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Design Circuit: IPC-2231 Captures Board Design Best Practices

A few months ago, at the height of the global shutdowns due to COVID-19, I highlighted how working from home gave IPC volunteers more time to focus on standards development activities. For the superstitious readers out there, don’t worry; while typing “the height of the global shutdowns” with one hand, I was knocking on wood with the other! Regardless of the unfortunate circumstances that enabled it, the labor of the past few months has started to bear fruit, and there are new document revisions being prepared for industry review throughout the IPC standards development ecosystem. This month, I would like to focus on one such document: the IPC-2231 DFX Guidelines, which is currently being revised into IPC-2231A. 

DFX Guidelines 
The IPC-2231 DFX Guidelines establish best practice methodology for use in developing a formal design for excellence (DFX) process for laying out printed board assemblies that utilize surface-mount and through-hole devices. But the X in DFX means so much more than a catchy way to stylize “eXcellence.” It is a variable that can represent the many factors for a robust board design, including design for manufacturing, fabrication, assembly, testability, cost, reliability, environment, and reuse. 

If you have not used IPC-2231 before, then think of it as a compendium of best practices to consider while designing your boards. For example, if your board includes any vias in thermal pads, then you might want to read the IPC-2231 section on thermal pad outgassing before going any further with your design. Therein, you will find paragraphs of recommendations on how to mitigate outgassing, as well as references to other IPC and non-IPC guidelines and requirements for that specific issue.
Proposed Revisions to IPC-2231

While it is still in development and may change (more on that later, and how you can help shape it), the current proposed draft of IPC-2231A builds on its predecessor by proposing greater depth to many existing sections, streamlining others, and even adding entirely new content to better address design challenges faced by board engineers. 

The printed board assembly design process section is proposed to be enhanced to better elaborate on the steps necessary to iterate through the design process: concept design and analysis, detailed design, first build, product validation, manufacturing validation, and support. Specifically, the detailed design step is proposed to be reinforced by additional detail concerning design documentation. An entirely new step in the process—manufacturing validation—is also being considered for addition to IPC-2231A. The largest proposed addition to the IPC-2231A is a brand-new section on design impacts on fabrication processes and includes discussion, recommendation, and references to help the user design for critical fabrication processes—such as the application of surface finishes or preparing a board for laser drilling. 

Standards Development
But these proposed changes are exactly that—proposals. The servants of industry who have made these proposals comprise the IPC 1-14 DFX Subcommittee responsible for the development of IPC-2231A. As the IPC staff liaison to the 1-14 Subcommittee, I had the pleasure of attending every bi-weekly development meeting for the past year and listening in on how some of the leading experts in the field conduct their meetings and build their document. This group has three co-chairs from around industry: Karen McConnell of Northrop Grumman Corporation, Steve Golemme of Google Inc., and Dock Brown of DfR Solutions. 

Along with a small group of dedicated volunteers, these three individuals have coordinated the recent efforts to revise IPC-2231. For those who might be unaware of how IPC standards are developed, the most common strategy is to deploy A-Teams who handle chapters, sections, or even single figures for a larger standard or guideline. The 1-14 Subcommittee employed these A-Teams to great effect by selecting individuals with the most expertise of the various DFX topics to work on those sections. 

While this might seem so obvious as to be a trivial point, I think that it is worth exploring as a call to action. Even if you think that your expertise is only applicable to 5% of a given standard—not even necessarily an IPC standard—then that expertise is welcome. In the case of IPC-2231, there are many discrete sub-sections that deal with related, but not necessarily linked, topics. For example, in contrast to the thermal pad outgassing issue noted above, there is a section detailing design guidelines for system enclosures only five pages later. If you know very little about thermal pad outgassing but quite a bit about best practices for designing system enclosures, then your input on only that small fraction is critical for the good of the whole document. Of course, there are individuals who know “a whole lot about a whole lot,” and they are more than welcome to sprinkle their knowledge over the entire document. This was the case for many of the dedicated industry veterans who donated their time and talent to the production of IPC-2231A. 

IPC-2231A is currently in working draft and planned to be reviewed by the committee by September 18, 2020, at which point it may be tweaked per any feedback received after review. The final draft of the document will then be delivered to the industry for a mandatory 30-day review period. The beauty of transparent and open document development is that during this industry review period, any individual can render comments on the document, even if they are not members of the committee or have not previously worked on the document. 

Summary
In conclusion, I will thread the sections of this column together. IPC-2231A is currently in the working draft, and there are proposals for additions to the document that greatly enhance its usability and value to designers everywhere. Your input into the document is welcome, and if you review the draft document and find that it is missing some critical other value for X, then you are invited to join the effort and have your voice be heard. If you would like to join the IPC 1-14 DFX Subcommittee, or if you would like to review the document as part of the final draft for industry review, please contact answers@ipc.org. 
At its core, IPC-2231 is built to capture board design best-practices and condense them into a repeatable, reliable guide for creating excellent boards. After all, as the philosophical historian William Durant once wrote, “We are what we repeatedly do. Excellence, then, is not an act, but a habit.”  

This column originally appeared in the September 2020 issue of DESIGN007 Magazine.