A key mistake designers make while designing PCBs is focusing more on the circuit design and components rather than giving time to the PCB design. As a result, the design you have in mind does not translate into physical reality. Here we have prepared for you a list of top five PCB design guidelines which you can follow and make your PCB design more accurate and efficient.
1: Fine-Tuning Your Component Placement:
Correct component placement with reference to total area available is highly crucial for a well-designed PCB. There aregeneral guidelines available to help in placement of components, but there are also some specific guidelines that must be kept in mind. These include:
- Orientation: Similar components should be oriented in the same direction as this will ensure efficiency in the soldering process
- Placement: Components should not be placed on the solder side of a board that rests behind plated through hole components.
- Organization: Try to place all your SMT components (Surface Mount Components) on the same side and all the TH components (Through-Hole) on the top side; this will minimize the number of assembly steps.
- Also, keep in mind that using mixed technology components such as TH and SMT both will add to the overall fabrication costs.
2: Placing Your Power, Ground & Signal Traces:
Once you have decided your components placement, you move on to routing the power, ground and signal traces. Here are some guidelines you should follow:
- Orienting Power and Ground Planes: Try to keep the power and ground planes internal to the board while keeping them symmetrical and centered. Also, try to use common rails to supply power to your ICs and keep solid and wide traces. Avoid daisy chaining different power lines from one part to another.
- Connecting Signal Traces: While connecting signal traces try to keep the traces direct and short between components. If your component placement forces a horizontal trace routing on one side of the board then always place traces vertically on the opposite side.
- Defining Net Widths: Your required net width depends on the range of currents the nets will carry. Try to provide a 0.010” width for low current analog and digital signals. If your traces carry more than 0.3A then keep them wider. You can use to a Trace Width Calculator to help you.
3: Keeping Things Separate:
In order to ensure your larger voltage and current spikes do not interfere with lower voltage and current control circuits, follow these guidelines:
- Separation: Separate the power ground and control ground for each power supply stage. In case you have to tie them together in your PCB make sure it’s towards the end of supply path.
- Placement: If your middle layer is the ground place make sure you place a small impedance path to reduce the risk of any power circuit interference. Follow the same guidelines for keeping your digital and analog ground separate.
- Coupling: Keep your analog ground crossed only by analog lines. This will help reduce capacitive coupling due to the placement of a large ground plane and the lines routed above and under it.
4: Combating Heating Issues:
Without proper measures to ensure heat dissipation, your board is at a risk of damage and your circuit performance may be degraded. Some guidelines to help combat heat issues include:
- Identifying Troublesome Components:
Firstidentify the components that dissipate heat and their thermal resistances. Then take measures such as heat sinks, cooling fans etc. to keep the component temperatures down. Alsokeep critical components away from heat sources.
- Add Thermal Reliefs: Using thermal reliefs on TH components will help maintain process temperatures and make the soldering process as easy as possible. This is because it slows the rate of heat sinking through component plates.
- You can use teardrops in addition to thermal reliefs where traces join pads to provide additional copper foil/ metal support and to reduce mechanical and thermal stress.
5: Checking Your Work:
Always remember to recheck your work a couple of times to make sure there are no errors. You can start with these systems: Electrical Rules Check (ERC) and Design Rules Check (DRC) to make sure you’ve met all the requirements. They will help you to enforce gap widths, trace widths, common manufacturing setups, high-speed requirements, and short circuits. Once you’ve completed the ERC and DRC check move on to checking the routing of signals to make sure you didn’t miss anything. Finally, make sure your PCB layout matches your schematic with the help of your design tool’s probing and masking feature.
That’s all for our top five PCB design guidelines. Follow each of these steps and you will be able to design a well functional and manufacturable PCB easily. Keep in mind; these design rules form the foundation of the entire PCB design practice.