PCB Trace Resistance-What Is It and How To Use

Abstract

Each and every material in the universe has resistance along side with other parasitic properties. PCB trace resistance is one of the important factors that needs to calculated and analyzed during the design stage. Although copper is the most used material in the printed circuit boards, it comes with different composition and properties. The PCB trace resistance may lead to various design and implementation issues. The issues increase with the increase in the circuit complexity.

 

Content

1.Calculation in PCB Trace resistance

2.Power loss and interference

 3.Design optimization

 

PCB trace resistance

 

1.Calculation in PCB Trace resistance

Calculating the PCB trace resistance is as simple as using the ohms law with the known parameters. Most of the design suits and development environments have integrated PCB trace resistance calculator which can estimate the resistance of the final copper trace on the board by providing the required and manufacturing profiles. And the calculator uses a standard formula to calculate the resistance so the it will be constant universally.

 PCB trace resistance

 

Where L, W and T represent the physical area of the trace i.e., height width and length. Ρ represents the resistivity of the material and α represents the temperature coefficien of the copper. But all of these calculation can only detrmine an close enough approimate value. Physical value after production will vary slightly.

PCB trace resistance

 

2.Power loss and interference

The major issue in the trace resistance is the power loss. Small signal PCB will only have negligible effect on the PCB trace resistance. But, power circuits on the other hand will have significant impact even for a slight variation in resistance. Power loss will eventually lead to temperature rise and reduction in conductivity.

 

In power circuits un compensated PCB trace resistance may act as a fuse in case of a power surge and burn the trace. Leaving with a permanent damage. While in high speed digital boards PCB trace resistance along with parasitic capacitance may create oscillation and cause EM interference to the circuitry. Long PCB tracks may also lead to increase in reissuance.

 

3.Design optimization

The most effective ways to compensate the PCB trace resistance is to compensate the resistance by increasing the trace area. Design tools can be configured to layout traces with sufficient width to avid such issues. And power circuits use addition methods other than a wide PCB trace like solder brides to reduce the power loss and increase the current capacity. While sensitive circuits have compensation sub circuits to get rid of the impact of PCB trace resistance. And High speed circuits have matched lines to cancel out the potential interference that may occur due to oscillation.

PCB trace resistance

Fill out my online form.