An electronic circuit board connects the electronic components electrically and also supports mechanically. The electronic circuit board technology is evolving since many years. In early days of electronics the components were mounted over a board or sheet and then wire wrapping technique is used to make connections between pins such as shown in fig 1. Later on the components were mounted and the connections were made with connecting the pins by using a wire and soldering them to the pins of the component such as shown in fig 2. The breadboards are also used very frequently for prototyping and concept testing. However, for a marketable product a ruggedized board is a mandatory requirement that fulfils certain qualification standards. For a standardized product the electronics industry has moved towards printed circuit boards for its high reliability, low cost, good efficiency, easy availability and manufacturing facilities. Although, the wiring boards were used in the industrial and even defense applications till early 1970s. The printed circuit board technique rapidly replaced the wiring boards due to their performance and reliability as shown in fig 3.
Fig 1:- Wire wrapping electronic circuit board
Fig 2:- Varoboard type electronic circuit board
A printed electronic circuit board is available in many different material types and can be manufactured under different standards. They also mechanically support the components as well as electrically connect the components. The connectivity is, through thin sufficiently spaced copper tracks, pads and vias, improved significantly over the predecessors. They are produced by etching of thin layer of copper sheet glued over the fire retardant materials or specialized insulating materials. The PCBs for low volume and prototyping are also manufactured by milling machine where the required copper tracks remains intact whereas extra copper is removed. The components such as resistors, capacitors, inductors and ICs are mounted and soldered on the outer sides of PCB. The thin copper connections or tracks may switch from one layer to another by vias or pads. In newer and advanced PCBs the components like resistors may be made inside the copper connections or inner layers of the PCB. The higher the layers in an electronic circuit board the denser the tracks and solderable components. A printed electronic circuit board (PCB) is shown in fig 3.
Fig 3:- Printed circuit board type electronic circuit board
The printed electronic circuit boards require design effort that lowers the manufacturing time and assembly by automated machines. Manufacturing with PCBs intends to lower cost and higher yield when compared to other circuit production methods like wiring methods or varo-boarding. A PCB with populated and soldered component is called a printed circuit board assembly or PCBA.