Nov 20, 2018|Blog

What is a Trace Width?

Printed circuit boards have traces that electrically connect components to various connectors. They are the continuous paths of copper you see on a PCB. The size of the traces is crucial to the PCB working correctly. Because there is electricity that runs through the copper traces, it produces an immense amount of heat.  Controlling the width of the trace helps reduce heat buildup on your board. The wider the trace, the smaller the amount of resistance that the electricity will encounter.

When developing a PCB, you may notice that there is a default trace width available. However, that default trace width is not always the best for your board. One of the main reasons why you would use a different trace width is because of the current carrying capacity.

Determining the right trace width isn’t always easy. There are many factors to consider, including the following:

  • The thickness of the copper layer
  • If the track is on the bottom or top layer
  • The length of the track
  • If the trace is on the inner layer, which heat cannot easily escape

Thankfully, there are tools available to determine the trace width. Using a trace width calculator can help you get a good idea as to what you need. If you have the room on your board, and as long as you meet your PCB manufacturer requirements, going for larger traces will help prevent broken connections on your board.

What is a Current Table?

A current table is essential to understanding the relationship between the PCB trace width and the current carrying capacity. This relationship enables you to determine the trace width needed for your PCB.

The current carrying capacity is the maximum current that can run through the trace without exceeding the top temperature rating.

Recommended Trace Width for 1oz Copper PCB

IPC Recommended Track Width For 1 oz cooper PCB and 10˚C Temperature Rise

Current/ATrack Width(mil)Track Width(mm)
1100.25
2300.76
3501.27
4802.03
51102.79
61503.81
71804.57
82205.59
82606.60
103007..62

Relationship Trace Width and Current Carrying Capacity

There is a direct relationship between the trace width and the current carrying capacity of your board. If there is a cross-sectional area of trace and temperature rise, that will determine your current carrying capacity. The cross-sectional area of trace is directly relational to the copper thickness and trace width.

With that said, this isn’t the only factor that determines the current carrying capacity. There is not one simple calculation to determine the capacity. Many other factors help define the carrying capacity.

Factors That Determine Maximum Current Carrying Capacity

Many factors determine the maximum current carrying capacity in addition to the temperature rise and cross-sectional area of the trace. You also have to consider elements like the number of pads, vias, and components within the PCB.

If you have multiple pads distributed on your board, the capacity of the tinning trace will be much higher than ordinary traces. Without taking this factor into account, you may end up using too much solder, which will lead to a significant transient surge or even the trace burning down entirely.

Other factors include whether you are dealing with any turning traces. The acute angle in the trace could negatively affect the smoothness of the transfer. Outside elements like dust or contaminant pollution need to be considered because pollution can cause partial trace breakage. Also, slim current carrying margins could create issues for your board.

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