“Throwing it over the wall” refers to transferring a project from one group to another, and in the case of PCB design, the transfer of data between design and manufacturing. Electronics were originally conceived and built by hand, but as the industry moved into mass production, design, and manufacturing grew into two different processes. At first, fabricators used photo-tooling to build circuit boards. Reduction cameras were used to develop 1:1 images of the designs laid out by hand at 2, 4, or even 10 times their actual size. However, this process was slow, imprecise, and limited the growth of design technology.
Now, PCB designers and manufacturers exchange data digitally. Although multiple formats are available for data transfer, the industry has primarily relied on two main formats over the years: Gerber and ODB++. There is a lot of debate within the industry as to which format is better, and this article will examine each, describing their benefits and potential problems. The chart below highlights a few of the differences between ODB++ vs. Gerber:
| ODB++ vs. Gerber: Which is Best for You? | ||
|---|---|---|
| Advantages | Disadvantages | |
| Simplicity | Complete data set for manufacturing | |
| Extensively used worldwide | Fewer errors during data transmission | |
| Portability | Facilitates better communication | |
| Easy to understand and debug | Enables production automation | |
Gerber: Reliable PCB Design Data Through the Years
Gerbers are open text files in simple ASCII format describing images using vectors and control codes for a photoplotter. The PCB layout designer will output the image data from their CAD tools in a set of Gerber files to create manufacturing data. Each layer of the circuit board to be built will have one or more Gerber files assigned to it, and those layers will be designated by their file names.
Initially, Gerber data had many limitations, and the files only painted a 2D picture of the layers they represented. Phtotoplotter aperture information, PCB layer stackup definitions, and other design attributes had to be communicated in separate data files. However, the Gerber format has since been enhanced to include these definitions and attributes, making it more versatile. Gerber data has a long and trusted history in PCB design despite its limitations for the following reasons:
- Gerber Data is the most common data format in use today for PCB manufacturing.
- The Gerber format is easy to understand, work with, and debug.
- Gerber files are portable and can easily be transferred via various mediums.
- There are many free Gerber viewers available.
- Gerber data is useable in most PCB design, CAM, and photo tooling equipment.
- Recent enhancements to the Gerber format have added advanced PCB definitions and attributes while maintaining backward compatibility.
However, as we stated before, the Gerber data format has limitations. The Gerbers must be gathered together with drill, routing, test, and definition files to exchange data between design and manufacturing. This process is ripe for introducing design continuity errors and lacks many of the checks and balances offered by a true database format, leading us to ODB++.
ODB++: the Next Generation of PCB Design and Manufacturing Data
In contrast to the singular file nature of Gerber data, ODB++ is a complete database of manufacturing information populated in multiple folders and files. The database not only contains the image data for the different layers in the design but also all of the information needed to fabricate and assemble the circuit board. This information includes layer stackup details, drill locations and tools, routing data, location of parts, board dimensions and materials, test data, net information, and much more. However, from the designer’s perspective, the entire database is output into a single file for transmission with the manufacturer.
ODB++ was created to provide accurate data transfer between designers and manufacturers and their CAD and CAM systems. The nature of the database allows for greater design history continuity and tracking due to how the CAD information is collected, processed, and stored automatically by the design system. This level of automation resolves many of the inherent errors of the more manually driven Gerber file process. Here are some of the key benefits ODB++ provides to its users:
- Transferring ODB++ between design and manufacturing has less chance of error.
- All fabrication and assembly information is included in the ODB++ database.
- The stability of the ODB++ database allows manufacturers quick and easy access.
- Automated definitions and attribute files reduce communication problems and delays.
- The ODB++ database encourages design and manufacturing automation.
- The nature of the database discourages manual file changes that can result in unintended data corruption.
However, using ODB++ for manufacturing data also has some inherited problems, chief of which is its complexity. For instance, workflows that rely on updating a board layer by sending a single Gerber file to manufacturing are more challenging with ODB++. Some would argue that this is a virtue of the ODB++ system, while others view it as a detraction. Along with that complexity is the need to properly configure the ODB++ output in your design system to generate your desired data. All of this brings us to the question of which of these manufacturing artwork formats is better, ODB++ vs. Gerber, which we will look at next.
ODB++ vs. Gerber; Which Is Best?
The Gerber format will give you simple, portable, and easy-to-work-with files that have been the PCB design and manufacturing industry standard for decades. The drawbacks of the Gerber format are that it doesn’t provide all of the manufacturing data that the industry now expects and requires a lot of manual intervention to create and maintain its data. ODB++, on the other hand, provides all the data that Gerber files do not and is a more stable and secure platform that requires little user intervention beyond the initial setup. However, ODB++ is a complex format, making manual interaction difficult.
Ultimately, the decision will be up to the PCB designer and the manufacturer as to which artwork format is best for their design workflow. Each format has pros and cons, and you must choose which will be best for you. Thankfully, you have a partner in the industry that can help you decide. PCB contract manufacturers, like VSE, can give you the best advice as to what will be the most efficient artwork format to match your combined workflows.
