Unless you have a photographic memory, you probably don’t have every single design formula memorized. It’s understandable; looking throughout the compendium of knowledge in physics and engineering, there are far too many formulas for any one person to memorize. Thankfully, some folks have created useful calculators that help you save time when designing a new system.
The resistance and impedance of traces in your PCB have major impacts on power distribution and signal integrity throughout your device. Understanding the differences, limitations, and applicability of each calculator is important for preventing design mistakes that can be overlooked, even by experienced designers.
What is the structure of PCB trace?
The signals that a trace conducts are made of electricity, so any material that makes a trace has to be both highly conductive and relatively stable. The most popular material that is used as a trace in a PCB is copper, but it is not the only option. Traces can be made of aluminum and even gold!
How to determine the PCB trace width?
These trace width calculators will prompt you to enter design specifications such as the thickness of copper, the maximum amperage that will pass through the trace, the length of the trace, and the acceptable increase in temperature due to the resistance of the trace dissipating power. After entering these values you will be presented with a calculated trace width. It is important to note that this value is a minimum width required to meet the design criteria inputs.
Now, a PCB trace acts as a resistor and the longer and narrower the trace, the more resistance is added. If we assume some general things like a 1-ounce copper pour and ambient room-temperature during normal operation, we have what we need to calculate both the minimum trace width and expected voltage drop at that width.
What are the applications of PCB trace resistance?
The microstrip is a popular device in microwave radio technology. It was invented because of the physical limitations to the manufacturing of inductors and capacitors at such very high frequencies. A microstrip is made out of printed circuit boards whose dimensions are carefully set to meet required parameters. One of those required parameters is the trace resistance.
From Ohm’s law, we know that resistance is inversely proportional to current. That is, the lower the resistance, the higher the current and vice versa. Current is also proportional to power according to P = VI. Thus, resistance also becomes a factor when calculating power consumption. It is important to determine the resistance of the trace of a microstrip so that the power dissipated by it can be determined.
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