A printed circuit board or PCB, may be a plate or board used for putting the various components that adapt associate degree circuit that contains the electrical interconnections between them.
The most easy computer circuit boards area unit those that contains copper tracks or interconnects solely on one amongst its surfaces. These types of boards area unit referred to as one layer computer circuit board or one layer PCB.
The most common PCB's factory-made these days area unit those that contain a pair of layers, that is, you'll realize interconnects in each surfaces of the board. However, looking on the physical quality of the look (PCB layout), the boards are often factory-made of eight or additional layers.
Soldermask
For mounting the electrical elements on the computer circuit boards, associate assembly method is needed. This method is done by hand or through specialized machinery. The assembly method needs the utilization of solder to position the elements on the board. For avoiding or to stop the solder to accidentally short-circuit 2 tracks from totally different nets, PCB makers apply an end or varnish referred to as soldermask on each surfaces of the board. The foremost common color of soldermask employed in computer circuit boards is inexperienced, followed by red and blue.
In EDA software package, typically exist a rule associated to the growth of the soldermask. This rule specifies the space that exists between the pads' borders and also the soldermask's border. This idea is illustrated in figure two (a).
Silkscreen or Overlay
Silk-screening is that the method wherever the manufacturer prints data on the soldermask contributory to facilitate the processes of assembly, verification and repair. Typically the silkscreen is written for indicating check points additionally the position, orientation and reference of the electronic elements that square measure a part of the circuit. Additionally it is used for any purpose that the designer could need, for instance, the corporate name, configuration directions (this was usually employed in recent computer motherboards), etc. The silkscreen is written on each surfaces of the board. Additionally the term silkscreen is understood as overlay. Figure two shows a section of a circuit, all the printings created in white correspond to the silkscreen.
Layer Stackup
As noted before within the starting of this text, the computer circuit boards will be made from many layers. Once a PCB is meant with the help of Associate in Nursing EDA software system, usually area unit specified many layers that does not necessary correspond to semi-conductive material (copper). For instance, the silkscreen and soldermask area unit non-conductive layers. Having semi-conductive and non-conductive layers might result in confusion, as a result of makers use the term layer after they area unit relating the semi-conductive layers solely. From currently on, we tend to area unit progressing to use the term layer while not the suffix "CAD" only if relating semi-conductive layers. If we tend to use the term "CAD Layer" we tend to area unit relating all types of layer, that is, semi-conductive and non-conductive.
Pads
A pad may be a little surface of copper in an exceedingly computer circuit board that permits fastening the element to the board. You'll think about a pad as a chunk of copper wherever the pins of the element are automatically supported and soldered. There are two varieties of pads; thru-hole and smd (surface mount).
Thru-hole pads are meant for introducing the pins of the parts, so that they will be soldered from the alternative aspect from that the element was inserted. These varieties of pads are terribly the same as a thru-hole via.
The smd pads are meant for surface mount devices, or in different words, for fastening the element on identical surface wherever it absolutely was placed.
Figure three depicts four parts. The parts IC1 and R1 have eight and a pair of SMD pads severally, whereas each parts Q1 and PW have three thru-hole pads.
Copper tracks
A track is semi-conductive path that's wont to connect a pair of points within the PCB. As an example, for connecting a pair of pads or for connecting a pad and a via, or between vias. The tracks will have completely different widths reckoning on the currents that flow through them.
It is necessary to focus on that in high frequencies is important to calculate the tracks' dimension in order that interconnect may be electrical resistance matched on the trail created by the track.
Plated Holes (Thru-hole Vias or Full Stack Vias)
When associate degree interconnect should be made up of a part that's settled on the highest layer of the computer circuit board with another that's settled at the lowest layer, a via (Vertical Interconnect Access) is employed. A via could be a plated hole that enables the present to suffer the board. Figure v depicts two tracks that begin at the pads of a part on the highest layer and finish at the pads of another part at the lowest layer. For conducting the present from the highest layer to the lowest layer, a via is employed for every track. The tracks and pads that belong to the lowest layer are visually low-beam, thus you'll be able to differentiate them from those that are on the highest layer.
@ Shayan Khan