PCB Trace Width

Dated:2018-02-01      Popularity:1224


Ohm's law shows the direct relationship between current and voltage and indicates that the voltage equals the current time resistance through which the current is passing. An important factor of the PCB design is the PCB trace width which needs to meet the current requirements of the circuit and accept increased PCB temperature. 

In addition to the current carrying capacity of copper, the PCB trace width is important to control the impedance of copper traces which directly affect the signal passing through it. Telecommunications and analog circuit designs require great importance in choosing the right PCB trace width to provide the correct impedance (also known as impedance matching).

Many users use the default PCB trace width setting when designing their PCBs, but if the PCB is designed for power applications and the PCB frequency is greater than kilohertz range, the PCB trace width must be modified based on signal and power requirements.

PCB trace width depends on many factors. Some of these factors are the thickness of PCB copper layer, whether the copper layer is on the top or bottom of the PCB, heat dissipation from the PCB, type of cooling available for PCB, track length in the circuit, and thermal coefficients of the material used to insulate in printed circuit board.

The standard practice of copper thickness is measured in ounces/feet2. In fact, an ordinary PCB has 1 oz of copper, a thickness of 35um. Other available thicknesses are 0.5 oz, 1 oz and 2 oz. In digital circuits, a typical 5 mil PCB trace width is widely used. It can withstand nearly 750mA of current, at the expense of increasing 10oC temperature. 

The chart of IPC Standard Number 2152 can be used to determine the best PCB trace width relative to the available copper thickness, as shown in the following figure.

PCB Trace Width


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