APPLICATION NOTE 01
Bright Lights. Bright Ideas. TM
LIFE, LUMEN MAINTENANCE AND
RELIABILITY
Light emitting diodes (LEDs) are solid state devices offering many
advantages over conventional lighting sources. A primary advantage
is that LEDs typically do not fail suddenly or burnout, but gradually
degrade. Unlike LEDs, conventional lighting sources commonly fail
catastrophically.
PREDICTED LIFE
A primary metric for judging useful life of conventional lighting sources is lamp lifetime,
commonly expressed as the time to failure or burnout. Life of conventional lighting
sources is based on the time it takes for 50% of lamps to fail. LEDs, being semiconductors, express their failure rate using 'mean time to failure' (MTTF), a well-defined statistical
term commonly used in the semiconductor industry. LED manufacturers typically predict
high brightness LED MTTF to be on the order of 100,000 hours, provided LEDs are properly packaged and used in accordance with manufacturers' recommendations. These predictions apply to catastrophic failures where the device is rendered completely inoperable.
Lamina light engines are built using exclusive proprietary packaging technology, which
ensures an excellent thermal path from the LED junction to the outside of the light engine
(where application specific heat sink takes over). Lamina's packaging also provides an
excellent thermal coefficient of expansion (TCE) match to the LED. This ensures that the
bond between the LED and the package is not subject to undue stress as the entire
assembly expands and contracts with heating and cooling. By minimizing both the LED
junction temperature and the mechanical stress on the device, Lamina's packaging system
provides one of the best operating environments available for high brightness LEDs.
AVERAGE LUMEN MAINTENANCE
Conventional lighting sources and LEDs both experience lumen depreciation (loss of
lumens) over time even when operated within specified conditions. Therefore, whenconsidering the useful life of very long life products such as LEDs, lumen depreciation must
also be taken into account. Lumen depreciation is typically expressed as lumen maintenance-the percentage of initial lumens remaining after a specified period of time.
Lumen maintenance of LED light sources is dependent on many factors including ambient
temperature and humidity, the method of electrical control, drive current, and effective thermal management. For Lamina monochromatic LED arrays with a 25ºC maintained junction temperature the predicted lumen maintenance is shown in Figure 1.
Figure 1. Predicted Lumen Maintenance*
*Maintained junction temperature 25ºC.
LAMINA SUPER-BRIGHT
LED ARRAYS
AS THE MARKET LEADER IN THE DEVELOPMENT AND MANUFACTURE OF SUPERBRIGHT LED ARRAYS, LAMINA BRINGS
SOLID STATE LIGHTING TO APPLICATIONS
WHICH UNTIL NOW WERE ONLY POSSIBLE
WITH TRADITIONAL LIGHTING SOURCES.
LAMINA'S STANDARD PRODUCTS, AVAILABLE IN WHITE, RGB AND MONOCHROME, ARE DESIGNED TO DELIVER
1W TO 100W OF SUPER-BRIGHT LIGHT.
IN ADDITION, LAMINA PROVIDES CUSTOMIZED LED ARRAYS AND PACKAGE
CONFIGURATIONS. APPLICATIONS
INCLUDE ARCHITECTURAL LIGHTING, GENERAL ILLUMINATION, AUTOMOTIVE, SIGNAGE, AND SIGNALING.
LAMINA LED ARRAYS ARE MANUFACTURED BY COMBINING HIGH BRIGHTNESS
LEDS FROM INDUSTRY-LEADING LED
MANUFACTURERS WITH LAMINA'S PROPRIETARY PACKAGING TECHNOLOGY, MULTILAYER LOW TEMPERATURE CO-FIRED
CERAMIC ON METAL (LTCC-M). LTCCM IS A BREAKTHROUGH IN THERMAL
PERFORMANCE FOR LED PACKAGING
TECHNOLOGY, A KEY FACTOR IN DETERMINING LED LIFE AND RELIABILITY.
UNMATCHED THERMAL PERFORMANCE
COUPLED WITH PACKAGE INTERCONNECTIVITY ALLOWS LAMINA TO DENSELY
CLUSTER MULTIPLE LEDS TO ACHIEVE
EXCEPTIONALLY HIGH LUMINOUS INTENSITY IN VERY SMALL FOOTPRINTS.
APPLICATION NOTE 01
Bright Lights. Bright Ideas. TM
High LED junction temperatures accelerate degradation in
lumen maintenance and result in a temporary reduction in luminous flux. The relationship between luminous flux versus LED
die junction temperature is illustrated in Figure 2. Lamina's
unique packaging technology provides exceptional thermal management, a critical factor in optimizing lumen maintenance and
luminous flux with high density LED arrays.
Figure 2. Luminous Flux vs. Junction Temperature
ESD PROTECTION
LEDs are static sensitive and susceptible to electrostatic discharge (ESD) damage. Lamina LED arrays must be handled
using ESD damage control precautions.
ASSEMBLY RECOMMENDATIONS
Lamina BL1000 Series LED arrays are designed as surface
mount devices with attachment to a printed circuit board
(PCB) using surface mount processes. Heat sink attachment
can be achieved by soldering to thermal vias on the PCB or
with conductive epoxy or thermal grease in a bolt down
arrangement.
Lamina BL2000 and BL3000 Series LED arrays are designed
for attachment to heat sinks with conductive epoxy or screw
down with thermal grease in the joint.
For attachment using screws, the following is recommended:
•BL-2000 Series: 2-56 UNC fillister head slotted machine
screw 18-8 SS
•BL-3000 Series: 6-32 UNC fillister head slotted machine
screw 18-8 SS
COLOR CONSISTENCY
To minimize the inherent variation in LED die color, lumen output, and electrical properties, LED die manufacturers use a
process of selection or sorting, commonly referred to as binning.
In addition to utilizing binned LEDs, color and lumen consistency in Lamina LED arrays are further improved through the
reliance on multiple die per array as opposed to dependency on
the output of a single die.
THERMAL MANAGEMENT
Lamina LED arrays provide efficient transfer of heat from the
individual LED die to a customer supplied heat sink. As with
any LED-based light source, the junction temperature of the
LEDs within a Lamina LED array must be maintained at or
below 125ºC. In order to achieve this, the light engine must be
heat sinked with sufficient cooling capacity to keep the die junction below 125ºC during full-power operation at maximum ambient temperature.
Maximum torque is 4 inch-pounds. Required flatness of surface light engine is mounted to is 0.001 inch/inch.
Thermal transfer tape can be used with Lamina LED arrays
but is not recommended as it will result in higher than
desired thermal resistance creating excessive heat and
reducing light output and die life.
Lamina Ceramics
120 Hancock Lane
Westampton, NJ 08060
1-800-808-5822
1-609-265-1401
Please see Lamina Application Notes for detailed information on
proper attachment, heat sinking requirements, and heat sink
selection.
HANDLING PRECAUTIONS
Contact with the silicone based encapsulant on the surface
of the light engine must be avoided to prevent damage. Do
not apply pressure to the silicone based encapsulant or allow
it to come into contact with sharp objects. Lamina LED arrays
must be handled from the sides.
FM-0058,08.02.04
© 2004 Lamina Ceramics