Introduction to CadSoft EAGLE and DRU Files

CadSoft EAGLE (Easily Applicable Graphical Layout Editor) is a powerful PCB design software used by engineers and hobbyists worldwide. One of the key features of EAGLE is its Design Rule Check (DRC) functionality, which ensures that your PCB design adheres to a set of predefined rules and constraints. These rules are defined in Design Rules (DRU) files, which are essential for maintaining the integrity and manufacturability of your PCB designs.

With the release of EAGLE V6, CadSoft has introduced new DRU files that offer enhanced flexibility and customization options for PCB designers. In this article, we will explore the new CadSoft EAGLE DRU files for EAGLE V6, their features, and how they can benefit your PCB design process.

Understanding Design Rule Check (DRC) in EAGLE

Before diving into the new DRU files, let’s briefly discuss the importance of Design Rule Check (DRC) in EAGLE. DRC is a process that verifies your PCB design against a set of predefined rules and constraints. These rules ensure that your design meets the manufacturing requirements and prevents potential issues such as short circuits, insufficient clearances, or incorrect trace widths.

When you run a DRC in EAGLE, the software compares your design with the rules defined in the active DRU file. If any violations are found, EAGLE highlights them, allowing you to make necessary corrections before proceeding with the manufacturing process.

Key Design Rules in EAGLE

Some of the key design rules that are typically defined in a DRU file include:

1. Minimum trace width
2. Minimum clearance between traces and pads
3. Minimum drill size for vias and holes
4. Minimum annular ring size for vias and pads
5. Copper-to-edge clearance
6. Solder mask expansion
7. Silkscreen width and clearance

By adhering to these rules, you can ensure that your PCB design is manufacturable and reliable.

New Features in CadSoft EAGLE DRU Files for EAGLE V6

With the release of EAGLE V6, CadSoft has introduced several new features and enhancements to the DRU files. These improvements offer greater flexibility and customization options for PCB designers. Let’s explore some of the key features:

1. Enhanced Clearance Rules

EAGLE V6 introduces more granular control over clearance rules. You can now define clearance rules based on specific net classes, allowing you to have different clearance requirements for different types of signals. For example, you can specify a larger clearance for high-speed signals to minimize crosstalk and interference.

Here’s an example of how you can define clearance rules based on net classes in a DRU file:

clearance("High Speed") {
    value = 0.2mm
    class = "High Speed"
}

clearance("Default") {
    value = 0.1mm
    class = "*"
}

In this example, the “High Speed” clearance rule sets a clearance of 0.2mm for nets belonging to the “High Speed” class, while the “Default” rule sets a clearance of 0.1mm for all other nets.

2. Improved Pad and Via Sizing Rules

EAGLE V6 offers more flexibility in defining pad and via sizing rules. You can now specify different pad and via sizes based on the drill size, allowing you to optimize your design for manufacturability and reliability.

Here’s an example of how you can define pad and via sizing rules in a DRU file:

padSize("Small") {
    diameter = 0.6mm
    drillDiameter = 0.3mm
}

padSize("Large") {
    diameter = 1.0mm
    drillDiameter = 0.6mm
}

viaSize("Default") {
    diameter = 0.8mm
    drillDiameter = 0.4mm
}

In this example, two pad sizes are defined: “Small” with a pad diameter of 0.6mm and a drill diameter of 0.3mm, and “Large” with a pad diameter of 1.0mm and a drill diameter of 0.6mm. Additionally, a default via size is defined with a diameter of 0.8mm and a drill diameter of 0.4mm.

3. Copper-to-Edge Clearance Rules

EAGLE V6 introduces the ability to define copper-to-edge clearance rules in the DRU file. This allows you to specify the minimum distance between copper features (traces, pads, etc.) and the edge of the PCB. Maintaining proper copper-to-edge clearance is crucial for ensuring the structural integrity of your PCB and preventing damage during the manufacturing process.

Here’s an example of how you can define copper-to-edge clearance rules in a DRU file:

copperToBoardEdge() {
    value = 0.5mm
}

In this example, the minimum copper-to-edge clearance is set to 0.5mm.

4. Solder Mask Expansion Rules

Solder mask expansion rules define the additional area around pads and vias that should be covered by the solder mask. EAGLE V6 allows you to customize solder mask expansion rules in the DRU file, giving you control over the solder mask coverage on your PCB.

Here’s an example of how you can define solder mask expansion rules in a DRU file:

solderMaskExpansion() {
    value = 0.1mm
}

In this example, the solder mask expansion is set to 0.1mm, meaning that the solder mask will extend 0.1mm beyond the edges of pads and vias.

5. Silkscreen Width and Clearance Rules

Silkscreen is the text and graphics printed on the surface of a PCB for identification and assembly purposes. EAGLE V6 introduces the ability to define silkscreen width and clearance rules in the DRU file, allowing you to control the appearance and legibility of your silkscreen.

Here’s an example of how you can define silkscreen width and clearance rules in a DRU file:

silkscreenWidth() {
    value = 0.15mm
}

silkscreenToPadClearance() {
    value = 0.2mm
}

In this example, the minimum silkscreen width is set to 0.15mm, and the minimum clearance between silkscreen and pads is set to 0.2mm.

Benefits of Using CadSoft EAGLE DRU Files

Using CadSoft EAGLE DRU files offers several benefits for PCB designers:

1. Consistency: DRU files ensure that your PCB designs adhere to a consistent set of rules and constraints, regardless of the designer working on the project. This helps maintain uniformity and reliability across different designs.

2. Manufacturability: By defining appropriate design rules in the DRU file, you can ensure that your PCB design is manufacturable and meets the requirements of your chosen PCB fabrication vendor. This reduces the risk of manufacturing issues and delays.

3. Customization: EAGLE V6 offers enhanced customization options in the DRU files, allowing you to tailor the design rules to your specific needs and requirements. This flexibility enables you to optimize your designs for performance, reliability, and cost-effectiveness.

4. Time-saving: Using well-defined DRU files can save you significant time during the PCB design process. By catching design rule violations early on, you can avoid costly revisions and iterations later in the development cycle.

5. Collaboration: DRU files can be shared among team members, ensuring that everyone is working with the same set of design rules. This facilitates collaboration and reduces the chances of errors and inconsistencies in the design.

FAQ

1. Q: Can I create custom DRU files in EAGLE V6?
   A: Yes, EAGLE V6 allows you to create and modify DRU files to suit your specific design requirements. You can either start from scratch or modify an existing DRU file to create your custom design rules.

2. Q: How do I apply a DRU file to my PCB design in EAGLE?
   A: To apply a DRU file to your PCB design, go to the “Tools” menu in EAGLE and select “DRC…” from the dropdown menu. In the DRC dialog box, click on the “Load…” button and navigate to the location of your DRU file. Select the file and click “Open” to load the design rules.

3. Q: Can I use the same DRU file for different PCB designs?
   A: Yes, you can use the same DRU file for multiple PCB designs as long as the design requirements and constraints are similar. However, it’s always a good practice to review and modify the DRU file based on the specific needs of each project.

4. Q: What should I do if I encounter a design rule violation in EAGLE?
   A: If EAGLE reports a design rule violation during the DRC process, you should carefully review the violation and make necessary changes to your design to resolve the issue. EAGLE provides detailed information about the violation, including its location and the specific rule that was violated, helping you identify and fix the problem.

5. Q: Are the new features in CadSoft EAGLE DRU files for EAGLE V6 backward compatible with earlier versions?
   A: The new features and enhancements introduced in the DRU files for EAGLE V6 may not be fully compatible with earlier versions of EAGLE. It’s recommended to use the DRU files specifically designed for EAGLE V6 to take advantage of the latest improvements and ensure compatibility with the software.

Conclusion

CadSoft EAGLE DRU files play a crucial role in ensuring the integrity, manufacturability, and reliability of PCB designs. With the release of EAGLE V6, CadSoft has introduced new features and enhancements to the DRU files, offering greater flexibility and customization options for PCB designers.

By understanding and utilizing the new features, such as enhanced clearance rules, improved pad and via sizing rules, copper-to-edge clearance rules, solder mask expansion rules, and silkscreen width and clearance rules, you can optimize your PCB designs for performance, reliability, and cost-effectiveness.

Incorporating CadSoft EAGLE DRU files into your PCB design workflow can save you time, ensure consistency, and facilitate collaboration among team members. By adhering to well-defined design rules, you can minimize the risk of manufacturing issues and delays, ultimately leading to successful PCB projects.

As a PCB designer, staying up-to-date with the latest features and best practices in EAGLE is essential for creating high-quality and reliable PCB designs. By leveraging the power of CadSoft EAGLE DRU files for EAGLE V6, you can take your PCB designs to the next level and achieve optimal results in your projects.