They contain the circuitry that allows a device to function as a complete system by connecting all components on the circuit with copper-lined “wires.” The wires are a critical part of the board as they carry electrical current and pass energy from one component to the next. The wires themselves are made from conductive materials that are able to transmit energy and information such as copper, aluminium, and gold. The components that populate the board are also essential to its functioning. They include resistors, transistors and capacitors among others. Resistors and capacitors are a critical part of the circuit board as they can store or dissipate electric current to control its flow. Inductors help to block electric currents that would otherwise interfere with other signals and cause damage.
A computer circuit board is also made up of diodes which protect the electronic devices from voltage spikes and interference. The circuit boards are plated with copper and soldered together using solder which is made up of silver, palladium and other precious metals. The copper used on modern boards can be quite thin and is usually covered with a layer of epoxy.
The first step in constructing a circuit board is to design the circuitry. Several software programs can be used to create the schematic for a PCB. The schematic will be imported into a CAD program where the layout and routing of the board can be done. The resulting files can be output to the manufacturer for fabrication and assembly.
How do circuit boards work can be made from a variety of materials but most often are based on FR-4, a woven glass cloth impregnated with an epoxy resin that is typically 0.8, 1, 1.5 or 2 mm thick. The thickness can vary depending on the application and there are various grades of laminate with differing properties. Some of the more complex PCBs will use multiple layers of copper which are interconnected via copper holes (vias, PTHs). The number of layers and the complexity of the design between them can impact signal integrity, long term reliability and production cost.
When the PCB has been designed and manufactured it can be soldered and tested. The traces will often be printed with a legend (sometimes called silkscreen or silk) that provides indicators for the component locations, switch settings and test points on the board. The legend can be applied to the PCBs by silk screen printing or liquid photo imaging and can be printed in a wide range of colors including the standard green and blue.
Some PCBs are very complicated and require a high level of engineering expertise to design and build. The most sophisticated systems are populated with a variety of chips, including processors and memory chips, which are highly integrated into the circuit. These can be loaded with sophisticated features and provide a wide range of computing capabilities. Most importantly, the underlying logic will ensure that all components work together to deliver the performance and functionality that we expect from our devices.
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