Comment concevoir pas à pas le schéma d'un circuit imprimé ?

Designing a circuit board is a crucial step in customizing electronic systems, as it involves creating a blueprint for the physical realization of the circuit. By integrating various components like resistors, capacitors, and circuits intégrés onto a single board, PCBs offer a compact, efficient, and reliable solution for electronic systems. The PCB design process encompasses several essential steps, including schematic creation, component selection, footprint design, and meticulous routing, ensuring optimal signal flow, minimal interference, and efficient power distribution.

Let’s consider a project for a linear power supply that takes 220V and 50Hz frequency as input and provides a 12V DC output. Although there are many kinds of Logiciel de conception de circuits imprimés for you to choose from, this article uses FS Technology EasyEDA as an example to design our products. To begin, open a new project by navigating to FILE > NEW PROJECT > “LINEAR_POWER_SUPPLY”, and you will be presented with a blank page to start the design process.

Step 1: Component Selection

The function of a circuit board is to serve and support electronic components, securely holding them in place and ensuring they function as intended. Therefore, before proceeding with the formal layout, it is essential to carefully consider the selection of components. This step plays a crucial role in ensuring the overall function, performance, and manufacturability of the circuit. Here are a few key points to focus on during this stage:

  • Functionality: Prioritize selecting components that meet the required functionality for the circuit. Verify their specifications, including voltage ratings, current handling capabilities, and frequency response, to ensure they align with the circuit’s intended operation.
  • Footprint and Package: Confirm that the components’ footprints and packages are compatible with your PCB layout. Ensure they fit within the available board space and comply with the design rules specified by your PCBA manufacturer.
  • Disponibilité et coût : Opt for readily available components in the market to avoid potential production delays. Take into account the cost of components to meet budget constraints while maintaining the desired level of quality.

Place all the components that you require for the power supply. For this, we need:

  • Two terminal blocks, one is for input and the other is for output.
  • Transformer, bridge rectifier
  • The capacitor of 10Uf for smoothing the pulsating DC
  • LED as an indicator
  • Linear voltage regulator 
  • 7812 to get the voltage at 12V DC.
Click on the library in the left middle of the screen. A tab will appear on the window. You can write the component name of the tab and choose the best one which suits you.
change project name

Next, place all the required components one by one on the schematic sheet, ensuring that each selected component has a corresponding footprint available in the library. If a component’s footprint is not available, you may need to create one by referring to the dimensions provided in the component’s datasheet.

Carefully arrange the components on the schematic sheet, keeping the connections neat and organized. Ensure that the connections between components are accurately represented in the schematic diagram.

Once all the components are placed and connections are made, you can proceed to the next step of the PCB design.

Step 2: Schematic Design

After placing all the components on the schematic sheet, the next step is to connect them using wires. To do this, access the wiring tool in the software. Click on the wire symbol and start connecting all the components with appropriate wires.

connect electronic components

After connecting all the components, the circuit will show like that.

Schematic diagram after connecting components

For grounding the circuit go to the common library and get the GND symbol to place the grounding. Connect all the ground symbols with the wire.

access public library

The complete schematics of the circuit are shown below. Press ctrl+s to save all the changes before going to the next step.

ctrl+s save all changes

Step 3: PCB Layout

Once the schematic design is complete, the next step is to convert it into the PCB layout. To do this, click on the PCB symbol located at the top of the toolbar in the software.

Start PCB layout

Or you can click on the design>create a new PCB, then you can go to the next tab.

After clicking on the PCB symbol, two new PCB tabs will open in the software. These tabs represent the default settings for the PCB layout. At this point, you can either proceed with the default settings by clicking “Apply,” or you have the option to customize the settings according to your specific requirements.

Customizing the settings allows you to define parameters such as board size, layer stackup, trace width and spacing, via styles, and other design rules.

Open two new PCB tabs
default setting

To begin the PCB circuit layout, start by placing the components on the board. Organize the components in a logical manner, considering signal flow and minimizing the length of traces. You can do this by using drag and drop to position the components and then fix them in place on the board.

place the component in the layout

Step 4: Routing

By default we choose the two-layer PCB, so start with the bottom layer by clicking at the top right side with blue.

Two-layer PCB

Start routing the connections between the components. This involves drawing traces to establish electrical connections.

Keep traces as short as possible to reduce signal interference and noise. Use appropriate trace widths for different currents to avoid overheating.

You can also use the online calculator to measure the trace width.

Give them the PCB thickness and estimated current that you want to pass from the circuit, it will give you the thickness of the trace. Normally for signal trace, we use a 1mm trace and for power current, we increase the trace width according to the value of the current.

Connect the components with the wire and then select the bottom face of the PCB. 

Wiring connections between components

When the routing wires are covered from the bottom layer, move toward the top layer with red and connect the components with it and complete the routing.

Move to the red top layer

When the routing is complete the thickness of the power wire is increased with the help of the above link, in which we calculate the width of the track. 

Calculate the width of the track

For this, we click on the wire which we want to increase the width. A table is shown on the right side. Here we see the width block change from 0.254mm to the required width, in our case let’s say we increase it to 1.5mm.

wires of increased width

Step 5: Ground and Power Planes

Add a ground plane and power planes if applicable. These planes help in better grounding and power distribution, reducing noise and providing stability.

Connect the ground pins of components to the ground plane and do the same for power connections.

In our project, we ground the bottom layer of the PCB. For that click on the copper area.

And connect all the GND with it. By doing this we connect the bottom layer with the ground so that our signal integrity will increase.

Select GND as a net and then click OK. After that, a line will appear with the mouse cursor. Select all the edges of the board which is purple in line and press Esc from the keyboard. So we ground the bottom layer of the board.

Step 6: Design Verification

Perform a thorough review of your PCB layout design to ensure all connections are correct and according to your schematic. Run the Design Rule Check (DRC) again to catch any remaining errors. For DRC error check click on the design and then click on the CHECK DRC.

DRC check

On the left side table, you can find the DRC rule error if any exists. In our case, the DRC error is zero. If it exists we should resolve it before progressing further.

List of DRC rule errors

Step 7: Exporting Gerber Files

Once your circuit board design and layout are complete, generate Gerber files. These files are the industry standard for PCB manufacturing. Check with your PCBA manufacturer for their specific requirements regarding Gerber files. To generate the Gerber file click on the fabrication>PCB Fabrication File (Gerber)

Générer des fichiers Gerber

After clicking it will ask you to check the DRC error again. Click YES, and check DRC. 

And then generate a Gerber file. Your file is downloading automatically in zip format. 

Automatic download in zip format

Step 8: PCB Manufacturing

Send your Gerber files to a PCBA manufacturer of your choice. Choose the appropriate specifications, such as material, thickness, and copper weight. You can order the PCB from their Technologie FS and add a Gerber file or any other manufacturer that you want.

Step 9: PCB Assembly

If your design includes surface-mount components (Composants SMD), you will need to consider the Processus d'assemblage des PCB. PCB assembly is the manufacturing process of soldering electronic components onto the PCB to create a fully functional electronic circuit. The assembly process can be done using different methods, but the most common one for SMD components is reflow soldering.

Step 10: -Testing

Once you receive your manufactured PCBA, perform a thorough functional test to ensure everything is working as intended.

Remember that PCB design is a skill that improves with practice. Be patient and don’t hesitate to seek guidance from experienced designers or online resources as you learn.

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