Path: utzoo!attcan!uunet!snorkelwacker!usc!samsung!emory!bluemtn!greg
From: greg@bluemtn.uucp (Greg Richter (2XS))
Newsgroups: sci.electronics
Subject: Re: Blue and UltraViolet LED's
Message-ID: <1990Jul19.134539.16970@bluemtn.uucp>
Date: 19 Jul 90 13:45:39 GMT
References: <17596.2699d803@uctvax> <1990Jul11.233848.29098@zoo.toronto.edu> <1551@oucsace.cs.OHIOU.EDU> <38692@cci632.UUCP> <1990Jul18.033929.13442@zoo.toronto.edu>
Reply-To: greg@bluemtn.UUCP (Greg Richter (2XS))
Organization: blue mountain software
Lines: 29

In article <1990Jul18.033929.13442@zoo.toronto.edu> henry@zoo.toronto.edu (Henry Spencer) writes:
>In article <38692@cci632.UUCP> rdi@ccird3.UUCP (Rick Inzero) writes:
>>Unless there's some problem with actually generating the UV from the 
>>light emitting diode chip itself...  So far, all I remember is postings 
>>that the plastic housing was the problem.
>
 and gets the response:

>...  The mechanisms and materials that fairly easily yielded IR,
>red, yellow, and green simply can't be stretched to blue, let alone
>further.  ... 

Actually, the emitters are silicon carbide, and are quite the bitch to
bond to.  We are working with this nasty material, so this is not idle
speculation.  The problem with blue is not the material or the mechanism,
it's actually putting it in a usable industrial form.  Making them small
is even tougher.  You get what is known as 'dark line cracks' where the 
substrate cracks under the thermal stress of the lead weld.  Makes dark
lines appear in the LED.

Pleasantly - 

-GR


-- 
"Nothing to say, no place to say it."    | Greg Richter 
                                         | ..{uunet,emory}!bluemtn!greg 
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