Preparing for Manufacturing
Designing a PCB is great, but the final step in the design process is to prepare the design for manufacturing. Even after the layout is completed and is ready for fabrication, there are some final cleanup steps that are needed to get the board ready for production. After the board is cleaned up and thoroughly reviewed, manufacturing and production files will need to be created from the design data. At the end of the process, these design files will be sent in for another round of review with a manufacturer. The goal in all of these review processes is to ensure the design can be produced reliably and without defects.
While this all sounds like a ton of work, modern CAD software includes utilities that help speed up each of these steps. If you’ve followed our advice from Unit 3 and you set your manufacturer’s specifications as design rules, you will have a head start on passing through a design review and getting into production quickly.
In this lesson, we want to look at some of the outstanding points to check in a design review before a board is sent out for fabrication and assembly. We’ll also look at some of the basic files PCB manufacturers use to create the tooling needed to manufacture a PCB.
Design Review and Manufacturing File Creation
Before a design can go into production, it should be thoroughly reviewed by the design team for any outstanding problems before manufacturing data is prepared. Before preparing manufacturing files, the design team should follow the high-level design review process outlined in Unit 2, Lesson 2.
Before finalizing the board and preparing the manufacturing files, it is often the case that some cleanup will need to be applied to the PCB layout. The video below shows some common cleanup and finalization steps that are needed before the board is prepared for manufacturing.
After the design has been reviewed and cleaned up, manufacturing files can be created. We gave a brief overview of these files in Unit 2, Lesson 2. In this section, we want to go deeper into the manufacturing files used in the industry as a designer will use these to communicate with their manufacturer. As the electronics manufacturing industry has matured and adopted standardized file formats, circuit board manufacturers require a specific set of files in order to fabricate and assemble a PCB. When you generate your manufacturing files, you’re typically generating all the required files in a single instance, and you’ll send these out to the fabricator or assembler as needed.
One element that may need to be included in a PCB layout before manufacturing is fiducials. These are small marks in the corners of a PCB that allow an imaging system to determine the orientation of the PCB. This is important for assembly, automated optical inspection, and in other systems that may need to grab and rotate the board while passing it between equipment in a PCB factory.
Fiducial marks are small pads of copper placed near the corners of the PCB.
As a designer, you are advised to place fiducials in 3 corners of the board, similar to the arrangement shown above. However, your manufacturer may also place them if they are not present in the PCB layout. To place fiducials, simply place a pad in the corners of the PCB on both sides of the board. The video below shows how to do this with the standard pad tools, as well as the settings that are needed to ensure these marks are interpreted as valid fiducials.