Would a book be convenient if the chapters weren’t bound, were scattered among different locations, required translation, and handwritten? That’s akin to what PCB manufacturers face every day when piecing together Gerber files, drill files, board drawings, notations, netlists, BOMs, and pick-and-place coordinate files, to interpret what designers expect them to build. That collection of files, none of which (except the Gerbers) share the same format, is almost always the way PCB designs are submitted for fabrication and assembly, except for a relatively few designs that are output in the ODB++ unified format. But salvation from the hodgepodge of design documentation is at hand, however, thanks to Revision B of the IPC-2581 standard for formatting PCB CAD data, which was released in late 2013.
RevB eliminates the need for any drawings among the design data to convey build intent.
In my November 2013 column, I wrote about how this standard consolidates all the data for a design into a single file that manufacturers can easily read, check to verify that the design is ready to build, and then use to drive CAM tools. The implementation of RevB by the CAD tool companies, DFM software vendors, and the CAM sector is underway. But there is far more in store for IPC-2581 to document designs as the standard evolves, as I learned from a recent conversation with Gary Carter. He is the senior manager of CAD engineering at Fujitsu Network Communications, and a founding member of the IPC-2581 Consortium.
Carter first pointed to what the revised standard already enables. “With the PCB stackup section that’s been incorporated in RevB, we’ve eliminated the need for a profile drawing entirely,” Carter began. I won’t steal his thunder about that provision, other than to say it will facilitate interplay between a PCB designer and manufacturing resources at the outset of a project to nail down the optimum stackup. He’ll reveal the details on March 24 in a presentation at IPC APEX EXPO in Las Vegas. In fact, RevB eliminates the need for any drawings among the design data to convey build intent.
Carter explains, “We can render directly from an IPC-2581 file what otherwise takes several sets of drawings.” He then referred to a network line card that has cutouts for optical modules, which was fabricated three-up per palette by several manufacturers as a demonstration project.
“There were the V-scores and the mills and drills, which along with the stackup structure used to involve a couple of different drawing sets,” Carter continued. “Now, no drawings are required at all. You’ve got the specific tools spelled out in the file that are required for the V-cut, where those V-cuts are located, all described in a spec tied to that V-groove. The details on the milling outline can be described by ‘2581 so you know how that cutout is achieved. And by the way, back-drill information is also conveyed by ‘2581, so there’s no requirement to specify that in a separate file set.”
The upshot is that the revised standard now in place reduces the number of files for export to just one, but provides much more thorough and coherent documentation to clarify build intent than the legacy method of conveying a design to manufacture. This will include assembly operations. But wait, there’s more on the horizon.
Product Lifecycle Management
Carter envisions a bridge to product lifecycle management (PLM) environments, which integrate all data about a product from a systems perspective from cradle to grave, including but far from limited to parts and production processes. As he explained, PLM is intended to be a part-centered view of any object, which encompasses all the attributes that define each part of the object and whether those part descriptions apply to the preliminary stages of product development, whether a part is actively being sourced for the product, or whether it is obsolete.
But Carter described a hook within the standard that could tie to more than hardware descriptions. “Contained in IPC-2581 is the ability to include external references to firmware configuration,” he said, “so this is another aspect of the PLM story. I could export design data from my CAD tool into the PLM environment and thereby bring up a product configuration function that will be identified through the attributes I’ve assigned parts: ‘Hey, I’m programmable. I need my reference guide to be related to a binary file that contains the program information that manufacturing needs to inject during the assembly process.’”
Most likely, the IPC-2581 file will merely point to an external file that could have a part number, which would be the program file.
Carter added, “I believe there’s even the ability to inject that into a dictionary inside IPC-2581, but I don’t think I would ever do that. It would add too much burden to the size of the design file.”
He speculated about sometime merging such mechanical elements as 3D rotatable parts views with the IPC-2581 domain. That’s a story for future iterations of the standard. Meanwhile, at the moment, RevB is the most flexible, comprehensive way to document a design so that a PCB manufacturer will understand exactly what you intend to be built.
For more information on IPC-2581, check out our IPC-2581 Tech Talk video.
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