PCB board design is the backbone of every reliable electronic product. This article provides a comprehensive guide to PCB board design, covering fundamental rules, panelization, trace spacing, crosstalk, standard grids, software tools, and practical steps for creating multi-board designs.

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What Is PCB Board Design?

PCB board design refers to the process of transforming an electrical schematic into a physical layout where components and copper traces are arranged to form a working circuit. It bridges the gap between conceptual circuitry and real, manufacturable hardware.

The basic process of electronic product design includes several key stages such as project initiation, market research, project planning, detailed design, schematic creation, PCB layout and routing, PCB fabrication, soldering, and functional or performance testing.

In practice, electronic product design is usually carried out through the following steps:

• Define the functions that the product needs to achieve.
• Determine the design plan and prepare a list of required components.
• Create a component symbol library based on the component list.
• Use the symbol library to draw the schematic according to the desired functions and perform circuit simulation using dedicated software.
• Build the component footprint library based on the actual physical dimensions of each part.
• Generate the PCB layout by combining the schematic and the footprint library.
• Proceed with PCB prototyping and fabrication.
• Carry out circuit assembly, debugging, and performance testing. If the design does not meet the expected requirements, the process is repeated and refined.

Among all these stages, PCB design plays the most critical role and serves as the core technology in electronic product development. After the schematic and circuit simulation are completed, the actual components are finally mounted on a Printed Circuit Board (PCB). The schematic defines the circuit’s logical connections, while the copper traces on the PCB realize the physical connections that make the circuit work.

What Is the Basic Rule of PCB Design?

One clear rule stands above all: keep it simple. Straightforward routing leads to fewer issues later. Start by planning power and ground. Then place key components logically, keeping signal paths short and direct. Maintain clean separation between power, signal, and ground layers. Simplicity builds stability. Stability cuts risk.

Key points to follow:

• Short traces for critical signals.
• Solid ground plane to reduce noise.
• Clear power delivery paths.
• Proper spacing between high-speed lines.

What Is PCB Panelization Design of the Boards?

PCB panelization design is a standardized manufacturing technique used to combine multiple individual circuit boards (subpanels) into a single, larger panel (array) to optimize production efficiency, assembly, and testing. Below is a structured overview based on the provided documentation:

1. ​Purpose of Panelization​

Panelization enhances suitability for mass production by:

• Improving assembly and testing processes.
• Reducing production cycles.
• Ensuring consistency, manufacturability, and higher production yield.

2. ​Panelization Methods​

a. ​Sequential Panelization​

Subpanels are arranged in a linear sequence to form the main panel.

b. ​Center-Symmetric Panelization​

Subpanels are symmetrically arranged around the center of the panel.

c. ​Yin-Yang Panelization​

Top and bottom sides of the same subpanel are placed on the same side of the main panel. Requirements:

• Both sides must meet reflow soldering criteria.
• PCB layer stack must be symmetric.
• Mark points must align on both sides.

3. ​Process Edges​

Process edges are auxiliary borders added to PCBs to facilitate handling during SMT or wave soldering. They are removed after production. Key points:

• Used when PCB shape is irregular or has high layout density.
• Width of process edges: ​W = 5 mm.

• If the conveyor edge has a gap longer than ​20 mm​ or exceeding ​20% of the edge length, process edges must be added to fill the gap.

4. ​Panelization Connection Methods​

a. ​V-Cut​

• Suitable for board thickness ​L: 1.2 mm – 2.0 mm.
• V-groove depth ​d:
  • For L ≤ 1.6 mm: d = L/3.
  • For L > 1.6 mm: residual thickness (L – 2d) = 0.4 mm – 0.6 mm.
• Tolerance: ±0.15 mm.
• Angle ​α: 30° – 45°.
• Alignment accuracy between top and bottom V-cuts: ​e ≤ 0.1 mm.

b. ​Stamp Holes​

• Suitable for boards with thickness ​​≤1.2 mm.
• Uses bridges with circular through-holes (similar to perforated stamps).

5. ​PCB Shape and Size Guidelines​

• Ideal shape: ​Rectangle​ with aspect ratio ~10:8.
• Recommended thickness: ​0.8 mm – 3.5 mm​ (standard values: 0.8, 1.0, 1.2, 1.6, 2.0, 2.2, 2.4, 2.6, 3.0, 3.5 mm).
• Panelization is required if:
  • Long side ≤ 120 mm and short side ≤ 80 mm.
  • Irregular shape (e.g., L-shaped, circular).
• Panelization may be optional if long side ≥ 130 mm and short side ≥ 90 mm.

6. ​Maximum Panel Size​

• Company machine limit: ​X × Y = 240 mm × 200 mm.
• Factors to consider: PCB thickness, V-cut depth, and panelization method.

7. ​Conveyor Edge Requirements​

• The longer edge is typically used as the conveyor edge.
• The shorter edge may serve as the conveyor edge if its length is ≥80% of the longer edge.

What Is Crosstalk in PCB?

Crosstalk in PCB refers to the unwanted coupling of signals from one trace to a neighboring trace, which can interfere with the intended signal and degrade circuit performance. It is a common phenomenon in high-speed and high-density PCB designs. Below is a structured explanation of its causes, effects, and mitigation strategies:

1. How Crosstalk Occurs

1. Electromagnetic Induction: When alternating current flows through a trace, it generates a magnetic field. If two traces run parallel, the magnetic field of the “aggressor” trace can induce voltage in the adjacent “victim” trace.
2. Electric Field Coupling: Adjacent traces also couple through electric fields. The changing voltage on the driver trace induces a current in the victim trace proportional to the rate of voltage change.
3. Parallel Trace Length: The longer two traces run in parallel, the greater the potential for crosstalk, though it reaches a practical limit as not all energy is transferred and induced fields on the victim trace can partially cancel the aggressor signal.

2. Where Crosstalk Appears

Crosstalk can occur at multiple levels of a PCB system:

• Within the chip core itself.
• Between the chip package and pins.
• On the PCB traces.
• Across connectors and cables.

As systems move toward miniaturization and higher speeds, the impact of crosstalk becomes increasingly significant.

3. Effects of Crosstalk

1. Signal Integrity Issues: Crosstalk alters the impedance and propagation speed of affected traces, causing timing errors in digital circuits.
2. Noise Introduction: Induced currents appear as voltage noise on victim traces, lowering signal quality and reducing noise margins.
3. Dependence on Switching Patterns: The magnitude of crosstalk depends on the activity of adjacent traces, their spacing, and the switching speed of drivers.

4. Key Mechanisms

1. Mutual Inductance (Magnetic Coupling): The magnetic field from a driving trace induces current in nearby traces, represented in circuit theory as mutual inductance. The induced voltage is proportional to the driving current.
2. Mutual Capacitance (Electric Coupling): The electric field between traces couples voltage changes to adjacent traces, represented as mutual capacitance. The induced current is proportional to the rate of voltage change in the driver trace.

5. Crosstalk During Signal Transitions

Crosstalk mainly occurs during the rising and falling edges of signals. Faster rise and fall times increase induced noise. Parallel trace length directly influences the amplitude of crosstalk, but beyond a certain distance, further increases do not significantly raise interference.

6. Strategies to Reduce Crosstalk

1. Increase Trace Spacing: Where possible, increase the distance between parallel traces or reduce their parallelism. Routing traces on different layers is ideal.
2. Optimize Layer Stack-Up: Minimize dielectric thickness between signal layers and reference planes to strengthen coupling with ground or power planes, reducing interference between traces.
3. Use Differential Pairs: For critical signals, differential routing can cancel coupled noise. Placing differential traces between ground planes further reduces crosstalk.
4. Select Appropriate Components: Using lower-speed components can reduce the rate of change of electric and magnetic fields, lowering crosstalk.
5. Prefer Surface Routing: Signals routed on the outer layers experience less coupling than inner layers with multiple reference planes.

7. Simulation and Verification

Modern PCB design software such as Altium Designer allows engineers to simulate signal integrity and crosstalk. By analyzing routing, rise/fall times, and layer stack-up, designers can predict and minimize crosstalk before manufacturing, ensuring reliable and stable product performance.

How Far Apart Should PCB Traces Be?

The spacing between PCB traces is a critical factor that affects both manufacturability and electrical performance. Designers must carefully consider trace-to-trace distances to prevent short circuits, maintain signal integrity, and comply with industry standards. The appropriate spacing depends on board type, application, and manufacturing capabilities.

1. IPC-2221 Standard

1. The IPC-2221 standard, issued by the Institute for Printed Circuits (IPC), provides guidelines for minimum trace spacing based on PCB class and complexity.
2. For Class 2 boards (typical commercial products), the minimum spacing is usually 0.15 mm (6 mil).
3. For Class 3 boards (high-reliability or high-density designs), the minimum spacing can be reduced to 0.1 mm (4 mil).
4. This standard ensures manufacturability while maintaining signal integrity and reducing the risk of defects.

2. JPCA Standard

1. The Japan Electronics Packaging and Circuits Association (JPCA) also defines trace spacing rules.
2. These guidelines vary depending on board type and design requirements, offering an alternative reference for designers, especially in high-density or high-frequency applications.

3. Industry-Specific Standards

1. Certain industries such as automotive, aerospace, and medical devices may have stricter or specialized requirements.
2. These standards are usually established by relevant industry associations to ensure reliability and safety under demanding operational conditions.

4. Practical Considerations

1. The standards above serve as references, but the actual spacing should be determined by project requirements, PCB fabrication capabilities, and electrical considerations.
2. Designers are encouraged to collaborate closely with manufacturers to verify that the chosen trace spacing is feasible for production.
3. Maintaining adequate spacing helps avoid short circuits, crosstalk, and signal integrity issues, especially in high-speed or high-density circuits.

To sum up, choosing the right trace spacing is a balance between electrical performance, manufacturability, and cost. By adhering to recognized standards like IPC-2221 or JPCA and considering specific industry requirements, PCB designers can optimize their layouts for both reliability and efficiency.

What Is the Standard Grid for PCB?

The standard grid in PCB design is a reference system used to maintain orderly placement of conductors, components, and silkscreen markings. Proper grid selection is essential for routing efficiency, manufacturability, and signal integrity. Below is a structured explanation of its purpose, typical values, and practical considerations:

1. Purpose of the PCB Grid

1. Maintain Orderly Layout: The grid ensures that traces and components are aligned and evenly spaced, which improves both aesthetics and manufacturability.
2. Support Routing: In many CAD systems, trace routing is guided by the grid. A well-chosen grid helps the routing engine efficiently find paths without overloading the system.
3. Silkscreen and Clearance: The silkscreen layer, which contains text, symbols, and markings, must maintain a minimum clearance from conductive traces. Typically, the distance between silkscreen elements and traces is 0.635 mm or greater.

2. Effects of Grid Density

1. Too Dense: A very fine grid increases the number of routing points, resulting in larger data files and higher memory requirements. It may also slow down computer processing in CAD systems.
2. Too Sparse: A coarse grid reduces routing options, negatively affecting routing efficiency and potentially limiting layout flexibility.
3. Optimal Density: An intermediate grid ensures enough routing options while avoiding unnecessary complexity.

3. Common Grid Values

1. Standard Component Spacing: Typical through-hole components have a pin spacing of 0.1 inch (2.54 mm).
2. Derived Grid Values: Based on this standard, grids are often set to 0.1 inch (2.54 mm) or fractions thereof, such as 0.05 inch, 0.025 inch, or 0.02 inch.
3. Practical Application: These grid increments allow designers to place components and route traces with precision while maintaining alignment with standard component footprints.

In summary, choosing the right grid system is a balance between routing flexibility, computational efficiency, and manufacturability. By adhering to common grid standards and maintaining adequate clearances for silkscreen and traces, PCB designers can ensure orderly, reliable, and production-ready layouts.

What Is the Best Software for PCB Designing?

There are many PCB board design software options for different skill levels.

• Altium Designer offers advanced simulation and collaboration tools.
• KiCad and Eagle provide solid options for professionals and hobbyists.
• For quick prototyping, PCB board design online tools like EasyEDA are widely used.

Some engineers also start with PCB board design software free versions to learn before upgrading to professional packages.

Popular PCB design software:

• Altium Designer – powerful and professional.
• KiCad – open-source and flexible.
• Eagle – lightweight with a clean interface.
• EasyEDA – online and beginner-friendly.

How to Make PCB Board Design?

Creating a PCB layout involves more than drawing traces. It’s a step-by-step process built on structure and clarity.

• Build your schematic with accurate component symbols.
• Set the board outline and mechanical constraints.
• Place components logically following signal flow.
• Route power and ground first, then signal lines.
• Use copper pours for solid grounding.
• Run design rule checks to catch errors early.
• Export Gerber files for manufacturing.

Every step matters. A careless layout can trigger delays, rework, or functional issues. A structured flow prevents surprises at the production stage.

Multi Board PCB Design

1. Multi-Layer PCB Stackup Structure

Before designing a multi-layer PCB, designers need to determine the board structure based on the circuit scale, PCB size, and electromagnetic compatibility (EMC) requirements. This includes deciding whether to use 4, 6, or more layers. Once the layer count is fixed, the placement of inner layers and the distribution of different signals on these layers must be planned. The stackup structure greatly affects EMC performance and is an essential measure to suppress electromagnetic interference.

1.1 Layer Selection and Stackup Principles

1. Layer Number Considerations:
   • More layers facilitate routing but increase manufacturing cost and complexity.
   • Symmetry in the stackup is crucial during PCB fabrication.
2. Determining Signal and Power Layers:
   • Experienced designers analyze layout bottlenecks and routing density using EDA tools.
   • Signal layers, including differential pairs and sensitive lines, are prioritized.
   • Power and ground layers are determined according to power type, isolation, and anti-interference requirements.
3. Layer Arrangement Principles:
   • Signal layers should be adjacent to inner power/ground layers for shielding.
   • Inner power and ground layers should be closely coupled with minimal dielectric thickness (e.g., 5mil / 0.127mm) to increase capacitance and raise resonance frequency.
   • High-speed signal layers should be sandwiched between two inner layers to limit radiation and enhance shielding.
   • Avoid placing two signal layers directly adjacent; insert a ground plane to reduce crosstalk.
   • Multiple ground layers lower grounding impedance and reduce common-mode noise.
   • Maintain overall stack symmetry whenever possible.

1.2 Common Stackup Configurations

4-Layer PCB Examples:

1. Top Signal, Inner GND, Inner Power, Bottom Signal – Preferred for most designs as components are mainly on the top layer.
2. Top Signal, Inner Power, Inner GND, Bottom Signal – Used if bottom layer components dominate or top-bottom coupling is weak.
3. Top Power, Inner Signal, Inner GND, Bottom Signal – Not recommended due to poor power-ground coupling.

6-Layer PCB Example:

1. 4 signal layers + 2 inner power/ground layers: good routing space but poor power-ground coupling and adjacent signal layers prone to crosstalk.
2. Improved power-ground coupling but still adjacent signal layers issues remain.
3. 3 signal layers + 3 inner layers: optimal solution. Ensures:
   • Tight power-ground coupling.
   • Every signal layer is adjacent to an inner layer for isolation.
   • High-speed signals transmitted between inner power/ground layers are well shielded.

Key Design Priorities:

• Power-ground coupling must be satisfied first.
• High-speed signal layers must be sandwiched between inner layers.

2. Component Layout and Routing Principles

2.1 General Component Placement Principles

1. Prefer single-sided placement of components. If double-sided, place through-hole components on the bottom and SMDs only.
2. Place interface components at board edges, ensuring correct orientation for cable routing. Clearly label interface and power specifications.
3. Maintain wide electrical isolation between high-voltage and low-voltage components.
4. Place electrically related components together, following modular layout principles.
5. Keep noisy components (e.g., oscillators, high-current circuits) away from sensitive logic and memory circuits.
6. Place decoupling capacitors close to component power pins to reduce high-frequency noise.
7. Clearly label component orientation and numbering; provide sufficient space for heat dissipation and soldering.

2.2 General Routing Principles

1. Clearance Settings:
   • Determined by insulation, manufacturing process, and component size.
   • High-voltage circuits require extra spacing for safety (e.g., 200V/mm).
2. Trace Angles:
   • Prefer 45° or curved corners over 90° to improve manufacturability and aesthetics.
3. Trace Widths:
   • Power traces wider than signal traces; ground traces wide enough for stable reference.
   • Example: 0.05mm thick copper can carry 1A per 1mm width. High-current traces ≥ 40mil width, spacing ≥ 30mil.
4. Interference and Shielding:
   • Route analog and digital grounds separately; connect at a single point if necessary.
   • High-frequency signals can be “shielded” with surrounding ground traces.
   • Apply large copper pours on top/bottom layers to reduce impedance and suppress EMI.
   • Minimize vias to reduce parasitic capacitance (~10pF per via) and preserve mechanical strength.

3. Multi-Layer PCB Layout and Routing Requirements

1. Group components by power and ground type to simplify inner-layer routing and improve interference resistance.
2. Prioritize signal routing first, then power routing using inner layers to lower impedance and simplify signal paths.
3. Connect pads/vias through inner layers according to network names; unconnected copper is removed during etching.

4. Creating and Setting Up Inner Layers

1. Use PCB design software (e.g., Protel Layer Stack Manager) to add, modify, and manage layers.
2. Set properties: layer name, copper thickness, network connection.
3. Inner layers consist of copper planes for power/ground; separated into regions via vias for network connectivity.
4. Dielectric layers (Core and Prepreg) provide electrical isolation; Core has copper on both sides, Prepreg is insulating material only.
5. Layer creation modes: Layer Pairs, Internal Layer Pairs, or Build-up. Typically, Layer Pairs is used.

4.1 Adding and Modifying Layers

1. Add Signal Layer: Insert between existing layers (e.g., between GND and Power).
2. Add Plane Layer: Insert internal power or ground plane.
3. Move/Remove Layers: Top and bottom layers cannot be deleted; middle layers can be moved or deleted if not yet routed.
4. Set Properties: Adjust copper thickness and network connection.

5. Inner Layer Design

1. Inner layers improve signal isolation and reduce interference.
2. Pads and vias connect to the copper plane if network names match.
3. Power Plane Clearance: Sets safe distance between unconnected pads/vias and copper plane.
4. Power Plane Connect Style: Defines pad-to-plane connection: Direct Connect, Relief Connect (default), or No Connect.
5. Splitting Planes: Divide power/ground planes by voltage or network; define borders, track width, and insulation gaps.

Multi-layer PCBs allow complex routing, improve EMC, and enhance signal integrity. Proper stackup, component placement, routing, inner-layer setup, and plane splitting are crucial for optimal performance. While principles guide design, practical experience and EDA tools ultimately determine the best layout.

To conclude, great PCB design is not luck. It’s the result of structure, precision, and smart choices. From panelization to spacing, from trace routing to software selection, every step impacts performance. By following clear design rules, avoiding common mistakes, and partnering with a trusted manufacturer like Best Technology, you can build boards that perform reliably and scale easily. Don’t hesitate to contact us at sales@bestpcbs.com for any custom PCB board design inquiry or technical questions.