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OCTOBER 2025 I DESIGN007 MAGAZINE 53 the external layer conductor may require increas- ing copper thickness from that defined for the inter- nal layer conductor. The circuit board material, num- ber of via holes, and SMT component land patterns within the circuit path can also affect current-car- rying capacity. The factors in Table 2 are a conser- vative guide for estimating conductor width as it relates to copper foil thickness. Note: For greater detail in determining the cur- rent-carrying capacity for printed circuit conduc- tors, refer to IPC-2152. This document is the indus- try standard for defining the appropriate sizes for both internal and external conductors as a function of the current-carrying capacity required, and calcu- lating the finished copper conductor's temperature rise potential. Developing Dedicated Power and Ground Layers If multilayer circuit board construction is needed, the power and ground distribution will be most efficient if placed on one or more subsurface cir- cuit layers. The power/ground may be furnished as wider conductors routed on the subsur- face layer(s), enabling a direct path to the primary voltage management com- ponents mounted onto the outer sur- face through plated vias. Although wide power and ground conductors may be adequate for less demanding applica- tions, dedicating entire layers of the cir- cuit board to accommodate power and ground will significantly benefit product performance. I recommend establishing copper power and ground layers (or planes) before beginning the circuit routing process for the multilayer circuit board. This may be simply furnishing a large copper area on an internal layer of the circuit board or dedicating entire circuit layers of the board for the power and ground distribution function. The power plane uniformly distributes voltage to different parts of the board, while the ground plane allows the current to run smoothly, keeping power steady and reducing noise. Unlike thin signal traces that carry one signal at a time, these planes are wide and cover large areas. Think of signal conductors like small roads, and power and ground planes like highways for electrons. Having a common ground on the PCB is essential because it ensures that all conductors connected to the ground have the same reference point for measuring voltage. They let current move quickly and cleanly, which is important for modern, high-speed circuit boards. Furthermore, assigning entire layers of the multi- layer circuit board to power and ground functions simplifies circuit interconnect for each component and also enhances product performance. Dedicated Power and Ground Planes When the power and ground potentials are retained on dedicated circuit layers, they help improve sig- nal integrity by suppressing electromagnetic (EMI) noise and interference. Power and ground can be discrete areas of copper foil or cover the entire sur- face of the internal layers of the circuit board. How this is achieved will depend on the type of circuit D ES I G N E RS N OT E B O O K Ta b l e 2 : Est i m at i n g c u r re nt - c a r r y i n g c a p a c i t y of c o p p e r fo i l ( S o u rc e : A l l f l ex )