Dielectric materials in PCB

[engr_joni_ee]

Hi,

I am wondering about dielectric materials that we use in PCBs stackup. I am looking for information regarding material characteristics, dielectric constant, insertion losses and cost comparison of standard FR4 compared to MEGTRON and ROGERS. In which document I can find this information. Please suggest.

 

[psach27]

Hi,

In this page you have a table of comparisons between different dielectrics.

https://www.microwaves101.com/uploads/microwave-laminates-composition-chart.pdf

Regards

 

[engr_joni_ee]

Thanks, I notice that lower the dielectric constant, Dk, higher the CTE-Z.

CTE-Z is coefficient of thermal expansion, right ? what does it means if CTE-Z is high, more expansion or less expansion in z-direction ?

Also I am looking for which material is FR4, what is the name, ID or part number of FR4 dielectric ?

I also don't find cost comparisons between the followings.

Rogers Corporation (Rogers_4350)
Panasonic (MEGTRON 6)
Isola Group (Standard FR4_LP)

 

[psach27]

Hi,

Thanks, I notice that lower the dielectric constant, Dk, higher the CTE-Z.

CTE-Z is coefficient of thermal expansion, right ? what does it means if CTE-Z is high, more expansion or less expansion in z-direction ?

the CTE is the Coefficient Thermal Expansion, when your PCB heats ups it changes a little its dimmensions. If your CTE-z is high, the PCB experiments more expansion in the z-axis. The parameter has the units ppm/ºC.

Also I am looking for which material is FR4, what is the name, ID or part number of FR4 dielectric ?

For FR4 you can find plenty of manufacturers, you can google them.

I also don't find cost comparisons between the followings.

Rogers Corporation (Rogers_4350)
Panasonic (MEGTRON 6)
Isola Group (Standard FR4_LP

If you don't find prices maybe you have to ask manufacturer for a quotation.

Regards

 

[engr_joni_ee]

Thanks for reply.
High CTE-Z means more expansion in z-direction due to heat. Then I guess the lower dielectric constant materials are not good to use in heat environment in PCBs.

 

[psach27]

Thanks for reply.
High CTE-Z means more expansion in z-direction due to heat. Then I guess the lower dielectric constant materials are not good to use in heat environment in PCBs.

I don't know how CTE-z is related with dielectric constant, but if you have a heat environment you have to get a good Thermal coefficient of the dielectric constant (Dk) and a good thermal conductivity.

 

[engr_joni_ee]

Oh, I get it now. The CTE-Z is Not linearly related to dielectric constant (Dk). But lower CTE-Z material will expand less in thermal/heat environment, right ? So, we should chose a dielectric material with lower CTE-Z in PCB stackup if running in heat environment.

 

[psach27]

Oh, I get it now. The CTE-Z is Not linearly related to dielectric constant (Dk). But lower CTE-Z material will expand less in thermal/heat environment, right ? So, we should chose a dielectric material with lower CTE-Z in PCB stackup if running in heat environment.

That is correct. Now you have to choice a good one.

 

[marce]

There are numerous variations of FR4, the term is a generic reference to Flame Retardant, 4 refers to woven glass reinforced . Look at ISOLA as well as manufacturers already mentioned. There are different glass weaves such as :

What is the Fiber Weave Effect in a PCB Substrate?

The fiber weave effect is known to cause skew, but it causes other signal integrity problems as well. Learn more about the fiber weave effect in this article.

www.nwengineeringllc.com

For any design you are best talking to at least 2 PCB manufacturers, give them any specific requirements such as impedances required, layer count, copper weights etc. and they will provide builds based on readily available laminates that will fulfill your requirements... Fancy laminates usually incur increased production costs, so only use what is needed for the design.