I was recently given a rearview camera system for my truck and trailer. Everything was carefully packaged, and all of the individual components of the system were present and accounted for. What was missing, however, were the instructions for how to install it. Other than one small pamphlet discussing power and ground wires, I couldn’t find any information, even online, about how the system should be mounted and connected between my two vehicles. This means I’ll have to visit my mechanic to see what he recommends, which will frustratingly cost me time and probably a little money, too.
Problems like this are also common with PCB documentation. Incomplete customer documentation can force delays in the production of PCBAs because the manufacturer must go back and confirm with the customer exactly what they require. Delays like this can cost you time and money, and outright errors can even result in bad board builds. To guard against this and to get your project through production as quickly and smoothly as possible, here are some ideas on how to best create and manage your PCB manufacturing documentation.
Don’t Let Documentation Be an Afterthought
Often, the job of creating PCB manufacturing documentation is treated more as an afterthought instead of getting the attention that it deserves. It is very normal for PCB designers to speed through the process of creating documentation so they can move on to the next project.
Let’s face it—it’s a lot more interesting to place components and route nets than it is to specify dimensions and verify the bill of materials (BOM). But just as my rearview camera system was useless without installation instructions, so is a PCB without complete and precise assembly documentation.
Fortunately, there is a lot of help in PCB design tools these days for quickly creating accurate manufacturing data files. It is still very important, though, that you are prepared with all of the data and tools you need before you jump into creating the documentation. Consider the following to ensure accuracy and streamline the documentation process:
- Use templates: Drawing and report templates in your design software can save you a lot of time creating documentation so that you aren’t constantly reinventing the wheel with each design job.
- Use copies carefully: We can’t tell you how many times we’ve found mistakes in PCBA documentation due to someone creating new documentation from old copies, and then forgetting to edit or delete incorrect data.
- Establish design review and sign-off processes: Make sure that you have a system in place in which all key personnel can review and sign-off on their portion of the design. Many documentation corrections occur because someone’s input into the final design was missed and the job was finished without it.
- Make sure the documentation is concurrent with the completed design: Documentation that is created before the design is completed or that isn’t checked for changes will run the chance of having data that is not current with the finished design.
To sum it up, take the time to do the best job possible when creating documentation. It is human nature to want to rush through the end of a job so you can move on to other tasks. However, that is where simple little mistakes can happen. It’s all too easy for the wrong layer stackup to get used on a drawing, or for a component to be updated inaccurately on a BOM, simply because someone rushed through their work or wasn’t prepared for the task in the first place.
PCB Manufacturing Documentation Best Practices
Once your design is complete and ready to be manufactured, it’s time to create or update your documentation for production. Here are some recommendations that can help you ensure that your CM has the information they need to manufacture your product accurately and on time:
- Always change part numbers on updated components: When updating components, such as converting old leaded parts to lead-free RoHS-compliant parts, always make sure to assign new part numbers to the new parts.
- Work with your CM when making changes to the approved vendor/supplier/manufacturer parts list: Components on your approved parts list will change as you add new equivalent parts or remove parts for incompatibility reasons. However, if a component is removed for obsolescence or manufacturer buyouts, it can create confusion about the status of those parts that are functional and have been allowed and previously used. This is why it’s important to keep the lines of communication open with your CM when making changes to your approved parts list.
- Avoid putting the BOM on the assembly drawing: BOM lists on drawings are often poorly maintained and not updated with new drawings. It is a much better practice to include a separately controlled and independent BOM document with the assembly drawing.
- Update and archive all final documentation: Make sure to collect all feedback from PCB fabrication and initial prototype validation processes and include these with the final documentation package. If fabrication changes were needed to the Gerber files, make sure to go back and update the actual design database as well. This way, you will have all knowledge and changes incorporated into the database, so you won’t resurrect a previously solved problem in any future builds or redesigns.
Making sure to follow steps like these can help you to avoid confusion and delays due to erroneous part numbers during manufacturing. It can also help prevent potential database integrity problems that could hinder future redesigns.
How Your CM Can Help with PCB Manufacturing Documentation
In addition to the following these recommended best practices when creating your documentation, your CM can also ease the documentation process for you. The right CM will work with you on any changes or corrections to your PCB manufacturing documentation. This could mean making requested changes by redlining your existing documents or creating entirely new documentation for your approval and implementation with the rest of your design database. A CM with engineering expertise can also suggest part alternatives that include exact details about the component’s level of interchangeability.
As a PCB designer, completing the manufacturing documentation for your board probably isn’t your favorite thing to do. But, it’s a critical step in the process. Considering these tips and best practices, and working with a CM who will partner with you to maintain accurate PCB manufacturing documentation, will help ensure your board is produced correctly and on time.
