[time-nuts] LED reliability

Tim Shoppa shoppa at trailing-edge.com
Wed Apr 30 18:55:39 EDT 2008

Hal Murray <hmurray at megapathdsl.net> wrote:
> > LEDs been viable since at least the early 70's?  Talk about planned
> > obsolescence... 
> How reliable were the early LEDs?  When did they start to get used in high 
> reliability applications?
> I remember getting a rack of memory for a PDP-10 that used LEDs because the 
> normal lights burned out all the time. That was back in the early 80s when 
> real computers had lots of lights.  I think LEDs were pretty new then.  (at 
> least new to me)
> The best reliability story I heard (many years ago) was about installing 
> another trans-Atlantic telephone cable.  They used tubes long after 
> transistors were out.  They knew how long the tubes would last.  They didn't 
> have much data on transistors yet.

LED's from the 70's are not particularly reliable today. Like transistors,
the problem was the packaging. Get a poor seal or some contaniments,
and the lifetime was years, not decades.

Now, there are some 70's era LED's in metal TO-style cans with epoxy
windows. Those tend to be more reliable.

It was in the 70's that they worked out the last kinks in plastic
packaging. There are still a few aerospace applications where they
still insist on metal applications for all semiconductors but really
most modern plastic packages are more than good enough for most
all applications.


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