PCB, short for printed circuit board, is a support used to connect electronic components (such as resistors, capacitors, diodes, etc.) to circuits. In the PCB design , all designers know that right angles are a very difficult problem, because right angles will introduce many problems during the manufacturing process and use. Therefore, why PCB layout cannot have right angles becomes an interesting question.
Table of Contents
- PCB Design Basics
- PCB Layout Process
- Why PCBs cannot have right angles?
- Why do we need to route lines at 45 degrees?
- How to use 45 degree angle in PCB layout?
- Conclusion
PCB Design Basics
PCB Design Basics are foundational principles and practices used to create effective and reliable printed circuit boards (PCBs).
Understanding PCB Components:
Layers: PCBs can have one or multiple layers. Single-layer PCBs are simple and inexpensive, while multilayer PCBs can accommodate more complex circuits with additional layers of conductive paths.
Traces and Pads: Traces are the conductive pathways that connect different components, while pads are the areas where components are soldered onto the board.
Designing the Circuit:
Schematic Design: Start with a schematic diagram that represents the electrical connections between components. This is the blueprint for your PCB and includes all the components and their interconnections.
Component Placement: Once the schematic is complete, you’ll need to place components on the PCB layout. Proper placement is crucial for minimizing signal interference and optimizing performance.
Routing Traces:
Trace Routing: Connect the components by drawing traces on the PCB. This involves planning the paths that electrical signals will travel along. The layout should minimize trace lengths and avoid sharp angles to reduce signal loss and interference.
Design Rules and Constraints:
Clearances: Ensure there’s enough space between traces and components to prevent electrical shorts and ensure manufacturability.
Trace Widths: Select appropriate trace widths based on the current they will carry. Wider traces are used for higher current to prevent overheating.
Signal Integrity and Power Distribution:
Signal Integrity: Design for signal integrity by controlling impedance and reducing noise. Use techniques like grounding and shielding to maintain signal quality.
Power Distribution: Ensure adequate power delivery by using power planes or thicker traces to handle the current requirements of your components.
Thermal Management:
Heat Dissipation: Consider the heat generated by components and incorporate heat sinks or thermal vias to manage and dissipate heat effectively, preventing damage and ensuring reliable operation.
Manufacturability:
Design for Manufacturing (DFM): Design your PCB with manufacturing constraints in mind to ensure that it can be produced efficiently and cost-effectively. This includes adhering to standard PCB sizes, hole diameters, and trace widths.
Testing and Validation:
Design Validation: Before finalizing the design, use simulation tools to test the circuit’s functionality and performance. Prototype testing is also essential to identify and fix any issues before mass production.
PCB design involves creating a schematic, placing components, routing traces, and ensuring that the design meets electrical, mechanical, and manufacturability requirements. By understanding these basics, you can create effective and reliable PCBs that perform well in their intended applications.
PCB Layout Process
The PCB layout process is a crucial step in designing a printed circuit board (PCB), involving several detailed phases to ensure the final board functions as intended.
Define Requirements: Start by understanding the functional and mechanical requirements of the PCB. This includes the circuit design, component specifications, size constraints, and environmental factors.
Schematic Design: Before laying out the PCB, create a schematic diagram that outlines the electrical connections between components. This schematic serves as the blueprint for your PCB layout and ensures that all connections are correctly planned.
Component Placement: With the schematic in hand, begin placing components on the PCB layout. This involves positioning each component on the board according to the design requirements and optimizing their placement for both functionality and manufacturability. Consider factors like signal integrity, heat dissipation, and ease of assembly.
Routing Traces: After placement, route the electrical connections between components by drawing traces. Traces are the pathways that carry electrical signals across the PCB. Effective routing involves minimizing trace lengths, avoiding sharp angles, and managing signal integrity to reduce noise and interference.
Define Design Rules: Establish design rules and constraints, such as minimum trace widths, clearances between traces and components, and hole sizes. These rules ensure that the PCB is manufacturable and meets electrical performance standards.
Incorporate Power and Ground Planes: Add power and ground planes to distribute power efficiently and provide a stable ground reference. This helps in reducing noise and improving overall circuit performance.
Review and Optimize: Conduct a thorough review of the PCB layout to check for potential issues. Use design rule checks (DRC) and electrical rule checks (ERC) to identify and resolve any errors. Optimize the layout to improve performance, such as by rearranging components or adjusting trace routes.
Create Gerber Files: Once the layout is finalized, generate Gerber files. These files are the standard format used to communicate the PCB design to manufacturers. They include information on trace patterns, drill holes, and other critical details required for production.
Prototype and Testing: Produce a prototype of the PCB and test it to verify that it meets the design specifications and performs as expected. This phase may involve debugging and making necessary adjustments before finalizing the design for mass production.
Finalize Design: After successful testing, finalize the design and prepare for manufacturing. Ensure that all design documentation is complete and that the design meets all required standards and specifications.
The PCB layout process involves defining requirements, designing the schematic, placing and routing components, setting design rules, and preparing for manufacturing. This methodical approach helps ensure that the final PCB is functional, reliable, and ready for production.
Why PCBs cannot have right angles?
First of all, it needs to be clear that during the PCB manufacturing process, right angles will cause many problems due to manufacturing and inspection requirements. The main problem is that when there are right angles in the circuit board, it will cause the finished circuit board to have great mechanical stress, especially under high temperature and humidity conditions.
During the manufacturing process, PCB needs to be manufactured through a series of process steps, including PCB drilling, copper plating, PCB etching, gold plating, printing, etc. If there are right angles in the PCB design, the right angles will be easily corroded during the etching process, resulting in uneven or incomplete patterns. In addition, right angles can cause etching imbalances that may damage cold-welded joints and affect the service life and reliability of the finished product.
In addition, during the manufacturing process, PCBs also need to undergo AOI (Automated Optical Inspection) inspection to ensure that the quality of the circuit board meets the design requirements. If there is a right-angle design during the AOI inspection process, it will be difficult to guarantee the accuracy of the inspection results. Because of the height of the right angle and the shape of the edge, the inspection instrument may not be able to obtain correct data. Moreover, right angles tend to harbor dirt and grime, making detection more challenging.
Secondly, even if there are no problems during the PCB manufacturing process, right angles will have an adverse effect on the circuit board during use. Circuit boards occupy very small spaces in electronic devices and need to withstand various mechanical stresses and temperature changes. If the circuit board has right angles, the vertical force will not be distributed evenly, the risk of corrosion will increase, and the circuit board will be more likely to be damaged during use.
In addition to these hard manufacturing and usage issues, right angles can also affect the aesthetics of PCB design. Although this issue may not be that important, designers still try to avoid using obvious right angles in designs whenever possible, especially in high-end products, and do not like to create an unsightly impression.
Why do we need to route lines at 45 degrees?
In PCB design, why should we use 45-degree inclined lines for routing? There are several reasons to explore here.
The first is electromagnetic compatibility (EMC). In PCB design, EMI (electromagnetic interference) will occur between many signal lines and power lines. During PCB layout, if you want to minimize EMI, you need to pay attention to avoid right-angle connections.
Right-angle connections create very strong charge edges from the electric fields of signal and power lines. This causes electrons to collect at the edges and form high-energy states, creating a flow of electrons. This flow of electrons can cause high-frequency leakage, causing EMI. The 45-degree angle connection will make the charge at the edge more uniform and the electron flow smoother, thus effectively reducing the level of EMI interference.
Second is continuity and reliability. At right-angle connections, tiny gaps between circuit traces can cause signal reflections and impedance changes, which can lead to signal loss and instability. The 45-degree angle connection can reduce this reflection and change to a certain extent, thereby improving circuit conductivity and reliability.
Finally, there are the visual effects. Using a 45-degree angle connection can make the PCB traces look neater and more beautiful. This is particularly important for products with commercial applications.
How to use 45 degree angle in PCB layout?
Using 45-degree connections in PCB layout is usually very simple. Here are some basic practices:
The first is to use 45 degree angle connections as the default for the PCB layout. When designing PCB diagrams, right-angle connections should be avoided as much as possible, and 45-degree angle connections are encouraged to reduce EMI and improve conductivity and reliability.
The second is to use the 45-degree angle connection tool provided in the PCB software. When wiring, PCB software usually provides hotkeys or shortcuts for 45-degree angle connections. This results in faster routing and fewer errors.
Finally, during the wiring process, the overall arrangement of the wiring must be considered rationally. In extensive circuit routing, the routing needs to be refined based on considerations such as the importance of connections and crossovers between different layers. This can effectively reduce EMI and improve conductivity and reliability.
Conclusion
In summary, right angles have many problems for PCB manufacturing and use. In the design and manufacturing of PCBs, designers should avoid using right-angle designs to ensure the reliability and stability of the circuit board. If a right angle must be used in a design, careful consideration and care must be taken to ensure that the right angle has the least impact on the equipment.
In the future, the continuous advancement and innovation of PCB manufacturing technology may reduce the problems caused by right angles, but the principle of prohibiting the use of right angles will still persist. This is also a basic principle that a PCB designer needs to follow.
