Impedance controlled PCB advice

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Hi All

 

I am developing a RF PCB and would like to know what is the difference between?:

 

  1. Asking the PCB manufacture for their standard PCB stack up along with their Substrate Dielectric and using the calculator to work out track thickness and spacing

OR

     2. Or giving them the PCB design and requesting a them to adjust their process to achieve the desired impedance 

 

Thank You

 

DJ

Thanks

Regards

DJ

Last Edited: Wed. Dec 27, 2017 - 12:15 PM
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Option 1 is the usual method. Option 2 has the problem that the pcb manufacturer doesn’t have infinite choices - he has constraints, so you end up back at option 1.

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djoshi wrote:
what is the difference between?

Well, any time you ask any supplier to do specific, custom work for you (ie, your option 2) - the difference is going to be a higher price!

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Thanks

 

Yes i have noticed price increase. 

 

I have designed my board based on there stack up.

 

If option 2 was to selected then what exactly do they do? Would i be correct in saying that they simply change the stack up so that my tracks achieve the desired impedance? And as a pcb would deviate from there standard process that is the reason for a price increase? 

 

 

Thanks

Regards

DJ

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As we on the topic of impedance, just would like to know on micro strip differential pair , the spacing between the two track are specified to 0.2mm but what should the spacing be between the tracks and GND pour on the same layer. Would it be 0.2mm like the spacing between tracks or 0.113mm like the spacing between the tracks and GND layer below it.

 

 

Thanks

Regards

DJ

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As slightly off question, but related to PCB design.

 

I have 0402 components, that are 0.5mm by 0.5mm in each each pad with 0.5mm spacing between them. And my impedance trace goes through such 0402 components.

 

 

If i was to choose to keep a trace thickness of say 0.2mm, then at point of the component the trace would be seen as 0.5mm due to component pad, what effect would that have on overall impedance. 

 

Or should i simply keep my trace 0.5mm in width and 0.5mm in spacing , and request PCB manufacture adjust stack up to get the 50 ohms impedance?

 

Options 1, is sticking to there stack up.

 

Option 2, is changing there stack up but getting a full trace with same width all the way through.

 

Thank YOu 

 

Thank You

Thanks

Regards

DJ

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Seems like it's the choice between putting your time and effort in it and desinging it yourself or putting your money in it to have it designed by somebody else.

 

A few years back I read a story about the design for a multi GHz radar PCB.

After a lot of design iterations they came to the conclusion that the only way to achieve the accuracy needed was to mill the edges of the pcb traces.

The sides of etched pcb traces were not straight & square enough and reflections caused too much signal distortion.

 

I usually buld my AVR prototypes on a breadboard with lacquered wire, throw in a few decoupling caps and be done with it :)

I've looked at some youtube vid's of spectrum analysers but those boards mostly look like voodoo to me.

Paul van der Hoeven.
Bunch of old projects with AVR's:
http://www.hoevendesign.com

Last Edited: Sat. Jan 13, 2018 - 09:57 PM
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Paulvdh wrote:
... but those boards mostly look like voodoo to me.
Converse - the art of the masters ... that's even more impressive because these can be manufactured.

 

"Dare to be naïve." - Buckminster Fuller

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Happen to have draw a normal stack for 4-layer board,

 

Stack of 4-layer board

 

One of our customer need this stack so that he can design the board, he have requirement of impedance, to be honest, we produce the project by customer's design.

For the project have demand in impedance, we'll EQ them after place the order. Eh, this is the process.

Juvtmall produce normal PCB, FPC and HDI

D