Printed circuit boards are integral components of almost every device. From smartphones to electrical display systems, printed circuit boards provide seamless functionality and operational systems for devices.
One of the most important components when designing is the trace width. It is a game-changer because it carries the current without overheating. The wrong width can cause errors in the current carrying capacity.
Today, we will discuss the PCB trace width calculator, understand how it works, and how to use it to calculate the trace width.
What is a PCB Trace Width Calculator?
A PCB Trace width calculator is a necessary design tool that gives an accurate idea of the minimum copper trace width. Copper is essential as a conductor of current in the circuits. To avoid overheating, a proper copper trace width is required for the circuits to operate successfully.
The PCB trace width calculator combines the IPC-2152 standards and provides detailed insights into the overall width. The benefits of the trace width calculators are:
- Safe current flow
- Reduced heat generation
- Lower voltage drop
- Improved circuit reliability
- Longer PCB lifespan
- Better electrical efficiency
- Compliance with industry standards
How a PCB Trace Width Calculator Works
The PCB trace width calculator works straightforwardly with the provided calculations. Here are five essential steps to fully understand its functionality.
Step 1: Required Current Entry
How much current do you want to enter through the PCB? If the current demand is higher, the trade width will be wider. Based on the current requirements, there can be variations.
Step 2: Select Copper Thickness
Copper thickness determines the current-carrying capacity along with the trace width. The usual measurements are in ounces per square foot.
They can be:
- 0.5 oz
- 1 oz
- 2 oz
- 3 oz
- 4 oz
Thick copper typically carries more current with fewer traces.
Step 3: Choose Trace Locations
There are often two locations with their heat dissipation systems.
- Internal layers lie inside and often dissipate less heat, and can overheat.
- The external layers are exposed, offering better heat dissipation.
Trace location decisions are critical for choosing the right location.
Step 4: Set Temperature Rise
What is your acceptable temperature rise? Lower rise requirements mean you should have a higher width.
Typically, the rise can include:
- 10°C
- 20°C
- 30°C
Step 5: Calculate Trace Width
Once you have set all the parameters and are ready to determine the trace width, the calculator helps with the calculation.
However, a few advanced calculators measure extra factors, such as:
- Resistance
- Voltage drop
- Power loss
- Current density
- Thermal performance
Key Inputs in PCB Trace Width Calculation
Trace width depends on several factors. Here is the list of inputs that help provide the insights into the PCB trace width calculation.
Current
Current is the fundamental and most critical factor for the inputs. A higher current can generate higher heat and may overheat the whole system.
For example:
- Signal traces may carry only milliamps.
- Power traces may carry several amperes.
- High-power boards may carry tens or even hundreds of amperes.
Copper Thickness
Copper thickness also impacts the current capacity.
Here is how it varies.
| Copper Weight | Approximate Thickness |
| 0.5 oz | 17 µm |
| 1 oz | 35 µm |
| 2 oz | 70 µm |
| 3 oz | 105 µm |
| 4 oz | 140 µm |
Thick copper carries more current while maintaining the same trace width. In simple words, you can install the thickest copper in a narrow width to handle the same current ratings.
Temperature Rise
Since heat loss increases temperature, a slight rise can be an issue. You should define the acceptable temperature rise for your applications. For example:
- 10°C increase in temperature is acceptable for sensitive electronics
- 20°C for general-purpose designs
- 30°C for high-power applications
Trace Length
As the trace length increases, the resistance increases along with the temperature rise. However, engineers use trace width calculators to measure the current, but you should also check other factors, such as:
- Voltage drop
- Power dissipation
- Signal integrity
PCB Layer
Internal and external layers of the PCB can behave differently. Internal traces can’t dissipate heat as well as external layers due to the insulation layers. Here is more to know:
- Internal traces usually require greater width.
- External traces can often be narrower.
Common PCB Trace Width Design Mistakes
When designing a PCB trace width, you should understand all the factors and select the appropriate width based on the conditions. Here is the list of common mistakes.
Ignoring Temperature Rise
Never ignore the temperature rise. Electrical circuits have resistance that produces heat. If you ignore the allowable heat rise, the overheating of the circuit can damage the whole PCB or its components. Therefore, you should define acceptable temperature rises and design traces based on the current handling capacity without overheating.
Using Uniform Trace Width
Not all circuits have the same current. Different conditions prompt different situations. Using the uniform trace width may be suitable for one circuit but not for the other. It can damage the other circuit components. Therefore, you should calculate the trace width before installation.
Forgetting Copper Thickness
High copper thickness can handle more current compared to low copper thickness. Ignoring copper thickness can lead to incorrect trace width selection and serious issues.
Ignoring Voltage Drop
Even if the current carrying capacity is good and you get current safely, long traces can cause a voltage drop due to resistance. Therefore, you should not ignore the voltage drop.
Underestimating Peak Current
Many circuits experience a sudden surge in current. Your trace width might handle the average currents but fails to provide the essential safety during the peak currents. As a result, the circuit may overheat and damage the other components. Measure peak currents before you design your PCB.
Conclusion
A PCB Trace width is critical when designing a printed circuit board. The calculations give insights into the data and provide real-time identification. You should choose and prefer the trace width according to your circuit requirements. Keeping the width very low or very high can be problematic for your PCB circuits.
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