Trace width is an important consideration in every PCB design. This is why it must be calculated for when designing a printed circuit board. There are factors which determine the PCB trace width during the PCB design process. Trace width is usually calculated and determined after considering some factors.
However, to calculate PCB trace width, one needs to understand how trace width works first. This article explains how to calculate trace width.
What is Trace Width?
A PCB trace connects electrical signal from one junction to another. This junction can be a component’s pin, a branch off a plane or a test-point designed for probing. The PCB trace width is crucial when designing a circuit board. PCB designers need to determine an appropriate width for their circuit in order to save it from damage as a result of an increase in temperature.
Traces on a PCB have the capability to handle the greatest current load before any failure. When a higher amount of current passes through a path, heat is usually generated. However, the trace will damage the PCB laminate when the current load passes the maximum limit. This can result in a permanent damage of the circuit board.
Traces are believed to be wires that link several components without any resistance. However, this isn’t a fact as all paths on a circuit feature a particular resistance, which gives a crucial consideration when determining the PCB trace width.
It is important to determine the current carrying capacity and resistance to know the appropriate width to make use of. There are several factors that determine PCB trace width. One of which is the increase of temperature applicable to a circuit board. Temperature increase indicates the trace’s hotness when current passes through it. PCB trace widths are usually measured in thousands of an inch or mils.
What is a PCB Trace Width Calculator?
A PCB trace width calculator helps in determining a PCB conductor’s width or trace. This calculator makes use of programmed formulas. Since trace width is a crucial parameter in a circuit board design, it is important to make accurate calculations. Trace width is crucial for passing currents via PCBs while maintaining trace temperature below a particular input value in order to prevent any form of overheating.
A PCB trace width calculator can help you determine different trace components like voltage drop, trace temperature, power dissipation, maximum current, and resistance. You can determine the trace width according to ampere capacity when using the trace width calculator.
Therefore, you have to determine the design specifications in the calculators like the total length of the path, the greatest current in amperage that passes through the trace, and more. After the specifications have been provided, the PCB trace width calculator will generate a calculated trace width.
Trace width calculator determines the minimum width that will match the specifications you provided. The calculated trace width will enable the flow of current without any damage to the circuit board. In reality, internal layers have more extensive trace width than external layers. This is because the internal layers generate more heat compared to the external layers.
Therefore, it is advisable to integrate the internal traces’ width for the whole circuit board to ensure safety.
How is PCB Trace Width Calculated?
The PCB trace width is usually calculated using a formula. You need to get familiar with some formulas to get started with this process.
Maximum current
To determine the maximum current, you need to use this formula. A= (T x W x 1.378 [mils/oz/ft2]).
Where A is the cross section area, [mils 2] T is the trace thickness, and [oz/ft2] W is the Trace width.
Trace temperature
The trace temperature helps you calculate the trace width. Trace temperature is determined by using this formula T TEMP = T RISE + T AMB. Three parameters help to determine trace temperature. While T TEMP refers to trace temperature, T RISE is the maximum desired temperature rise and T AMB is the ambient temperature
Resistance calculations
Trace resistance is R= ρ * L / A’) * (1 + α * (TTEMP – 25 °C)).
Voltage drop calculation
Voltage drop describes the drop in electrical potential as it passes through a current in a circuit. You can determine voltage drop using this formula V DROP = I * R. I refer to the maximum current while R is the trace resistance.
Power dissipation calculations
When the heat produce by an electrical device causes energy loss, there is power dissipation. You can determine power loss by using this formula P LOSS = R * I2
R Refers to resistance while I is maximum current.
PCB Calculator Trace Width Applications
The PCB calculator trace width is crucial for PCB design process. This calculator can help you determine the traces’ minimum width while passing the required current. Also, the PCB calculator trace width will need your design parameters to determine the required width. Therefore, you will need to provide values for the rise in temperature, trace length, the trace thickness, and current to pass in amperes.
Furthermore, this calculator will offer the necessary results needed for the external trace layers and internal trace layer in the air. Also, these values are applicable to your circuit board design to confirm the functionality of the board.
Also, PCB calculator trace width helps in determining the lowest trace width for power trace and power signal applications. However, the PCB traces transmit calls that make use of small amounts of current. Therefore, you need to consider other PCB parameters to determine the width.
Types of PCB Calculator Trace Width Based on Industry Standards
There are different calculators for determining trace width. All of these calculators function according to industry standards. There are industry standards guiding their calculations. In industrial and commercial applications, the most common standards are the IPC 2152 and IPC 2221.
IPC 2221 PCB Calculator trace width
The IPC 2221 calculator integrates an equation and a single graph to determine the track current. The equation is I=kΔTbAc
In this equation, the value of K is 0.0048 for the visible traces while the value of K for the internal traces is 0.024. ΔT indicates temperature change measured in Celsius. The value of B is 0.44 and the value of C is 0.725. A in this equation indicates the cross-sectional area.
To determine the trace width with an IPC 2221 calculator, you can integrate only a range of values. The current ranges between 0 and 35 amperes, the track width ranges from 0 to 10.16mm, the copper width ranges from 0.5 to 3 oz, and the temperature rise ranges between 10oC and 100oC. The results won’t be accurate if you fail to use these values.
IPC 2152 PCB Calculator trace width
This PCB calculator trace width uses a more recent standard for its calculation. The IPC 2152 calculator is more accurate in calculating the maximum trace current capacity via an improved technical approach. The equation used by this calculator is not as simple as that of the IPC 2221 calculator. The IPC 2152 calculator must integrate a Universal chart to know the unadjusted cross-sectional area.
Therefore, this calculator makes use of various parameters to get a series of modifiers. These parameters include the PCB thermal conductivity, the distance between the copper plane and the passing tracks, and the current’s thickness passing trace.
Guidelines for Calculating PCB Trace Width
Your design specifications and the current that passes via the tracks will determine your PCB trace width. However, there is a rule of thumb to follow for the applications. 10 mm/A is the minimum trace route to apply. This is applicable for a copper thickness of 1.0 oz/ft2.
PCB trace width is more complex to calculate. Therefore, you need to understand some rules when calculating your PCB trace width. The circuit can work on a maximum current, i.e the trace thickness, the ambient temperature, and the unit of the measurement traces. These will determine the width’s input ranges.
When you input these figures into the trace width calculator, you will get some output figures. The figures you get is the trace width. You can view all the input information on the PCB datasheet or on the physical PCB. You shouldn’t have any guesswork in this case. Any given PCB should contain this information.
The calculator won’t allow any calculations to be performed if you fail to input the exact measurements and numbers. You may need to use a magnifying glass to view the input information since circuit boards are usually tiny.
How to Ensure Efficient PCB Trace Width
Determine the standard track width
You should determine or know the size of your standard track you will be using within the design. Your circuit will likely experience shorting if the standard track is too close or too narrow. There can be restrictions on the number of tracks in a particular area if the tracks are far apart. In this case, you may have to integrate additional planes in the circuit boards to be sure the circuit board can be routed.
Determine the circuit pad shapes
Component libraries usually feature libraries for PCB footprints and schematic for various components. However, these depend on the manufacturing process. You need to determine the manufacturing process before starting the design. Therefore, you can easily select the optimum pad sizes and then integrate it on the PCB CAD system.
Evaluate the track size for lines carrying current
PCBs have thin tracks which can carry a limited current. Therefore, you need to consider the trace size for any track that transmits power rails instead of low level signals.
Determine the dimensions of the hole and pad
It is crucial to determine the dimensions of the hole and the pad once you commence the PCB design. In most cases, the pad to hole ratio is 1:8. Sometimes, a pad that is larger than the hole can be used to measure. The PCB manufacturer can give you the required standards for their own process. As the holes and pads’ size decreases, the ratio becomes very crucial.
What to Consider when Deciding PCB Trace Width and Spacing Values
PCB trace widths can impact the performance of a circuit board in several ways. There are factors to consider when deciding PCB trace width value.
Signal integrity and electrical performance
Most digital routing on PCBs already have default value for their trace widths, however, some nets need various sizes. For example, controlled impedance nets require the calculation of their trace widths according to the PCB layer stackup’s consideration.
Sometimes, analog routing may need unique trace widths based on the applications of the circuitry. In some scenarios, you may reduce the default trace width in tight areas. However, you need to ensure it doesn’t extend across the printed circuit board.
A PCB trace is easier to fabricate if the trace is wider. The etching process has a much better effect on long and isolated traces. Therefore, it is advisable to make the traces wider. For instance, a 20 mil trace will offer better tolerance compared to a 3 mil trace. Also, the copper weight determines the trace widths.
Power and grounding routing
Traces used for power and ground routing must be wide enough to conduct higher amounts of current. Traces can get really hot and burn through if they are very thin. Also, power traces on the PCB’s internal layers should be wider to ensure heat dispersal. Power traces routed on the external layers don’t need to be too wide since exposure to air can help to cool off.
Traces integrated in power supply circuitry should be kept short and wide enough to handle the current. Ensure the spacing for traces carrying greater amount of current is more.
Conclusion
A PCB trace calculator can help you determine different trace components like voltage drop, trace temperature, power dissipation, maximum current, and resistance. You can determine the trace width according to ampere capacity when using the trace width calculator. We provided information about PCB trace width calculator and we hope this information helps you in determining your PCB trace width.
