Regarding John's E-Mail shown below and presuming the "dissipation 
loss" is the same as dissipation factor or loss tangent.

IPC-D-316 defines dissipation factor as the ratio of the energy 
dissipated in a material to the energy stored. 

The title for IPC-D-316 is "Design Guide for Microwave Circuit Boards 
Utilizing Soft Substrates".

Below is an extract of what Clyde F. Coombs, Jr., in his Third Edition 
of the "Printed Circuits Handbook, says about dissipation factor.

"Dissipation factor - Method: ASTM D 150. Unit if value: 
dimensionless. In an insulating material, the dissipation factor is 
the ratio of the total power loss, in watts, in the material to the 
product of the voltage and current in a capacitor in which the 
material is a dielectric. It varies over a frequency range [it goes 
up as frequency goes up]."

Not being formally schooled in the Laws of Physics that explain it, I 
have found it easy to think about the dissipation factor as the ratio 
of electrical energy lost in the form of heat through the dielectric 
material, to the electrical energy being transmitted through a 
conductor path. 

I think that the higher the loss, the more signal attenuation there 
is, which leads to increases in rise times, which are critical in 
high speed and microwave applications. Hopefully other Technet 
members will confirm this relationship.

Both the IPC-D-316 and the Coombs Handbook list values for various 
dielectric materials used to fabricated printed circuit boards.

Regards,

Luis Rivera
CompuRoute, Inc.
Dallas, TX
[log in to unmask]
(214) 340-0543




------- Forwarded Message Follows -------

From: [log in to unmask]
Date: Wed, 28 Aug 96 10:54:46 CST
To: [log in to unmask]
Subject: FAB:  Dissipation Loss Specs

     
     I am having trouble understanding what EXACTLY "dissipation loss" is 
     WRT laminates.
     
     Can someone please enlighten me?  What are the units, etc.?
     
     Enquiring minds want to know.
     
     Regards,
     
     John R. Kretsch, P.E.
     Sr. Engineer, Design Assurance
     [log in to unmask]

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