,

Billerica, MA 01821

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