This Tutorial explains PCB setup and placing components in DesignSpark PCB.
Please see the video tutorial below to get our expert's perspective on this subject and read the text further down the page for complementary look-up information.
Converting the Schematic to PCB
If you are following the tutorial, you would have already processed your ‘logical’ Schematic design into the ‘physical’ PCB design layout editor using the Translate To PCB option and PCB Wizard. If you didn’t do this, go back to the previous chapter (Converting your Schematic to PCB) and convert your schematic into a PCB design ready to carry on with this tutorial.
At this point you would normally be ready to start laying out the PCB design. For our example, we created the board outline, placed the components and routed the connections. This enabled you to see the full process working.
The board outline is displayed with the components placed (and routed), we are going to undo this and do it all manually.
Unroute the Design
You may sometimes have a requirement to unroute all or part of the design, as we do now. Unrouting is the process of removing tracks leaving only the connections remaining.
Unroute the design
Selectthe Unroute Nets>All Nets optionon the Tools menu to unroute the whole design removing all the tracks already routed. Three Unroute options available to control the amount of unrouting to perform – All Nets, Browse and Selected Nets.
Don’t forget, once unrouted, you can always restore the routes using Undo<Ctrl-Z>.
Changing the Number of Layers
If you decide at any time to change the number of physical layers or the type of manufacturing, you can do this using the Settings menu and the Design Technology option, choose the Layers tab.
Be aware that reducing the number of layers using Delete could lead to information on the inner electrical layers being lost.
Creating a Board Outline Interactively
If you require a custom board size and shape, and decide not you use our pre-defined shapes of rectangle or circle, this can also be easily achieved.
Deleting an existing board outline
DesignSpark only requires one board outline so you would need to delete any previous one first. You can edit an existing board outline as well. If you do need to delete it, simply select the outline and click the Delete button on your keyboard.
Adding a new board outline
Board outlines can be created easily in DesignSpark; by adding board shapes (including circles). The Add Board option on the Add menu allows you to interactively create a board outline by drawing it into the design. Four shape styles are provided: Rectangle, Shape, Circle and Square. There is also a shortcut on the PCB Design toolbar to add a Board Polygon.
Board outlines are created as a Closed shape so during addition, you’ll see the ‘trailing’ board segment trail back to the start point. Click to add corners. After adding the last corner, use double-click to finish. If during the insert, you wish to cancel, click the <Esc> key on the keyboard. This will create you a board outline as a continuous shape starting and finishing at the start point.
Once the board has been added, it can be modified afterwards, extra segments can be added and the corners can be mitred or made curved.
For this tutorial, during the Schematic To PCB conversion process earlier we have specified the board outline as a square of 3000x3000 thou. If you require cutout shapes in your board, add these using the Add Board Shape option. DesignSpark understands that board outlines inside the main board outline will act as cutouts.
Importing a new board outline using a DXF file
Instead of drawing a board outline, you can also import a DXF file previously created in your mechanical CAD system, such as AutoCAD.
If you wish to import a DXF file, use the Import option on the File menu. You are presented with a dialog to map shapes and text in the DXF file into your DesignSpark layers. You can also change the import Units to adjust the import scale. More information about this option is available in the Online Help.
Placing Components
Placement can be an automatic or manually process. Automatic placement can be either during the conversion phase or by using the Auto Place Components> option from the Tools menu. Manual placement can be done at any point in the Design editor, even after using the automatic placement option.
We’ve started the design with the board outline and are now ready to try manually placing the components. Currently, our design has been placed during use of the New Board Wizard option. We will un-place the design first.
Drag a box around the components in the design to select them.
Now pick and drag them outside the board outline. Had you chosen the option Arrange Outside theBoard, this would havestacked them neatly outside the board outline ready for manual placement. Once outside the board outline, release the mouse to place them. Click in free space to deselect the components.
To place components
DesignSpark uses standard Microsoft Windows methodology throughout, moving or placing components is a simple case of picking and dragging the selected component. At any time during move, the drag may be cancelled by pressing the <Esc> key, or once released by using Undo<Ctrl-Z>.
Using the pick and drag method, place all the components to look like the picture below.
We suggest you place CONN1, U1, U2 and U3 first and place the other components around these. Placement on this design isn’t critical but improve it if you feel you want to.
When placing U3 we have rotated it to get it closer to the connector CONN1. We will also place the decoupling capacitors close to this device as they are pretty sensitive and are there to reduce noise of the voltage regulator.
Place capacitors C6, C7, C8 and C9 as close as you can to U3. To follow our example exactly as the picture below, you will need to rotate some of the components.
Once you have these components placed, we will fix them. On a real design, let’s assume you might have some critical components which are placed specifically. You would then want to fix these so they cannot be moved accidentally.
To fix components
To fix components, select the component and use Properties from the shortcut menu.
On the Component page, select the Fixed check box and press OK. This will fix the component.
The Fix Item option is also available on the shortcut menu for a selected component.
To rotate components
During Place or after placing components, use the shortcut key <R> to Rotate them and <F> to Flip (mirror) surface mount components to the other side of the board. These options (and more) are available on the shortcut menu during Place by clicking the right mouse button.
To flip (mirror) components to the other side of the board
For our design, no mirroring (Flip) will be required. The placement and overall connection lengths could be improved by rotating some of the components. If you feel you would like the practice placing components, select a component and click <R> to rotate it. Component names can be rotated back to be a readable direction separately using the same pick and rotate method.
Once fully placed, the design should be routed.
To use the autoplace option
We’ve placed some of the critical components and fixed them in-place. Now we will place the remaining components using the Autoplace option.
From the Tools menu, select Auto Place Components>, choose AllComponents.
From the selection available, we want to View Component Placement so check the box. Also check the Don’t Place Fixed Components box, we want the fixed components to remain in-place.
Set the Minimum Space Allowed Between Components and Placement Grid values to 100 thou each. You can play about with these values if you like. Place the remaining components and use Undo if you wish to try a different placement pattern. Perhaps changing the Grid to 50 thou.
Press OK to make the placement. The remaining components are placed around the fixed ones in the space available.
Save the design
Save the design using the Save option from the File menu or click the Save icon on the toolbar.
The PCB design has already been named when you translated from Schematic to PCB, we named it Tutorial.pcb. We named it this so it matches the name of the Schematic. This will become more important later on when you run the integrity checks before plotting.
If you have any suggestions on how to improve this tutorial please drop us a comment below