SMT | Ready-made | Designing | Making
Printed circuit boards (PCBs) are used to make permanent, soldered circuits. They can be used for all circuits, from simple ones like the projects on this website to the most complex circuits used in computers and other electronic equipment. Professionally made circuits are almost always constructed on PCBs.
PCBs are designed specially for each circuit and they make construction very easy. With fewer holes there is less chance of placing a component in the wrong place.
Printed circuit boards have copper tracks on one side, or sometimes both sides, of the board. The tracks connect the holes where the component leads and wires are soldered. On single-sided PCBs the components are placed on one side of the board with the copper tracks on the other.
Tracks on a PCB can run in any direction and include bends to route them around connections and other tracks. Tracks cannot cross one another but where necessary this can be achieved by using a wire link on the component side of the board to bridge across one or more tracks.
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Professionally made PCBs usually use surface-mount technology (SMT) where the components are soldered onto small pads on the PCB instead of being placed through holes. Surface-mount device (SMD) components are made for this purpose with contact pads or very short leads instead of traditional wire leads.
Surface-mount device (SMD) components are not suitable for educational or hobby circuits, requiring great skill and a very fine-tipped bit to solder by hand.
This is the best way to start using printed circuit boards. Projects with a ready-made PCB are usually easy to construct and it is possible to build more complex projects with confidence. In many cases the PCB supplied for the project will have the component positions marked on the board. The only disadvantage is that PCBs are relatively expensive to produce and this will be reflected in the cost of the project.
The best layout of components on the board will rarely be the same as their layout on the circuit diagram, the important point is to concentrate on the connections between components. Because the tracks can be drawn in any position it can be easier than designing a stripboard layout.
Remember that tracks cannot cross but you can often avoid this by careful positioning of components or drawing the track around an indirect route. If crossing cannot be avoided you can form a bridge using a wire link on the other side of the board, like a wire link between tracks on stripboard. Expect to make several attempts before you come up with a good layout.
Check your planned layout very carefully for errors. This is even more important than with stripboard because errors on a PCB are very difficult (and often impossible) to correct once it is made.
Making a PCB requires specialist equipment and hazardous chemicals so many people will find it best to use the services of a PCB manufacturer. They will transfer your design to a blank PCB and then etch it to leave just the copper tracks you require.
Holes need drilling in the etched PCB, mostly about 1mm diameter but some components need larger holes. A small electric drill and stand are required for this (using a hand-drill is likely to snap the drill bits) so it is usually best to have the drilling done by the manufacturer.
The website build-electronic-circuits.com provides good instructions on designing, creating and soldering your own PCBs.