⚫ Overview of PCB trace width
The traces in the PCB are used to connect various components to various connectors. These traces can be identified as continuous paths of copper present on the surface of the circuit board. The trace width is critical because it directly affects the work of the PCB. In addition, increasing the current flowing through the PCB traces will generate a lot of heat. Monitoring the trace width also helps to minimize the heat buildup that normally occurs on the circuit board. The conductor width also determines the trace resistance that directly affects the current.
Many manufacturers choose the available default trace widths, which may not be suitable for high frequency applications. Moreover, depending on the application, the trace width will vary, which will affect the current carrying capacity of the trace. Trace width is considered one of the most important design parameters in PCB design. Determining sufficient trace width to ensure the quality performance of the PCB becomes critical. This also helps to ensure the safe transmission of current without overheating and damaging the circuit board.
⚫ A related video in PCB design
This video show how to edit and adjust one or several tracks at once for a quicker, smoother work flow in the Proteus EDA Software during the PCB layout process.
⚫ PCB current and line width
The calculation of PCB current carrying capacity has always lacked authoritative technical methods and formulas, and experienced CAD engineers can make more accurate judgments based on personal experience. But for CAD novices, it is not a problem.
The current carrying capacity of PCB depends on the following factors: line width, line thickness (copper foil thickness), and allowable temperature rise. We know that the wider the PCB trace, the greater the current carrying capacity. Assuming that under the same conditions, a 10MIL trace can withstand 1A, how much current can a 50MIL trace withstand, is it 5A? The answer is absolutely no. Then we can see the following data from international authorities:
The unit of line width is: Inch (1inch=2.54cm=25.4mm)
Data source: MIL-STD-275 Printed Wiring for Electronic Equipment
⚫ PCB design copper platinum thickness, line width and current relationship
Before understanding the relationship between PCB design copper platinum thickness, line width and current, let us first understand the conversion of PCB copper thickness in ounces, inches and millimeters: "In many data sheets, PCB copper thickness is often used in ounces. As a unit, its conversion relationship with inches and millimeters is as follows:
1 ounce = 0.0014 inches = 0.0356 millimeters (mm)
2 ounces = 0.0028 inches = 0.0712 millimeters (mm)
Recommended Tools:
Weight Conversion
Length Conversion
Ounce is a unit of weight, and the reason why it can be converted to millimeters is because the thickness of the PCB copper coating is ounces/square inch"
The relationship between PCB design copper platinum thickness, line width and current:
You can also use the empirical formula to calculate: 0.15 × line width (W) = A
The above data are all line current carrying values at a temperature of 25℃.
Wire impedance: 0.0005×L/W (line length/line width)
⚫ Establish the relationship between the current carrying capacity of the conductor and the trace width
The criticality of the trace width calculation also depends on the cross-sectional area of the PCB copper foil, the maximum current carrying capacity, and the constant temperature rise. In addition, parameters such as conductive material selection and current-carrying capacity vary according to the conductor type including the inner conductor and the outer conductor. We have defined the maximum current carrying capacity of the inner conductor as half of the outer conductor.
The cross-sectional area of the copper foil is proportional to the trace width. We can also say that the temperature rise and the maximum current carrying capacity depend on the outer conductor and the inner conductor.
⚫ The importance of maximum current carrying capacity
Due to various factors, the maximum current carrying capacity of the copper trace is usually different from the theoretical value. Some factors include component count, pads and vias. In addition, large transient surges can cause traces between pads to burn during the initial power supply or to implement order modifications on the traces.
In order to solve such complex problems, we tend to increase the trace width. However, there may be situations where a smaller trace width is required, so a solder mask can be applied on the trace. Solder masks are often applied to potentially burn the PCB trace area. Solder paste can also be applied to SMT (Surface Mount Technology) procedures. With the help of reflow soldering, the current carrying capacity of the conductor is also increased.
In simple terms, it is best to calculate the current carrying capacity of the PCB trace to determine the precise trace width. However, other external factors such as dust or pollutant contamination are also considered in the actual printed circuit manufacturing or assembly. Excessive pollution caused part of the trace to crack.
⚫ Frequently asked questions
1. How is PCB trace width calculated?
Width[mils] = Area[mils²] / ( Thickness[oz] * 1.378[mils/oz] )
2. How wide should PCB traces be?
3 mils
Each fabricator will have its own minimum trace width that they will build, but 3 mils is a common minimum spacing value. Copper weight also must be factored in here as well. The higher the weight, the larger the minimum spacing is needed by the fabricator to build the board.
3. What is trace thickness in PCB?
The thickness of copper clad on a circuit board is usually given in ounces (oz). It is the weight of copper on one square foot of board. One ounce copper is 1.378mils (~35um) thick. Normal PCB copper thicknesses are 1/4oz, 1/2oz, 1oz, and 2oz.
4. How to measure PCB thickness?
The number of layers your PCB determines the overall thickness of your PCB. Some applications require a thicker PCB while some require a thinner type. SO the thickness has very varying standards. The typical range of thickness for the core and prepreg combined is between 0.008 -0.240 inches.
5. Why is PCB green?
It is due to the solder mask, which protects the copper circuits printed on the fibre glass core to prevent short circuits, soldering errors, etc. The colour of the solder mask gives the board its appearance.
6. What is the thickness of 1 oz of copper on a PCB?
1.4 mils
1 oz copper (~35µm thick or 1.4 mils) — Standard internal layer copper thickness for "standard construction product for 1 oz and 2 oz finished copper weight selections.
7. What is copper pour in PCB?
Copper pour - an area of a PCB layer that is filled with copper. The layer may be the top, bottom or any internal to the PCB stackup and the pour may be used as a ground, reference or to isolate specific components or circuitry from the rest of the elements of the layer.
8. How thick is a 2 layer PCB?
0.2mm to 6.3mm
The thickness can be specified from 0.2mm to 6.3mm in hundredths of a millimeter increments. Yes, we can make 2 layer PCBs as thin as 0.2mm! Some PCB Stack Ups and layer-counts will have higher minimal thicknesses due to additional material needed to manufacture the Stack Up.
9. How to change the trace width in Altium?
To change the track width source while routing, press the 3 key on the keyboard. Press Shift+W to select a different value for the User Width. When you change the track width mode, you move between the values defined in the applicable design rule (min/preferred/max), and User Choice.
10. How to trace a PCB circuit?
Use the free multimeter's probe to touch a single spot on the board. Then using your finger with the foil move it over the components touching the soldered parts. Thus you will cover more area quicker and when you hear the multimeter beeping - you have found your track on the PCB.
11. How do you find the width of a track?
Width[mils] = Area[mils²] / ( Thickness[oz] * 1.378[mils/oz] )
For IPC-2221 internal layers: k = 0.024, b = 0.44, c = 0.725
For IPC-2221 external layers: k = 0.048, b = 0.44, c = 0.725
Note: k, b, and c are constants resulting from curve fitting to the IPC-2221 curves.
12. How thick is a 4 layer PCB?
We process four layer PCB boards with final thickness of 0.020", 0.031", 0.040", 0.047", 0.062", 0.093" and 0.125". You may select ½, 1 or 2 ounce inner layer copper foil for your printed circuit board. While our 4, 6, and 8 layer PCBs are limited to 16X22 inches the 10 layer maximum size is 14x20.
13. How to calculate PCB trace resistance?
This calculator calculates the trace resistance of a PCB. The resistivity is calculated as 1.74 x 10-8 (Ω⋅m), the resistivity of copper at 20°Celsius. Usually, a PCB is manufactured with a predetermined copper thickness, such as 0.5oz/ft*ft, 1oz/ft*ft, and 2oz/ft*ft.
14. What is the standard PCB thickness?
Today, boards are made to be larger and smaller than this standard, but the standard probably remains the most common thickness for designs. Today, it is more accurate to say there is a range of common or standard PCB thicknesses. These include 0.031in (0.78mm ), 0.062in (1.57mm) and 0.093in (2.36mm).
15. What is temperature rise in PCB?
Higher current flow increases the temperature of the copper traces therefore, temperature rise is a design parameter for how much added heat you would like to design for. Based on this limit the formula chooses a width to stay within it. Ten degrees is a safe rule of thumb for most applications.
16. How big is a PCB panel?
18 × 24 in
The typical PCB manufacturer runs a standard panel size of his choice, very commonly 18 × 24 in. They will want a 1/2-in. perimeter clearance for handling the panels when processing double-sided boards and a 1-in. clearance when processing multilayer PCBs.
17. What is the PCB material?
The main elements of the PCB are dielectric substrate (rigid or flexible) with copper conductors on it, vias and holes both plated and non plated. As the dielectric substrate the glass-epoxy laminates or composite materials are used.
18. Can a PCB be repaired?
PCBs with simple or slight damages can be easily repaired. Depending on the PCBs functionality issues, does repairing the PCB solve the problem or not. For instance, short-circuiting, or open circuit. Some electronics' PCBs are restricted for repair.
19. How much heat can a PCB take?
Any electronic device that transfers more than 130 degrees celsius of heat within its circuits will require materials for circuit boards that can withstand higher Tg levels. Going by this theory, high-temperature PCBs are any PCB that contain materials that can withstand 170 degrees celsius of transferred heat.
20. How many types of PCB are there?
There are single layer board, double sides board and multi-layer board if you categorize by the application. 2 layers PCB and 4 layers are quite popular for it is easy to design and cheaper for prototype. ( Like in Seeed Fusion PCB service, you can just have 10 pieces for $4.9 2 layers PCB.