On 1/25/2013 9:24 AM, Joe Mastroianni wrote:
In another thread, it was mentioned that CFLs and LEDs
last longer than incandescent bulbs.

We all know incandescent bulbs fail due to the filaments
being made so thin that they oxidize and burn up, over time.

I believe incandescents fail because tungsten evaporates (the bulb
blackens somewhat) and hot spots develop. Small lamps are under vacuum.
At about 40W they are gas filled (not including oxygen). The gas reduces
evaporation of the filament.

In halogen lamps, the halogen transports the evaporated tungsten back to
the filament. As a result the filament can run hotter, producing a
smaller percentage of heat.


But, what causes CFL bulbs to fail?

I suspect in a significant percentage it is the ballast electronics that
fail.

In general, flourescents have a filament, or cold cathode, at each end
that produces electrons. The electron emitting surface slowly fails and
when it gets too low the lamp won't start. Sometimes the filaments open.


And, what causes LED bulbs to fail?

I would guess cumulative damage from heat. Semiconductors (and
electronics in general) don't like heat.

One of the problems in LED lamp design is removing the heat from the LED.