Data Preparation: Data Formats

The first step in the manufacturing process of a printed circuit board is commonly referred to as data preparation. This is an operation in which information provided by the customer or designer is converted for use by the manufacturer to build the pcb. There are standard data formats required by the bare board manufacturer. The commonly accepted formats are as follows…

1) RS-274-X is the Gerber extended photo plotter language. Each layer of artwork is provided in its own Gerber file. Each file specifies the location, shape and size of all features on the artwork layer in one data file. Common file extensions include .PHO, .LGX and .GBX. This is the second generation of the Gerber format. The original version of the artwork format provided the data locations in one Gerber file and the shape and size in a second file called an aperture list.

2) Excellon 2 CNC drill format. Each file contains the through hole locations used by a pcb design. The file specifies location and size of drilled holes. Drill locations and size for blind and buried vias are provided in their own unique drill files. Common file extensions are .DRL, .NCD and .TXT.

3) IPC-356 net list format. The Gerber and Drill formats are non-intelligent data formats. They only specify location, shape and size. CAM software reads in the Gerber and drill information and generate a generic net list based on what is interpreted by the software as being connected based on applied rules. The IPC-356 net list file contains the connectivity information from the designer’s CAD software. The CAM software imports the IPC-356 data format and compares it to the generic net list. Differences between the two net lists are then identified. Doing so minimizes the possibility of interpretation errors. Common file formats are .356 and .NET.

Most printed circuit board manufacturers rely on these three formats to build the design. They are common and widely accepted by all manufacturers.

There is another less common format available that combines all three pieces of information. The format is called ODB++. This format contains all of the artwork, drill and CAD intelligence in one database file. The file is typically provided with a .TGZ file extension which is in a UNIX compressed TAR file. Supplying the data in the ODB++ format has not gained wide acceptance as of yet. Although acceptance is slowly gaining. Specialty software is required is required to export and import this data format in some cases.

ODB++ is not the first all inclusive data format to be released to the pcb industry. There were at least two other all inclusive database formats prior to ODB++. These are IPC-350 and Gencam. These two database formats were an attempt to simplify the transfer of printed circuit design data errors between the designer and the manufacturer. Each format is controlled by a design specification and were driven by the IPC. Unfortunately, there were dozens of software providers writing code to allow their software to take advantage of these formats. Interpretation errors of the specifications were a concern to some and unfortunately some errors were made that resulted in non-conformances. The same problem happened when the extended Gerber format was first being incorporated into pcb software. After the bugs were worked out of the extended Gerber format it was stable and reliable. New formats introduce the potential of mistakes from human error. IPC-350 and Gencam never gained wide acceptance. Why risk scrapping out a design on a new format when the extended Gerber format already works?

ODB++ on the other hand is the working environment of the Frontline Genesis CAM software platform. This is the driving force behind the ODB++ format gaining acceptance by the industry. The extended Gerber format became accepted because it was a photo-plotter format used by many printed circuit board manufacturers. The format gained acceptance by designers in part because it was already being used by the manufacturing industry. Unlike IPC-350 and Gencam, the ODB++ format is slowly gaining acceptance. This is in part due to the fact that it (like extended Gerber) is being used by the industry by companies that use Fronline Genesis as their front end CAM platform. There are still some concerns over data interpretation by programmers. However, as time progresses I believe the ODB++ format shall ultimately become the data transfer format of the pcb industry.

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5 Responses to “Data Preparation: Data Formats”

  1. djspcb Says:

    “as time progresses I believe the ODB++ format shall ultimately become the data transfer format of the pcb industry”

    I had used ODB++ for over 10 years, but unfortunately Valor and the ODB++ standard is now property of Mentor Graphics. This likely ensures it will become a tool specific data format.

  2. David Duross Says:

    I’ll have to follow up on that one. Both Mentor Graphics and Orbotech are close by to where I am. I’ll be meeting with both over the next month or two regarding current and future projects on my plate. The Frontline Genesis CAM software platform was a joint venture between Valor and Orbotech. It’ll be interesting to see where they go with it.

    This could be a major move on the part of Mentor Graphics. ODB++ is the database format for Genesis (CAM). It shall be interesting to see if Mentor migrates to ODB++ as well. This could be the first data format that would truly bridge the gap between CAD and CAM.

    There is a lot of appeal to a designer that sends ODB++ data to a PCB prototype shop, has samples built and then gets a copy of the working ODB++ data back from the PCB shop. The working data still has all of the design intelligence. The working data can then be sent to a large volume PCB manufacturer with all of the prototype fixes or assumptions made that reflect the prototype samples made. I know a few designers that would love to be able to take my working data, change one part and then send it back to me as a new revision part.

    Anyone can program to the ODB++ database format. It looks like Mentor may get there first. This could be very big when you think about it. I guess we’ll have to wait and see.

  3. David Duross Says:

    Finally a follow-up on the Valor-Mentor Graphics thing. Mentor Graphics has bought out Valor. This does give Mentor Graphics a leg up on the competition. Where as Frontline Genesis was a joint venture between Valor and Orbotech it is now a joint venture between Mentor Graphics and Orbotech. Whether or not ODB++ becomes design platform specific is something only time will tell.

    However, I do have several customers that refuse to use it for a very surprising reason. They have all been victims of piracy. Their designs were manufactured off-shore. The designs were reverse engineered. They now compete against foreign versions of their own designs. It is important to point out that they were not using ODB++ at the time. However, after their experience they are concerned providing data in ODB++ just makes it easier for a pirate to steal their design. There are many excellent suppliers across the globe and I believe ODB++ is the best format out there. This is more of an example of not knowing your supplier well enough. Something to think about when dealing with a manufacturer that you’ve never seen face to face.

  4. David Duross Says:

    I have received many emails regarding this post. djspcb and the emails have all stated a concern that ODB++ shall become a captive format. Its a valid concern and the future of ODB++ as the accepted industry format is unknown. I would like to point out some historical parallels.

    RS-274-X is a photo-plotter language. It was used by Gerber Scientific as their laser photo-plotter data format. One could point that RS-274-X was a captive format. It was a program language written by Gerber Scientific for use with their equipment. The competition of the day all had their own native data formats but they made sure that they could accept the market leader’s format. Competitors of note were Optrotech, Barco Graphics, Macdonald Dettwiler (MDA), Tibor Darvas, etc… They had their own data formats and could accept RS-274-X either directly or through a front end system. Gerber Scientific could be considered the market leader of their day.

    The same can be made for the Excellon 2 data format. This was Excellon’s data format for their CNC equipment. Excellon was the obvious market leader of their day. It was rare to find a printed circuit board manufacturer in the 80s and 90s without an Excellon in the facility. Competitors all recognized the need to accept the market leader’s format.

    Gerber Scientific got out of the board business in the late 90s but their data format is still the standard. Excellon is still in the board industry but is no longer the market leader. Even still their data format is still the industry standard.

    I know I stick with what works. I find that RS-274-X and Excellon 2 are reliable proven data formats that work. I have no data errors when these formats are provided. Problem free data improves manufacturing yields. I also find ODB++ to be an excellent data format. It also makes my job easier since the layer, drill and netlist data are pre-defined and usually ready for DRC and DFM to start.

    However, a software programmer can still make an error when writing code for their system that introduces a translation error when accepting any format. Frontline Genesis is widely used across the globe. Data errors that may be introduced by a code programmer are usually resolved immediately once discovered. Companies that provide error ridden software tend to go out of business. Well run companies that provide a reliable product consistently tend to succeed. Personally I like the idea of a data format with a company behind it. As the industry introduces new technology the data format needs to keep up. ODB++ has the potential to grow with the industry.

    Wait till OPCB technology becomes main-stream. OPCB shall be the end of RS-274-X and Excellon 2 data formats as the standard. ODB++ still has companies behind it with growing market share to adapt to this new technology. It’ll be interesting to see if another data format appears though.

  5. marmata Says:

    My group at Celestica takes legacy CCA data sometimes as films or even hard samples (usually from our Aerospace & Defense customers, some from Medical) to create ODB++ in cases where the data doesn’t exist (i.e. usually designs over 20 years old). I thought that it was smart for Mentor Graphics to buy out Valor; it could be a great benefit to the industry, and under the right mindset they would be very motivated to keep it open and support it. From my past experience, I know a partner company who owned a format/IP who then wrapped a brand around that proprietary technology and freely licensed it, with a main condition. The move was a marketing one – the industry users adopted it, and even all of their competitors had to mention their name (the main condition), which in my eyes became very powerful.

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