Rick

I have never seen the variations in Dk you are describing. Something is
obviously going on. Does the supplier concur that this is the case? If so
what is their explanation.

 On the positive side, most electrical parameters vary with the square root
of Dk so a variation of 1.3 has the effect of 1.14 impact on most
performance parameters. Thank nature for small favors.

Best regards

Lee

J. Lee Parker, Ph.D.
JLP Consultants LLC
804 779 3389


----- Original Message -----
From: "Smith, Richard" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Friday, September 15, 2006 11:46 AM
Subject: [TN] Laminate Material DK


I've seen differences of as much as 30% between a laminate manufacturer's
specified DK value and the board fabricators "effective DK" value for the
same material (FR4). Often the disparity is well outside of the range
specified by the material manufacturer. I understand that DK values can
change due to resin/content and frequency however, a 30% difference just
seems awful big.

Here's the part where I seek help from the experts. Thanks!

Is 30% difference in manufacturer DK versus Effective DK really possible?

Assuming the same material, will the DK difference be the same from
fabricator to fabricator?

Thanks Much!

Rick

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