LED failures: How to stop them dead David Scott-Maxwell Technical Director, Forge Europa.

LED failures: How to stop them dead

David Scott-MaxwellTechnical Director, Forge Europa

• Before we start – what are ‘LEDs’?:

• Before we start – these are ‘LEDs’:

‘LEDs’ ARE NOT MUCH USE ON THEIR OWN!

• Before we start – ‘LED failures’ = ‘Whole system failures’

• What’s in a ‘Whole system’?

Heatsink

Driver/PSU

Heatsink

Driver/PSU

Enclosure

Heatsink

Driver/PSU

Enclosure

Optics

Heatsink

Driver/PSU

Enclosure

Optics

AdhesivesTIMsetc

Heatsink

Driver/PSU

Enclosure

Optics

AdhesivesTIMsetc

Testing

Heatsink

Driver/PSU

Enclosure

Optics

AdhesivesTIMsetc

Testing

Packaging

Heatsink

Driver/PSU

Enclosure

Optics

AdhesivesTIMsetc

Testing

Packaging

The user!

Heatsink

Driver/PSU

Enclosure

Optics

AdhesivesTIMsetc

Testing

Packaging

The user!

LED failures:

• Electrical Overstress (EOS)• Overheat• Chemical Contamination• Electrostatic Discharge (ESD)

LED failures: Electrical Overstress (EOS)

Causes• ‘Hot Plugging’ #1 LED killer - VERY easily done!• …during in-factory test, luminaire installation• …can be latent• Reverse connection

Effects • Lights out (often short circuit)

Prevention• BE EOS AWARE, design-in circuit protection, lock down factory

procedures, educate

procedures, Educate

LED failures: Overheat

Causes• Modern Lighting Class LEDs can run HOT…• …but there’s a limit to how much power they can handle• …and adequate heatsinking must be provided• …and users can/will overheat products

Effects • Reduced lifetime [LM80/TM21], colour shift

Prevention• Heatsink design is tough – don’t underestimate• Educate customers

XM-L / 105° / 2AL70>70khrs

LED failures: Chemical Contamination

Causes• Silicones particularly vulnerable to ‘charring’• LED manufacturer’s black lists & white lists• Sometimes reversible, sometimes not…

Effects • Reduced lifetime, colour shift

Prevention• Check the lists, do your own tests, be aware of ‘hidden’ chemical

usage.

LED failures: Electrostatic Discharge

Causes• Rare due to protected LED components, good ESD handling, protection via circuitry• BUT - can be latent…

Effects • Lights out

Prevention• Install & audit ESD handling procedures, design-in circuit protection

Driver/PSU failures:

• Electronic product reliability• Key component lifetime• Soldering

Driver/PSU failures: Electronic Product Reliability

• Electronic products can be extremely reliable!• … but ‘you gets what you pays for’…• ‘0.2%/1000hrs’ de-facto standard for lighting electronics

Driver/PSU failures: Electronic Product Reliability

• Electronic products can be extremely reliable!• … but ‘you gets what you pays for’…• ‘0.2%/1000hrs’ de-facto standard for lighting electronics

Driver/PSU failures: Key Component Lifetime

Causes• Electrolytic capacitors• Freewheel diodes• Bridge rectifiers• Optocouplers• … etc etc …

Effects • Lights out, flickering, EMC non-compliance, …

Prevention• Design for product lifetime, control manufacturing

Driver/PSU failures: Soldering

Causes• Low operator skill• Poorly controlled processes• Exotics

Prevention• Control manufacturing, IPC-A-610-E

Conclusion:

Don’t worry too much – LED lighting can be extremely reliable!

Conclusion:

BUT – you need to be profoundly aware of all the issues to achieve this…

Thank you – and good luck!

David Scott-MaxwellTechnical Director, Forge Europa

LED failures: How to stop them dead David Scott-Maxwell Technical Director, Forge Europa.

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Transcript of LED failures: How to stop them dead David Scott-Maxwell Technical Director, Forge Europa.