Space constrained applications might require very thin boards containing several layers and a limited copper pour thickness of half an ounce (0.7 mil thickness). In contrast, some high-power designs might require very large traces or planes consuming an entire layer and at thicker ounce pours than standard. High density designs incorporating PCB footprints such as very fine pitch BGAs or high signal count parallel buses might require trace widths as thin as 2.5 mils and special kinds of vias such as laser-drilled micro-vias containing diameters of 6 mils or less. Trace thickness thinner or thicker than 1 ounce (which equates to 1.4 mils)ĭifferential pairs and controlled lengths or trace impedance Via holes with a diameter smaller than 8 mils Trace widths narrower than 5 mils (0.005”) The costs become considerably higher due to tighter PCB tolerances and higher end equipment needed to both manufacture and inspect or test the PCBs: Trace-Related Specifications in PCB FabricationĪs a general rule, the following trace-related specifications begin to drive up bare PCB fabrication costs. If a board has specific design requirements such as speed optimization, noise or coupling mitigation, or high current/voltage, the trace widths and types might be more important than optimizing for manufacturing cost of the bare PCB or overall board size. The application will often drive the trace widths and types in a PCB design and at a certain point, there is usually a balance with regards to PCB fabrication cost, board density/size, and performance. A standard trace width for an ordinary signal (no special requirements) may be in the 7-12 mil range and be as long as a few inches, but there are many things that should be considered when defining the width and length of a trace. Trace widths are often measured in mils, or thousands of an inch. The junction can be the pin of a component, a branch off of a larger trace or plane, or an empty pad or test-point intended for probing.
What exactly is trace width and why is specifying a particular trace width so important? The point of a PCB trace is to connect any kind of electrical signal, whether it be analog, digital, or power, from one junction to another. This article will dive into a variety of applications that demand specific trace layout characteristics and how or when to incorporate them into your PCB design. There are several factors that drive trace width, length, and style during the PCB design process of your next PCB prototype. The Importance of PCB Trace Widths in PCB Design
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