Working with a Board Shape Object on a PCB in Altium Designer

Introduction

In the world of printed circuit board (PCB) design, the board shape is a crucial element that defines the physical dimensions and outline of the PCB. Altium Designer, a powerful electronic design automation (EDA) software, provides designers with a flexible and intuitive way to create and manipulate board shapes using the Board Shape object. This object allows for precise control over the PCB outline, enabling designers to create unique and custom PCB shapes that meet specific design requirements.

Understanding the Board Shape Object

The Board Shape object in Altium Designer is a specialized type of polygon that represents the physical boundaries of the PCB. It serves as a container for all the components, traces, and other objects placed on the board, ensuring that they remain within the defined board outline. This object is essential for various aspects of the PCB design process, including:

1. Physical Layout: The Board Shape object defines the physical dimensions and outline of the PCB, allowing designers to create boards with unique shapes and sizes.
2. Manufacturing Preparation: A properly defined board shape is crucial for generating accurate manufacturing files, such as Gerber files, which are used for PCB fabrication and assembly.
3. Design Rule Checking: The Board Shape object plays a role in design rule checking (DRC), ensuring that components and traces are placed within the specified board boundaries.
4. 3D Visualization: The Board Shape object contributes to the accurate representation of the PCB in 3D visualization and rendering, providing a realistic view of the final product.

Creating a Board Shape Object

To create a Board Shape object in Altium Designer, follow these steps:

1. Open the PCB design project in Altium Designer.
2. In the PCB editor, navigate to the "Board Shape" layer using the Layer Stack manager or by selecting the appropriate layer from the drop-down menu.
3. From the main toolbar, select the "Board Shape" tool or use the shortcut key (typically the "B" key).
4. Start drawing the board shape by clicking on the canvas to create vertices. Double-click or right-click to complete the shape.
5. Once the shape is created, you can modify its properties, such as layer assignment, line width, and fill style, using the Properties panel.

Modifying the Board Shape Object

Altium Designer provides various tools and techniques for modifying the Board Shape object to suit your design requirements. Here are some common methods:

1. Vertex Editing

You can edit the vertices of the Board Shape object by selecting them and dragging to a new location. This allows you to reshape the board outline as needed. Additionally, you can add or remove vertices by right-clicking and selecting the appropriate option from the context menu.

2. Using Shape Tools

Altium Designer offers several shape tools that can be applied to the Board Shape object. These tools include:

• Union: Combines two or more shapes into a single shape.
• Subtraction: Subtracts one shape from another, creating a cutout or hole.
• Intersection: Creates a new shape from the overlapping areas of two or more shapes.
• Chamfer: Adds chamfers (beveled edges) to the corners of the Board Shape object.

3. Importing Board Shapes

If you have a pre-defined board shape or outline, you can import it into Altium Designer. Supported file formats include DXF, STEP, and IDF files. Once imported, the board shape can be further modified or used as is.

4. Dimensioning and Constraints

To ensure accurate dimensions and maintain design integrity, you can add dimensions and constraints to the Board Shape object. This helps prevent unintended changes and ensures that the board shape meets the specified requirements.

Best Practices and Considerations

When working with the Board Shape object in Altium Designer, it's essential to follow best practices and consider the following:

1. Design Rules: Ensure that the Board Shape object adheres to the design rules defined for your project. This includes clearances, spacing, and other manufacturing constraints.
2. Keepout Areas: Define keepout areas within the Board Shape object to prevent components or traces from being placed in restricted regions, such as mounting holes or areas reserved for connectors.
3. Layer Assignment: Assign the Board Shape object to the appropriate layer, typically the "Board Shape" layer, to ensure proper visibility and interaction with other design objects.
4. Version Control: Implement version control for your PCB design projects, including changes to the Board Shape object, to maintain a historical record and enable collaboration with team members.
5. Documentation: Document any modifications or special considerations related to the Board Shape object in your design documentation for future reference and to facilitate communication with manufacturers or collaborators.

Design Example: Creating a Custom Board Shape

To illustrate the process of working with the Board Shape object, let's consider a design example where we create a custom board shape resembling a hexagonal outline.

Step 1: Create a New Board Shape

1. In the PCB editor, navigate to the "Board Shape" layer.
2. Select the "Board Shape" tool from the main toolbar.
3. Click on the canvas to create the first vertex of the hexagon.
4. Continue clicking to create additional vertices, forming the desired hexagonal shape.
5. Double-click or right-click to complete the shape.

Step 2: Modify the Board Shape

1. Select one of the vertices of the Board Shape object.
2. Right-click and choose "Add Vertex" to create additional vertices along the edge.
3. Adjust the position of the new vertices to refine the hexagonal shape.
4. Repeat steps 2 and 3 for the remaining edges, if necessary.

Step 3: Add Dimensions and Constraints

1. Select the "Dimension" tool from the main toolbar.
2. Click and drag to create dimensions between vertices or edges of the Board Shape object.
3. Specify the desired dimensions for the hexagonal shape.
4. Apply constraints, such as parallel or perpendicular constraints, to maintain the hexagonal shape integrity.

Step 4: Perform Design Rule Checks

1. Run design rule checks (DRC) to ensure that the Board Shape object adheres to the defined design rules, such as clearances and spacing requirements.
2. Resolve any violations or errors identified by the DRC.

Step 5: Generate Manufacturing Files

1. Once the custom board shape is finalized, generate the necessary manufacturing files, such as Gerber files, for PCB fabrication.
2. Review and verify the manufacturing files to ensure accurate representation of the custom board shape.

FAQs (Frequently Asked Questions)

1. Q: Can I create multiple Board Shape objects on the same PCB design? A: No, Altium Designer allows only one Board Shape object per PCB design. If you require multiple board outlines, you can create separate PCB designs or consider using keepout areas within the single Board Shape object.
2. Q: How do I ensure that components and traces stay within the Board Shape boundaries? A: Altium Designer's design rule checks (DRC) and interactive placement features help ensure that components and traces are placed within the defined Board Shape boundaries. Additionally, you can create keepout areas to restrict placement in specific regions.
3. Q: Can I import a Board Shape object from another design software or file format? A: Yes, Altium Designer supports importing board shapes from various file formats, including DXF, STEP, and IDF files. This allows you to use pre-defined board shapes or outlines from other design tools or sources.
4. Q: How do I create cutouts or holes within the Board Shape object? A: To create cutouts or holes within the Board Shape object, you can use the "Subtraction" shape tool. This tool allows you to subtract a shape (e.g., a circle or rectangle) from the existing Board Shape, creating the desired cutout or hole.
5. Q: Can I export the Board Shape object as a separate file for further modification or sharing? A: Yes, Altium Designer provides options to export the Board Shape object as a separate file in various formats, such as DXF or STEP. This allows you to share or modify the board shape using other CAD software or tools if needed.

By following the guidelines and best practices outlined in this article, you can effectively work with the Board Shape object in Altium Designer to create custom PCB outlines that meet your design requirements. Remember to always adhere to design rules, maintain version control, and document any modifications or considerations related to the Board Shape object.