# Information about PCB

## 1. ***What is a PCB?***

A PCB(Printed Circuit Board) is the board base that provides mechanical support to the electrically connected components using conductive tracks and pads. A PCB allows signals and power to be routed between physical devices.They come in different dimensions for example, 0.8mm,1.6mm(common) etc. PCB can be single layered, double-layered or multilayered.(photos of both)(top layer bottom layer)

## ***2. Layers of PCBs:***

A PCB consists of alternating layers of different materials that are laminated together with the help of external forces such as heat and adhesive. These different layers are explained below in the order they come(from top to bottom).![](https://lh3.googleusercontent.com/aP_UQ0PyRBBDlM2fdHahdc1jQDJbDqK2LjKNYhrw_XvaxLWD8_eBNPtKvD5pZGHNYMZP-_yk1sOH2NXANwhjaY4lsbcbrYa4o7eMSETIGMyA-VcQzKsk5LDAVzMLtYkyNpckImoS)

**A) Silkscreen:** The silkscreen layer(more commonly white in colour) is applied on the top of the soldermask layer. To make the PCB more informative,we add letters,numbers and symbols on this layer which act as indicators for humans to better understand the board. The silkscreen labels are also used to indicate the functions of various pins.The silkscreen layer is just ink. The ink is non-conductive and can be placed on top of traces without interference.

**B) Solder mask:** It is a thin lacquer-like layer of polymer that is usually applied to copper traces of a PCB for protection against oxidation,corrosion and electrical shorts.It also provides electrical insulation that allows higher voltage traces to be placed nearer to each other.The solder mask ensures that the solder does not form bridges (unintended connections) from one element to another.

**C) Copper:** The next layer is a thin copper foil which is laminated to the board with heat and adhesive.The layer of copper can either be on one side or on both sides of the substrate.In lower cost electronic gadgets the PCBs may have copper only on one side. In multilayer PCB, various layers of copper may exist.

**D) Substrate:** The Substrate is the foundation of PCB and is made of rigid fiberglass laminate. The most common designator for this fibreglass is “FR4”. Other substrates which are made of epoxies or phenolics lack the durability of FR4.These types of substrate give a distinctive bad smell when solder is applied to it.

## ***3. Types of PCBs:***

Single sided PCB is the basic simple PCB, components are on one side and the circuit on the other side i.e. there is only one layer of conductor(copper generally). In double layer PCB, there is conducting layer of copper on both sides. Multi-layer PCBs ( 4, 6 or more layer PCB) can also be manufactured using industrial fabrication process.
