Does anyone know of a Good Free EDA design package

Hello I have been looking for a good free EDA design package, I have looked at Design Spark ,Ki cad, and Easy EDA. Has anyone recommend a EDA package that has stable parts and components and that is easy to use,

I'm not sure any decent EDA suite will have "stable parts and components". That may suggest it is stagnant!

Of all the free EDA tools, I can recommend EasyEDA.

It is still in the earlier stages but is developing rapidly into a very capable EDA tool for schematic capture and PCB layout (up to about 6 layers).

It includes simulation too.

It has a lot of library parts but the single thing that makes it stand out is that it is easy to learn to drive.

That means that even if the part you need is not there already, it's easy to create your own and that automatically gets shared with the whole library so the library builds up very quickly.

EasyEDA has several import options for Eagle, KiCad and LTspice files. It also has several export options (have a look at their Tutorial).

KiCad and gEDA are more powerful cross-platform tools but are quite hard to learn. Being FOSS, they have open file formats. Simulation is not well integrated with them.

Design Spark is developing well but I don't know much about using it. I assume it has open file formats. It's import and export look reasonably good.

expressPCB is another free tool but watch out for being tied into buying PCBs from them.

Even though EasyEDA offers a low cost PCB service, they don't tie you into using it. Gerbers can be downloaded and sent to any PCB fab.

Hello Andy

I have just used PCBexpress it is quite easy to use, when you get the PCB'S they are good quality, I might try EasyEDA as I may need to do some microstrip design, which you cant do in PCBexpress.

The thing I don't like about being tied to a PCB vendor is that you do all the work and then you end up with nothing you can carry away with you.

And if you seriously want to do controlled impedance work then you must have the freedom to choose your PCB materials, stackup and maybe even fab house.

EasyEDA supports a single set of PCB track design rules but tracks can be modified on a per track basis so you can manuall define tracks that you need to be specific widths.

For a defined impedance you will then have to specify a substrate material and - if it's really important - a material manufacturer.

You will also have to specify the layer spacings. EasyEDA currently uses a default set of layer spacings and the material is uncontrolled. You can contact EasyEDA via their support email address to discuss your requirements or to find out what the default stackup and materials are and then design the trace widths to suit.

If that isn't enough then you still have the option to specify what you want in the design in EasyEDA, generate and download the Gerbers at the end of the design _and then take them to a PCB fab house than can make exactly what you want_.

That's the crucial bit that you can't get with a tied-in free tool.

I don't think any online tool (certainly not a free one, unless the free version of Upverter supports it?) allows you to define a trace impedance and then have it work out the required trace width for you on a given substrate and stackup.

KiCad has a trace impedance calculator built into it but that is not tied into any form of Design Rule definition or checking. There are many similar online trace impedance calculators that would give adequate trace dimensional information consistent with the degree of impedance control precision you might be able to achieve using EasyEDA.

It's not unitil you get up to the higher end tools like Altium (maybe), Cadence and Mentor that you get true controlled impedance design capability. In tools like that you can specify the detailed layer stackup and then specify trace impedances in the schematic. Then they are passed through into PCB layout and actually define the trace dimensions.

All of that information is then used to run Signal Integrity simulations and, in some tools, RF and Microwave simulations.

That said, it is possible to create quite effective simulations of controlled impedance circuits in EasyEDA because the underlying ngspice engine supports a range of transmission line structures.

It's fiddly to set up and again is not tied into the PCB design rules in any way: it just shows what the circuit would do if the PCB had all the right impedances in it. You still have to manually calculate all the PCB trace width and stackup dimensions, taking into account the dielectric constant of the substrate material. That can be partially automated by building parameterised expressions into the simulation to incoporate those given substrate parameters. If you wanted to go into that much depth, I'm sure contacting support at EasyEDA would get you some further guidance on this.

:)

Hello Andy

I was going to take the default layer stack up and material of a tool that can support sandwiched track layers, and use an on line impedance calculator to calculate out my impedance of the net, I was hoping that was going to give me characteristics that would meet my needs. I could then use that to define the track width.

I am only working with signals less than 500MhZ, so I don't think it's really critical what i'm doing but I want to achieve the best signal characteristics I can with noise immunity with as few iterations of PCB layout that I can.

:)