On 11/20/16 9:31 AM, J. Clarke wrote:
In article ,
says...

On 11/19/16 8:15 PM, J. Clarke wrote:
In article ,
says...

Simple - I used to design and test semiconductor material -
I started in the mid 70's and went pro in 1980.

I remember some of the first high speed CMOS HMOS and NMOS
that ran really fast but shorted power to ground in the output
transistors in the process. It seemed ok in theory - but after
millions of cycles the part melted the epoxy off the IC !

All semiconductor heats up. It is conducting current. Current flow
causes vibration heating.

But in actual tests is that the major failure
mode of commercial LED lighting?


At least for consumer lighting, the failure point is typically the power
supply, more specifically the electrolytic capacitors which dry out and
are degraded by heat.

Based on forensic analysis of how many failures
of consumer LED replacement bulbs over what span
of time?


I follow the LED industry as part curiosity and I also build some custom
LED lighting devices. This means I read a lot of stuff about failures
and always read through the various "tear-down" articles where they
dissect new lamps and also do forensics on failed units. With anything
electronic, the manufactures produce reliability figures (MTBF, mean
time between failures) for components and also degradation numbers tied
to life-killers like heat.

Some of the trade journals touch on this stuff. If you are really
curious (or really bored 8^)

http://www.electronics-eetimes.com/n...t-led-lighting

http://www.osram-os.com/Graphics/XPic6/00102625_0.pdf

http://www.lumileds.com/uploads/167/WP15-pdf

http://www.digikey.com/en/articles/t...ng-led-failure

http://www1.eere.energy.gov/building...e_june2011.pdf

http://d3eurf9v83z5xo.cloudfront.net...eliability.pdf

Some general info, seems reasonable given the source:

https://en.wikipedia.org/wiki/List_of_LED_failure_modes

-BR


The LEDs do fail, mostly from the same heat
degrading the thermal bond between the actual LED emitter and the heat
sink, but often the root cause of this is poor assembly. LEDs as devices
are very stable and robust, as long as they operate within there design
specs for maximum junction temp.

-BR