Printed circuit boards are integral in today’s technology. And more designs keep making their way to the spotlight. However, there are several factors to consider before achieving the perfect design, one of which is the PCB’s current trace width.
Also, you must consider multiple factors before setting the appropriate width for your PCB’s current trace. But you may find this aspect of PCB designs tricky. Thankfully, we’re here to make it less difficult.
Are you ready? Let’s explore!
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
|
Current/A |
Track Width (mm) |
Track Width (mil) |
|
10 |
7.62 |
300 |
|
9 |
6.60 |
260 |
|
8 |
220 |
5.59 |
|
7 |
180 |
4.57 |
|
6 |
150 |
3.81 |
|
5 |
110 |
2.79 |
|
4 |
80 |
2.03 |
|
3 |
50 |
1.27 |
|
2 |
30 |
0.78 |
|
1 |
10 |
0.25 |
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.
IMAX = (k x TRISEb) x AC
The values also translate to:
- [mils] IMAX= 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 * (TTEMP – 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]TTEMP = Trace temperature
Power Dissipation Calculation
You can calculate your trace’s power dissipation using the following formula:
PLOSS = R * 12
The values in the formula represent:
- PLOSS = 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:
TTEMP = TRISE + TAMB
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.
VDROP = I * R
- VDROP = 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 overall board temperature.
However, using the appropriate current trace width will help counter unwanted overheating issues and enhance your circuit board designs. Also, you can use a trace width calculator to get the best values for your application.
Do you have more questions? Don’t hesitate to send us a message; we’ll be happy to help.