Latest IPC-2581 Revision Gaining Widespread Appeal

August 1, 2014

Enhancements to the stackup and assembly data have the supply chain signing on to the electronics data transfer format.

Eighteen months ago, Fujitsu Networks Communications CAD engineering manager Gary Carter shipped CAD files for a 12-layer PCB in the IPC-2581A format to a major board fabricator. The fabricator responded, asking for a drawing and profile information. It’s all there, Carter said, it just has to be derived from the CAD file.

The fabricator proceeded, and other than missing some data for machine routing for cutouts and V groove, Carter recalls, “They worked around what their CAM tool couldn’t handle, and they built it.”

In the history of electronics data transfer, that alone was a significant achievement. And in the time that’s followed, the IPC-2581 Consortium charged with improving and marketing the standard has made even greater gains toward a comprehensive and robust data transfer format.

IPC’s release of IPC-2581B in November 2013 marked the culmination of a massive group effort to move forward the goalposts of electronics data exchange. But
once the standard was issued, the real work of implementation began. Here’s an update on where that stands.

Behind the latest adoption efforts are several major OEMs, Cisco, Fujitsu and Ericsson among them. What these companies shared was the need for a means to move data from design to the assembly line processes.

The B revision provides enhanced features around drilling and drill types to permit a more robust data set for drill and drill processes. “Some drill technology that’s been around for awhile is passed through drill files, documentation notes and phone calls,” explained Cadence product engineer Ed Acheson, one of the authors of the standard. “We can now expect to pass along that info associated with each of these objects. In particular, for backdrill, a spec definition can be created, the size and tolerances specified, and the drill specified, such as initial drill, backdrill, and so on.”

The revision also embeds information on panelization and V-groove definitions, including tops, bottoms and offsets. Drill features such as slot and cavity were combined and now can include width, length, depth and tolerance. Whereas Fujitsu had to supply the details of V grooves and cutouts when using Rev. A, that’s been overcome with the latest revision.

Significant improvements were made to the stackup definition. Data now embedded include layer structure, layer stack sub-groups, materials definition, dielectric materials, conductive materials, coatings, and material characteristics. Stackup can be defined in analysis tools and imported into CAD tools and exported to manufacturing (Figure 1).

FIGURE 1. The new data format provides a comprehensive stackup definition, and permits the import and export of key data to enable thorough simulation prior to prototype build.

Enhancements to the stackup represent the largest improvement in terms of saving time and effort for both the design house and their fabrication partners. With the improvements in stackup definition, materials information and more, IPC-2581B can be used to electronically exchange stackup definition, saving several hours per iteration. The electronic exchange also eliminates keystroke or manual entry errors on both sides.

Using IPC-2581B, fabricators can pass the details and properties of the selected materials back to the OEMs, which in turn can import this information into simulation tools that validate the design performance prior to fabrication.

“This is one of the innovations that exemplifies the power of collaboration between the PCB design and supply-chain companies; innovation is part of the charter of the Consortium for an open, neutral, global design data hand-off to manufacturing,” says Hemant Shah, product marketing group director, Cadence. “This is the beginning of the transition from hand-off, which is one way, to a bidirectional data exchange that enables collaboration through an intelligent electronic format.”

Syncing the assembly systems. It’s the assembly improvements that will capture many new converts, some of the standard’s authors believe. The first phase of prepping for assembly is determining the orientations and rotations so assemblers can sync their placement systems to match. IPC-2581B automatically flags that data, cutting an estimated 30 to 60 minutes from the tooling time setup.

IPC-2581B allows users to add polarity markings, thus indicating which is the positive or the anode or the cathode, in a way CAM systems now understand. For the primary pin (pin 1) and polarity marking, the silkscreen is a “+” sign (Figure 2). When picking a component, the centroid isn’t always the best location, depending on the placement machine and location and weight of a device, thus the standard indicates the desired pickup point.

FIGURE 2. IPC-2581B communicates the parts library orientation to the assembly placement system, and also designates the desired pickup point.

Footprint references came about after requests by OEMs, whose footprints vary depending on where parts are mounted. For instance, components on the top side might have one mounting configuration, while footprints on the bottom side might be different due to company-specific processes. For each reference designator, a link to the specific land pattern  is defined. BoM logistics, such company information, contact and role data, design revision/history data and software data, and footprint/land pattern definition can be included. Variant design support hierarchy allows users to create multiple BoMs based on various versions of a design.

Moreover, while BoM stackup info isn’t critical, to the design center assemblers stock inventories based on a particular design. The method common among assemblers, however, relies on basic spreadsheets and manual entry. Updating IPC-2581 to perform that planning is beneficial to all involved.

“The way we exchange stackup info today is arcane: graphics and Excel spreadsheets,” Sanmina IT project manager Larry Frost says. “No one wants to rekey the info, but that’s what we all do. Being able to have a format that’s defined is why we’ve jumped on this so hard. This will save time and solve a lot of problems.”

Up for adoption. There remain several hurdles to the widespread adoption of IPC-2581. Chief among them is the OEM insistence on using the format, something the aforementioned blue chip players are set on changing.

CAM support will be critical as well. While most of the CAM vendors have already indicated they will support the latest revision, Frontline PCB, the largest CAM provider, has not made its intentions publicly known. Frontline’s Genesis, InSight and InCAM tools do support IPC-2581A.

Where the IPC-2581 Consortium has clearly succeeded is in bringing together the supply chain to promulgate the standard. Recent members include Viasystems, Elmatica, Electrostein, Zetta One, ICD, Graphicode Inertia CAD, Altium and KwikTik. The Consortium has demonstrated unprecedented collaboration, meeting at least every other week to hammer out details, compared to the typical standards task group frequency of once a quarter (or less).

“We are able to refine definitions much more quickly than once a quarter,” Acheson said. “We were prepared for questions that we knew would come.”

OEMs are now pushing their suppliers to comply with the standard. Certain business units of Fujitsu, Ericsson and Cisco are in testing with Sanmina and other major fabricators, and an OEM of solar-powered skylights and other window accessories said three of its fabricators in China are using IPC-2581A, and the company hopes to make a universal switch to IPC-2581 starting next year.

Future enhancements are on the drawing board, although the task group is being cautioned not to move so quickly that manufacturers can’t keep up. The next revision will automate the inclusion of industry specifications into the transferred data, to further the bidirectional exchange between the design house and manufacturer.

Sanmina’s Frost is excited over the prospects, saying, “Instead of having an engineer have to read and remember all these specs, we can program them into our CAM.”

Revision C will also address test results sent from the fabricator to the customer – a huge time saver, as every company today has its own variation. Also under discussion for Rev. C are the parameter requirements for enabling request for quote (RFQ) processes to plan for cost and time to delivery.

With nearly 60 companies now actively involved in the Consortium, momentum is building toward the day when – at long last – a complete printed circuit board assembly can be built from a single comprehensive data file.

MIKE BUETOW is editor-in-chief of PCD&F (; moc.p1669704978uorga1669704978idemp1669704978u@wot1669704978eubm1669704978.

Printed Circuit Design and Fabrication, 01 August 2014