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FR4 dielectric constant

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Olxx

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fr4 dielectric constant

Hi everybody,

Could someone tell me what value of dielectric constant should I use for FR4 substrate in the 1-2GHz frequency range?
I’ve tried to find out this searching via google and I was surprised by a results!!! Everyone indicate different value for 1 GHz starting from 3.9 and up to 4.9. I have no idea why the difference is so huge!!!
Is it possible to make a precise modeling of FR4 at 1GHz at all? If yes, then which value for dielectric constant should I use?
Thanks in advance.
 

cybq

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fr4 epsilon

Generally we take the value of 4.5 or 4.6, not considering the frequency diffusion.
 

flatulent

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dielectric constant fr4

This is because this is not a standard parameter and everyone makes different ratios of resin to fiber glass. GETEK is similar, but this is a standard parameter they keep in a narrow range.
 

rfdipper

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fr4 permittivity

hi Olxx,

i think you can make the measurement yourself if if not inconvenient to measure. at least it will give you a more accurate value.

regards,
rfdipper
 

sugm

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fr4 dielectric

4.2 at 10GHz
 

mr_ghz

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fr4 capacitance

Hi Olxx,

as written above the problem is that every manufacturer uses another 'recepture' to create his FR-4 material. If you want accurate results, you have to choose one manufacturer and measure out his FR-4. Perhaps you can also get er values of this manufacturer. But again: These values cannot be used for FR-4 from others!

Bye
 

drwho78

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fr4 dielectric constant vs frequency

FR4 is not a good material to use at 1 GHz. Use high frequency materials that has a more stable dielectric constant with less loss.
 

jupitorcuu

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dielectric constant of fr4

I think dieletric constant for FR4 is 4.5 in inner layer's 2GHz .It maybe decrease to 4.2 when frequency up to 10GHz. If you want to design a microtrip the effcient dieletric constant is 2/3 of it due to the surface air is 1.
Another important thing is tangent constant of material,for FR4 is maybe 0.015 it is too big for microwave design.That means very short length may cause big insertloss.That is why seldom microwave designer will choice normal FR 4 as their PCB material
 

IICCEE

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fr408 dielectric constant

common 4.3 for example in the genesy examples.
 

molloy

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epsilon fr4

4.5 is usually used in those frequencies, but probably if you want to know more precisely the value, FR4 is not the material you want to use. In those frequency you could use better materials not so much expensive and that you could use without any kind of carrier (the material is glass reinforced hydrocarbon/ceramic)

regards
 

toonafishy

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permittivity of fr4

It is totally dependent on your PCB vendor. I've seen it range from 3.8 to 4.5 depending on who I use for a vendor. I usually do my design at 4.2 and when the final vendor is chosen, do a final tweak on my design before sending it out. I always use FR4 @ 2 GHz and have used it successfully at 5 GHz. When designing consumer products, you just don't have the option of using nice material such as Rogers.
 

egemini

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dielectric constant of fr4 material

Hello
exact value of Dielectric constant can be obtained from the manufacturer at the specified operating frequency.
You may use Rogers RTDuroid at high frequencies , since it is less lossy
 

g579

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fr406 dielectric constant

My opinion is a good mix of toonafishy and jupitorcuu. Additionally, it is difficult to avoid using FR4 in commercial design.
g579
 

aaiiwwaa

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fr4 dielectric properties

3.6 @ 30MHz
4.1 @ 1GHz
 

sammy

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fr4 pcb dielectric constant

At this frequency I suggest you PTFE or Duroid materials.
 

eladg

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fr4 dielectric constant frequency

drwho78 said:
FR4 is not a good material to use at 1 GHz. Use high frequency materials that has a more stable dielectric constant with less loss.

fr4 is goog for 1 ghz.
i work with it at 3.1-3.5 ghZ and got good results
 

guoqiang

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fr-4 dielectric

I'm fused above the delectic of FR4
and after i 'v seen all the abave .
i'm fused still,
 

flatulent

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fr-4 epsilon

guoqiang

Here is a summary for you. [ Your comment reminds me of the Indian restaurant owner in At Bertram's Hotel by Dorothy L. Saysers. He was talkng with Canon Pennyfather. (No relation with Miss Moneypenny.) ]


1. The constant is a function of frequency and vendor.

2. Hay is cheaper after passing through the horse. FR4 is used for consumer products where cost is everything.

3. Getek is slightly better and slightly more expensive.

4. Duroid is much better and much more expensive.
 

sigint

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fr4 epsilon r

I genarally use 4.3 for calculations for a suggested stack-up, but on my drawings this is listed as reference only and then I include a note telling the board shop that they may make adjustments to meet the impedance requirement. The problem here is also that since the Er (DK) is frequency dependant and the TDR test equipment is fixed, (usually at a very fast rise time at a very high frequency), it kind of complicates things

SiGiNT
 

mr_ghz

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epsilon r fr4

Hi guoqiang

I've used FR-4 for several consumer (=very price sensitive) applications up to 10GHz. If you buy the material every time from the same vendor it's working well. But for these frequencies the high loss could also be a problem.
Using 'high performance' material like rogers' Duroid is a question of price. If it's possible: take it! If no, there are also other (cheaper) materials that are similar to FR-4, but are well defined. One example is LD-621 from Polyclad.

Bye
 
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