RE: [SI-LIST] : RE: 2.5 GHz in FR4

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From: Larry Miller (ldmiller@rhapsodynetworks.com)
Date: Tue Apr 24 2001 - 12:50:49 PDT


>> How do you connect a surface mount part to stripline without using vias?

Well, I don't think you can unless you are using psychic connections.
 
Seriously, I guess I should have been more specific. The HS-3 connectors are
through-hole and the impedance characteristics include this fact. AMP has
very definite rules for routing through a pin forest, escaping out from the
connector, etc.
 
So I guess when I say "no vias" in this context I mean no additional vias
except for the pin connection at each end. I have done TDR measurements for
this and there are small impedance bumps at the pins, but they are very
small in amplitude and short in length, corresponding in both respects to
very high frequencies above those for which the connectors (and the system)
are rated.
 
As a matter of fact, for the plug-in boards we had the surface mount
situation: both the fiber optic transceiver and the SERDES chip were surface
mount, so we did not dive into inner stripline layers, We stayed on the top
layer and used microstrip for this very short (1") trace length. Again, "no
vias", but in this case REALLY no vias.
 
So you are not confused.
 
Regards,
 
Larry Miller

-----Original Message-----
From: RMELLISON@aol.com [mailto:RMELLISON@aol.com]
Sent: Saturday, April 21, 2001 2:46 AM
To: ldmiller@rhapsodynetworks.com; j-gaboian@ti.com;
zabinski.patrick@mayo.edu; si-list@silab.eng.sun.com
Subject: Re: [SI-LIST] : RE: 2.5 GHz in FR4

Larry, Im confused.
How do you connect a surface mount part to stripline without using vias?
Richard Ellison
ph. 972-569-8317

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