AN1149-6 Lumileds Lighting, LLC, AN1149-6 Datasheet - Page 6

• Manufacturer Part Number: AN1149-6
• Description: Reliability Considerations for SuperFlux LEDs
• Manufacturer: Lumileds Lighting, LLC

Recommended LED
Assembly Validation Tests
Lumileds recommends that customers use the
tests listed in the Table 6.2 to validate the
durability of assemblies containing SuperFlux
LEDs. Other tests (such as vibration, or
corrosion resistance) may be included to check
the performance of other components,
materials, or interconnections in the assembly.
Please realize that Lumileds cannot guarantee
LED performance during durability tests if the
maximum operating or storage temperature
ranges, or the maximum junction temperature
listed in the SuperFlux LED Technical Data
Sheet are exceeded. In some applications, such
as high mount stop lamps mounted in the
headliner behind rear window glass, the local
Verifying Root Causes of Power & Temperature Cycle Failures
The most common causes for SuperFlux LED
failures during Power & Temperature Cycle
testing are excessive heat during soldering,
thermal shock, and exceeding the devices
absolute maximum junction temperature.
Separation between the leadframe and the
encapsulant is usually caused by excessive
solder heat or thermal shock. If this type of
failure is suspected, the root cause can be
confirmed by measuring the wave solder station
temperatures and the temperature gradients
that the SuperFlux LEDs were exposed to
during assembly. This is accomplished by
attaching a thermocouple to the lead of an LED
on the solder side of the PCB and recording its
temperature profile during each operation. This
should include any preliminary operations such
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ambient temperature can reach temperatures in
excess of 100°C. Lumileds recommends that
Lighting System Suppliers work with vehicle
manufacturers to perform temperature
measurements on similar vehicles or mock ups
to determine the actual operating and storage
conditions to which the LED assembly will be
exposed. During these studies it is important for
the Lighting System Suppliers to record both
temperature and supply voltage measurements.
Both of these parameters will be required when
designing assemblies for ‘worst case’ conditions
(reference Application Brief AB20 3 Electrical
Design Considerations for SuperFlux LEDs.)
as surface mount glue cure, the soldering
operation, any subsequent rework or touch up
operations, and any post solder heating or
cooling cycles such as conformal coating cure.
(Reference Application Note 1149 2 Mechanical
Design Considerations for SuperFlux LEDs for
precautions required when attaching thermo
couples to the leads of LEDs.) The heating and
cooling rates must not exceed ± 3°C per second,
and the preheat and soldering temperatures
should follow the recommendations provided in
Application Note 1149 2 Mechanical Design
Considerations for SuperFlux LEDs.
Exceeding the maximum junction temperature
of the SuperFlux LEDs during Power &
Temperature Cycle testing usually results in a
necked down wire break above the ball bond on