Heavy Copper PCBs

Heavy Copper PCB Manufacturing & Assembly

Turn your high-power design into reality with San Francisco Circuits - the powerhouse manufacturing/assembly partner behind your heavy copper PCB designs and high-power applications.

We specialize in delivering robust, high-performance heavy copper PCBs fast. Whether your design requires 4 oz or 10 oz copper builds, our network of advanced fabrication partners can meet your toughest electrical and thermal demands.

Engineers choose San Francisco Circuits for our deep technical expertise, fast turnaround times, and proven ability to deliver complex, high-current boards with unmatched reliability. Our heavy copper solutions are ideal for demanding environments, including mission-critical applications in defense, aerospace, and industrial power systems.

From quick-turn prototypes to full-scale production runs, our team ensures your heavy copper boards are built to perform.

Heavy Copper PCB Lead Times

We can turn your heavy copper PCB manufacturing order in as little as 72 hours.

Our Capabilities

Call us at 800.SFC.5143 or get an instant PCB quote.

What are Heavy Copper PCBs?

Heavy copper PCBs are generally defined as printed circuit boards that utilize copper weights of at least 3 oz/ft² per layer, significantly more than standard PCB copper thicknesses that are from 0.5 to 3 oz/ft².

Heavy copper PCBs are primarily used to increase current-carrying capacity and enhance thermal management, which is essential for power electronics and other high-demand applications. By increasing copper mass, the board is able to carry high currents with only minimal increases in trace width compared to using lower copper weights.

These boards, also referred to as thick copper PCBs, can be fabricated with copper weights up to 10 oz/ft².

A four-layer PCB with three layers of one-ounce copper with GETEK dielectrics and one of solid 45-oz Cu base.

Heavy Copper PCB Construction

Heavy copper PCBs are manufactured using four primary methods, each balancing cost, accuracy, and performance.

1. Thin Base, Full Plating

This high-precision but costly method starts with a very thin copper layer. Heavy copper is built up entirely through plating, then the base layer is etched away. Because this approach often requires 20+ hours of plating, it's reserved for high-performance applications where thicker copper in holes improves current capacity and thermal management. Best for fine-line, high-current designs.

2. Mid-Weight Base, Partial Plating

This common method uses a copper layer about half the final desired thickness. Additional copper is plated, then the full thickness is etched. It offers good cost-efficiency, though resolution is lower than the thin-base method. Plated features are more precise than etched ones, and designers must carefully calculate copper buildup in holes.

3. Thick Base, Minimal Plating

In this budget-friendly option, a thick copper base is lightly plated and etched. It’s the least expensive but offers limited trace resolution and poor current handling in holes. Typically used in low-tech applications where performance demands are minimal.

4. Ultra-Thick Copper

Copper thicknesses from 0.020" to 0.040" can be achieved for high-power applications, like Buss Bar replacements. However, extended plating times lead to surface bumps, and imaging through thick photoresist reduces resolution and edge quality. Despite this, the method allows for very robust conductors and high-current paths.

How to Choose the Right Copper Thickness

By choosing heavy copper PCB materials and construction, engineers mitigate excessive trace widths, minimize voltage drop, and improve heat conduction - capabilities beyond those of standard copper PCBs.

1. Current Requirements

   • Calculate the maximum continuous current per trace. Use IPC-2221A or equivalent calculators to relate trace width, copper thickness, and allowable temperature rise (typically <30 °C above ambient).
   • For internal layers, assume ∼50 % current capacity compared to external layers.

2. Trace Geometry and Layout

   • Determine minimum trace width and spacing given heavier copper’s plating tolerances. Thick copper requires larger clearances to compensate for increased etch compensation.
   • Employ trace width calculators that iteratively solve for trace width (W), current capacity (I), and ΔT. If two variables are known, the third is derived.

3. Temperature Rise Tolerance

   • Establish maximum permissible temperature rise based on component reliability and substrate Tg. Dielectric materials generally tolerate up to +100 °C above ambient, though most designs target <30 °C rise for reliability.
   • High-temperature substrates allow for higher ΔT but add cost and process complexity.

4. Substrate Material

   • Evaluate dielectric options (FR-4, polyimide) by their Tg, CTE, and cost. A mismatch between copper and laminate CTE can lead to delamination during thermal cycling.

   Read more details on PCB material selection.

5. Via and Hole Plating

   • Heavy copper PTHs require extended plating times to achieve uniform barrel thickness. Specify via annular ring tolerances accordingly.
   • Thermal vias (heat vias) should be placed strategically under high-power devices to connect to on-board heatsink planes.

   Read more about PCB via types.

6. Mechanical and Environmental Considerations

   • If boards operate under vibration or shock, heavier copper at connectors and PTHs increases mechanical robustness.
   • For extreme environments (military, aerospace), perform thermal cycle testing to verify heavy copper reliability.

7. Cost vs. Performance Trade-offs

   • Heavier copper increases material and plating process costs. Determine if a mixed-weight design (heavy copper only on power layers) can meet performance goals while limiting expense.
   • Consider whether parallel standard copper layers might suffice for moderate current, rather than full heavy copper.