I. Course Objectives

1.1 Knowledge Objectives

Master the core principles of PCB design for high currents in the hundreds of amperes, including the thermal effects of current, wire resistance calculations, and thermal management techniques. Understand the mechanisms by which different materials and layouts affect current-carrying capacity, and become familiar with the professional standards for industrial-grade high-current designs.

1.2 Skill Objectives

Capable of independently completing PCB designs for currents exceeding 100A, with the ability to reasonably select copper thickness, trace width, and thermal management solutions. Proficient in the implementation essentials of alternative solutions such as terminal blocks and busbars, and equipped with the capability to address practical challenges in high-current design.

II. Core Theory: The Three Key Factors Determining the Current-Carrying Capacity of PCBs

2.1 Principle of the Thermal Effect of Resistance

The current-carrying capacity of PCB traces is fundamentally limited by resistive heating and the resulting temperature rise. According to the formula P = I²R, the heat generated when current flows through a conductor is proportional to the square of the current. When the heat generation exceeds the heat dissipation capability, the temperature rise can lead to failures such as copper foil delamination and carbonization of the board material.

2.2 Key Parameters Affecting Current-Carrying Capacity

Copper foil thickness is expressed in ounces (OZ), where 1 OZ equals 35 μm. An increase in thickness directly reduces resistance and enhances current-carrying capacity.

Conductor width: Increasing the width can enlarge the cross-sectional area, but the current-carrying capacity does not increase linearly with the width.

Permissible Temperature Rise: The safe temperature rise for conventional FR-4 boards is typically limited to 10–30℃.

Table: Reference Current-Carrying Capacity for Different Copper Thicknesses and Line Widths (10℃ Temperature Rise)

III. Four Major Solutions for Achieving a 100A Current Carrying Capacity

3.1 Scheme 1: Optimize PCB Trace Design

Design highlights:

The “Short and Thick” Principle: High-current paths should be as short and straight as possible, avoiding unnecessary bends.

Increase copper thickness: We recommend using copper boards with a thickness of 4 OZ or higher to significantly reduce resistance.

Increased trace width: A current of 100A requires a trace width of at least 15mm (with 4-oz copper thickness).

Multi-layer wiring: Utilize double-sided or even multi-layer routing simultaneously, and connect the layers via a sufficient number of vias (the number of vias must be calculated appropriately).

Thermal enhancement measures:

Solder mask window: Open a window in the routing area, apply solder mask, and deposit a thick layer of solder to enhance heat dissipation through the solder.

Additional heat sinks: Install heat sinks on critical power paths.

Metal substrates: In extreme cases, aluminum or copper substrates can be used.

3.2 Scheme 2: Terminal Connection Method

When PCB traces are unable to meet the requirements, a terminal block transition solution can be adopted.

Implementation steps:

PCB or enclosure-mounted 100A-rated terminal posts (surface-mount nuts, PCB terminals, etc.)

Connect large-gauge wires using copper lug terminals.

The current is primarily transmitted via external wires, reducing the load on the PCB.

Advantages: Avoids localized overheating of the PCB, offers controllable costs, and is suitable for medium-scale mass production.

3.3 Scheme Three: Customized Copper Busbar Integration

Industrial-grade solution suitable for applications involving continuous high currents.

Design considerations:

The custom copper busbar is directly mounted above the PCB and connected via soldering or screws.

The copper busbar cross-section can be customized according to current requirements (significantly larger than the PCB trace cross-section).

Widely used in industrial applications such as transformers and server cabinets.

Advantages: Extremely high current-carrying capacity, high reliability, and excellent thermal performance.

3.4 Scheme Four: Special PCB Process

High-end solutions, such as Infineon’s three-layer copper-plated design:

Top and Bottom Layers: Conventional Signal Routing

Intermediate layer: 1.5mm-thick pure copper layer, specifically designed for power distribution.

Capable of delivering over 100A performance in a compact size.

Important note: This type of specialized process has limited processing resources domestically, so it’s necessary to confirm supply chain capabilities in advance.

IV. Real-World Design Process and Checklist

4.1 High-Current PCB Design Process

Requirement Analysis: Clearly define the continuous current, peak current, and operating ambient temperature.

Solution Selection: Choose the appropriate solution based on cost, space, and supply chain considerations.

Parameter Calculation: Calculate the minimum line width and copper thickness requirements, and allow a margin of 30-50%.

Layout Planning: Prioritize arranging high-current paths and keep them as short and straight as possible.

Thermal Design: Integrated heat sinks, ventilation holes, and other thermal management measures.

Prototype testing: Measure temperature rise and voltage drop under actual load conditions.

4.2 Design Checklist

[ ] Has the current path been minimized?

[ ] Does the linewidth meet the 100A requirement (including a safety margin)?

[ ] Is the copper thickness sufficient (recommended: 4 oz or higher)?

[ ] Are the cooling measures adequate (e.g., opening windows, heat sinks)?

[ ] Are the number and size of vias sufficient (e.g., for multilayer wiring)?

[ ] Whether there are sharp bends, to avoid concentration of current density.

V. Key Points for Customer Communication

5.1 Proposal Selection Recommendations

Recommend suitable solutions based on different application scenarios:

5.2 Frequently Asked Questions and Answers

Q: Why is it necessary to leave a current margin of 30-50%?

Answer: Prevents transient overcurrent, material aging, manufacturing errors, and performance degradation in high-temperature environments.

Q: What are the key considerations for via design when using double-sided wiring?

Answer: The number of vias should be sufficient (not a single via), evenly distributed, with an appropriate aperture size, and free from bottleneck effects.

Q: How do we evaluate whether a design solution meets the requirements?

Answer: The actual operating temperature rise can be measured using a thermal imager to verify whether it is within the safe range.

VI. Training Arrangements and Assessment

6.1 Teaching Plan

Theoretical Instruction: 4 class hours (Principles of High-Current Design, Comparison of Design Schemes)

Practical Exercises: 6 class hours (PCB design, thermal simulation, sample testing)

Case Study: 2 class periods (in-depth analysis of successful and unsuccessful cases)

Assessment: 2 class periods (theory + design practice)

6.2 Training Effectiveness Evaluation

Written Examination: Proficiency in the Principles of High-Current Design (30%)

Design Practice: Complete the PCB design for a 100A current (50%)

Proposal Presentation: Explain the design concept and advantages to the client (20%)

Conclusion: Hundred-ampere-level PCB design is a key technology in high-end hardware development. Through systematic training and hands-on practice, Leakin Technology ensures that engineers master the full range of skills—from theory to practice—providing customers with highly reliable, high-performance solutions for high-current applications.

This document is copyrighted by Shenzhen Leakin Technology Co., Ltd. and may not be distributed externally without permission.

Revision date: September 29, 2018

Target audience: Internal hardware engineers, customer technical support engineers