Basic of PCB -2

In previous article, we learn about basics of PCB. 
https://articleelectrical.blogspot.in/2017/12/basics-of-pcb-1.html

In this article, we will see different parts of PCB, material used in PCB and different PCB designing software.

Different parts of PCB

Pad: The pad is a piece of copper. Lead of components are mounted on pad and on which soldering are done. Pad provides the mechanical support to the components.

Silk layer: The silk layer is used for printing line, text or any art on the surface of PCB. It can be used in top and/or bottom layer of PCB. Which is known as silk screen TOP and silk screen BOTTOM. The epoxy ink is used for screen printing. 

Layers: User can choose the layer of PCB according to application. But for choose number of layer user have keep in mind the cost and available space of circuit. The single layer PCB is easy to design and used in routine life and construction of this PCB is simple compare to double layer and multi layer PCB. The double layer PCB or Multi-layer PCB is most prefer compared to single layer PCB cost and available space of circuit for large and complicated circuit. In multi-layer PCB 10-12 layer can be connected. In multi layer PCB most critical thing is to make communicatation between the component in different layer.

Top and bottom layer: All components are mounted in this part of PCB. This layer is green or blue coloured, but it is not a rule you can choose any colour. 
PCB is coated with green colour layer in top and/or bottom layer. This layer is known as solder mask. All components are soldered through the hole and lead of components is known as bottom layer of PCB. 

Trace: The components are not connected with the help of wires in PCB. All components are connected with a conducting material like copper. This copper part of PCB which is used to connect all components that is known as trance.

PCB materials: 
The main material of PCB is dielectric substrate. The dielectric substance is rigid or flexible and this is used according to the application. This dielectric substrate is used with conducting material like copper. The glass epoxy laminates or composite materials are used as dielectric material. 

FR4: FR is stand for FIRE RETARDENT. For all type of PCB manufacturing, most common glass laminated material is FR4. The FR4 is a composite material based on woven glass-epoxy compounds. FR4 is most used dielectric substance because it provides very good mechanical strength.

FR-1 and FR-2: FR1 and FR2 is made up from the paper and phenol compounds. This material is used for only single layer PCB. FR1 and FR2 has similar characteristic. The glass transition temperature is different for both dielectric substance. FR1 has higher glass transition temperature compared to FR2. These material is sub divided in standard, halogen free and non-hydrophobic.

CEM-1: CEM1 is made up from one layer of the paper and two layer of the woven glass epoxy and phenol compounds. CEM-1 can used instead of FR4, but price of CEM1 is higher than FR4. This material is used for Single sided PCB only. 

CEM-3: CEM3 material is white coloured and glass epoxy compound material. This material is mostly used in double layer PCB. CEM-3 has lower mechanical strength compared to FR4. But CEM3 is cheaper than FR4. CEM3 is a good alternative of FR4.

Polyimide: The polyimide is a flexible dielectric substance. So, this material is used in flexible PCB. The polyimide is made up from kepton, rogers and dupont. This material has good electrical properties, felicity, wide range of temperature and high chemical resistance. Working temperature of this material is -200 ͦC to 300 ͦC.

Prepreg: Prepreg is stands for pre-impregnated. Prepreg is a Fibre glass impregnated with resin. These resins are pre-dried. This resin flows, sticks and completely immersed when hetated. The Prepreg has adhesive layer. This adhesive layer gives strength similar to FR4. According to resin content, there are many versions of this material, SR- standard resin, MR- medium resin and HR- high resin. This is chosen according to required thickness, layer structure and impedance. This material also available in high glass transition temperature and halogen free.

PCB designing software:

EAGLE: EAGLE is a most popular and easiest way to design PCB. EAGLE stands for "Easily Applicable Graphical Layout Editor". This software is previously developed by CadSoft Computer and currently Autodesk is developer of this software. EAGLE provides a schematic editor for designing a circuit diagram. 
EAGLE file extension is .SCH
Different parts and components are define in .LBR extension. (Library) 
Board file extension is .BRD

MULTISIM: Multisim is also very powerful and easy learning software. This software is widely used in academic and also in industry for circuit education. This software is originally developed by "Electronics Workbench". Presently this software is a division of "National Instruments (NI)". 

EasyEDA: EasyEDA used to design and simulate circuits. Most important advantage of this software is that, it is web based software and used in browser window. So, this software is independent from OS. This software is an integrated tool for schematic capture. This software provides environment for SPICE circuit simulation and PCB layout. 

Altium Designer: Altium designer is developed by Australian software company "Altium Limited". This is first software which offer 3D visualisation and clearance checking of PCB directly from PCB editor. The main feature of this software is schematic capture, 3D PCB design.

KiCad: KiCAD is developed by "jean-pierre charras". This software has tools to create BoM (Bill of Material), artwork and 3D view of PCB. Many components are available in the library of this software and there is feature that user can add their custom components. This software is support many human languages.

CircuitMaker: Circuitmaker is also developed by "Altium". This software is used to design advanced multichannel and hierarchical schematics. Schematic editor of this software includes basic component placement. All schematic is uploaded to server. These files are available to view by anyone, provided that you need a CircuitMaker account.