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

[Jim G Roberts <jgroberts@xxxxxxxxxx>]

Jim,
        I would like to concur with you that the fields are not weak and not
negligible. Our model for evaluating the impedance accounts for the soldermask
types we use on our products.
The order of magnitude is not great but we consider significant.
--
Regards,    __________   James G Roberts
           /___  ____ |  jrobert@xxxxxxxxxxxxxxxxxxxxx
 Jim      __  / /___/ /  jgroberts@xxxxxxxxxx
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Jim DeLap wrote:

> Ray,
>
> I disagree with your assumption below that the fields above the line are =
> "so
> weak." The fields above the line are dependent upon the dielectric =
> material
> above and below the line. The fields will concentrate in regions of high
> dielectric constant. Therefore, for lower permittivities such as those =
> in
> FR4, you may have a significant portion of the fields propagating in the =
> air
> or soldermask.  Now for high permittivity materials such as ceramics and =
> Si
> or GaAs, your statement is fairly valid since the er is so high, most of =
> the
> fields are constrained to the dielectric rather than the air above.
>
> -Jim DeLap
> Ansoft Corporation
>
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] =
> On
> Behalf Of ray_waugh@xxxxxxxxxxx
> Sent: Thursday, March 06, 2003 7:03 PM
> To: si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Re: Loss Tangent of Solder Mask
>
> Michael...
>
> Unless you are forming a transmission line using a conductor over a =
> ground
> plane with solder mask as the dielectric, it does not much matter.  If =
> you
> are concerned about solder mask over the top of a microstrip line (for
> example), the e-fields above the line is so weak that you'll never be =
> able
> to tell (by measurement) if there is solder mask there or not.  We =
> commonly
> use solder mask on our 2 GHz CDMA test boards (on top of microstrip or
> coplanar waveguide lines) and it has no effect whatsoever.
>
> Ray
>
> Raymond W. Waugh
> Agilent Technologies
>
> -----Original Message-----
> From: Chan, Michael (Eng Hou) [mailto:Michael.Chan@xxxxxx]
> Sent: Thursday, March 06, 2003 9:23 AM
> To: si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Loss Tangent of Solder Mask
>
> Hi:
>     Anybody has any idea what is the loss tangent of solder mask? =
> Thanks.
> =20
> =20
> Regards,
> Michael Chan
> H-P Corp.
>
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