FreeLists / si-list / [SI-LIST] Re: Loss Tangent of Solder Mask

["Michael Khusid" <mkhusid@xxxxxxxxxx>]

Scott, Gustavo,

Based on the description of the experiment, I thought that dispersion
may something to do with the perceived loss of signal magnitude in the
microstrip structure. In brief, the dispersion is caused by the
difference of dielectric constants, and thus, different propagation
speeds of the high frequency signal content in different layers. The
difference of propagation speeds causes deformation of the edge as
measured in time domain.

While stripline dielectric layers make relatively homogeneous structure,
microstrip is surrounded by at least three very different dielectric
layers - FR4 on the bottom, aforementioned soldermask, and air above
that.

Mike

-----------------------------------------------------------------
Michael Khusid
Ansoft Corporation
SI/HF Application Engineer
 
25 Burlington Mall Road, 6th floor
Burlington, MA 01803-4100
 
Tel 781-229-8900 Ext. 34
Fax 781-229-8624
--------------------- http://www.ansoft.com ---------------------
 

-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of gustavo.duenas@xxxxxxxxxxx
Sent: Friday, March 07, 2003 1:02 PM
To: scott@xxxxxxxxxxxxx
Cc: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: Loss Tangent of Solder Mask



Scott,

I saw an app note from Accelerant Networks (16_0008_A.pdf) that states
the
loss tangent of solder mask is rather lower than fr4 (0.001), yet you
said
you determined it must be higher than 0.02? Are there different types of
maks? Anybody would like to clarify? I'd appreciate it.

Thanks,

Gus

*******************************************************************
Michael,

At the time we believed that the loss tangent of soldermask was about
0.02.  Based upon high frequency eye losses that we were seeing, we
determined that the loss tangent must be higher.  We didn't make any
additional measurements to determine the loss tangent precisely, nor did
we go back and make corrections to our model and resolve for the higher
loss tangent.

scott

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