PCB Design Basics

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Printed Circuit Boards are the pulsing heart of all electronic devices.  Their detailed construction may lead people to think they are prohibitively complex items to understand, but to help break down that myth, here at Hi5 we have drawn up a kind of ‘beginners guide’… PCBs 1.01.

Printed Circuit Board Schematics

Before you manufacture your PCB it needs to be designed, based on your requirements for what it will do.  Firstly, a schematic capture will create a graphical representation of the circuit board and its varied components, and a netlist will test their interconnection.  Using software, a dummy design will be created, which also allows for the possibility of interaction, and testing, at this crucial, early design stage.  Obviously, this also eliminates the cost and inconvenience of testing with an actual physical PCB, using instead the virtue of digital simulation.

Laying out your PCB

The layout programme will then create the structure of the PCB in terms of its wiring – perhaps a single layer, but more commonly over several, insulating layers, each from 0.005” to 0.038” in thickness.  These are known as multilayer PCBs and each individual layer is named at this design stage – for instance ‘power’ or ‘ground’, to ease manufacture.  Think of your PCB as a wafer biscuit, containing within each layer all the wiring and mechanical structure of your design. These conducting layers are made of copper foils with the inner circuitry sandwiched in between; the foils etched away in the areas where you don’t want connections to happen.

So a double-layered PCB will have two layers of copper foil, whilst a four-layer board will contain the signal routing within the top and bottom layers, and the ground and power planes routed within. Multilayered PCBs then build up and up in this same way, with additional levels of copper foil added depending on the complexity of the PCB and the circuitry it is expected to carry, with extra layers usually added in pairs, in what is called Layer Stack Up.  The layers are positioned on top of one another, with ground planes and signals routed through key layers for reasons of electromagnetic protection.  The Finished PCB Height is the final thickness of your circuit board, taking into account all the copper and substrate layers.  The most involved printed circuit boards can carry 32 layers and at that level, you will really need an experience manufacture such as Hi5 to advise you on the build.

You can then generate the necessary CAD files – computer aided design files, or ‘gerber’ files – that you will send to your PCB manufacturer.  The usual gerber file format is RS-274X.   Numerically controlled (NC) drill files will also detail where the holes will be placed for the wiring to connect through the varied layers of the PCB.  It will also include the size of the holes required, necessarily a very precise measurement.

The Manufacturer

That’s where Hi5 comes in.  When your PCB has been designed to this level, Hi5 will then manufacture your chosen PCB in whichever type and quantity you require, to our extremely high standards.

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