If you earn your living through the design of printed circuit boards, then the right tools might make a critical difference to both the quality of the final product, and the speed and ease with which you produce it. The time and energy that you spend wrestling with the tools might instead be spent on refining your layouts and improving your skills as a designer.
But exactly which tools are consequential, and what’s the best way to approach each stage of the design process?
From Schematic to Netlist and Libraries
The cleaner your approach to symbols and footprints, the less likely you’ll be to commit serious errors that don’t reveal themselves until painfully late in the process. Electrical and Design Rule Checks should also be built into the tools that you’re using throughout the process. This is where modern PCB design software excels.
Board Stack-Up, Clearances, and Thermal Considerations
Sometimes, problems result not just from the components and their arrangement, but also from the way that the layers are composed. Outer layers tend to be reserved for signals, while interior ones are largely left as solid planes for ground and voltage.
You’ll also need software that can spot creepage and clearance, which refer to the distances between components, respectively through the air and along the board’s surface.
Routing Priorities (Power, Clocks, High-Speed, Analogue)
If you’re sending signals next to one another, then it’s vital that you anticipate and deal with crosstalk. You’ll also need to worry about impedance, and the return path of your signals.
Thermal reliefs matter a great deal, too. These are interruptions that prevent pads from inadvertently acting as heat sinks, which can disrupt solder joints. This might be a particular concern in smaller pads that sit beside large expanses of copper.
Design for Manufacture (DFM) and Test (DFT)
Getting a circuit that works is one thing. Designing a circuit that’s practical to manufacture might be quite another. A combinations of global and local fiducials will help to minimise the risk of misalignment. The board should ideally be easy to troubleshoot and test, with quality test points and silks. As a general principle, it’s worth assuming that the person (or people) who will create the physical product will understand nothing of your design – which means that you’ll need to make things as obvious as possible.
Final Checks and Handover
Before the board is handed over for fabrication, you’ll need to ensure that it’s been tested in the virtual world. You’ll also need to provide documents that specify tolerances, impedance, and copper weights. Your gerbers and Bill of Materials should be as clear and transparent as possible – if they aren’t, then what comes back from the manufacturer might not entirely meet with your expectations.
