Do you want to make professional grade PCBs using EAGLE? If so, using a well defined PCB project directory structure is a great place to start. I’ve outlined my preferred directory structure for EAGLE projects in this post.
In my work for clients, I design many PCBs. To ensure a high-quality deliverable for my clients, I consistently use the same PCB project directory structure.
There are probably as many opinions on the optimal directory structure for a PCB project as there are hardware engineers.
I use a variety of PCB design tools. For many clients, EAGLE is the preferred PCB design tool. The PCB project directory structure outlined below has tended to work well for me over the years when using EAGLE.
Not every sub-directory is included in every project but using a consistent structure helps me to maintain quality and makes it obvious if I’ve overlooked something.
I am also an advocate of the “hit by a bus” school of risk management. Despite the morbid name and low likelihood of being hit by a bus, I believe that it is worth maintaining a “what if” mentality.
Over time, it is quite common for project responsibility to be transferred between engineers or even between firms.
A well-defined, intuitive directory structure permits a seamless handover of project ownership between engineers.
Finally, it is worth sparing a thought for your future self. Years may pass between PCB revisions. Even if you are the creator of all the previous PCB revisions, a familiar directory structure with all relevant material available locally will help to ease you back into the design.
PCB Project Directory Structure
Archive <Rev 1> ... <Rev n-1> Current <Rev n> Zip Files <Rev 1> ... <Rev n>
PCB Revision Directory Structure
<Rev n>
Application Notes
Assembly
Bill of Materials
Board Model
Calculations
Collateral
Component Datasheets
Documentation
Design Rules
Manufacturing Data
PDF
Layout
Schematic
Pictures
Reviews
Schematic
Layout
Simulations
eagle.epf
[Project Name].brd
[Project Name].sch
Directory Contents
Application Notes
Integrated Circuit (IC) vendors regularly provide Application Notes to assist with the integration of their ICs in a user’s design.
If an Application Note is particularly relevant and novel, I will store it in this folder.
Assembly
The “XY files” used to program automated pick and place machines for PCB Assembly are stored in this folder.
Instructions to assist with manual assembly may also be stored in this folder, if appropriate.
Bill of Materials
The PCB Bill of Materials (BOM) files are stored in this folder.
Typically, a Parts List and an Order List are included. These are usually supplied in both CSV and PDF file formats.
Board Model
3D models of PCBs populated with components are becoming increasingly common. This is particularly true in applications where the enclosure form factor is a critical design constraint, e.g. wearables.
Support for 3D models has continued to improve within EAGLE, particularly since the Autodesk acquisition.
If I have generated a 3D model of the PCB, the files are stored in this folder. These files can be shared with an industrial designer, as appropriate.
Calculations
Occasionally, calculations need to be carried out for component selection, e.g. LED series resistor values.
If the calculations are sufficiently complex or novel, I will store them in this folder. Normally, the calculations are stored in an Excel spreadsheet and allow for process, voltage and temperature (PVT) variation in the relevant component parameters.
Collateral
Secondary documentation that is beneficial to the board designer or user is stored in this folder.
For example, if the board is a daughtercard for a main board or development kit, a PDF of the schematic or user guide for the main board may be included in this folder.
Component Datasheets
I maintain a library to store the datasheets for the components in my EAGLE libraries.
Upon project completion, I use a batch file to copy the datasheet for each part listed in the BOM into this folder.
This ensures that documentation for each component is available to the project owner indefinitely. Experience has thought me that this is well worth doing for several reasons.
For example, over time parts will inevitably become obsolete or hard to source. Some vendors are less focused than others on maintaining access to documentation for obsolete parts. Debugging or updating a design many years after it has been created is usually much easier when all relevant documentation is available. Murphy’s Law ensures that the datasheet you can’t source is the one that you’ll need most!
Also, for project activities such as achieving and maintaining a CE marking, having all relevant datasheets easily available greatly helps with the audit trail, technical file generation, etc.
Documentation
End user documentation is crucial for certain types of boards. For example, development kits and evaluation boards often require explanatory documentation in addition to the standard schematics, BOM, etc.
If appropriate, additional documentation such as a user guide is stored in this folder.
Design Rules
EAGLE uses a .dru file to apply design rules to a PCB project. The .dru file for the project is located in this folder.
I maintain a library of .dru files for a variety of board stack-ups and PCB vendors. I copy the appropriate file from this library using a batch file when creating the project.
Manufacturing Data
The Gerber and Drill files for the board are stored in this folder.
Details of the PCB stack-up and instructions for the PCB fabricator are also included in this folder.
PDF versions of the schematic and layout are stored in this folder (and the associated sub-folders).
The PDF versions of the schematic and layout tend to be very useful. They are convenient for colleagues or partners that don’t have access to the PCB design tool. For example, I regularly share the PDFs with firmware engineers and industrial designers.
Pictures
A picture tells a thousand words and are invaluable for documentation. High resolution photographs of the PCB (both pre and post assembly) are stored in this folder.
PCB fabrication services such as OSH Park may provide illustrations of a PCB before it is fabricated. If these are available, I will include them in this folder also.
Reviews
When developing PCBs for clients, formal schematic and layout reviews are an integral part of the development process.
To be meaningful, these reviews should be documented. The details of these reviews are stored in this folder.
Simulations
In some PCB designs, simulations are quite important to ensure that the design specifications are met. If so, the simulation files are included here.
Typically, I simulate analog circuits using LTSpice. I use tools such as HyperLynx for signal integrity and power integrity simulations.
About EAGLE
EAGLE is an acronym of Easily Applicable Graphical Layout Editor.
EAGLE includes a schematic editor and PCB layout tool.
Though not as powerful as Altium Designer or Mentor Graphics PADS, for example, EAGLE is still widely used by both professional engineers and hobbyists.
About Me
I am the Managing Director of Mixed Signal Systems Limited. I’m an experienced Electronic Engineer focused on Mixed-Signal Electronics, Embedded Systems and the Internet of Things (IoT).
Please contact me if you’d like to discuss how I can help bring your product to market, resolve existing product issues or provide relevant industry insights.
