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Printed Circuit Boards
OrCAD PCB Editor is based on Allegro PCB Editor, so this book will be useful to new Allegro printed circuit boards Editor users as well. Allegro PCB Editor is a powerful, full-featured design tool. While OrCAD PCB Editor has inherited many of those features, including a common file format, it does not possess all of the capabilities available to the Allegro PCB tiers, such as Allegro High-Speed Option, Analog/RF Option, FPGA System Planner, Design Planning, and Miniaturization Option. Consequently most of the basic tools and features are described here, but only a few of the more-advanced tools are covered, as outlined later.
PC board traces must be sized appropriately (both in width and thickness, or copper weight10) to carry the current that you need without excessive temperature rise. A rule of thumb is that a 10-mil-wide, 1-ounce PC board trace can carry in excess of 500 mA with a 20 °C temperature rise above ambient. PC board copper weight vs. trace thickness is shown in Table 15.5. An estimate of the current-carrying capability for 20 °C temperature rise of PC board traces is shown in Figure 15.12. The fusing current (Figure 15.13) for PC board traces is significantly higher.
OK – So What’s a Printed Circuit Board?
I’ve just mentioned a printed circuit board, but what exactly is a printed circuit board? Well, look inside any modern electronics appliance (television, computer, mobile phone, etc.) or even many electrical appliances (washing machine, iron, kettle, etc.) and you’ll see a printed circuit board – often known by the multilayer PCB.
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