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Measurement of different PCB trace width with R&S ZLNE-3 VNA / JLCPCB

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thinkfat:

--- Quote from: nctnico on January 07, 2022, 02:57:54 pm ---Again: Use Sonnet to check your trace geometries!

--- End quote ---

Without access to Sonnet, I tried my hands on openEMS. I use KiCADs "HyperLynx" export feature to get a PCB into openEMS, but it's tough going. openEMS is used through Matlab modules and getting a simulation going involves writing a matlab program, manually adding (in code) excitation, ports, components and a mesh. Although the mesh can be automatically generated, it is frequently not optimal and leads to long simulation times and garbage output.

I hope Sonnet doesn't have an as steep learning curve, but I can imagine you'd have some work ahead to getting it going. But I'm not getting what is the gain here. The goal for this thread is to understand the manufacturing process of JLCPCB and for this purpose it should be enough to poke some numbers into a pcb calculator, get the boards made and then measure them.

nctnico:

--- Quote from: thinkfat on January 10, 2022, 08:34:26 am ---
--- Quote from: nctnico on January 07, 2022, 02:57:54 pm ---Again: Use Sonnet to check your trace geometries!

--- End quote ---

Without access to Sonnet, I tried my hands on openEMS. I use KiCADs "HyperLynx" export feature to get a PCB into openEMS, but it's tough going. openEMS is used through Matlab modules and getting a simulation going involves writing a matlab program, manually adding (in code) excitation, ports, components and a mesh. Although the mesh can be automatically generated, it is frequently not optimal and leads to long simulation times and garbage output.

I hope Sonnet doesn't have an as steep learning curve, but I can imagine you'd have some work ahead to getting it going.


--- End quote ---
There is a free version for Sonnet called Sonnet Lite. You have to ask for a license but this is not a difficult process.  However, I would not recommend to use Sonnet for simulation entire PCBs; it is too slow and needs too much memory for that. AFAIK Sonnet is aimed at simulating small chunks. Think about resonators, trace discontinuities, microstrip filters, etc. What goes for 2cm of microstrip also goes for 20cm of microstrip.


--- Quote ---But I'm not getting what is the gain here. The goal for this thread is to understand the manufacturing process of JLCPCB and for this purpose it should be enough to poke some numbers into a pcb calculator, get the boards made and then measure them.

--- End quote ---
As the OP already noted: every calculator gives a different answer, the calculator doesn't take the actual PCB geometries into account and there can be large errors in case the geometries are far from what is ideal for the calculator. In the end the calculators are using formulas derived from empirical data.

OTOH Sonnet will give the right answer based on the actual geometry you provide. In Sonnet you define a PCB stackup, the surroundings and PCB layers. From there you can run a simulation. The free version has limits where it comes to memory use (which in turn limits size versus granularity).

ogden:
Video about trace impedances: https://youtu.be/U60y4JC0Wxs?t=1

evb149:
There are also these wrt. TL calculation by CEM:
http://atlc.sourceforge.net/
http://mmtl.sourceforge.net/

I've used them from time to time.


cgroen:
Thanks for all the input and discussions so far, was very helpful and informative!

I have just ordered the board below, I'll get back once it arrives and I have it assembled. I selected to get it with HASL surface instead of ENIG as JLCPCB does not do ENIG boards before feb 8 again (CNY)
(I have ordered 5 pcs, if any of you wants one of the 4 "leftovers" you can have it for free, except for the shipping from me to you ;) Only caveat is that you publish whatever you find out here in this thread  ^-^)

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