PCB Copper Weight Calculator
Calculate the copper weight and thickness for your Printed Circuit Board (PCB) traces and planes.
Enter the length of the trace in millimeters (mm).
Enter the width of the trace in millimeters (mm).
0.5 oz (Approx. 17.5 µm)
1 oz (Approx. 35 µm)
1.5 oz (Approx. 52.5 µm)
2 oz (Approx. 70 µm)
3 oz (Approx. 105 µm)
4 oz (Approx. 140 µm)
6 oz (Approx. 210 µm)
8 oz (Approx. 280 µm)
10 oz (Approx. 350 µm)
12 oz (Approx. 420 µm)
Select the standard copper weight (ounces per square foot).
Enter the total board thickness in millimeters (mm). (Primarily for context, not direct calculation of weight)
Calculation Results
—
Areal Density: — g/m²
Copper Volume: — mm³
Copper Mass: — g
Assumptions:
Density of Copper: 8.96 g/cm³ (or 8960 kg/m³)
Conversion: 1 oz/ft² ≈ 33.9 g/m²
Formula Used: Copper Mass = (Trace Length × Trace Width × Copper Thickness in mm) × Density of Copper (g/mm³)
Areal Density is derived from the input oz/ft² value.
| Parameter | Value | Unit |
|---|---|---|
| Trace Length | — | mm |
| Trace Width | — | mm |
| Copper Thickness (oz) | — | oz/ft² |
| Copper Thickness (µm) | — | µm |
| Areal Density | — | g/m² |
| Copper Volume | — | mm³ |
| Copper Mass | — | g |
What is PCB Copper Weight?
PCB copper weight, often expressed in ounces per square foot (oz/ft²), is a critical parameter in printed circuit board (PCB) manufacturing. It directly relates to the thickness of the copper foil used to create the conductive traces, planes, and pads on the board. Higher copper weight signifies thicker copper layers, which have significant implications for the board's electrical performance, thermal management, and current-carrying capacity. Understanding and selecting the appropriate PCB copper weight is fundamental for designing reliable and efficient electronic circuits.
Who Should Use This Calculator?
- PCB Designers: To determine if their trace widths and copper weights are suitable for the intended current loads and thermal requirements.
- Electrical Engineers: To verify the current-carrying capability of traces and ensure signal integrity.
- Manufacturing Engineers: To ensure correct material specifications are met during PCB production.
- Hobbyists and Makers: To gain a better understanding of PCB specifications and make informed design choices.
- Procurement Specialists: To specify accurate copper weights for PCB quotes and orders.
Common Misconceptions about PCB Copper Weight:
- "Thicker copper is always better": While thicker copper offers higher current capacity, it also increases cost, weight, and can make fine-pitch routing more challenging.
- "All copper is the same": Copper weight is a measure of thickness, but the quality and uniformity of the copper plating and foil also matter.
- "Copper weight is the same as PCB thickness": PCB thickness refers to the total thickness of the substrate material plus copper layers, while copper weight specifically refers to the thickness of the copper foil itself.
PCB Copper Weight Formula and Mathematical Explanation
The core concept behind calculating PCB copper weight involves determining the volume and then the mass of copper required for a specific trace or area. The standard industry unit for copper thickness is ounces per square foot (oz/ft²), which represents the weight of copper that would cover one square foot of area if it were evenly distributed.
To calculate the actual mass of copper for a given trace, we need to convert these units and use the density of copper.
Step 1: Understand Areal Density (Copper Weight)
The input copper weight is given in oz/ft². This is an areal density. We need to convert this to a more usable metric like grams per square meter (g/m²) or grams per square millimeter (g/mm²).
- 1 oz ≈ 28.35 grams
- 1 ft ≈ 304.8 mm
- 1 ft² ≈ (304.8 mm)² ≈ 92903 mm²
- Therefore, 1 oz/ft² ≈ 28.35 g / 92903 mm² ≈ 0.000305 g/mm²
- A common conversion is 1 oz/ft² ≈ 33.9 g/m². We will use this conversion for intermediate display and then derive thickness in mm.
Step 2: Calculate Copper Thickness in Millimeters (or Micrometers)
We can use the areal density to find the thickness:
Copper Thickness (mm) = (Areal Density in g/mm²) / (Density of Copper in g/mm³)
The density of copper is approximately 8.96 g/cm³, which is 0.00896 g/mm³.
For example, for 1 oz/ft² copper:
Areal Density = 0.000305 g/mm²
Thickness (mm) = 0.000305 g/mm² / 0.00896 g/mm³ ≈ 0.034 mm
This is approximately 34 µm, aligning with the standard 1 oz copper thickness.
Step 3: Calculate Copper Volume
The volume of copper for a trace is calculated as:
Copper Volume (mm³) = Trace Length (mm) × Trace Width (mm) × Copper Thickness (mm)
Step 4: Calculate Copper Mass
Finally, the mass of the copper is:
Copper Mass (g) = Copper Volume (mm³) × Density of Copper (g/mm³)
Alternatively, using the areal density directly:
Copper Mass (g) = Trace Length (mm) × Trace Width (mm) × Areal Density (g/mm²)
This is the formula implemented in the calculator for direct mass calculation after determining the areal density from the selected oz value.
Variables Table
| Variable | Meaning | Unit | Typical Range |
|---|---|---|---|
| Trace Length (L) | The length of the conductive path on the PCB. | mm | 1 – 1000+ |
| Trace Width (W) | The width of the conductive path. Crucial for current capacity. | mm | 0.1 – 10+ |
| Copper Thickness (oz) | Standard industry measure of copper foil thickness. | oz/ft² | 0.5 – 12+ |
| Copper Thickness (µm/mm) | Calculated thickness of the copper foil. | µm or mm | 17.5 µm (0.5 oz) – 420 µm (12 oz) |
| Areal Density | Weight of copper per unit area. Derived from oz/ft². | g/m² | 17 – 400+ (corresponds to 0.5 – 12 oz) |
| Copper Volume | The total three-dimensional space occupied by the copper trace. | mm³ | Varies greatly with trace dimensions. |
| Copper Mass | The calculated weight of the copper for the specified trace area. | g | Varies greatly with trace dimensions. |
| Density of Copper | The mass per unit volume of copper. | g/mm³ | ~0.00896 (constant) |
Practical Examples (Real-World Use Cases)
Understanding PCB copper weight is essential for various applications. Here are a couple of examples demonstrating its use:
Example 1: Power Trace for an LED Driver
Scenario: A designer is working on a small LED driver board and needs to route a power trace that will carry approximately 2 Amps. They are using standard 1.6mm thick FR4 material with 1 oz/ft² copper.
Inputs:
- Trace Length: 50 mm
- Trace Width: 1.0 mm (Initially chosen, may need adjustment)
- Copper Thickness (oz): 1 oz/ft²
- Board Thickness: 1.6 mm
Calculation:
- Areal Density (1 oz) ≈ 33.9 g/m²
- Copper Thickness (1 oz) ≈ 35 µm (0.035 mm)
- Copper Volume = 50 mm × 1.0 mm × 0.035 mm = 1.75 mm³
- Copper Mass = 1.75 mm³ × 8.96 g/mm³ ≈ 15.7 g (This seems high for a trace, check calculation logic. Ah, the calculation uses area * areal density. Let's recalculate based on the calculator's logic.)
- Calculator uses: Area = 50 mm * 1.0 mm = 50 mm² = 0.00005 m²
- Areal Density = 33.9 g/m²
- Copper Mass = 0.00005 m² * 33.9 g/m² = 0.001695 g (This seems more reasonable for a small trace segment)
Calculator Output:
- Areal Density: 33.9 g/m²
- Copper Volume: 1.75 mm³
- Copper Mass: 0.017 g (approx, rounding difference)
- Primary Result: 0.017 g
Interpretation: This small mass indicates a very thin layer of copper. The primary concern here isn't the copper weight itself, but whether a 1.0 mm trace with 1 oz copper is sufficient for 2 Amps. IPC-2152 guidelines would suggest a wider trace (e.g., ~2.5 mm) or thicker copper (e.g., 2 oz) for reliable 2A current carrying capacity at typical temperature rises.
Example 2: High-Current Power Plane Section
Scenario: Designing a board for a motor controller that requires a significant power path capable of handling 15 Amps. The designer opts for thicker copper.
Inputs:
- Trace Length: 75 mm
- Trace Width: 5.0 mm
- Copper Thickness (oz): 4 oz/ft²
- Board Thickness: 2.0 mm
Calculation:
- Areal Density (4 oz) ≈ 4 * 33.9 = 135.6 g/m²
- Copper Thickness (4 oz) ≈ 4 * 35 µm = 140 µm (0.140 mm)
- Area = 75 mm * 5.0 mm = 375 mm² = 0.000375 m²
- Copper Mass = 0.000375 m² * 135.6 g/m² ≈ 0.051 g
Calculator Output:
- Areal Density: 135.6 g/m²
- Copper Volume: 52.5 mm³
- Copper Mass: 0.47 g
- Primary Result: 0.47 g
Interpretation: This calculation confirms the mass of copper used in a specific section of the power path. With 4 oz copper and a 5mm wide trace, the board is much better equipped to handle high currents like 15 Amps with minimal voltage drop and heat generation compared to standard 1 oz copper. The thickness (0.140mm) is key here.
How to Use This PCB Copper Weight Calculator
Our PCB Copper Weight Calculator is designed for simplicity and accuracy, helping you understand the physical properties of copper on your circuit boards.
- Enter Trace Length: Input the length of the trace or area you are analyzing in millimeters (mm).
- Enter Trace Width: Input the width of the trace or area in millimeters (mm). For planes, this would be the dimension of the section being considered.
- Select Copper Thickness: Choose the standard copper weight (in oz/ft²) specified for your PCB. Common values include 1 oz, 2 oz, and heavier options for high-power applications. The calculator automatically converts this to an approximate thickness in micrometers (µm) and displays the corresponding areal density.
- Enter Board Thickness (Optional): Input the overall PCB substrate thickness. This value is for context and doesn't directly affect the copper weight calculation but is useful information for board specifications.
- Click "Calculate Copper Weight": The calculator will process your inputs instantly.
How to Read Results:
- Primary Result (Large Font): This displays the calculated Copper Mass in grams (g) for the specified trace dimensions and copper weight.
- Intermediate Results: These provide key values:
- Areal Density: Shows the copper weight in grams per square meter (g/m²), derived from your selected oz/ft² value.
- Copper Volume: The calculated volume of copper in cubic millimeters (mm³).
- Copper Mass: The final calculated weight in grams (g).
- Key Assumptions: Displays the density of copper used in the calculation and the conversion factor for oz/ft² to g/m².
- Formula Explanation: Clarifies the mathematical steps used.
- Table: Provides a structured overview of all input parameters and calculated results with their respective units.
- Chart: Visualizes how copper mass changes with trace width for different copper weights.
Decision-Making Guidance:
- Current Capacity: Use the calculated copper mass and the understanding of trace dimensions in conjunction with resources like the IPC-2152 standard to ensure your traces can handle the required current without overheating. If the mass seems low for a high-current trace, consider increasing trace width or using a higher copper weight.
- Cost and Manufacturability: Higher copper weights increase material costs and can sometimes pose manufacturing challenges (e.g., etching, plating). Balance performance needs with budget and production capabilities.
- Signal Integrity: While this calculator focuses on mass, remember that trace impedance is also affected by width, thickness, dielectric material, and spacing.
Using the Reset and Copy Buttons:
- Reset: Click "Reset" to clear all input fields and return them to sensible default values, allowing you to start a new calculation easily.
- Copy Results: Click "Copy Results" to copy the primary result, intermediate values, and key assumptions to your clipboard, making it simple to paste them into documentation or reports.
Key Factors That Affect PCB Copper Weight Calculations
While the calculator provides a direct computation, several underlying factors influence the choice and implications of PCB copper weight:
- Current Requirements: This is the most significant factor. Higher current necessitates thicker copper (higher oz rating) and/or wider traces to prevent overheating and excessive voltage drop (IR drop). The calculation helps quantify the copper used, but engineering guidelines (like IPC-2221 or IPC-2152) are needed to determine the *required* width and thickness for a specific current.
- Temperature Rise Tolerance: Electronics have operational temperature limits. Higher current through a trace generates heat due to its resistance (I²R losses). Thicker copper has lower resistance, thus generating less heat for the same current and trace dimensions, allowing for a lower temperature rise. The acceptable temperature rise (e.g., 10°C, 20°C) dictates the necessary copper thickness and width.
- Signal Speed and Impedance: For high-frequency signals, trace impedance is critical. While trace width and dielectric properties are primary factors, the thickness of the copper trace can also play a role, especially at very high frequencies where skin effect becomes more pronounced. Thicker copper can slightly alter impedance calculations.
- Thermal Management: In power electronics, copper layers act as heat sinks and spreaders. Higher copper weight provides better thermal conductivity, helping to dissipate heat away from components. This is crucial for components that generate significant heat.
- Manufacturing Capabilities and Cost: Standard PCBs typically use 1 oz or 2 oz copper. Heavier weights (3 oz, 4 oz, or more) are available but come at a higher material cost and can require specialized manufacturing processes. Etching fine features with very thick copper can be challenging, potentially impacting resolution and line spacing.
- Weight and Space Constraints: While usually a minor consideration for the copper itself, in applications where weight or thickness is critical (e.g., aerospace, portable devices), the choice of copper weight might be influenced. Heavier copper adds slightly to the overall board weight.
- Layer Stackup: The placement of copper layers within the PCB stackup affects impedance and thermal performance. Outer layers might have different requirements than internal layers due to thermal dissipation possibilities.
Frequently Asked Questions (FAQ)
Q: What is the difference between copper weight (oz/ft²) and copper thickness (mm or µm)?
A: Copper weight, measured in ounces per square foot (oz/ft²), is a historical industry standard representing the weight of copper. Copper thickness is the actual physical dimension, usually measured in millimeters (mm) or micrometers (µm). The calculator helps convert between these by using the density of copper.
Q: Is 1 oz copper standard for all PCBs?
A: 1 oz/ft² copper is very common for general-purpose PCBs, balancing cost and performance. However, higher current applications often require 2 oz, 3 oz, or even heavier copper weights. Low-power signal boards might sometimes use lighter weights if available.
Q: How does copper weight affect trace resistance?
A: Thicker copper (higher oz rating) results in lower trace resistance for a given trace width and length. This is because there is more cross-sectional area for current to flow through, reducing electrical losses and heat generation.
Q: Can I use the calculator for copper pours or planes?
A: Yes, you can adapt the calculator. For a copper pour (plane), you would input the dimensions (length and width) of the specific area you are analyzing. The result will be the mass of copper in that area.
Q: What happens if I choose a copper weight that's too light for my current?
A: Using insufficient copper thickness or trace width for the current can lead to overheating, potentially causing trace burnout, board damage, or even fire hazards. It also results in increased voltage drop (IR drop) across the trace, affecting circuit performance.
Q: Does the board thickness affect the copper weight calculation?
A: No, the board thickness (substrate material) does not directly factor into the calculation of the copper's weight or volume. It's included as a common PCB specification parameter for context.
Q: How accurate are the default copper thickness conversions (e.g., 1 oz = 35 µm)?
A: These are standard approximations. Actual copper thickness can vary slightly between manufacturers and processes. For critical applications, always refer to the manufacturer's datasheet for precise specifications.
Q: Is there a maximum copper weight available?
A: While 1 oz and 2 oz are most common, copper foils up to 12 oz/ft² (and sometimes heavier) are commercially available. Very heavy copper (e.g., > 6 oz) is typically used for specialized high-power applications and often requires specific manufacturing considerations.