When it comes to the Printed Circuit board designing, there needs to be a working schematics or simulations for that PCB manufacturing. The schematics or simulations are made on various software like Altium, Eagle, Ki Cad, Dip Trace, Multisim, PSim, Proteus, etc. The beginner level software is the Proteus for schematic designing and PCB designing. Without working schematics, there is a waste of time on designing the PCB board because the PCB board will not work. So, let’s see how the schematics should be designed and then we will move onto the PCB layout and then board designing.
Schematics PCB Design Steps:
The schematics should be designed accordingly in the following steps.
- The first step is to create a rough idea/sketch that what kind of system you want to create i.e. what kind of input you want to give and what kind of output you desire from your system.
- Then move onto creating the rough schematics onto the paper.
- Then open the schematics software and find the required components for your schematics designing.
- Wire all the components according to the working schematics idea/sketch.
- Then place the grounds, isolated grounds and power onto the schematics.
- Then run the schematics and place the oscilloscope to view the desired outputs/results.
- If the desired results are obtained then move onto the PCB board designing.
- One thing that should be kept in mind that schematic designing results and getting the practical results are two different things. If you don’t get the practical results the way you are getting in the simulation, then we are discussing it in PCB layout and board designing steps.
The whole discussion is going according to the Proteus software.
Following is the detailed discussion about designing the PCB layout and board.
PCB Design Steps:
First of all, if your schematic is designed fully and functional, then move onto the PCB layout designing.
- Placing the component packages: First of all, when layout will be opened and there will be a blank screen. Place the packages of all the components you placed in the schematic design. Instead of placing power and ground terminals, place a two-pin header or connector in place of that because we have to give the power physically and not the virtually, that’s why there must be a connector/header for power and ground. One thing must be kept in mind your board edge must be defined properly for printing purposes.
- Routing: Then after placing the packages, move onto the routing of all the connections like did in the schematic design. The routing is of two types which top and bottom routing which makes the 2-layer PCB layout design. When it comes to the PCB layout routing, the size for control signals must be at least T30 otherwise when the board will be manufactured, the routed trace will be very small which is not the feasible way. And when the routing is being carried out, it must be kept in mind that the routed trace should not be passed in between the pads of the controller or some IC package because when manufacturing will be done the trace will not be there. One more thing is that the route trace from one pad to another one must be short as possible because when the control signal is passing through that routed trace, the longer the trace the longer the delay in the signal. When it comes to larger power trace the control signals routed traces and power routed traces must be kept separate otherwise there will be electromagnetic interference (EMI) which will cause the control signal to distort. The control signal ground should be common and then meet with the power ground otherwise the layout will not work. The size of the routed trace for power signals must be at least T100.
- Vias: The vias are placed where the top and bottom routing need to be met. Sometimes, it is difficult to route the bottom side to the component package and then there come the vias which come in handy to combine the top and bottom route to meet to the pad of the component package.
- Pad Selection: The pad selection for control signals must be designed manually and not be used the default ones because those pads are too small to be manufactured and then they often wiped out when they are seen practically. The pads used must be rectangular in shape and the drill holes must be according to the diameter of the pin package of the components.
- Exporting the layout design: When the layout designing is finished which includes top silk, top, and bottom layer usually and the zone mode is often cases, then the top and bottom routing designs and the top silk design in separate files are exported through Gerber files and mostly the PDF files respectively.
- Manufacturing: Following is the detailed process for manufacturing the PCB board.
- Board Selection: The board is selected the fiber sheet of having the top and bottom copper on it.
- Design Placement: The exported designed layout is printed onto the butter paper and then placed onto the board using the ironing process and then waits for little time to cool down the board so that the butter paper has fully placed the design on the board.
- Etching: Then tracks are filled using permanent marker if there is any distorted trace otherwise it is left as it is. The etching is done then using boiling and the ferric chloride in it in a little amount to make a hot solution so that copper on the board is etched properly. Then the board is placed into the boiling ferric chloride solution and then the tub holding the solution is stirred here and there so that the copper etching is done properly. When one side of the board etching is done, then move onto the other side and repeat the process. When etching is done, wash the board with the tap water and your board is manufactured.
- Drilling: When the etching is done, then drilling is done through the holes in the board where you need to place the components.
- Component placement and Soldering: When the drilling is done, components are placed starting with the smaller ones and ending with the bigger ones. The IC beds are used for the IC’s so that in future if the IC is burnt out, it can be replaced easily. When the component placement is done, the soldering process is carried out using a soldering gun and soldering wire. One thing must be kept in mind that soldering gun must be at least of 60W. The soldering gun must be heated fully and when soldering is being carried out, the solder mask must be placed for a very short period which must ensure that the leg of the component and the pad placed on the routed trace must be connected fully. If you are not sure that the leg of the component and the pad are not connected, then you can checkout using the short circuit test on DMM.
- Finishing the PCB Board: When the soldering is done properly, then the board is cleansed using the varnish on the brush so that there is no unwanted signal is being carried out which can cause the noise in often cases. Now, the PCB board is ready and then the checking of the results can be tested.