FR4 dielectric constant

• Jul 2, 2003

• #21

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rfdipper

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permittivity fr4

hi mr_ghz,

i also used FR-4 like board from GILAM, and its good esp at freq above 3GHz. i think this is also more cost effective than Duroid.
you can check it out at:

http://www.gilam.com

 

• Jul 2, 2003

• #22

htforever

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capacitance fr4

Is FR4 good enough to be used to design LNA at 2GHz??

 

• Jul 2, 2003

• #23

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mImoto

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fr 4 dielectric constant

I have use FR4 with power modules, antenna modules at 900Mhz and 2Ghz.I used 4.2 for that frecuencies.

Best regards,

mimoto

 

• Jul 2, 2003

• #24

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eladg

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fr4 epsilon r:4.0

htforever said:

Is FR4 good enough to be used to design LNA at 2GHz??

Click to expand...

i work with it up to 3.5 ghz, and got good results

 

• Jul 2, 2003

• #25

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mr_ghz

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reported post sep problems with isola fr406

Hi htforever,

If you can live with a little decrease in gain (<1dB) and you measure out your specific FR-4 material before you design your LNA you can use it.

Bye

 

• Jul 4, 2003

• #26

rainer

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fr4 epsilon

In my simulation I use a value of 4.4 for FR4 in this band.
But you are right, you can find different values because it depends on the manufacture, from this point of view the FR4 is not a very good material for the high frequency.

 

• Jul 5, 2003

• #27

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vanderspunk

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dielectric constant for fr4

Government regulations (for example in the EU) will soon ban materials that are hazardous to people or environment, for example halogens like brominated resins used in FR4. Looks like one have to avoid FR4 in new low-cost RF designs.

Searching Google for halogen-free FR4 gives me a lot of hits, but was is your impression of these new FR4 materials? How do these new materials compare to old FR4 at high frequencies?

 

• Jul 5, 2003

• #28

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mr_ghz

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epsilon of fr4

Hi vanderspunk,

We use halogen-free material for longer time, also for HF designs. They are comperable to 'standard' (older) FR-4 but they aren't better. You will already have the problem of big differences between different manufacturer.

Bye

 

• Jul 8, 2003

• #29

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tiger4z

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dielectric value of fr4

i usually use 4.5

 

• Jul 14, 2003

• #30

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Camak

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fr4 dielectric constant manufacturers

Another example of parameters scattering:

A part of ISOLA documentation
( www.isolaAG.com )

 

• Jul 17, 2003

• #31

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hca41316

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pcb fr4 capacitance

Take care! Er of FR4 is a function of temperature !

 

• Jul 18, 2003

• #32

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VSWR

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cheapest fr4 material

FR4 epsilon-r varies a lot from batch to batch, even from the same manufacturer. The eplilon-r can be ANY VALUE in the range 4.0-4.6 at 2-3 GHz frequency range from my experiance. Be very careful and do a worst case analysis of your design, taking into account the epsilon-r variation. E.g. narrowband sidecoupled microstrip filters implemented on FR4 will show large variations in center frequency and resonator coupling.

 

• Jul 19, 2003

• #33

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harkonnen

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fr4 dielectric value

Hello,

I agree with GaAs FET. The dielectric constant can be anywhere especially between various FR4 manufacturers.

An beware, most manufacturers quote the eps_r at low frequencies in the MHz or even Khz range and extrapolate. But the function of eps_r over a broad frequency range is not linear.

If you use FR4 or GETEK at high frequencies, always measure the eps_r yourself. You can either make a resonator or use two microstrip lines of diffrerent length and compare the phases of both lines. In both cases you will need to calculate or use a simulator to extract the eps_r from eps_r_eff.

 

• Jul 22, 2003

• #34

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cross coupling

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planar capacitor dielectric fr4

In fact ,the dielectric constant of FR4 is not a fixed value.
It can vary from 3.9-4.8. depend on different suppiler or manufacturer.

The dielectric constant of many FR4 material varies .Cause in common case it just used as printetd wires connetting different components,not considering the effect when the frequency up to radio an microwave.such as loss or transimisson line,etc

The dielectric constant of FR4 laminate from some suppiler is strict and fixed,low loss tangent angle, which can be used up to 2GHz.
The supplier can give you such data or you can measure it in simple ways.

 

• Jul 25, 2003

• #35

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sagivas

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dielectric constant of fr4 10 ghz

i am using 4.5, and get a good preformance.

 

• Jul 25, 2003

• #36

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sagivas

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dielectric constant fr-4

Im using FR4 @ 1.2 GHz and Its very good.

 

• Jul 27, 2003

• #37

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Velund

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fr4 dielectric constant versus frequency

Some non-standard question... Does someone heard about using different laminates in production of a multi-layer PCB? For example outer layers is FR4 and two inner layers, where microstrips reside, is another dielectric (better at high frequencies and more thermally stable)...

Is this practical? Can it be done?

I have a project where a lot of low-frequency stuff should co-exist with some ~1.5ghz amps/mixers/oscillators. I never used multi-layer PCB before, but now I see that I need at least 4 layers just to fit all low frequency stuff in necessary size (currently all SHF connections is tiny rigid coax soldered to a outer ground layer - good enough for prototypes/small test lots, but may become a real pain in a production). Is there any reason to add 2 more layers and use microstrips instead of coax lines?

 

• Jul 27, 2003

• #38

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Velund

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fr4 constant

One more question - can someone recommend good prototype PCB manufacturer that can produce milti-layer PCBs in a reasonable time and for a reasonable price? Preferably in US or Germany...

Our first order from local company turned to 6 weeks of delay, and it was best available offer... Regular double-sided PCB in prototype quantities can be made here within 24 hours (sometimes even faster if order is placed in a beginning of business day), but multi-layer boards is completely different story.

 

• Jul 29, 2003

• #39

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mr_ghz

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fr4 dielectric constant vs. frequency

Hi Velund

It's possible to mix different materials inside one print. A 4-layer PCB is made of 3 boards (top copper to inner layer 1, bottom copper to inner layer 2 and inner layer 1 to inner layer 2). It's often done that the outer dielectrics are made of a better material (e.g. teflon) than the inner dielectric. You have to pay attention to thermal expansion.
I know some PCB manufacturers in Switzerland who are able to do such boards in short times. Is this too far?

Bye

 

• Jul 29, 2003

• #40

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Velund

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fr4 for 3.5ghz

Hello mr_ghz! Thank you for reply.

I need to check how easy I can place orders in Switzerland, but anyway I'd like to have this PCB manufacturers in my bookmarks.

Concerning thermal expansion - it was first thing that concerned me.. I checked around for information and found that most glass-reinforced dielectrics have pretty similar expansion coefficient in X/Y axis (probably due to glass fibers used). Z axis coefficient varies much larger...