Complete Guide to PCB Trace Width

What is a Current Trace Width?

Copper traces

Every PCB feature traces that link components to multiple connectors electrically. In truth, current traces are lengthy copper paths visible on a circuit board’s surface.

Typically, your trace’s size is directly linked to the PCB’s working efficiency. And since electricity runs through the copper traces, it’ll produce incredible heat that may lead to unwanted overheating problems.

However, controlling your current trace width can reduce the circuit board’s heat buildup. In a nutshell, a wider trace translates to lesser electrical resistance.

Moreover, you may notice a default trace width when designing your PCB. But it’s not always the best choice. The varying current carrying capacity is one of the primary reasons we recommend using a different trace width.

How to Choose a Current Trace Width?

PCB with wide and slim traces

Choosing the appropriate trace width is not a smooth process. You must consider multiple factors to avoid making an incorrect decision. Here are some factors to consider:

• The copper layer’s thickness
• Determine if your trace is on the inner layer (where heat won’t escape easily)
• Examine your track’s length
• Check if the track is on the top or bottom layer

Luckily, you can access some tools to help determine the best current trace width. For instance, you can use a trace width calculator to grasp what your board needs. Alternatively, you can use a current table.

Note: Going for larger traces has its benefits. For starters, it’ll help prevent broken connections. But you can only use them if you have enough board space and it doesn’t cross your manufacturer’s requirements.

IPC Recommended Track Width for 1 Oz Copper PCB and 10˚C Temperature Rise

How to Calculate Trace Width with a PCB Trace Width Calculator

PCB scheme with traces

A trace width calculator can help you determine various trace components, like trace resistance, voltage drop, maximum current, power dissipation, and temperature. Here are some formulas to help you understand your calculator results better.

Maximum Current

You can determine your trace’s maximum current by using the following formula:

A = (T x W x 1.378 [mils/oz/ft²])

Where the values represent the following:

• A = Cross-sectional area.
• [oz/ft2] W = Trace width
• [mils2] T = Trace thickness

After getting results from the previous calculation, you can use the following equation to calculate your maximum current.

I_MAX  = (k x T_RISE^b) x A^C

The values also translate to:

• [mils] I_MAX = Maximum current
• [A] TRISE = Maximum desired temperature rise.
• [°C] k, b, and c = Constants

Trace Resistance Calculation

Start your calculation by converting the cross-section area from [mils²] to [cm²] with the following formula:

A’ = A * 2.54 * 2.54 * 10^-6

Next, measure the trace resistance using: 

R = (p * L/A’) * (1 + a * (^T_TEMP – 25°C))

The values in these formulas represent:

• T = Trace thickness
• [oz/ft²] W = Trace width
• [mils] R = Trace resistance
• p = Resistivity parameter
• L = Trace length
• a = Resistivity temperature coefficient
• [1/°C]^T_TEMP = Trace temperature

Power Dissipation Calculation

You can calculate your trace’s power dissipation using the following formula:

P_LOSS = R * 1²

The values in the formula represent:

• P_LOSS = Power loss
• R = resistance
• I = Maximum current

Trace Temperature

Trace temperature is another crucial factor to determine when calculating trace width. Thankfully, we can determine the values with the following formula:

^T_TEMP = ^T_RISE  + ^T_AMB

The values in this formula translate to:

• TTEMP = Trace temperature
• TRISE = Maximum temperature rise
• TAMB = Ambient temperature

Note: Keep in mind that we calculate the values in Degrees Celsius.

Voltage Drop Calculation

Here’s the formula to help determine voltage drop.

^V_DROP  = I * R

• ^V_DROP  = Voltage drop
• I = Maximum current
• R = Trace resistance

Rounding Up

Traces are current-carrying paths on a printed circuit board. Interestingly, they can connect electronic components to various connectors on PCBs. However, current traces can generate immense heat due to the electricity flowing through them, inadvertently increasing the board temperature.

However, using the appropriate current trace width will help counter unwanted overheating issues and enhance your circuit board designs. You can also use a trace width calculator to get the best values for your application.

Do you have more questions? Don’t hesitate to message us; we’ll be happy to help.