What are the effects of copper thickness on a PCB?

In PCB manufacturing and design, copper thickness plays a crucial role. The choice of different copper thicknesses directly affects a PCB’s electrical performance, thermal stability, mechanical strength, and manufacturing cost. Let’s take a closer look at these aspects.

1. Unit of Copper Thickness

Copper thickness is typically measured in “oz” (ounces). In the PCB industry, "oz" is a critical technical parameter used to indicate the thickness of the copper foil. Specifically, 1 oz represents the thickness of copper uniformly distributed over an area of one square foot.

The conversion formula is:

Thickness (μm) = (Weight in ounces × 28.35g) / (Density 8.96g/cm³ × Area 929.03cm²) × 10⁴ From this calculation, we get:

1 oz ≈ 34.8 μm ≈ 1.37 mil

2. Impact of Copper Thickness on PCBs

① Current Carrying Capacity

The most direct impact of copper thickness is its ability to carry current. Thicker copper provides a larger conductive area, allowing it to handle higher current loads. This is especially important in high-power circuits such as power supply boards, automotive electronics, or high-power LED drivers.

② Trace Width and Layout Space

Copper thickness affects the minimum trace width. In high-density PCB designs, layout space is critical. Thicker copper may require wider traces to maintain manufacturing precision, which can limit routing density. Therefore, in high-density or high-speed digital circuits, thinner copper foils—such as 0.5 oz—are often used to ensure clean routing and signal integrity.

③ Thermal Management

Copper has excellent thermal conductivity. Increasing the copper thickness enhances the PCB's heat dissipation capability, which is especially important in circuits with dense power components. Thicker copper helps dissipate heat quickly from components, reducing the risk of localized overheating and improving system stability and lifespan.

④ Mechanical Strength

Copper thickness also affects the mechanical strength and durability of the PCB. In multilayer boards, thicker copper layers can increase the overall rigidity of the board and improve resistance to bending and thermal shock. This is crucial in high-reliability applications such as aerospace and military equipment.

⑤ Cost and Manufacturing Complexity

Thicker copper also results in higher manufacturing costs and complexity. Thick copper PCBs require more stringent processes for etching, lamination, and drilling, and they tend to have lower yield rates. Therefore, when designing a PCB, it's important to balance performance requirements with cost control to choose the most suitable copper thickness.