The Importance of PCB Assy Trace Routing in Signal Integrity

PCB Assy Trace Routing in Signal Integrity

Signal integrity is a key factor for successful PCBs. Whether operating at a low or high frequency, digital or analog, signal integrity issues must be addressed as they can result in unwanted electronic noise, electromagnetic interference (EMI), data corruption and more. While these issues are less noticeable at lower frequencies, they become increasingly important as the operating frequency increases.

Signal integrity issues are often a result of impedance, with inductance and capacitance influencing the shape and amplitude of a signal as it travels along a trace. These factors increase as the operating frequency increases, which is why it’s essential to pay attention to trace widths, lengths and routing in order to ensure that the signals are delivered correctly.

PCBs are typically made of copper, with traces providing the paths for the flow of electric current between components. A photosensitive material is applied to the board, which is then exposed to UV light to define the circuit pattern and etched away leaving behind the copper areas that form the traces. Choosing the right trace widths and arranging them in consistent ways helps minimize signal interference, crosstalk and electromagnetic interference.

Differential pair routing is also vital to ensure that high-speed signals travel without affecting one another. The traces should be parallel and closely spaced, with each trace carrying the opposite phase of the same signal. This reduces common-mode noise and improves noise immunity.

The Importance of PCB Assy Trace Routing in Signal Integrity

Trace length is also a crucial consideration, with longer traces causing signal degradation through delay and attenuation. This can be minimized by matching the length of adjacent traces and minimizing skew between the signals, as well as routing them around ICs, connectors and other circuits that may cause additional delays.

The pcb assy power and ground planes are also vital for maintaining good signal integrity, as they provide low-impedance return paths for signals and decrease electromagnetic interference between devices. Ensure that the traces that connect to these planes are routed on separate layers so they don’t get in the way of other components, and that they run through the appropriate sections of the circuit board.

Impedance control is essential for maintaining signal integrity, especially in high-speed digital designs. This can prevent a variety of problems, including interference, distortion and reflections, which can significantly impact the performance of the circuit. The best way to achieve controlled impedance is to identify the signal’s values and types during schematic design and notate them as net classes so that the PCB manufacturer knows which traces require specific impedance values.

In addition, it’s important to ensure that the traces are routed in a manner that will help them maintain their impedance during manufacturing. This can be achieved by specifying a slightly different width value for the controlled impedance traces in the Gerber files, or simply by indicating that they’re differential pairs in the schematic file. This will help the manufacturer distinguish them from single-ended traces and avoid accidentally routing them as differential pairs. This is the best way to ensure that the circuit’s designed performance will be met during the assembly process.

Leave a Reply

Your email address will not be published. Required fields are marked *