IPC compliant footprints
This article is about IPC compliant footprints and in more detail how to create a footprint that is IPC compliant. I will also explain what IPC basically is and why everybody should care about it. Finally, you will find useful links at the bottom of the post.
What is IPC?
The IPC is an association called IPC – Association Connecting Electronics Industries with the goal of developing industry standards in the area of pcb and interconnection production. The various standards released by IPC not only regulat the process of the production but also specify guidelines and certifications for pcb design, assembling and testing. IPC represents a main building block that represents a common basis for pcb designers, assemblers and test facilities. Therefore, anybody working in one of these fields will likely have encountered the term IPC or may even have read some of their standards.
Why should you care about IPC standards?
If you are not able to talk in the language the rest of the industry is talking you will never achieve the desired result when using external designers, assemblers or test facilities. You will have to rework your pcb designs many times and/or may have to pay an extra charge because you are not following international standards.
What is IPC not?
The IPC is not a complicated study with lots of mathematical proofs and complex algebra and tons of formulas rather than an assortment of best practices. These best practices are build on years of experience from many different experts (pcb design, assembling, testing, etc.). IPC also concludes quite a few studies to investigate certain processes of the whole chain, in order to find new ways to improve the production of electronics. The IPC is written in a clear easy to read language to make it understandable for practically anybody in the electronics industry.
By the way you won’t get any IPC document for free. They also need to earn money, so in order to be able to read and learn from their standards, you will have to pay for it.
What are the most important standards in the case of footprint design?
In the figure on the right you can see the IPC standards tree. In the case of footprint design the standards IPC-2221 and IPC-7351 are among the most important. You can buy a copy at www.ipc.org.
Note: The figure on the right is not up-to-date anymore. I still post it because it seems to be available under the creative commons license also used by Wikipedia. You can find the most up-to-date version on IPC’s website.
Ways to create IPC compliant footprints
There are various ways to create a IPC compliant footprint, all depending on the knowledge one has about the related IPC documents. However, there are also some ways to get an IPC footprint for free :).
- IPC compliant footprint wizard – Some eda design tools like the popular Altium Designer have an IPC compliant footprint wizard included. It is possible to generate footprints that come quite close to the IPC specifications. However, it is best to not always trust the tool and double-check the most important dimensions.
- IPC documentation – The IPC documents also contain useful tables and figures to aid in the design of footprints. Choosing this method means that you will have to buy one or a multiple of the IPC documents. Which is what I’d recommend if you are a company doing serious designs.
- IPC-7351B IPC Calculator – IPC offers a free calculator to calculate IPC compliant footprints based on the dimensions of the package.
- Library Expert – This is a tool from a software company that is related to the IPC standards committee. Library Expert comes in different versions (free and commercial licenses).
We will have a closer look at the options 3 and 4.
3. IPC-7351B IPC Calculator
The IPC-7351B IPC Calculator offered by www.ipc.org is basically a reduced version of the Library Expert tool. It will let you create footprints based on the package size and you’ll be able to change some settings but much of the full functionality will not be available. The picture below shows a snapshot of the program.
All the cool features available in Library expert pro edition are disabled/grayed out. Therefore, the only option left is to check the dimensions either by checking the settings of the footprints primitives in the right pane of the program or using the tab “footprint” in the menu. In this tab the program would actually allow a user to define custom pad sizes. However, if you don’t check the check mark then it will just display the actual size of the pad and dimension of the spacing. That is very convenient since one can just easily use those dimensions to replicate the footprints basic appearance in the eda tool of choice. Although, this method works it’s quite a pain, because even though we have this beautifully made footprint right in front of us, we still need to invest effort to actually get it in the eda tool. Also, the courtyard and overlay data can’t easily be imported this way.
4. Library Expert
Library Expert is a program for footprint creation and library management, it is created by the company with the same name as their product “PCB Libraries”. On their website they state that they are involved in the development of IPC. Their software comes in 5 different versions, depending on the price (Viewer, Calc, POD, Lite and Pro). The pro version has a couple of features that you won’t get even with very expensive eda tools like Altium Designer or Mentor graphics, like bulk operations for a whole library (rotating all components, update to newest IPC standard, etc.). The tool can also automatically calculate a 3D step model for the generated footprint. Everything can be managed in the library and used by an eda tool. Last but not least, export to 21 different footprint formats (for different eda tools) is available. You can get the pro version at www.pcblibraries.com. For those of you who are looking for a free way to generate IPC compliant footprints can use the Lite version. It doesn’t support managing a whole library, no 3D models and also various other features are not supported. However, you will be able to generate footprints based on a components package size, you can change some settings (not all though) and finally you’ll also be able to export it to 21 different CAD formats.
The IPC standard is a major piece in getting a pcb manufactured for the lowest cost possible. This requirement is of course very important for big companies but also for small start ups when cost estimation is very critical. You will be able to create IPC compliant footprints with the tools presented above. However, just an IPC compliant footprint won’t be enough, you will actually have to read the IPC papers to fully apply all the knowledge presented. Therefore, I’d recommend it to anybody to read at least some of the IPC standards if you ever get a chance to do so.
There are different ways to get an IPC compliant footprint for free. What I haven’t gone into in this post is the POD license of the Library Expert. It’s a compromise between the Pro and Lite version and quite suitable for small companies. You will be able to use their extensive libraries and pay 1-2$ for an existing part and up to 5$ if you request a new part.