If this helps, the chart I have shows the temperature range from -20 to +80 at 
2 GHz.  The increase in Dk is also about 0.15.

Glenn Pelkey
Maxtek Components Corp.

[log in to unmask] Wrote:
| 
| 
| Hi Walther,
| Dk goes up by about 0.15 from 20 C to 120 C where my graph ends - so for 
example 4.8 | becomes 4.95. This holds true between 1 MHz and 100 MHz - again 
I have no data beyond that.
| If you go up to 150 C you are above Tg.  I can only guess that there will be 
a change at Tg but how | much and in which direction? This is not going to be 
a useful property as FR-4 is not stable long | term at 150C.
| Regards
| Dave Heywood.
| [log in to unmask]
|  ----------
| From: [log in to unmask]
| To: [log in to unmask]; Dave Heywood
| Subject: Dielectric constant of FR4 - temperature
| Date: 15 July 1997 22:26
| 
| <<File Attachment: ENVELOPE.TXT>>
| I have a question regarding dielectric constant of FR4. 
| How does Dk change in case you increase the temperature from room 
temperature 
| to maybe 150 degree C.| I remember I have seen once a curve somewhere, which 

| showed  Dk increasing drastically when the temperature went up.
| Is this correct and what would be the explanation behind.
| 
| Walther

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