The Case for IPC-2581: Interview with Ed Acheson

Estimated reading time: 5 minutes

Over the last few years, IPC-2581 has hit several milestones: Revision C was released in late 2020 and it now includes complete build intent for rigid-flex circuits. It is also integrated with IPC’s Connected Factory Exchange assembly format.  

To learn more, the I-Connect007 Editorial Team spoke with Ed Acheson, a senior principal product engineer with Cadence Design Systems. Ed is also one of the developers behind the IPC-2581 design data transfer format. He walks us through the ins and outs of IPC-2581, and explains why he believes this open-source format could be just what PCB designers and fabricators need today and tomorrow. 

Andy Shaughnessy: Ed, would you give us a basic background on IPC-2581 and how it developed out of the previous format efforts?

Ed Acheson: Back in the late 1990s, there was an effort to form a standard format for exchanging data from electronic CAD systems into manufacturing. At the time, there were a couple of formats that were fairly common. One was Gerber, and the other was ODB. The idea of having an IPC-recognized standard was to form something that everybody could work with. There would be nothing proprietary about it, and the idea was to make it more intelligent than the original format. People started thinking, “I could use this to archive data for an entire design.” As they were going through it, they said, “Okay, where do we start?” Well, you start with the GenCAM format and try to merge a couple other formats into it.

They spoke to the people at Valor and worked with them to get ODBX, which is the XLM version of ODB and the base that was the starting point for having an XML formatted file. The nice part about XML, they realized, is its being an extensible language that you can build on. You start with basic elements, and as new features and new technology changes, it’s very easy to adopt it into that format. They released the first version of it, version A, but it wasn’t too popular. Nobody could really see an advantage to using and adopting it as much as they wanted to make changes to it. With the lack of interest, it went by the wayside and was lost.

Then, in 2010, Valor was acquired by Mentor Graphics, which raised concern among non-Mentor users. They were concerned that ODB, a proprietary format for Valor, and which was considered independent, would now be controlled by Mentor Graphics. They were worried that Mentor would focus on its own customer base more than it would anyone else.

So, an effort was put forth to create the IPC-2581 Consortium, which is celebrating its 10th year in 2021. Driven by Hemant Shah, the 2581 Consortium began with about 10 members, and now is well over 100 members. When I became involved in 2011, we asked, “What can we do to 2581 to make it more acceptable in the industry? What data is missing, and what has been done to validate the data that was output at that time?” We spent a great amount of effort between various tool providers like Cadence, Downstream, Wise, Adiva, and Zuken. We all created 2581 output and compared the data outputs against each other. We learned that in formats, if you don’t explicitly state something, it’s like a Rorschach inkblot test where everyone sees something different. With that, we realized that we needed to have a consensus on how things should be and standardize everything.

We saw the benefit of the XML format and its ability to add more and more intelligent data, so that not only am I creating output like outlines, drill holes, and artwork layers, but now I can start embedding some BOM information. I can put in my company part number for a part and link it to manufacturers’ part numbers. I can add attributes to objects (which we call specs), where I can designate something specific in the format that must have particular attention paid to it—something like a chamfered edge, or a plated edge. We began to build and add more data into it until we got to what we see today.

Shaughnessy: I know IPC-2581 has been growing. What are the advantages? Why should someone be motivated to switch to 2581?

Acheson: Number one, it’s an open format. I don’t have to buy a license to use it. I can actually create software around it so I can embed or extract certain pieces of information from it. That’s a big advantage, especially if I’m an enterprise type of company that has the technology to do this. It’s also a one-file database; I can output everything I need in one file. I don’t have to worry about synchronizing multiple files and trying to merge them together to understand an end result. It’s all there in one file. It’s not binary. It’s XML.

Shaughnessy: We did a survey recently asking what would motivate any of the designer readers to switch to another data format, and the number one thing they said was, “Simplifying the process.” They said they don’t care about cost.

Dan Feinberg: They lie (laughs).

Shaughnessy: Designers wouldn’t lie (laughs).

Acheson: For users of a lot of the tools, and I can speak on Cadence Allegro and OrCAD, it is a simple process. You still go through the typical steps of saying, “Here are my layer structures, this is what makes the top layer, and this is what makes the bottom layer.” But when I go to output the data, I simply select where I want the file to be saved, what function mode I want, I hit my generate button, and the file is done.

To read this entire conversation, which appeared in the October 2021 issue of Design007 Magazine, click here.

Be sure to download a copy of Cadence's I-007e Book The System Designer’s Guide to… System Analysis by Brad Griffin. You can also view other titles in the full I-007e Book library here.