What is a Printed Circuit Board (PCB)?

What is a Printed Circuit Board (PCB)?

Most electronic equipment and products have circuit boards. Pprinted circuit board (PCB / PWB), is a board made out of non-insulating and highly heat-resistant insulating material such as fiberglass. These boards are also called substrates.

A PCB substrate may have only one single layer (single-layer circuit board) or more than one layer (multilayer circuit board). A conductive metal such as copper is used to make conductive pathway or traces to facilitate flow of electricity. Once PCB itching is done, it is termed as a “printed circuit board”.
Circuit Board Prototype

When designing a new circuit, it is important to draw a circuit board schematic prior to making a circuit board prototype. A circuit board schematic will help to debug and fix any mistake made during the process. If the circuitry on the circuit board is simple, one can use proto boards that are quite simple and easy to understand. In case of complex and customized circuit board, making a prototype board is a must.

Circuit Board Layout Editor

To start making a circuit board prototype, one will need a circuit board layout pattern. Layout editors are available for this purpose.

A circuit board layout editor is software to draw a layout of the circuit board with all of the traces and points where electronic components will be soldered on the board. The PCB layout will look like a diagram. PCB layout software allows editing the layout until the desired layout is achieved.
How to Make a Circuit Board

Making or manufacturing a circuit board involves several complex processes.

   1. Photoengraving: Under this process a mask or photomask is combined with chemical etching to subtract the copper areas from the circuit board substrate. The photomask is created with a photo plotter design using a CAD PCB software program. Photomasks are also created using a laser printer.
   2. Lamination: Multi-layer printed circuit boards are made up of multiple layers consisting of several thin etched boards or trace layers and are bonded together through the process of lamination.
   3. Drilling: Each layer of the printed circuit board requires the ability of one layer to connect to another; this is achieved through drilling small holes called "VIAS". Drilling is mostly done with the use of an automated computer-driven drilling machine.
   4. Solder plating: Pads and lands where electronic components are to be soldered on the circuit board are plated to allow soldering of electronic components. Bare copper is not easily solderable. It requires the surface to be plated with a material that facilitates soldering. Earlier lead based tin was used to plate the surfaces, but with RoHS (Restriction of Hazardous Substances) compliance enacted newer materials such as nickel and gold are now used for plating.
   5. Testing the circuit board: Prior to assembly of electronic components on to the board, it needs to be tested. This testing can be done using nails tester, flying probe tester are other computer-operated circuit board testing equipments.

PCB Design Rules

Layer Process Vs Standard Size

    * Minimum trace / space: 7 mils
    * Minimum via / hole size: 14 mils
    * Minimum pad for plated hole / vias: 26 mils
    * Minimum plated slot: 32 mils
    * Minimum soldermask Clearance: 4 mils
    * Minimum silkscreen Clearance: 4 mils
    * Minimum silkscreen line width: 6 mils
    * Minimum board copper/edge margin: 10 mils

Conclusion

While making a PCB prototype, it is important to follow the rules right from photoengraving to testing. Any slight mistake can make the circuit board useless. In case of mass production, PCB prototypes is a must.


Read more at Suite101: Printed Circuit Board Prototype http://www.suite101.com/content/printed-circuit-board-prototype-a236175#ixzz14r77OIfQ