#copperthickness

Introduction

Have you ever faced overheating traces, unexpected voltage drops, or PCB failures in high-current designs? In most cases, the root cause is not the component — it’s incorrect copper thickness. Copper thickness directly determines how much current a PCB can safely carry, how efficiently heat is dissipated, and how reliable the board remains over time. This blog explains how copper thickness impacts high-current PCB performance and safety, why it matters, and how to choose the right thickness for your application. By the end, you’ll clearly understand the relationship between copper thickness, current flow, thermal behavior, and long-term reliability.

What Is Copper Thickness in PCBs?

Copper thickness refers to the thickness of the copper layer on a PCB

Measured in ounces per square foot (oz/ft²) or micrometers

1 oz copper ≈ 35 microns thick

Thicker copper supports higher current flow

Plays a critical role in electrical and thermal performance

Incorrect copper thickness can cause overheating and PCB failure

How Does Copper Thickness Work in High-Current PCBs?

Copper thickness works by reducing electrical resistance and improving heat dissipation. When current flows through a PCB trace, resistance generates heat. Thicker copper increases the trace cross-sectional area, which lowers resistance and allows current to flow more efficiently. This reduces heat buildup and spreads thermal energy more evenly across the board, improving overall reliability and safety in high-current PCB designs.

Key Terms and Components Involved

Copper Weight — Thickness of copper measured in ounces

Trace Width — Width of the copper path carrying current

Current Carrying Capacity — Maximum current a trace can handle

Temperature Rise — Heat increase due to current flow

Voltage Drop — Loss of voltage across copper traces

Thermal Vias — Vias that help transfer heat between layers

Why Copper Thickness Is Critical for High-Current Designs

As current levels increase, even small resistance values can cause significant heat buildup. Insufficient copper thickness may allow a PCB to function initially, but long-term exposure to heat leads to thermal stress, trace degradation, and eventual failure. This makes copper thickness a safety-critical design factor, especially in continuous or high-load applications.

Common Copper Thickness Options and Their Uses

1 oz copper — Low-power and signal-level circuits

2 oz copper — Moderate current and power distribution

3–4 oz copper — High-current industrial and power electronics

6 oz and above — Heavy-duty power and automotive systems

How Copper Thickness Affects Heat Dissipation

Thicker copper acts as an effective thermal conductor, spreading heat over a larger area instead of allowing it to concentrate in one location. This reduces peak temperatures and minimizes thermal hotspots. When combined with thermal vias and proper layout, increased copper thickness significantly improves heat management in high-current PCBs.

Copper Thickness vs Trace Width: What Matters More?

Trace width is easier and cheaper to increase

Copper thickness improves both electrical and thermal performance

Thick copper supports compact PCB layouts

Thin copper requires wider traces for the same current

Space-limited designs benefit more from thicker copper

Real-Life Applications of High-Current PCBs

High-current PCBs are widely used in power electronics, industrial automation, and energy systems. In these applications, copper thickness directly impacts safety, efficiency, and operational life. Proper copper selection ensures stable performance under demanding electrical and thermal conditions.

Common Applications

Power supplies and DC-DC converters

Motor controllers and drives

Electric vehicle battery systems

Industrial automation equipment

Renewable energy inverters

High-power LED lighting

Benefits of Using the Right Copper Thickness

Using the correct copper thickness improves current capacity, lowers voltage drop, reduces operating temperatures, and enhances mechanical durability. These benefits increase product reliability, reduce field failures, and extend the overall lifespan of electronic systems.

Key Benefits Summary

Higher current handling capability

Lower electrical losses

Improved thermal performance

Better long-term reliability

Increased safety margin

Stronger PCB structure

Challenges and Trade-Offs

Despite its advantages, thicker copper introduces manufacturing challenges. These include higher fabrication costs, more complex etching processes, and limitations when using fine-pitch components. Designers must carefully balance these trade-offs against performance and safety requirements.

Common Challenges

Increased manufacturing cost

More difficult PCB fabrication

Reduced flexibility in fine-pitch designs

Limited supplier capability for heavy copper

Higher material usage

How to Choose the Right Copper Thickness

Choosing copper thickness should be based on electrical load, acceptable temperature rise, voltage drop limits, and physical constraints. Calculations, simulation tools, and industry standards help validate the correct choice before manufacturing.

Selection Checklist

Identify maximum current (continuous and peak)

Define allowable temperature rise

Calculate voltage drop

Consider PCB size and layout

Evaluate cooling methods

Match manufacturer capabilities

Common Mistakes to Avoid

Many PCB issues arise from underestimating current requirements or relying solely on trace width. Ignoring thermal effects and future load increases often leads to redesigns and reliability issues.

Frequent Design Mistakes

Assuming 1 oz copper is always sufficient

Ignoring temperature rise calculations

Not planning for future current increase

Relying only on trace width

Skipping thermal analysis

Conclusion

The result of choosing the right copper thickness is a high-current PCB that performs reliably under real-world electrical and thermal stress. A well-designed copper strategy delivers:

Safe and efficient current flow without overheating

Reduced voltage drop for stable electrical performance

Improved heat dissipation and thermal stability

Longer PCB lifespan with fewer field failures

Enhanced safety margins for continuous and peak loads

Let’s design high-current PCBs that are electrically robust, thermally stable, and built for long-term reliability — engineered with the right copper thickness from the start.

Let’s work together to turn your power design requirements into a dependable PCB solution.

Reference

Smarter electronics start with smarter design decisions. Explore practical PCB engineering insights and innovations: www.auckam.com