PCB Design – Adding Fiducial Marker and Tooling Strip To Your Design
What could have gone wrong for a PCB design that has been tested working on a prototype level? The circuit is working perfectly after hours of manually soldering on components on the prototype version. Surely, nothing could go wrong in the assembly process?
Well, this exact confidence of mass producing this PCB below caused me thousands of dollars in cost and money when the PCB assembly supplier highlighted that the PCBs are missing the fiducial markers and tooling strips. Both are necessary to facilitate the assembly process.
The Fiducial Marker
Fiducial markers are a feature or target printed on the copper layer of your PCB design. It is needed for pick and place assembly machines to locate the placement of surface mount components on your PCB accurately.
While local fiducials(above image) may not be necessary for every design, global fiducial is almost mandatory for most assembly machines, when you are using surface mount components in your design.
PCB Tooling Strip
One of the most common mistakes for a new designer is to be oblivious of what a PCB tooling strip is. While it has nothing to do with the complicated circuitry that made your design works, it is simply an extension of the PCB to be held in place by the machine as the components are being populated.
The PCB tooling strip is fabricated as a breakout section from the actual design and it could be easily removed after the PCB is assembled. You can place your global fiducial marker on the tooling strip if you’re running tight on space on your actual PCB itself.
While there are various suggestions on the fiducial marker specification, here is what I did for my design that works well with most PCB assembler.
- Eachfiducial marker is 1 mm in diameter.
- 3 of thefiducial markers are 5 mm from the edge.
- 1fiducial marker is 10 mm from the edge.
- The tooling stripis 6 mm wide.
(With that said, you should always check with your PCB assembler for the exact requirements.)
Again, adding in fiducial marker and tooling strip is no rocket science and may sound mundane to PCB designers. But ignoring this part of your PCB design may result in costly repercussion for your company.