After PCB manufacturing, PCB assembly is next in the process. Without assembly, a PCB is just a board made up of reinforced fiberglass with an etched copper traces in one side. Before assembly, a bill of materials (BOM) is furnished which specifies every part, how many are needed, the place of each component on the board and other data to assemble a working printed circuit board. PCB assembly begins when all of the components are available, and the machines and tools are ready.
What are these components? The electronic components are generally categorized into two types: the active and the passive components. Both are essential in making the board function accordingly. One component complements the other. Without one of the components, the PCB may become faulty or may even be useless for delivery.
Active Electrical Components
Active components need a current to make the device work. These are examples of active components.
These electronic components control the flow and amplify the current. In other cases, they are also used as switch. These are made of silicon or any other metal alloy with semi-conductor properties. Transistors are like brain cells that signals the device, passing billions of tiny electrons. A computer chip or any device has at least one transistor. Physically, a transistor has three pins. Each pin works differently. One pin collects electrical current (the collector pin). Another pin control (the base pin) and enables the current to pass or flow to the other pin (the emitter), which in turn will emit the current to the PCB.
These are semiconductors that make current flow into one direction, as well as reverse or rectify the flow of current. There are different kinds of diodes. Each has its own purpose when placed in the PCB. Light emitting diode (LED) emits light when electrons pass through it. On the other hand, photo diode works only when it is exposed to light. While rectifier diode stops electricity from conducting the wrong way, Schottky diodes switches off electronics when the voltage limit is reached. Basically diodes are rectifier electrical components.
Almost all electrical devices have diodes because these electrical parts act as a corrector when something is amiss with the electrical charge passing through, like for instance when inserting batteries the wrong way. Diodes also serve as protector for electronic devices highly sensitive to current fluctuations.
These are a series of active and passive components placed in one chip. They can either be digital or analog and can have specific or many purposes, depending on how they were assembled. They are typically enclosed in square or rectangular casing and mostly black in color.
Passive Electrical Components:
Passive components are incapable of bringing current flow into the device but can store it for later use. Below are examples of passive components.
As the name implies, these electronic parts resist current, thereby, allowing control on current passing through them. They reduce, resist or moderate electricity. They are made from different materials that conduct electricity. Resistors are important because some of the electronic components cannot function and may even be destroyed when too much voltage reach them.
They are two-way terminal electrical parts that store electrical charge. They act like batteries in PCBs. However, they do not produce electrons like batteries do. Capacitors in PCB assembly can be further categorized into dielectrics and electrolytes. They can be manufactured using any non-conductive materials that can store electrical charge. Most common materials used to manufacture capacitors are Mylar, glass, Teflon, ceramics, and porcelain.
They close or open the flow of current.
Each component is very important in a PCB assembly and one cannot work without the other. Thus, during assembly, proper handling and mounting should be followed to ensure functionality.