Bill,

I have attached an Excel file that contains a graph of Dielectric constant
vs temperature for FR4 and several Rogers high frequency/high speed
laminates(dielectric constant stability is critical to our business). For
the temperature range that you mention below, our measured data indicates a
change of about 2% upward at 70C. If your design is operating at high speeds
(1 Gbps or greater), you might also be interested in Dielectric constant
stability vs frequency, since you will be dealing with harmonics as high as
5 GHz. If you would like to discuss this offline please give me a call.

regards
Art Aguayo, Product Manager
Rogers Corporation, Microwave Materials Division
[log in to unmask]
480.961.8271



> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]]On Behalf Of Bill Beale
> Sent: Wednesday, June 21, 2000 10:14 AM
> To: [log in to unmask]
> Subject: [TN] Change in Dielectric over Temp
>
>
> Hi,
>
> I'm new to this list and not sure this is an appropriate question, but
> I'll try anyway.
>
> Does anyone know where I can get data on the change of propagation
> velocity, which really means relative dielectric, over temperature for
> FR4?  Specifically, I'm interested in standard FR4 material from ambient
> to 70 deg C.  This is very important to our timing.
>
> I already have one data point and another source.  Dr. Howard Johnson's
> book says that the relative dielectric can change as much as 10%.  Arlon
> sent me some data which showed that it only changed ~2% in my range of
> interest.
>
> If relative dielectric increases with temperature, then why?  What
> physical phenomena causes the material to increase charge storage with
> temperature?  Is that change really 10%, or much smaller?
>
> Thank you in advance for all your help,
> Bill
>
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