PCB (Printed Circuit Boards) is very crucial for electronics industry. This is most critical part inside electrical and electronics machine, which holds components and their interfacing on a single board. Various components as wired as a single unit to avoid and loose contacts and error from operator end.
Before PCB was invented, complex wiring was done using sockets, twisted or bolted wires, junctions, etc. These connections were very unreliable. To eliminate operational errors and increase reliability, prototype circuit boards were invented in early 1900. Charles Ducas, an American designed electrical conductive links using stencils and files patent for the same. This provided further thinking that it can actually increase reliability and accuracy of circuits. It was World War 2, when it started into application and then rest is history. The complete electronics industry started to modify as assembly chips on PCB was possible. The primitive PCBs were single sided and equipments like gramophone were designed using them.
The PCB helped equipments to get compact as wiring complexity was reduced. This was quality outcome as smaller devices based upon PCB were easy to move. The next step was to make it more compact and hence two-sided PCB evolved. The two layers were interconnected through conducting holes (now called vias). Side by side, PCB provided platform for large scale integration and circuits were designed using semiconductors (we say it ICs, i.e., Integrated Circuits). Now the PCB industry is producing and using multi-layer boards which have made devices really compact and more reliable.
Nowadays, we can get PCB manufactured on rigid as well as flexible surface. Rigid or solid surface PCB is most common type and usually manufactured with FR-4 (glass-reinforced epoxy laminate sheets). The rigid PCBs are designed to be fire-resistant in nature and self-extinguishing. In the other hand, flexible circuit board based upon laminates are also being manufactured. Flexible PCB has advantage as it can be bent, folded as per casing and hence custom devices can be designed.
PCB can be considered as composite material of FR4, copper, solder mask and silkscreen (in general). A thin copper film is taken on the top layer, which is conducting part. Based upon number of layers, copper wafer if put into PCB (4 layer PCB has 4 copper layers). The copper layer is insulated with soldermask, which is provided to protect copper lining/wires from scratch as well as act as insulation between component and copper. Soldermask is usually green as it comes as a best color for PCB manufacturing (due to resin, it tends to go brown, so red/blue gets muddy texture). However, intentional blue, red or white colour can be designed inprototype circuit boards manufacturing, which is additional cost. Silkscreen is another layer on PCB, which is provided to mark up PCB for specification like part number, version name, etc. This is important as it helps in component assembly. Usually it is white in colour, but different colours like grey, black can be used.
Another most commonly used term in PCB design/fabrication is via. It is metallic conductive hole, which connects two layer of PCB plane/copper. It is important aspect of design as it should not intersect with another via or copper wire. A Via can be between any two layer PCB. It can be through hole or blind. A blind Via is between inner layer and top layer of PCB. Using copper width and Via metal thickness, we can determine the impedance, inductance, etc of a PCB. It helps in design of PCB with high voltage, magnetic effect, RF based board designs, microwave circuit designs, patch antennas on PCB, etc.