PCB_Layout_Inst - Printed Circuit Board Layout Introduction...

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Ver. A Printed Circuit Board Layout Introduction Converting a circuit schematic to a circuit board layout consists of using CAD software to arrange the components of your circuit onto a virtual circuit board and then drawing traces between them, representing the copper conducting lines that will connect the components together on an actual circuit board. This virtual circuit board layout is then used as a template to physically create an actual printed circuit board (PCB). The Multisim Circuit Analysis Software Suite by National Instruments includes a software package called Ultiboard that does this printed circuit board layout. You will learn how to use Ultiboard in this tutorial. Rules of Circuit Board Layout There is one very basic rule that you must follow when laying out any circuit board: Traces (conducting lines) cannot intersect each other. This would be equivalent to having unshielded wires touch each other and is obviously very bad. In addition to this basic rule, there are some other good practices that you are required to abide by for this exercise: Always keep at least 1 trace width between adjacent pads and traces. If you don’t abide by this rule, Ultiboard will let you know by drawing a red circle at the point where you are too close. This is important because some circuitboard printing/etching/routing techniques have the potential to be quite inexact and you need space around your pads/traces to compensate for the margin of error. Also it is much easier to solder to pads that have space around them. If pads/traces are too close, the solder will often unintentionally connect them together resulting in unintended disaster or innovation, but most often disaster. All angles between trace segments should be greater than 90°. This means that instead of 90 ° corners, all corners should have a 45° chamfer. Ultiboard will usually do this for you. You may be wondering why this is a rule. Part of it has to do with what happens when you try to hand etch a circuit board. Intersections of traces tend not to come out very well. The other consideration is noise. Sharp corners tend to be susceptible to
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Ver. A electromagnetic noise. Remember that you can route traces underneath components. If you find yourself in a situation where it looks like you can’t find a path between two pins that need to be connected, consider routing your trace between the pins of a resistor or a capacitor. You can put as many traces under a component as you want as long as
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This note was uploaded on 03/11/2012 for the course E E 316 taught by Professor Ridiggio during the Spring '11 term at Penn State.

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PCB_Layout_Inst - Printed Circuit Board Layout Introduction...

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