I have been getting conflicting information in regards to a impedance question I have.

The question is simple.

Can the assembly process GREATLY effect the impedance?

I have been told that at worst case the assembly process could cause a .5 to 1 ohm difference.

I was also told that it could greatly effect the impedance 5 ohms or more.

I agree that the assembly can effect the impedance, what I don't know is by how much, what is common / average, what is extreme or uncommon.

Any help is appreciated.

 

Assembly of what?
Why is 5 ohms a lot of difference?

That said, I can make half a dozen nice, clean, mechanical connections without getting an ohm in the circuit.

You have, "sloppy"? Check the assembler, not the assembly.

 

A PCB was designed and fabricated as 100 ohm imp. +/- 4 % The coupons passed perfect, actually around 2%. The PCB was delivered and assembled. When the impedance test was ran on PCB it came out around 6-8%.

That's when I was told that assembly could effect the impedance and is likely what happened here. This is hard for me to accept as true. Like I said I understand the assembly process can effect the impedance I just don't feel it should have that big of an effect. However I don't know, that's why I am asking.

This is an RF PCB built on Rogers 3003 material.

 

What frequency does the circuit in question operate at? Think that might be important?

 

Apart from the operating frequency, could it also be that the connector or design is flawed? Did you manufacture this board before?