PCB Layout

Whether it be an electronic device, furniture, or even a house, the first phase of development is layout designing.

The layout enables the developer to analyze the design, spot potential flaws, and make possible improvements before the development begins.

The layout carries helpful information regarding the dimensions, shape, and size which are necessary for development.

The concept of the layout is no different in printed circuit boards (PCBs).

A Printed Circuit Board (PCB) layout, is a soft design of traces, holes, and vias that have to be developed on the physical board for circuit development.

The PCB layout elucidates how which and where components have to be connected.

An average PCB has several components, multiple connections, and holes.

The placement of several components on a small piece of PCB is not easy without a layout. PCB layout eases the development process by smartly organizing all components.

Most of the commercial PCB designing software output PCB layout in a machine-readable format and can be used for PCB development.

It helps fasten up the development process and also reduces the chances of inappropriate connections.

RF Transmitter Layout Developed on Altium Designer

How to Make PCB Layout with Altium Designer?

PCB layout designing usually begins after the schematic diagram designing as the layout is a sketch of the schematic design.

Commercially, PCB layouts are designed using certain types of tools but Altium is one of the most commonly used software.

Follows are the steps on how to design a PCB layout using Altium.

Step 1: Create PCB Layout from Schematic Diagram

A PCB layout cannot be finalized for development as long as the PCB schematic violates any design rules.

It is essential to ensure there are no duplications in design, no stranded components, or unusual connections.

This is essential for layout designing but it doesn’t mean that the schematic cannot be modified later; the schematic can always be edited without affecting the layout unless wanted.

To ensure the design is valid and doesn’t contain any flaws, Altium’s schematic editor is used.

The schematic design has to be compiled for generating the connectivity map of all the components and nets used in schematic design.

Apart from the connectivity checks, the compiler checks certain other aspects of the design by running various checks.

To check the configurations of these settings, go to the dropdown menu “Project” and open “Project Options”.

Four Tabs of Project Options

The project options open up in four tabs as shown in the above image.

In the first tab, you can change the configuration of errors and choose which error should be displayed and how you should be notified.

Since the connectivity between certain kinds of pins is not compatible in some projects, in the second tab, you can choose the connection between which kinds of pins should be acceptable.

You can also change the configuration of nets and components in the third tab. The fourth tab displays the configurations for the comparator.

The change in settings made on these four tabs alters the way the layout is created from the schematic (when imported).

Although the designers usually do not have to add many changes to these settings in some cases, for high precision, the changes have to be made.

These changes have a high impact on circuit reliability especially in designs where extra layers have to be added.

Once all the settings have been updated, the next step is to compile the project.

For compiling the project, click on the dropdown menu “Project” and then click on “Compile PCB Project”.

There are two possible outcomes to this step: either the design will compile successfully or it will show messages.

The design usually shows messages only if there are any rule violations in the design that need to be correct before Altium can compile the design.

Altium Compiler Showing Design Error Message

For demonstration, the design in the following image has been slightly altered; a rule violation has been introduced by removing the connection between the resistor and the transistor base.

Consequently, after compilation, a message appears stating “NetC1_1” only has one pin on it (Pin C1-1)”.

Now as long as this issue is not resolved, the second pin is not connected, the Altium will not proceed with the layout design.

If the connection is reestablished, the compiler successfully compiles the design.

Step 2: Schematic Data Import in Layout File

Once the schematic design is finalized according to the Altium design rules, the schematic is ready for import into the layout.

This is a built-in feature of Altium software, the designer can directly import a schematic design into the layout without designing every component from scratch.

Since Altium has a library of components, it automatically creates a layout of each component using the schematic design.

However, in the case of custom-made components, the designer has to create the layout manually.

Before importing schematic design, a new PCB file needs to be created.

The schematic capture tool is used to import the schematic design in the PCB layout.

Once the schematic design has been imported, the next step is to organize all the imported components and route traces.

Just in case if you already have a schematic file designed, you can use the same schematic file to design a layout file instead of creating a new schematic from scratch; you need to create a new file and import the schematic in layout design for that too.

To create a layout from the schematic file, follow the instructions shown in the following image.

Click on the dropdown menu “Project” and select “Add New to Project” and then select “PCB”.

Doing so will add a new PCB object which we are going to use as a schematic object.

New PCB Object Addition

Since every project is composed of multiple files and sometimes there are multiple files of the same type, it is recommended to rename this file as “Schematic Object” or any other name for clear identification.

To rename it, right-click on it and select “save it as a new name” and then write a new name.

The PCB object has been added but it still needs to be configured to make it compatible with your particular project and its requirements.

To adjust the origin, click on the dropdown menu “Edit” and click on “Origin” and to adjust the grid, click on the dropdown menu “View” and clicks on “Grids”.

Apart from managing grid and origin, you might want to edit the board outline as per your project specifications.

But the editing has to be done in the “Board Planning Mode” whereas the board is in 2D-view mode by default.

To change the view, click on the dropdown menu “View” and change the board view to “Board Planning Mode” then use relevant options to modify the board shape and size.

After these changes, now use the ”Schematic Capture” tool for transferring schematic to PCB design.

The tool will fetch the components of the schematic file to the PCB editor.

Although the components were connected in the schematic design but they won’t be connected in the PCB editor.

However, thin lines will show the link between components, these links show which connections have to be established with traces on the board. Carefully analyze these links when organizing the components in the PCB editor.

Now, click on the “Design” and then click on “Import Changes From….(Schematic file name)” and a new window “Engineering Change Order” will open as shown in the below image.

 Engineering Change Order Window

Now the design needs to be validated to ensure the design in the PCB editor is synchronized with the schematic design.

Use the “Validate Changes” option in the same window, the tool will start validating each item.

For all items that are successfully validated, the tool will mark them as checked with a green tick as shown in the following image.

However, if any item fails validation, the problem needs to be addressed.

When all problems are corrected, again click on the “Validate Changes” button. Once all items are successfully validated, green checkmarks will appear in front of all items.

Validation Green Checks in Engineering Change Order Window

By this step, the schematic design has been successfully exported to the board in the PCB editor window.

Now, the Engineering Change Order window can be closed as it is no longer needed.

Once closed, you will notice the presence of components besides the board as shown in the following image.

Successful Import of Schematic Data in Layout

By default, when the components are imported in layout, they are unorganized as shown in the following image.

All components need to be organized but before that, it is essential to resize the board and create a layer stack for the board.

This is important especially is the design includes the use of vias and individual layers for power and ground.

Step 3: Board Configuration for Physical Layer Stack

The third step is to configure the board for the physical layer stack.

This is important because each layer needs to be in the right position for proper functioning.

Moreover, in some cases, the impedance of each layer needs to be moderated which is also a part of the board configuration.

Click on the drop-down menu “Design” and then click on “Layer Stack Manager”.

As shown in the following Image “Layer Stack Manager” Window, Altium displays the type, material, thickness, dielectric material, and constant and several other parameters against each layer.

You can reorganize, add, remove or copy any layer in the stack.

You can also add dielectric or special layers for a particular signal, power, or ground. Moreover, the impedance of each layer can be calculated using the “Impedance Calculation” option as shown in the following image.

Layer Stack Manager Window

After organizing and configuring all layers, the next step is to set design rules.

Click on the dropdown menu “Design” and then click on “PCB Rules and Constraints Editor”.

Here, you will find all essential options for editing design rules.

Apart from the rules, the layers’ display also needs to be configured.

For that, use the set of options in the “View Configuration” panel.

View Configuration Window

Once all components have been exported to the board from the schematic file and all the above configurations have been made, the board is ready for detailed arrangement.

The components can be dragged on the board as needed.

After all, components have been organized, they must be traces must be routed between the components.

Since during the routing process, it is more convenient to see only useful layers and hide the rest of the layers, the unneeded layers can be hidden through the “View Configuration” Window.

It is recommended to turn off all layers except the surface, silkscreen, mechanical, and ground layer.

When designing a PCB, the designers have to take care of certain other factors, depending on the circuit.

For example, high-frequency circuits are prone to unwanted signals, the empty parts of the board must be grounded to avoid possible intervention.

Similarly, if a schematic design contains both analog and digital signals, the connections and components of both signals must not be placed close to each other as the analog signals can interrupt the digital part of the circuit.

Although software like Altium can analyze designs and notify regarding possible issues each must be thoroughly checked by the designer to eradicate chances of malfunctioning.

Evidently, PCB designing is an extensively technical process that requires both human and machine interaction.

Although the PCB design software like Altium performs most of the layout designing tasks the designer’s intervention is necessary.

A smartly developed PCB layout can save cost, reduce board size, number of connections, and even power.

Whereas an improper PCB layout can escalate cost, cause malfunctioning, and reduce the overall life of the circuit.