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[SOLVED] PCB Substrate: choice between FR4 or Rogers

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LandLack

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Hi to all,
I've never done a project with pcb, so I know only the basics and some theory. I need to make a circuit on a PCB with multitone signals, ranging from 130 MHz to 1.5 GHz. Between the various types, FR4 and Rogers RO4350B seem to be the most important; I have some questions:

1)Which should I choose? They say that FR4 is cheaper, but bad for f>1GHz, while Rogers is expensive but good with higer frequencies.

2)On the net (alibaba and others) I've seen prices like this: "FOB Price: US $0.5-6.5 / Piece"; what does it mean, is it 0.5$ or 6.5$?

3)How much does a Rogers RO4350B cost? If I purchase more than one, is there any discount?

4)What is the consequence of the Er change? Is it related to the equation: J=s*E ==> J=s*D/(Eo*Er) ?
(so the tones with higher frequencies have a higher J since Er is lowered, right? Isn't this good?)

5) On ADS the simulator asks me infos like: conductor thickness, conductor conductivity, cover height, Dielectric loss tangent, conductor surface roughness; I can't find these infos on the datasheets.

6)Do you know any good vendors?

If you know anything about any of these questions (even if you aren't sure), please reply; I don't want to do it alone with just my theories.
Thank you,

Best Regards,
LandLack
 

Ow@i$

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This may help.
well i recommend Roger since its high frequency
 

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  • Understanding When To Use FR-4 Or High Frequency Laminates.pdf
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marce

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FR4 is good into the low GHz, is easier to manufacture your boards etc.
How many layers are you looking at?
 

LandLack

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FR4 is good into the low GHz, is easier to manufacture your boards etc.
How many layers are you looking at?

I'll need problably only one layer. I would like to know mainly if 1.5 GHz may be still considered "low".
 

marce

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I presume two layers of copper.
Firstly how tight do you want your impedance tolerances, this really will determine what material to use, contact your PCB manufacturer and discuss this with him.
Secondly cost, how much do you want to pay.
I would if doing a commercial product with these frequencies, consult a PCB manufacturer for information on materials, achievable impedance figures etc. I would also determine the end use of such a product, for a high reliability/mission critical product I would probably use a more exotic material than FR4, for a basic product say a cheep Wi-Fi router I would use a good quality FR4.
 
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