Printed Circuit Board (PCB) Designing

What is a PCB?

If you want to describe PCB to someone who is outside of the industry, very simply put, it is a board that connects all the electronic components. Different kind of components like capacitors, resistors are all soldered in the main board of the PCB where and when find appropriate. These PCBs successfully fulfills the need of an electronic device the could fit well in a component within the smallest amount of space possible. Printed Circuit boards have now become an essential part of many electronic components so they can perform for their intended functions. Their design may appear a bit complex, but overtime it has gotten simpler and its size has decreased gradually.

 

Figure 1 A simple Printed Circuit Board

 

Figure 1: A simple Printed Circuit Board

 

Structure of a PCB:

 

An essential PCB comprises of a flat sheet of protecting material and a layer of copper foil, laminated to the substrate. Chemical drawing isolates the copper into independent leading lines called tracks or circuit traces, pads for connections, vias to pass connections between layers of copper, and features, for example, strong conductive areas for EM protecting or different purposes. The tracks work as wires settled in place, and are insulated from one another via air and the board substrate material. The surface of a PCB may have a covering that shields the copper from corrosion and decreases the odds of solder shorts between traces or undesired electrical contact with stray uncovered wires. For its capacity in anticipating weld shorts, the coating is called solder resist.

Further on, the main design and what are the necessary steps that are required in the design of a PCB shall be discussed.

 

Simple PCB Design:

 

There are many PCB design tutorials available on the internet, the essential PCB design steps and main PCB design software that are currently being used. But if you want the full guidance about the structure design and different types and models of the PCB, then a very informative portal about the PCBs is available on the internet called RAYMING PCB & ASSEMBLY. All the prototypes of a PCB and various PCB applications, everything can be found on this portal.

To design a PCB, first we have to draw the schematics of a PCB. Schematic will serve you as a blueprint of your PCB, which will layout the structure or tracing and the positions of various components on the PCB.

 

PCB Design Steps:

 

Following are the necessary steps that are required to design a PCB;

  1. Installation of software to Design the PCB.
  2. Designing the Schematic using the PCB design software.
  3. Setting of trace width.
  4. 3D view

PCB Design Software:

 

There are many different and useful software available in the market to design the schematics part of the PCB. This is how the schematic part of a PCB looks like;

 

Figure 2 Schematic of a PCB circuit

Figure 2: Schematic of a PCB circuit

 

To design the schematic part of a PCB, many software is used, mostly used are;

  • KiCad
  • Proteus
  • Eagle
  • Orcad

 

Designing a PCB on Proteus:

 

Proteus is a software that is currently being used to design the PCBs. It is very easy to use, any person that is new to it, will get familiar to it and with all its features within no time at all. This is due to the reason that it has a very unique and user-friendly interface. All the components that you want to add in to your PCB can be easily found in it. The different wires and their connections with each other can also be easily done.

 

Figure 3 Getting started with Proteus

Figure 3: Getting started with Proteus

 

Familiarizing with a software is very essential in order to get your work done. Proteus offers a lot ease in order to find all the necessary components that you want to have in your PCB. The connections and all the tools can easily be accessible from the main window as it can be seen in the figure above. The models of different components are also visible to the users, so they can select the device with a specific model that will be useful for them in order to design the PCB.

The complete design of a PCB, created on the Proteus is given below;

 

Figure 4 PCB Layout Design

Figure 4: PCB Layout Design

 

Figure shown above is the complete layout of PCB designed by using the Proteus software. One can easily see the different components aligned and structured together to fulfill the needs of a working PCB, the capacitors, LEDs and all the wires are connected in orderly fashion.

 

Routing:

 

Once the schematic part of the PCB design is done with the help of a software, on comes the routing of the PCB. But before routing the PCB user can check the validity of designed circuit with the help of simulation. Once the validity is checked, routing can be done. In routing most of the software’s provide two options.

  • Manual routing
  • Auto-routing

In manual routing the user places each component separately and then make connections according to the circuit diagram so in case of manual routing there is no need to draw schematic before routing.

In case of auto-routing user just needs to select the width of traces. Then through auto-routing software designs the PCB by auto-placement of components and then make connections depending on the schematic designed by the user. In auto-routing software tries different combinations of connections so that no errors occurs. User can design single layer or multi-layer PCB’s depending on the application.

 

Setting of trace width:

 

The width of trace depends on the amount of current that is going to pass through it. The formula used to calculate the area of trace is shown below:

 

Here “I” is current, “ΔT” is rise in temperature and “A” is area of trace. Now to calculate width of trace,

Width= area/(thickness*1.378)

 

For internal layers k=0.024 and for external layer k=0.048

The routing file of a double sided PCB will look like this:

 

Figure 1 Routing file

Figure 1: Routing file

The yellow line is for border of PCB which restricts the component placement and trace placement in auto-routing. While red and blue lines show bottom and top copper traces respectively.

 

3D view:

 

Some software’s like Proteus and KiCad provide a functionality of 3D view, this gives a 3D view of PCB with components placed on it for better visualization. One can easily judge that how will the circuit look like after fabrication. After routing, PDF or gerber files of copper traces can be exported and printed on negative sheet or can be sent to www.raypcb.com for fine quality fabricated PCB’s. This website provides services in both single and multi-layer PCB’s fabrication along with soldering using different materials depending on the working frequency of circuit and other parameters.

www.raypcb.com