A printed circuit board (PCB) is sometimes called a printed wiring board, and it’s used to build various electronic devices. The PCB serves two different purposes: components are mounted to it, and it provides a connection between those components. PCBs start out as thin sheets of non-conductive material, most commonly glass fiber/epoxy with a thin copper layer on each side. Below, you will learn how PCBs are made.
After the glass and copper are fused, the connection diagram must be printed onto the board. In the earliest days of electronics, the components were connected with wire; this is why PCBs are sometimes called printed wiring boards. Printing is done via photographic transfer with an acid-resistant material.
When printing is complete, the worker puts the PCB into an acid bath (after putting on their Repair Solder Mask). The acid strips the copper away, leaving it only on the areas with the acid-resistant material. The acid bath leaves the PCB with its connections printed on; next, small holes are drilled to allow workers to mount components and to in turn mount the PCB to the electronics case. Lastly, a protective layer is applied to prevent corrosion of the copper.
The process described above creates what is commonly called a double-sided or two-layer PCB. Printed circuit boards can be made of an almost infinite number of layers by simply repeating the above process and laminating the layers onto a single board. If you’re reading this on your home computer, the PCB inside your machine has at least four layers, and possibly eight or even twelve.
Today’s PCBs typically have their parts soldered to the board, and holes are no longer needed. Soldered components are referred to as ‘surface mounts’, and the PCB is called a surface-mount PCB. The surface mount technique allows workers wearing a Repair Solder Mask to mount more components on each board, or to mount components on smaller boards. Surface mounting requires stricter quality control processes, however.
Take a look around you-;if you see an electronic device, chances are, there’s a PCB inside. Printed circuit boards are the most common way to assemble and connect the many components of almost every kind of electronic device we use today.
