Which Data Transfer Format is Best for the Industry?
Not so long ago, board designers didn't lose much sleep over CAD-to-CAM data transfer. They finished each design, tossed it "over the wall" and forgot about it. Gerber data wasn't perfect, but it worked for everyone, from the designer to the assembler.
In 2000, CAD systems are in an almost constant state of improvement, but the flow of CAD-to-CAM data hasn't changed much since Gerber was introduced 30 years ago. Fabricators and manufacturers who have questions about designs are still forced to make "guesstimates" or call the design manager at midnight. And any such changes made during manufacturing involve costly non-value-added engineering.
Misunderstood design data costs the industry an estimated $150 million each year, and the worldwide total may top 10 times that annually. As the increase in outsourcing further exposes the inadequacies of the Gerber file, many in the PCB industry advocate the standardization of a single data transfer format that accurately represents every aspect of a board's design and allows the bi-directional movement of data.
The race is on between the top two formats, Valor's ODB++ and IPC's GenCAM. The tool-based ODB++ boasts more users at this early stage of the game, and as a commercial entity, Valor may be in a better position to respond quickly to user demands than a standards committee. But GenCAM is a formal standard supported by an industry standards organization, and it's very similar to GenCAD, a tool already in use by many assemblers.
Which one is the better format? In the long run, it will be the users' decision. You get to decide.
In this corner...
The Yavne, Israel-based Valor was founded in 1992, and focuses on providing CAD and CAM software, primarily DFM tools, to PDB designers, fabricators and assemblers. When Valor released ODB++ (open database) into the public domain in 1997, fabricators began downloading the free format soon afterward. Many fab houses were already using Valor's Genesis 2000 CAM tool when ODB++ was released. This installed customer base has enabled ODB++ to pull ahead of GenCAM, which is still in the process of being examined by the industry.
ODB++ is an expandable ASCII-based format that holds all the engineering data necessary for PCB fabrication and assembly in a single database. Graphics, drill information, routs, components, netlist, specifications, drawings, engineering process definitions, reporting capabilities, ECOs and DFM results are included in one file. Operators can update their original CAD databases with DFM improvements and corrections and try to identify all layout issues before the design reaches the assembly stage.
ODB++ is a bi-directional format, allowing the movement of data upstream and downstream. The ODB++ database is similar to the databases of most CAD systems. The data arrives at the board shop in ASCII form, and fabricators can start performing value-added engineering such as etch compensation, panel imaging and output to drill, rout and photo.
Designers were cautious about switching over to ODB++, no matter what the fab houses were doing. Gerber files, Excellon drill data and centroid files may be expensive and prone to errors, but the industry has had 30 years to make them work. Many designers who output ODB++ still send Gerber, "just in case."
Newbridge Networks, a manufacturer of wireless and networking solutions in Ontario, Canada, began using Genesis as a Gerber compare about five years ago, and eventually tried out ODB++.
"Last June, we started sending ODB to the board shops with the Gerber files, and we stopped sending the Gerber files in December," says Mike Spooner, senior designer at Newbridge. "All the major board shops we deal with use it. We find it's a lot cleaner method, just one filea big filebut it's just one file."
JoAnn Vigil, a senior electrical engineering manager at disk drive supplier Maxtor Corp. in Longmont CO, doesn't find the ODB++ files too big, considering the information they can hold.
"In the real world, it would take eight Cadence files to get the same things done the ODB can do," Vigil says. "The files that you see are documentation drawing files. You get my outline drawing with all my dimensions and I don't have to go to a third party and use Adobe to output."
ODB++ allows Vigil's team to exceed the fab house's specs if necessary. Rules checking lets the designers see which areas will be of concern to a fabricator and which violations are acceptable.
"Green means it will pass any fabricator's house, yellow means you've got some tight spots and red means you've got some violations," Vigil says. "It's at that point in time I can put a little note saying, 'I know this is outside your parameters, but build it anyway.'"
EDA vendors providing ODB++ tools include Mentor Graphics and VeriBest, Cadence Design Systems, PADS Software and Zuken-Redac. These companies comprise Valor's Open Systems Alliance, a group that gives Valor feedback, pro and con, on the format.Valor President Chuck Feingold says his company is able to respond quickly when format issues arise, and, referring to IPC, he points out that Valor doesn't have to wait until a committee convenes to make a format change.
"We have an average of two or three critical translation issues each week that, if we don't solve them, they may create scrap in the marketplace," Feingold says. "New technologies are coming out, someone is pushing the envelopes above us, and if we don't fix it, a company could hit the wall."
Valor has recently incorporated a bill of materials and component libraries into ODB++, and the company is in the process of adding XML to capitalize on the rise in e-commerce.
IPC Director of Technology Transfer Dieter Bergman has been involved with IPC in one capacity or another for 30 years. He's spent much of that time searching for a successor to the Gerber file. In the 1970s, Bergman helped develop IPC-350, a format that he believes was superior to Gerber, but nevertheless failed to catch on with EDA vendors and users alike.
Bergman doesn't expect to have that problem with GenCAM.
"Bottom line, GenCAM is a product that has been developed by the industry, for the industry," Bergman says. "It should be supported by the industry."
GenCAM 1.0 was created by the IPC Data Transfer Solutions committee and released in November 1998. GenCAM, an IPC/ANSI standard, is based on GenRAD Corp.'s GenCAD format, a system already in use by PCB assemblers. Like ODB++, GenCAM is an ASCII-based format that offers two-way data transfer and integrates all the functional descriptions of PCBs and circuit board assemblies into a single file. GenCAM uses 22 sections to convey design, fabrication and assembly requirements, including fixtures, panels, drawings, artwork, layers, padstacks and changes.
When GenCAM is describing a completed board and assembly, information in one section is derived directly from the preceding section. For example, data in the primitives section will receive color and texture in the artwork section. But each section can also operate independently of the others if the entire product is not being defined.
"What people have done with GenCAM, they've cherry-picked and said, 'I only need this and this,' Bergman says. "You can use as much data as you need."
With GenCAM, more than one design can be included in a single file. This comes in handy when an OEM wants an electronic assembly constructed in a subpanel format, with several PCB designs wired together to be tested as a unit. To add designs to the file, all the designer has to do is insert the information into the header section and append a "shorthand_name" to the boards in the file.
"When we were getting ready to come out with GenCAM 1.0, this guy came up to me and said, 'I have a problem. I have three boards I'm building separately, but I want them tested as a unit. Can you do that with GenCAM?'" Bergman explains. "This is one of our improvements."
With GenCAM in the public domain, IPC has decided not to alter the format for a while.
"The data model for GenCAM won't be changed until 2002. This will give the tool writers the chance to write for it and understand it," says Bergman. "You can reengineer a thing to death. We may convert BNF to HTML, but the data will still be the same."
EDA tools that output GenCAM include Mentor Graphics, VeriBest, OrCAD, PADS, and ACCEL Technology. Cadence and Zuken-Redac both support GenCAM through Ohio Design Automation. Router Solutions Inc. (Newport Beach, CA) has donated to the public domain a GenCAM viewer that allows users to see the actual design on the screen.
Walter Shenke, president of Router Solutions, believes GenCAM and ODB++ will each appeal to a certain niche once people have the chance to try them out.
"GenCAM doesn't go really good into the etching and wet process part, but it goes very well into the manufacturing area. ODB++ doesn't contain enough information to go into manufacturing," Shenke says. "To me, the content is much more important than the format."
Bergman has no idea how many GenCAM users there are at this stage of the game.
"I don't have case histories. I only have people preparing for it," Bergman admits. "But I haven't heard any complaints about GenCAM, except from competitors."
Standards operating procedure
The development of ODB++ and GenCAM are closely linked. Valor is a longtime member of IPC, and Feingold and Bergman have worked with (and against) each other for years. The two remain close friends with opposing views.
"We go fishing every year in Cabo San Lucas," says Bergman. "I like Chuck, but we disagree with each other on some things."
At a June 1999 meeting at IPC headquarters in Northbrook, IL, Valor offered to donate ODB++ to IPC and let the organization declare ODB++ an IPC/ANSI standard. But IPC declined, citing the potential conflicts with intellectual property rights and the need for all formats to go through a complete IPC consensus process.
IPC instead asked Valor to adopt GenCAM as its data transfer format and use ODB++ as its native database. Valor declined to back GenCAM.
Feingold isn't surprised IPC turned down his offer.
"For all practical matters, going to the IPC with ODB was like saying, 'Your child is ugly. You have to take mine,'" laughs Feingold. "I assumed the IPC would act as a company would and make a decision based on what was best for the IPC. But IPC is not a company."
Bergman says that if ODB++ were adopted as a formal standard, all changes in the format would be controlled by Valor. He explained that as a competitive company, Valor would have to focus more on increasing its profits than on serving the needs of the PCB industry.
And according to Bergman, serving the industry is what IPC is all about.
"Even if ODB was a formal standard, Valor would still have control. They have a very good tool and they have a very aggressive strategy," Bergman says. "The whole purpose of this is to grab the industry by the short hairs, and the industry is letting it happen."
Feingold admits his company may have certain advantages over an industry organization like IPC when it comes to promoting a data format. But he's sure ODB++ is a better format than GenCAM, and there's no chance Valor will try to "hold the format hostage."
"There's no doubt that we're biased, and we have a vested interest in ODB++ becoming a standard," Feingold said. "I'm not about to tell you we're doing this out of any sense of nobility. We intend to make money."
Bergman says IPC exists to provide services for its members, not make a profit. As a not-for-profit organization, most of IPC's income must be put back into the organization each year. The association brings in revenue in a variety of ways, including trade shows, sponsorships, members' dues and the sale of standards.
"We also do some educational things and we've gotten into certification, which we didn't want to do at first," explains Bergman. "GenCAM support comes out of the standards budget."
ODB++ costs Valor quite a bit annually, but it will probably more than pay for itself in the long run, Feingold guesses.
"It does cost several million per year to maintain it and keep it going. That's why only a commercial company could maintain a format like ODB++," says Feingold. "We justify it because we sell more systems to fab, OEMs and contract manufacturers or assembly markets because of the integration achieved by ODB++."
It may be years before either GenCAM or ODB++ is accepted as the industry standard for CAD-to-CAM data transfer. Despite that, data transfer will continue to improve. Some critics think the two formats' data models are so similar that the industry should just make up its collective mind right now.
Rob Henningsgard is president of FASTechnology, a CAM vendor in Elk River, MN. Henningsgard prefers ODB++, but he plans to work with whatever format becomes the industry standard.
In the meantime, the semi-friendly competition between ODB++ and GenCAM will probably force each of the formats to be its very best. Regardless of which one eventually wins the format game, the current rivalry isn't likely to harm the industry.
So, which one is the better format?
Valor Computerized Systems, www.valor.com
Reprinted with permission of Printed Circuit Design magazine, April 2000
IPC GenCAM vs. Valor ODB++
GenCAM (generic Computer-Aided Manufacturing) is an IPC/ANSI standard for CAD-to-CAM data transfer. The ASCII-based format is based on the GenCAD format developed by GenRAD Corp. GenCAM offers bi-directional transfer of data. All the functional descriptions of the completed PCB and board assembly are contained in a single file, and data defining more than one design can be included in the same file. The file also contains data about the fixtures used in testing.
Design requirements and manufacturing details are conveyed in 22 separate sections represented by a keyword, from header and administration through components, routs and testconnects. GenCAM allows the designer to maintain the relationship of the unique reference designators for each assembly. Each board can be assigned to a location on the fabrication panel and the subpanel. EDA tools that export to GenCAM include Mentor Graphics, VeriBest, OrCAD, PADS Software and ACCEL Technology. Cadence Design Systems and Zuken-Redac output to GenCAM through third party tools.
ODB++ (open database) is a tool-based CAD-to-CAM data transfer format that holds all of the engineering data related to PCB fabrication and assembly in a single file. Drill information, graphics, routs, components, netlist, specifications, engineering process definitions, reporting capabilities, ECOs and DFM results are all included in one file. ODB++ lets designers attach notes to X-Y locations and layers with instructions for fabricators.
ODB++ provides a WYSIWYG description of layers and complete component data, including outline, part numbers, pins and pin areas. Checklists let everyone from design through assembly easy view the design and permit verification of checks run and criteria used. Valor has added bill of materials and component libraries, and is in the process of making ODB++ XML-compliant. ODB++ tools are available for netlist verification and raster comparison of translated artwork and drill layers. ODB++ is supported by EDA tools available from Cadence Design Systems, Mentor Graphics, PADS Software, VeriBest and Zuken-Redac.