CAD Files: The Better Alternative to Gerber Files for PCB Fabrication

Back when I was a Boy Scout, the best time of the year was going to camp. At camp, we could participate in all kinds of activities like hiking, swimming and archery. I always enjoyed archery because determining the best path to the bullseye involves a high degree of precision. Creating PCBs also requires precision, as there is a “best path” that takes your design through fabrication to an accurately constructed board. If you stray from the best path, you may experience PCB fabrication issues and extended turnaround time for your PCB.

The accuracy of your PCB’s fabrication begins with your design files. Any errors or missing data can prolong the time needed to build your board. You can avoid these delays by ensuring that your design files contain all of the information necessary to accurately produce your board. Gerber files are generic design files accepted by many manufacturers and are a popular choice among PCB designers. However, this flexibility doesn’t always equate to smooth sailing. It is not atypical to have to make corrections to Gerbers, which increases the time required to have your board fabricated. Let’s examine the usage of Gerber files for PCB fabrication and discuss whether there may be a better alternative path to having your board built accurately and faster.

Gerbers consist of multiple files containing the complex information from your PCB CAD design

Generic PCB Fabrication Files: Gerbers

Gerber files are 2-D ASCII files that are widely used by PCB designers; most PCB design software programs are capable of generating them. In many cases, this format results in the distribution of the PCB design over several different files, with each containing a portion of the overall design. For example, the design may be broken up into individual files for each of the following:

Each of these files has to be inspected and debugged to ensure they align with the other files for a successful and accurate build. If discrepancies are found, it can take many back-and-forths with the manufacturer, or even a redesign and generation of new Gerber files prior to PCB fabrication. Eventually, you will get your design fabricated, but there is a better and faster alternative.

Custom PCB Fabrication Files: CAD

Having a generic format for PCB design files that virtually anyone can read can be convenient. However, this convenience comes at a price. Using so many files introduces opportunities for errors or discrepancies. Therefore, every file must be individually examined and compared with other associated files to ensure proper alignment. To minimize this source of errors, some manufacturers prefer (or require) a single CAD file as an alternative to Gerber files for PCB fabrication.

CAD files are typically formatted files generated by specific PCB design software programs. For a PCB, one file holds all of the information necessary for a manufacturer to fabricate the board. As these files are all-inclusive in terms of PCB design information, discrepancies or errors are virtually nonexistent and the design-fabrication process is therefore faster than when using other traditional PCB design formats, such as Gerbers. This was demonstrated as far back as 2012, when the first board design using the IPC-2581 standard was delivered for fabrication: it experienced a 30% decrease in the overall design-fabrication process time.

Compared to Gerber files, CAD files have the following strengths and shortcomings for PCB fabrication:

Advantages of CAD Files versus Gerber Files for PCB Fabrication:

• Only one file contains design information
• Undergoes DFM checks
• Transfers to fabricator easily
• Reduces turnaround time for fabrication

Disadvantages of CAD Files versus Gerber Files for PCB Fabrication:

• More complex (due to detail of information) than Gerbers
• Less widely used

Why Tempo uses CAD files Accuracy Only one file needed that includes fabrication, component and assembly information Includes DFM data used by the design program Includes electrical connecticity information so no separate netlist is required Less chance of error

Although Gerber files are widely used, they lack the comprehensiveness and accuracy of CAD files. Thus, having your board fabricated may require extensive back-and-forth with the manufacturer or even redesign and regeneration of your Gerber PCB design files. Popular CAD formats are ODB++ and the IPC-2581 standard (an open source CAD to CAM format); both contain all the information necessary to fabricate your board. ODB++ has been around for decades, but the IPC-2581 standard is supported by a number of the major PCB industry designers and manufacturers, and is intended to integrate PCB design and manufacturing seamlessly into a single process.

How CAD Files Perform During Assembly

CAD files include the DFM settings used for your board layout, as well as the component placement information necessary for the PCB to be assembled. This provides the opportunity for you and the manufacturer to synchronize the tolerances of their equipment with your design software, which ensures that your board can be manufactured. In order to place your components during assembly, the component location data has to be included with your design. With Gerbers, this requires an additional file, XY data, be included. Another file, the netlist—containing electrical connectivity data—is required if your manufacturer does post-assembly electrical testing for you. In contrast, all of this information is already included in the CAD file.

If you prioritize accuracy and minimal turnaround time for your product development, then CAD files are a better alternative to Gerber files for PCB fabrication and assembly.

At Tempo Automation, we know the best path to the precision your designs require. To make the manufacturing of your boards as seamless as possible, we accept the following native CAD file formats for your design:

• Altium (.PcbDoc)
• Eagle (.brd)
• Kicad (.kicad_pcb)
• DesignSpark (.pcb)
• Cadence (.brd)
• DipTrace (.dip)

CAD file data enables Tempo to visualize a board and automatically program machines on the line

And to help you get started on the best path, we furnish information for your DFM and enable you to easily create and download DRC files. If you’re an Altium user, you can simply add these files to your PCB design software.

If you are ready to have us put our connected factory approach to rapidly produce your PCBs, try our quote tool to upload your CAD and BOM files. If you want more information on CAD files or how to incorporate your design into a CAD format, contact us.