FR4 dielectric constant

[mr_ghz]

fr4 pcb dielectric constant 5ghz range

Hi Velund

Z axis coefficient is less interesting. X/Y coefficients are similar if you use comparable dielectrics (e.g. glass-reinforced). But if you have to use completly different materials (e.g. ceramics) The troubles can start...

Bye

 

[alongsh]

fr4 dielectric constant at 3ghz

I am using FR4(4.6 orso) @ 2 GHz and Its very good.

 

[martinthorn]

dielectric constant of fr4 materials

FR4, a few quick comments :

- cheap, works OK to at least 4GHz if keep 'lines short (eg. millions
of mobile phones use 6 or 8 layer FR4 PWB to >4GHz).. most tracks
less than 3cm long though.

- Er varies from manufacturer to manufacturer as already stated

- New Halogen free FR4 that I use has a higher Er than before, gives thinner strips : watch for tolerance on strip widths

- Vias on cheap FR4 multilayer boards go through all or most layers
which can cause unwanted signals to appear on many layers. Use
grounded vias liberally to protect signal tracks/vias.

- Multilayer boards can for example have 4/6 or 8 FR4 layers then
an extra RCC layer either side which adds tracking flexibility as
vias between top 2 layers are then possible.

Martin

 

[TDC]

fr4 over temperature er

Dielectric Constant is important, but so is the Loss Tangent.

In fact, loss Tangent for FR-4 can vary between resin types and
board manufactruers, as well as water content (which depends on
thickness of the pre-preg and how long it has been sitting on the
shelf). I normally use 0.02 and I have verified this on 70mm strip-lines.
Remember, loss tangent will effect striplines more than micro-strip.

My 2 cents anyway.

TDC.

 

[sugm]

dielectric permittivity of fr408

We use 4.2 for DRO design , it works on 10GHz.

 

[venus]

epsilon r fr4

hi,
fr4 is lossy at 1ghz & above, my recommandation is to use it only for upto 5 watts or less, use ptfe instead. dielectric constant is 2.22 . it is costlier also.it is your choice for price performance.

 

[g579]

can use fr4 for high frequency

I confirm TDC, loss tangent is about 0.02 in the 2 GHz range
g579

 

[g86]

fr-4 parameters

I did some experiments on planar resonators to calculate the dielectric constant of two types of FR4. One of them was yollowish and another one a bit greenish. I found yollowish was 4.3 and greenish one 4.4. I know the vallue varies from 3.9 to 4.9 but have not seen all variations. Better tou make a simple two port square resonator and calculate the approximate dielectric constant. This is an approximate method and due to radiation and probe inductance the value may change little bit. Once you have the calculated value, you can design your antenna with a shift in center frequency within 2%.

Otherwise do one thing. Design your antenna with Er = (3.9+4.9)/2 and then do experiment. Get the scalling factor and use that scalling factor for the next designs.

Take dielectric loss tangent = 0.02. Very lossy substate. So, it may give broad bandwidth but not suitable for high frequencies.

:!: :idea: :?:

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.

 

[harkonnen]

er of isola fr4 at 1ghz

g86,

keep in mind that the dielectric constant of FR4 ist frequency dependent. So whenever you give dielectric numbers you should give the frequency as well.

Getting the dielectric constant from a resonator is good method for getting good epsilon values. You can also just manufacture 2 different length lines from the same material and compute the phase difference (connectors should be soldered identical).

However, in both cases you will get the EFFECTIVE epsilon_r which includes fringing of the fields. Fringing depends on geometry/frequency, board thickness etc.

You can either use a empirical formula to calculate epsilon from epsilon_effective or you can use an EM-Simulator to match the eps-value.

 

[ghostdaemon]

laminat fr4 epsilon

An Aplication of Agilent's PIN Diode about Limiter ,it says the Er will decrease with the Freq increase ,at Freq about 3 GHz ,it will be 4.2(maybe, I forgot it).

 

[Chen]

difference between rogers to fr4

I am using FR4(4.3 orso) @ 950~2050 MHz and Its very good.
8)

 

[mrm]

fr-4 constant

Try to cut a Metallographic sample and look at the inner layer of an industrial PCB: the main problem is that not only er is not uniform from PCB to PCB, but even in the same PCB the heigh and the er of the layers varies for different poins. The rule I suggest is to buil your circuit taking 4,7-4,3 for er and to post simulate the effects of this variation. If U have to build a small number of circuits try to overlenght every stub and tune them by cutting their edge.

 

[cupcake]

difference between rogers and fr4 material

I am a graduate student working on a thesis project involving characterizing printed circuit boards. I would like to model stripline waveguides using an FR4 material as the dielectric.

What are the characteristics of FR4 materials that are available from manufacturers? Specifically, where can I find plots, tables, or charts that demonstrate the performance of FR4 as a function of frequency? I am particularly interested in permittivity as a function of frequency out to about 30 GHz.

Thank you very much for your help.

 

[pisoiu]

fr4 loss high frequency

What are the characteristics of FR4 materials that are available from manufacturers? Specifically, where can I find plots, tables, or charts that demonstrate the performance of FR4 as a function of frequency? I am particularly interested in permittivity as a function of frequency out to about 30 GHz.

Thank you very much for your help.

You can find some informations about substrates at www.isola.de , for example. But the manufacturers offers measured Er at 1 or 10 MHz. Obviously, at GHz range, it is another story. I have not seen manufacturers which offers what you request, mainly because FR4 is not a dedicated substrate for GHz range, so nobody bothers to measure the parameters at that freq. The losses are simply too high to be acceptable in a RF design (with very few exceptions - very short traces and only up to 1-2GHz, etc.).

/pisoiu

 

[student883]

fr4 dielectric constant 3 ghz

Hi all,

i am a student who doing a project on measuring the dielectric constant of FR4. I want to know how to measure it. Is it needed to follow some standard e.g. ISO or IPC ? and i only can get a LCR meter to measure it. Could someone suggest me a method to do the measurement, or some other information?

thank you very much for your help

 

[pokemon]

range of dielectric consts for fr-4

I think that for this frequency dielectric constant is 4.4

 

[flyhigh]

fr4 dielectric constant for low noise amplifier

Hi,

just to add my opinion. Considering that electrical length is proportional to square root of dielectric constant, it is not realy that important if it is 4.4 or 4.6, the error in electrical length is around 2%, while most of the close form expressions for calculating microstrip effective dielectric constant have error of 0.5-1% depending of particular values, so you can be sure that your design of a coupler, matching network etc is not suffering very much for inaccurate Er. If you add errors for modeing of bends, tees and other discontinuities you things are even worse. For resonators in filters or oscillators situation is a bit more complex, but even there the error in Er might not be predominant. One source of error can also be thicknes of FR4 layer that is also not controlable completely and is varying from batch to batch.

flyhigh

 

[student883]

fr4 substrate dielectric constant

hi,

i want to know can i measure the capacitance of FR4 @ 1MHz, then use the formula:

C=Dr*ε*A/d

to calculate the Dr @ 1 MHz ?

thanks
[/list]

 

[mr_ghz]

fr4 substrate dielectric constant 4.6

Hi student883

If you are interested in the er value at 1MHz you can create a plate capacitor on a double sided FR4 board, measure the capacitance and calculate the er.

In this discussion people were interested in the er at frequencies wide above 1MHz (say 10GHz). The measurement of the er at these frequencies is more complicated and mostly done with a resonant structure.

Hope this helps

 

[plasma]

fr4 dielectric loss

Hi All

I have some work made on FR4.


PL



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