Overview of PCB Design Outputs and Manufacturing Files

Before your board can be put into production and prepared for assembly, you have to generate a set of files that assist your manufacturer. These are your PCB design output files, also known as manufacturing files, fabrication data, assembly files, and a host of other names. Fabricators and assemblers will use different sets of output files to produce your PCBA, and the design team will have to generate these before a product can be quoted and put into fabrication.

Before you send your design file off to a manufacturer in an email, make sure to get a list of their required fabrication and assembly files first. If you’re a new designer, take some time to read over the basic PCB manufacturing file extensions below.

List of PCB Design Output Files

A list of common PCB manufacturing files is shown below. You might not need to generate everything on this list for every manufacturer, but it’s good practice to just create all of them so that you can ensure your device will be producible almost anywhere.

• Fabrication files - File formats used to create stencils for bare-board production include Gerber RS-274-X/X2, IPC-2581, and ODB++. NC drill files are used to program CNC drilling machines to place drill holes in the bare board.
• Assembly files - The two main files needed for assembly are the bill of materials (BOM) and pick-and-place file. Both are used to match up parts and placement during assembly. The paste mask file used for assembly will be generated with your fabrication files.
• Prints and drawings - Fabrication and assembly drawings are like the blueprints for your design and will contain a wealth of information. Normally you would put this information in a quote form, but creating a fabrication drawing helps ensure fabricators anywhere will understand exactly how you want the board produced.
• STEP files and 3D prints - These two sets of files go together and they give an assembler the ability to clearly see the orientation of some components with non-standard packaging.
• Testpoint report - This file includes a set of nodes that are designated for electrical measurements, either for continuity testing or more specific in-circuit testing.
• Miscellaneous files - There are some miscellaneous files that might be requested by certain manufacturers. These might include your schematics, netlist, mechanical layers photoplot files (e.g., Gerber Files), or other reports with comments and back drill requirements.
• Binaries and testing documentation - In high volume manufacturing, some products may require on-the-line flashing of binaries and subsequent functional testing to ensure each product that comes out of manufacturing is fully functional. These requirements need to be specified and a test fixture may need to be supplied to aid automated functional testing.

It Starts With Fabrication Files and Documentation

Before your design ever makes it into fabrication and assembly, your fabrication files must be sent in for DFM review and quoting. Your fabricator will examine these files to ensure the design is within their capabilities. This is done with more specialized CAM software, which will check your fabrication files for clearances, feature sizes, feature spacing, and any other aspects of the physical design that will present challenges in manufacturing. Gerber files are most commonly used in this stage of the process, but any fabricator should be able to use other standard fabrication file formats (ODB++ or IPC-2581).

• Read more about PCB fabrication file formats and how they are used.

Fabrication notes are also important as they provide all the other information used to fabricate a bare PCB. Things like conformal coatings, surface finishes, specific materials to be used (LPI soldermask, etc.), impedance requirements, your stackup layer/material specifications, and much more are specified in your PCB fabrication drawing. Complete and clear fabrication notes will help ensure your design can be produced anywhere.

• Read more about preparing your PCB fabrication notes.

Your design may also need to be viewed by your assembler to ensure the design can be reliably produced without defects. Your assembly drawing and BOM are used to quote the board and to ensure accurate assembly once bare boards and components are received by the assembler. Assembly drawings contain their own set of notes that aid this process and eliminate any ambiguity in manufacturing.

Additional Design Output Data

Some additional data that might be needed in manufacturing could include mechanical models or 3D prints, as well as MCAD data for an enclosure. The data required depends on the level of service being requested from the manufacturer and the scope of work. For example, in assembly, some radial or axial lead capacitors may need to be bent over on their side in a very specific orientation; your 3D prints and a STEP file can show this clearly.

In some cases, viewing design data in a STEP file or as a 3D model in your PCB layout tool allows you to spot some DFM violations that may not be flagged by the online DRC engine. In the example is shown below, the connector outline on the silkscreen layer falls outside the board edge. When working in 2D mode in the layout editor, these defects types of can sometimes be missed, but they may be easier to spot in a 3D view.

Another specialized assembly requirement is with press-fit connectors or crimped connectors, which aren’t applied in a standard PCB assembly procedure. Documentation on these components also needs to be provided; an assembly drawing or a specific requirements document might be the best place for this. If you’re unsure or you’re working with a new manufacturer, make sure to request this information and provide the right data accordingly.

Anytime documentation is missing or an important fabrication/assembly requirement is not specifically stated, your manufacturer will likely go with some “standard” capability and requirement that is applicable to most basic designs. If you aren’t worried about things like surface platings or solder mask requirements, then just focus on creating the main fabrication files and leave the rest up to your manufacturer. Different companies offer different levels of service and will be willing to help you get your first PCBA manufactured successfully.

Summary

In the past, designers had to prepare PCB design output files and manufacturing data by hand, which required compiling information from multiple design documents and manually preparing final deliverables. Today’s design tools can help you prepare this data package automatically so that you can save time and get through design reviews quickly. Next time you’re planning a new project, use the best CAD tools to help you quickly create a PCB layout and prepare it for production.

Once you’ve finished your PCB layout and you’ve completed a thorough design review, it’s easy to generate PCB design output files for your design in Altium Designer®. The OutJob file feature lets you create manufacturing file templates for your projects and quickly generate groups of files from your PCB layout and schematic data. When you’re ready to release these files to your manufacturer, the Altium 365™ platform makes it easy to collaborate and share your projects.

We have only scratched the surface of what’s possible with Altium Designer on Altium 365. Start your free trial of Altium Designer + Altium 365 today.