[SI-LIST] Re: Traces don't cause EMI - really?

In a message dated 10/23/2003 7:07:38 PM Pacific Standard Time, 
tom@xxxxxxxxxxxxx writes:
Were the resonances predicted radiate directly or did the resonances conduct
energy to other elements which radiated the energy?  How did you  determine
the contribution from the microstrip vs. the other radiators in a complete
PC?
The resonances were based on my analysis of the chip package size, material 
(Alumina, Er=9.5 to 10.5)), and associated propagation rate. There was energy 
passage to the PCB traces and planes via the power and ground pins of the 
package, plus direct radiation from the package. Adding a needed heatsink to 
the 
top of the package and grounding it at the four corners reduced the emissions 
by 
6 dB, but did not eliminate all of the EMI. The package resonant peaks were 
still detectable in the radiated emissions data at 10 meters. (I had 
recommended a similar improvement to Motorola/Phoenix for their Power PC models 
a few 
months earlier....very successful also).
The internal package corrective actions I recommended to AMD (that resolved 
many problems) are proprietary and will not be disclosed further. Note that 
this activity was immediately prior to the first release of the highly 
successful 
AMD K6 microprocessor. 

Mike


Michael L. Conn
Owner/Principal Consultant
Mikon Consulting
Cell: (408)821-9843

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