Oct
5
I know this series is very late, but the summer was much busier than expected. Well as they say, better late then never. So here it goes. I have decided to evaluate the different CAD tools that we use here at Vision Circuits based on specific topics that are critical to designing a board. This is based on my experience and feedback from the Vision team.
As the title mentions, the first evaluation will be of the libraries (footprints only). Libraries is a very important part of PCB design. There are thousands of parts developed by different manufacturers with different specs. Building a library is not necessarily difficult but great care must be taken as one erroneous footprint on a board can mean countless hours lost troubleshooting in the lab. This is why CAD tools must have a good library manager to facilitate the process.
Cadence Allegro
The first thing that comes to mind is the number of files needed to build a component. You need a pad or multiple pad files, the editable part, as well as the read only part. If you are using a 3rd party schematic tool , you will also need a text file. This is without counting the files you may need for other features such as shapes or flashes. This can get very chaotic if not well organized. Creating the footprint is a fairly simple task in Allegro. There is nothing fancy, no feature that make it stand out but there is nothing wrong with it either. It’s fairly intuitive and easy to learn for beginners. The component wizard is good but would need a revamp as many new footprint types exist today. I must say that the measuring feature is great and probably one of the best when compared with other tools.
For a high end tool, I am disappointed in the lack of a proper library management feature. Allegro’s library needs a good process in place otherwise it can become chaotic.
I give it 2.5 out of 5 stars
Mentor Expedition
Expedition has a completely different strategy for library management. Parts are still individual files but are in a structured folder which, when viewed using the library manager, is shown in a very well structured format. Included in the library manager is a padstack editor that lets you create and manage all the holes , pads and custom shapes easily. The footprint editor is quite good as well and has all the features to build your component. The wizard is OK, not very versatile but it helps speed things up a bit . It can also be a bit difficult sometimes to do some simple task such as removing pins for example. It’s a very powerful tool but you do need to know the tricks as it is not as intuitive as other EDA packages. Once the footprint is created you simply need to assign it to the part. The measure tool is quite good as well in this tools. One large issue is the fact that the padstacks can’t be locked after creation and can easily be modified at any time. If the user is not careful he could mistakenly modify padstacks and they would automatically be updated on all the assigned footprints without warning. This makes editing padstacks easy but risky. A simple “lock” feature would solve the issue.
Overall the library manger is quite good. There is however some features that could really be improved when it come to some of the most simple task. Expedition is a tool that is hard in the beginning, but the more you work with it, the more you learn to love.
I give it a 4 out of 5 stars
Mentor PADS
A PADS library consists of 4 files. There are really only 2 that are important for footprint creation. Decals and Parts. Decals are the actual footprints, and parts are the component details that the schematic needs to forward annotate. In the part, you can define several decals, pin details and swapping options. The Library manager is very easy to use. You can add, copy from one library to another very easily. Building the decals is not very difficult, but you will need to create specific views as changing layer display is very time consuming and there are a great number of unnecessary layers. The component wizard has just been improved and now uses the IPC naming conventions and builds decals per IPC recommended land pattern. This is the only tool that offers this and I must say it is a great value added to this tool. The biggest disappointment is the fact that there is not a measure tool available other than point to point. This makes creating parts that are not symmetrical extremely difficult. It is hard to comprehend how a CAD tool can be lacking a solid measuring feature. The software also has some great features that are not offered in other tools such as auto-renumber of pins and “associate shapes with pins” options.
This is really a great tool for library management. The features are great and the addition of the IPC land patterns give it a real advantage over the other tools. It is really too bad there is not a proper measure tool. Otherwise this would be one of the best library tools out there. Really do not understand Mentor decisions here.
I give it 3.5 out of 5
Altium Designer
The graphical interface of this tool is the first thing that I noticed. The software looks new and fresh compare to other CAD tools. The library consists of one single file. All CAD tools should follow this model. It makes transferring and sharing your library a breeze. Copying components from one library to the next is a simple copy and paste function. In general, the Library manager could not be much better. The wizard has many component types to choose from and is very easy to use. All objects can be modified using the property option which gives the designer lots of flexibility. The measure function is very good as well and provides all the necessary information (center to center, edge to edge). On a critical note, there are no padstack libraries and all the padstacks must be built from scratch each time, for each part. This is time consuming and increases the risk of errors. There is however and option to apply padstack changes to all components in the library. Not really sure if this is a good thing or a bad thing as it can really mess up a library if not used properly but can also be a very powerful feature. A downside to this tool is that there are no pre-defined assembly layers. There is a work-around but, by default all components should have assembly layers defined.
Overall this is really a great tool to build libraries and rivals (even surpasses in many ways) the “higher end” tools.
I give it a 4.5 out of 5
Libraries are taken for granted and it shows even with the CAD software companies. The time spent in adding feature on the layout side of the tools is far superior to what is spent actually developing a great library manager tool. This is unfortunate as libraries play a major role in the development of a product. Hopefully in future upgrades we will see some improvement to the CAD libraries.