Key Points in Industrial Control Equipment PCB Design
In the field of industrial control, the stable operation of control equipment is paramount. As the core component, the PCB directly determines the device’s performance, reliability, and stability. A well-designed PCB acts as the “heart” of the system, ensuring that all complex electronic components work in harmony to complete critical tasks such as signal transmission and power distribution efficiently. It not only defines the device’s electrical characteristics but also affects heat dissipation, electromagnetic immunity, and structural integrity. From programmable logic controllers (PLCs) in automated production lines, to power monitoring units in smart grids, and precision control systems in medical instruments—PCBs are indispensable, supporting stable operation and driving industrial modernization. Therefore, understanding the key aspects of PCB design for industrial control applications is essential to improving equipment quality, enhancing performance, and advancing control technology.
Preliminary Planning for Industrial Control PCB Design
(1) Define Design Requirements
Before starting PCB design, it is crucial to clarify the functional, performance, and environmental requirements.
Functional positioning:
Each device has distinct priorities. PLCs emphasize logic control and data processing, requiring stable interfaces and memory. Power monitoring systems focus on high-precision analog signal processing and strong anti-interference capabilities.Performance considerations:
High-speed equipment requires attention to signal integrity and routing to avoid reflections and crosstalk. High-power systems need optimized power conversion and thermal design to ensure long-term stability.Environmental factors:
Use high-temperature materials for heat-intensive conditions, apply moisture protection in humid environments, and implement strong shielding and grounding against electromagnetic interference.
Combining these factors helps determine the PCB’s size, layer count, and shape:
Double-layer boards suit simpler circuits, while multilayer boards (6-layer, 8-layer, or more) are used for high-speed or complex designs. Board outlines should fit device structure, balancing spatial and electrical performance.
(2) Choose the Right Design Software
Selecting appropriate design software is key to efficient and precise project execution.
Altium Designer:
A comprehensive solution integrating schematic capture, layout, routing, signal analysis, and 3D modeling. Its interactive routing, real-time rule checking, and 3D collision detection greatly improve design accuracy and manufacturability—ideal for small to medium projects and academic use.Cadence:
Tailored for advanced, high-complexity designs. With the Sigrity simulation suite, it accurately analyzes reflection, crosstalk, and timing issues—suited for high-speed, multilayer applications like communications, servers, and IC packaging. Its HDI capability and power-ground optimization are excellent, though it requires deeper expertise, making it preferable for experienced engineers and large enterprises.
Component Layout Essentials
(1) Functional Zoning
Components should be grouped by function to reduce interference and enhance stability.
Power section: Isolated from signal lines to avoid current fluctuation and noise coupling.
Signal processing section: Kept distant from power zones to preserve signal integrity.
Communication section: Independently arranged to ensure stable, accurate data transmission.
Clear zoning minimizes EMI, simplifies routing, and facilitates debugging and maintenance.
(2) Thermal Optimization
Heat-generating components (e.g., power transistors, regulators) should be placed near heat sinks or ventilation paths to enhance airflow and thermal conduction.
High-power parts go toward the top of the board, leveraging rising heat for dissipation.
Precision and temperature-sensitive components should stay away from heat sources, placed in cooler zones for stability.
Avoid air stagnation areas to maintain even temperature distribution.
(3) Routing Space Optimization
Proper layout improves routing efficiency and signal quality.
Place related components close together—for example, processors and memory—to shorten connections.
In multilayer designs, maintain perpendicular routing between adjacent layers to reduce crosstalk.
Keep high-speed differential pairs equal in length and impedance to prevent phase skew and signal distortion.
By integrating functional zoning, heat management, and space optimization, PCB designers can achieve superior electrical performance and higher manufacturing reliability.
Key Points in Routing Design
(1) Trace Width and Spacing
These directly impact circuit performance and reliability; both current capacity and signal type must be considered.
Current capacity:
Traces that are too narrow overheat or burn. On FR-4 boards, a 1 A current typically requires 0.5–1 mm width to maintain safe temperature rise. High-power circuits (e.g., motor drivers) require even wider traces.High-speed signals:
Wider traces lower impedance and delay. Spacing should be 1.5–2× trace width to reduce crosstalk.Analog signals:
Being noise-sensitive, they should be spaced further from digital lines and isolated by grounded guard traces for purity.
(2) Routing Rules
Proper routing ensures signal integrity and overall stability.
Avoid right-angle turns; use 135° bends or arcs to minimize reflection and distortion.
Reduce via usage; excessive vias add parasitic effects, causing signal loss and timing errors.
Widen power and ground traces; power lines should be 2–3 mm wide, and ground planes should have large copper pours to lower impedance and improve EMI immunity.
(3) Special Signal Routing
High-frequency and differential signals demand strict precision.
High-frequency lines: Shield or isolate them with grounding; use equal-length routing to maintain phase alignment.
Differential pairs: Follow “equal length, equal spacing, equal width” rules, keeping mismatch within ±5 mil. Impedance depends on width, spacing, copper thickness, and dielectric material, and should be verified through simulation.
By carefully controlling trace dimensions, adhering to routing principles, and optimizing high-speed signal paths, industrial control PCBs can achieve higher electrical performance, improved stability, and long-term reliability.
Key Points in Power and Ground Design
1. Power and Ground Layer Planning
In multilayer PCBs, proper planning of power and ground layers is critical for stable operation, noise reduction, and EMI suppression.
Common four-layer PCB stack-ups include:
Signal–Power–Ground–Signal: Provides a stable reference plane for high-speed signals and suppresses radiated noise.
Power–Signal–Signal–Ground: Forms electromagnetic shielding, suitable for high-EMI environments.
Designers should place power and ground layers adjacent to enhance capacitive coupling, reduce PDN impedance, and suppress power noise. Ground planes should remain continuous and unsegmented, with minimal vias. Additional ground vias can maintain electrical connectivity and stable signal return paths.
2. Power Filtering and Decoupling
Filtering and decoupling improve voltage stability and remove power noise.
Decoupling capacitors should be placed close to IC power pins, often using parallel capacitors of different values (e.g., 0.1 μF ceramic + 10 μF electrolytic) to filter high- and low-frequency noise.
Common filter circuits: LC, RC, and π-type:
LC filters: Suppress high- and low-frequency noise, suitable for switch-mode power supply outputs.
RC filters: Used in low-frequency or low-current circuits.
π-type filters: Provide steep attenuation, ideal for high-demand power inputs like processors.
3. Grounding Methods
Ground design affects interference immunity. Selection depends on circuit frequency and type:
Single-point grounding: For low-frequency (<1 MHz) circuits; avoids ground loops. Series connection is simple but may couple noise, parallel connection is independent but uses more wiring.
Multi-point grounding: For high-frequency or digital circuits (>10 MHz); shortens ground paths, reduces inductance, and improves EMI immunity.
Hybrid grounding: Low-frequency analog circuits use single-point grounding; high-frequency digital circuits use multi-point grounding, balancing system stability and interference rejection.
Proper layer planning, filtering/decoupling, and grounding strategies significantly enhance electrical performance and EMC.
Other Design Considerations
1. Vias and Pads
Vias and pads are core structures for PCB connectivity and soldering; their design directly affects signal integrity and solder reliability.
Via sizing: Consider current capacity and signal performance. Power vias should have larger diameters (0.5–1 mm) or multiple parallel vias to distribute current. High-speed signal vias should be smaller (0.2–0.3 mm) to reduce parasitics.
Pad sizing: Match component pins. For SMT, pad is 0.2–0.3 mm larger than the pin; for through-hole, via is 0.2–0.4 mm larger. Shapes (round, square, oval) are chosen for space efficiency and mechanical strength.
Via types: Through-hole (low cost, simple), blind vias (higher density, for HDI), buried vias (maximize space and signal quality but complex and expensive).
High-speed circuits: Back-drilling can remove via stubs to reduce parasitic inductance and reflections; maintain via spacing to prevent crosstalk. Pads should be flat and clean; teardrop pads improve mechanical and electrical reliability.
2. Silkscreen and Marking
Silkscreen and markings provide essential information for assembly, debugging, and maintenance.
Include component ID, type, polarity, and function; markings indicate version, batch, and production date.
Clear silkscreen improves assembly efficiency and reduces errors; font size 0.8–1.5 mm, high contrast with board color.
Use concise, standardized format: e.g., R1, C2, U3; polarity symbols: “+”, “-“, “→”; placed near components without overlapping pads.
3. Design for Manufacturability (DFM)
DFM ensures production efficiency and quality:
Maintain sufficient spacing: SMT ≥ 0.5 mm, through-hole ≥ 1.27 mm to prevent solder defects and facilitate inspection.
PCB edges: ≥ 5 mm reserved for equipment clamping; no traces or components in this area. Positioning holes (Φ1–3 mm) or optical marks improve placement accuracy.
Prefer standard components and sizes, avoid special processes/materials to reduce cost and improve yield.
Design Verification and Optimization
1. Design Rule Check (DRC)
DRC is critical to ensure PCB designs comply with manufacturing and electrical rules. It prevents shorts, opens, insufficient trace width, or spacing violations.
Electrical rules: clearance, shorts/unconnected nets, differential pairs, via size, layer constraints.
Manufacturing rules: minimum trace width, spacing, hole size, annular ring, solder mask openings, silkscreen spacing.
Engineers use DRC reports to locate and correct errors, iterating “check → modify → recheck” until all violations are resolved.
2. Simulation Analysis
Simulation evaluates PCB performance before production:
EMC simulation: Assess radiation and interference immunity. Tools: CST Studio Suite, ANSYS SIwave. Analyze electromagnetic fields to optimize layout, routing, and shielding.
Signal Integrity (SI) simulation: Evaluate high-speed signal transmission, detecting reflection, crosstalk, and delay. Tools: HyperLynx, Cadence Allegro PCB SI. Eye diagrams and timing analysis help optimize impedance and routing.
3. Optimization and Improvement
Based on DRC and simulation results:
Geometric optimization: Increase power trace width, adjust spacing and via size, optimize routing direction.
EMC optimization: Functional zoning, minimize current loops, add shields and filter components.
SI optimization: Impedance matching, control trace length, add termination resistors or shielding to reduce crosstalk.
Optimizations must balance performance, manufacturability, and cost. Re-run DRC and simulation to confirm stability and reliability.
Summary
PCB design for industrial control equipment is a systematic process, spanning preliminary planning, component placement, routing, power and ground planning, manufacturability, and final verification and optimization. Each stage affects the board’s overall performance and reliability.
By defining requirements, optimizing layout and routing, refining power/ground structures, and rigorously applying DRC and simulation, engineers can enhance electrical performance and manufacturing stability, ensuring industrial-grade quality.
Continuous learning, experience accumulation, and cross-functional collaboration are essential. Only through ongoing optimization and innovation can high-quality, reliable PCBs be produced to support safe and efficient industrial control systems.
