POLAR SI9000e and  Sarturn PCB - Page 1
Forum section: electronics / projects

author: Carrington
author_rank: Super Contributor
timestamp: October 28, 2013, 04:04:49 pm
content: Hello!I tried a demo of the last version of POLAR SI9000e, it have a utility to estimate the impedance of a via (via pad/anti-pad coaxial calculation). When I compare the result with the same utility in the sarturn PCB software I get a very different value, to the same via characteristics.At least similar results should be obtained, true? Why does it happen?SI9000e:--------------------------------------------------------------------VP=0,2540mm (via pad diameter)AP=1,0160mm (anti-pad diameter)Er1=4,6000 (substrate dielectric)Zo:38.74 Ohm--------------------------------------------------------------------------------Polar Application Note AP8178:http://www.polarinstruments.com/support/si/AP8178.htmlSaturn PCB:-----------------------------------------------------------------Via Hole Diameter=0,254mmInternal Pad Diameter=0,255mmRef. Plane Opening Diam.=1,016mmRemaining parameters by default.Zo:99.21 Ohm--------------------------------------------------------------------------------Kind regards.

author: Carrington
author_rank: Super Contributor
timestamp: November 04, 2013, 05:24:28 pm
content: Long time ago I contacted with Polar and Saturn, about this issue but I never received a response.Surely both are correct, and the result does not match because they are estimating different parameters. But I don't get.

author: thm_w
author_rank: Super Contributor
timestamp: November 05, 2013, 11:35:26 pm
content: Via length is 0mm in the first one and 1.575mm in the second screenshot, right?

author: penfold
author_rank: Frequent Contributor
timestamp: November 06, 2013, 12:03:15 am
content: The relative dielectric constant is also different between the two

author: jahonen
author_rank: Super Contributor
timestamp: November 06, 2013, 07:47:34 pm
content: Biggest fundamental difference between them is that Saturn PCB software is not a field solver, and uses an approximated formula for impedances so results are more or less approximate. Whereas Polar Instruments uses a field solver to calculate things by numerical solving of Maxwell's equations so it should produce more accurate results.Regards,Janne

author: Carrington
author_rank: Super Contributor
timestamp: November 06, 2013, 08:01:19 pm
content: Quote from: thm_w on November 05, 2013, 11:35:26 pmPOLAR SI9000e for the via pad/anti-pad coaxial calculation not seem to take into consideration the length of the VIA

author: Carrington
author_rank: Super Contributor
timestamp: November 06, 2013, 08:01:56 pm
content: Quote from: penfold on November 06, 2013, 12:03:15 amEr is 4.6 in both (Polar and Saturn). Via check and via pad/anti-pad coaxial calculation appear to be unrelated. Via check/via Stub check provides a simple color coded go/no go check on the potential for signal distortion of a via or stub.

author: Carrington
author_rank: Super Contributor
timestamp: November 06, 2013, 08:04:46 pm
content: Quote from: jahonen on November 06, 2013, 07:47:34 pmAlthough that, there's something wrong, there is a big difference in the estimated values.

author: Carrington
author_rank: Super Contributor
timestamp: November 06, 2013, 08:21:52 pm
content: Quote from: thm_w on November 05, 2013, 11:35:26 pmPOLAR SI9000e for the via pad/anti-pad coaxial calculation not seem to take into consideration the length of the VIA.But you're right, I think they are two different views of the same problem.

author: Carrington
author_rank: Super Contributor
timestamp: November 06, 2013, 08:23:28 pm
content: All this is starting to fit. They are two different views of the same problem (well, not exactly the same).- The first (Polar) only estimate the impedance of the via pad/anti-pad (coaxial) and separately estimate if the length of the via is OK for for a given (rise time, frequency or Bit rate).- The second (Saturn) seems to estimate the impedance of the total via. With all the changes over the structure of the same via (as a connector pin)? Or maybe it considered that the structure does not change and therefore only estimate that parameter for a multi layer board.It must be something like that (but I have the feeling that still does not fit completely).If someone has another point of view, go ahead, I'm all ears.This can help:http://www.polarinstruments.com/support/si/AP8178.htmlhttp://www.polarinstruments.com/support/si/AP8166.htmlExcuse my English, is not quite correct, sorry. And thanks to all.

author: Carrington
author_rank: Super Contributor
timestamp: November 07, 2013, 10:53:20 am
content: Is this the point of view of Polar respect to the vias? We must assume that for a multilayer board Antipad 1 is equal to 2?Note: A, B, and C. Length of the section with impedance mismatch.What is the geometry that Saturn considers to estimate the impedance?

author: Carrington
author_rank: Super Contributor
timestamp: November 07, 2013, 01:07:39 pm
content: Quote from: SPCBD on November 07, 2013, 12:58:15 pmHi!I gather that SPCD should be something like Satur PCB Designer. Woo hoo... Anyway, you are welcome to the forum.Thank you very much for your reply, but could you be a little more specific. For example: Where I can see these formulas?

author: SPCBD
author_rank: Newbie
timestamp: November 07, 2013, 01:10:36 pm
content: Not sure where the rest of my reply went:I am sometimes asked why the Saturn PCB Toolkit has a different Z number here or there with respect to Polar and the answer is...I have no idea. I do not know what Polar uses to calculate impedance's on any of their tools. I use stated formulas given by the IPC or other industry standards is really all I can say. A board house called me once claiming that the Saturn PCB Toolkit's numbers were closer than what they got from Polar in their actual measurements so they are pretty accurate.As far as the via impedance, I do not see how Polar is correct but maybe I'm just not familiar enough with their tool. Via capacitance is dependent on the via pad with respect to a reference plane opening, this can be thought of as a parallel plate in a sense. Via inductance however is dependent on the hole diameter and I do not see where Polar is using this information in its calculations. I use an approximated via inductance formula but it shouldn't be that far off as I have modeled the more involved formulas and didn't see much of a change. Via Z is simply Sqrt(ViaL/ViaC).Ken

author: Carrington
author_rank: Super Contributor
timestamp: November 07, 2013, 01:17:35 pm
content: Quote from: SPCBD on November 07, 2013, 01:10:36 pmOk, I now understand a little more. Thank you very much."Sqrt(ViaL/ViaC)" So then Saturn estimates Z value in a similar way to a conecctor's pin.

author: SPCBD
author_rank: Newbie
timestamp: November 07, 2013, 01:28:12 pm
content: Correct, there is nothing really special about a standard via. It acts just like a connector pin electrically.

author: Carrington
author_rank: Super Contributor
timestamp: November 07, 2013, 01:37:03 pm
content: Quote from: SPCBD on November 07, 2013, 01:28:12 pmI'll try that Polar also get involved in this. I hope to have luck.@ SPCBD, Thank you very much again.More info:http://www.saturnpcb.com/toolkit_help.htm->-> Via Capacitance:This is the approximated capacitance of the via with the given inputs. This value is only available for multi layer vias as it uses the internal pad and reference plane opening for the calculation.-> Via Impedance:This is the approximated AC impedance of the via with the given inputs. This value is only available for multi layer vias as it uses via capacitance for the calculation. via_zo = sqrt(via_l/ (via_c * 0.001))In the link above is all that I needed to know about Saturn. Why I did not look this before?

author: KenPolar
author_rank: Newbie
timestamp: November 12, 2013, 09:42:26 pm
content: The Polar Si9000e is a 2-D frequency dependent field solver used to accurately compute frequency dependent parameters such as Z, R, L, G, C, dielectric and copper losses for trace transmission lines on printed circuit boards. For vias, however,accuratecalculations require a 3-D solver. No exceptions. This is because via environments are not uniform along their length.So if you want impedance for a via, you have three choices open to you;* Guess. Not a good choice.* Use a 3-D solver. If you have one (expensive) and if you can drive the solver to define the structure (complex) and if you have the time available, then this is your choice for accurate 3-D characteristics.* Or, as Eric Bogatin says, "Sometimes a good approximation today is worth more than an accurate answer tomorrow." And that's what the Si9000e gives you, a good approximation of impedance.So you make the choice between these three.As for the basis of the calculation, Si9000e users will see an "i" information button to the right of the calculation leading to a website description of that.As for why other tools provide different answers... You'll have to ask them that question, what is the basis of their calculation etc. We don't comment on other suppliers' tools, only on our own.Incidentally, Si9000e users. Look at the Via Check tool above the via impedance calculator (it also has an "i".) This will give you a very good clue as to whether you really need to concern yourself with via impedance - before you spend a gazillion dollars and a day of your life on a 3-D solver, unnecessarily.Lastly, to address the comment about contacting Polar with questions; simply visit our websitewww.polarinstruments.comand look to our world-wide locations listed near the bottom of the index column on the left of your screen. Use the phone and a helpful human will answer you immediately during office hours. No menus and no wait times, we actually DO welcome your calls and questions. :-)I hope this helps and thanks for reading. Ken Taylor.

author: Carrington
author_rank: Super Contributor
timestamp: November 12, 2013, 10:30:04 pm
content: Ken Taylor is the president of Polar Instruments Inc. Awesome!Thank you very much for your reply and welcome to the eevblog forum.Ken Taylor:http://video007.com?725

author: EEVblog
author_rank: Unknown
timestamp: November 12, 2013, 10:42:43 pm
content: Quote from: Carrington on November 12, 2013, 10:30:04 pmYes, it's awesome when the companies respond and interact with the community on the forum level, and to do that at the President level gets Polar a big

author: Carrington
author_rank: Super Contributor
timestamp: November 12, 2013, 11:03:04 pm
content: About vias there are more articles, but these are interesting IMHO:http://m.eet.com/media/1135917/324403.pdfhttp://www.lamsimenterprises.com/SPI2008_43_Rel_Permittivity_Var_Via_Structure_Poster.pdfhttp://www.ieice.org/proceedings/EMC09/pdf/22Q1-3.pdf

author: Carrington
author_rank: Super Contributor
timestamp: November 12, 2013, 11:20:13 pm
content: Field solver, how closely are the results:Amazing, Polar is on the average.Source:http://www.alspcb.com/pdfs/controlled_impedance.pdf

author: xzswq21
author_rank: Frequent Contributor
timestamp: December 15, 2017, 04:17:47 pm
content: Hi allI have a question!in a 4 layers PCB, we have two Prepreg and one Core. for example the dielectric coefficient for the Prepreg is 4.2 and for the core is 4, now how should I calculate the impedance of a via?!

author: rx8pilot
author_rank: Super Contributor
timestamp: December 17, 2017, 12:58:40 am
content: I just started a trial of Polar Si8000 - really nice.Ken - if you are still listening....Are you willing to consider a subscription approach to these pieces of software? When I need it, I really need it - but I would guess that may only be for 5-6 designs per year. Those designs are likely to be crammed into a relatively short period of time. The cost is non-trivial for a tool that we will use so infrequently.It is really easy to use and offers the designer a ton of structure options. As a periodic user, it is hard to justify the cost.