Bill Dieffenbacher wrote:
> 
> Does anyone know if there are any design requirements for a product
> to be UL rated?  I thought that materials were rated by UL but that
> they did not delve into design requirements.  Perhaps I'm wrong.
> 
> Bill Dieffenbacher
> Lockheed Martin Control Systems

Hi Bill, 

Let me qualify first. I have been doing compliance work 
(FCC and UL stuff) for about 16 years now. I have never 
worked for a board fab house or an assy house. I deal 
with systems a customer like AT&T or NYNEX buys to use. 

UL approval can involve the design and layout of a 
PC board.  It's under "creepage" and "clearance" 
requirements in some of the standards. Creepage 
involves the distance along the surface of the 
board from one point to another. Clearance involves 
the distance from one point to another of a board 
through the air. 

Usually UL is concerned about high voltage. So if 
the board handles anything above a certain level, 
say taking in AC from the line to a DC-DC converter, 
they will look at it. 

I've given a very rough explaination but hope it 
helped. 

Regards ...

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