2010 Annual Conference and Business MeetingMay 9-11, 2010May 9 11, 2010Las Vegas, NV

Development of an Automated Measurement System for LED Lifetime Testfor LED Lifetime Test

Yuqin Zong1, Cameron Miller1, Yoshi Ohno1

Jeff Hulett2, and Greg McKee3

1 N ti l I tit t f St d d d T h l G ith b M l d

, g

1 National Institute of Standards and Technology, Gaithersburg, Maryland2 Vektrex, San Diego, California

3 Labsphere, North Sutton, New Hampshire

Motivation

Lifetime of an LED (L70)i d f E St lifi ti- required spec for Energy Star qualification

- believed to be long (eg. 50 K hours = 5.5 years!)- time-consuming and costly testing- time-consuming and costly testing

Possible solutions:

Perform a "short" period of time test (eg. 6000 hours (250

Perform accelerated test, but no acceptable approach yet.

days) in the IESNA LM-80-08), and extrapolate data to predict lifetime – requires a method/model (IES TM-21).

NIST Plan

Develop a fully automated measurement system by following LM 80 guidance

Select LEDs from the market.

following LM-80 guidance.

Add new unit(s) in the future if necessary

Perform lifetime test for 3-5 years.

Generate a database automatically with a large amount of

Add new unit(s) in the future if necessary.

data with assigned measurement uncertainties.

A typical workflow for a LED lifetime test

Mount LEDson a MCPCB

Measure LEDs(25 °C in a Lab)

Age LEDs, unattended(Hot in a Thermal Chamber)

Per 40 daysManually(25 C in a Lab) ( )Manually

Measure LEDs(25 °C in a Lab)

Analyze Datay

Typically instruments/equipment

ThermalThermal Chamber

LED MCPCB

X-Y ScanningLED

Power Supply,

Measurement System

Switching Unit

A new, fully automated system being developed at NIST

TE CoolerWarm airventing port

Automatic measurement under in-situ Calibration

condition and at 25 °C room temp.Can be very

Quartz fiber bundle

port

ALED

frequent!

ArraySpectrometer

Filtered cold air

LEDs on a MCPCB board

Aux. lamp

ComputerTE

controllerPowersupply

Filtered cold airintake port

Elec. Meas.Unit pcontrollersupply Unit

Key Component - Large temp-controlled heat sink

400 W input power.

6” x 8.5” cold plate.

280 W cooling power at 25 °C ambient temp.

Very affordable.

Key Component - Large 6” x 6” MCPCB board

Eight 10 LED arraysEight 10 LED arrays.

Total 80 LEDs.

Key Component - Power supply and switch unit

0-5A, 0-200 V

DC and pulsed operation<10 μs pulsing for junction

8 channels to power up the i ht LED

temperature measurement.

eight LED arrays.

Ability to turn on/off one LED at i f i la time for optical measurement.

Built-in multi-layer LED protections.

Key Component - Integrating sphere

80 cm diameter.Warm airventing port Fiber

BaSO4 coating with LED

Intake and venting ports to avoid contamination

venting portport 90 % reflectance.

Calibration port

LED port

to avoid contamination.source-detector adjacent geometry (by P. Hanselaer) to g y ( y )reduce the error due to change of spatial nonuniformity.

Aux lamp

Filtered cold air

Detachable LED & TE-cooler assembly for

Aux. lamp

Filtered cold airintake port measurement verification.

Multiple units, expandable

120 °C55 °C 85 °C

120 °C

“8 t 1”

ArraySpectrometer

“8 to 1” quartz fiber bundle or a fiber switch.

Computer

LED samples

- One model per manufacturerOne model per manufacturer,- Three operating currents per model,

Three case temperatures per model- Three case temperatures per model,- 10 LEDs per test condition.

Total 90 LEDs per model to be tested

Timeline (preliminary)

2010 June - overall design completed

2010 September – purchasing contract awarded

2010 November - system delivered

2011 January - system integration at NIST completed

2011 March - testing starts

Acknowledgements

Melissa Ford, VektrexDan Scharpf and Joe Jablonski LabsphereDan Scharpf and Joe Jablonski, Labsphere

US Department of EnergyUS Department of Energy

THANK YOUTHANK YOU