Design Rules Check (DRC) setup in PCB Design - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the main purpose of Design Rules Check (DRC) in PCB design?

DRC ensures that the PCB layout follows all manufacturing and electrical rules to avoid errors during production and operation.

beginner

Name two common types of rules checked during a DRC.

Clearance rules (minimum spacing between elements) and width rules (minimum trace width) are two common types checked.

intermediate

Why is setting up correct clearance values important in DRC?

Correct clearance prevents short circuits and ensures reliable electrical isolation between components and traces.

intermediate

How does DRC setup affect PCB manufacturing yield?

Proper DRC setup reduces errors that cause PCB failures, improving manufacturing yield and reducing costs.

beginner

What should you do if your DRC reports many violations after running it?

Review each violation, understand the cause, and adjust the layout or rules to fix the issues before finalizing the design.

What does DRC primarily check in a PCB design?

A Compliance with design rules like spacing and width

B The color scheme of the PCB

C The software version used for design

D The cost of components

DRC checks if the PCB layout follows the set design rules such as spacing and trace width.

Which of these is NOT typically a DRC rule?

A Minimum clearance between traces

B Minimum trace width

C Maximum component height

D Via size limits

Maximum component height is usually a mechanical constraint, not checked by electrical DRC rules.

If a DRC violation is found, what is the best next step?

A Fix the layout or adjust rules to resolve the violation

B Ignore it if it looks minor

C Change the PCB color

D Restart the design software

Violations should be fixed to ensure the PCB will function correctly and be manufacturable.

What impact does a strict DRC setup have on PCB design?

A Increases chances of errors

B Helps catch errors early and improves quality

C Makes the design process slower without benefits

D Changes the PCB size

Strict DRC rules help catch potential issues early, improving design quality and reliability.

Which tool feature is essential for setting up DRC rules?

A Cost estimator

B Color picker for traces

C 3D viewer for components

D Rule editor to define spacing and width

A rule editor allows you to define and customize the design rules for DRC.

Explain the importance of Design Rules Check (DRC) setup in PCB design.

Think about how rules help avoid mistakes before making the physical board.

Describe the steps you take after running a DRC and finding violations.

Focus on how to handle errors to finalize a good design.

Practice

1. What is the main purpose of setting up Design Rules Check (DRC) in PCB design?

easy

A. To ensure the PCB layout meets manufacturing and electrical requirements

B. To create the schematic diagram of the circuit

C. To program the microcontroller on the PCB

D. To generate the bill of materials automatically

Solution

1. Step 1: Understand DRC role in PCB design

   DRC is used to check if the PCB layout follows specific rules for spacing, sizes, and electrical constraints.

2. Step 2: Identify the main goal of DRC setup

   The goal is to catch errors early to ensure the PCB can be manufactured and works correctly.

3. Final Answer:

   To ensure the PCB layout meets manufacturing and electrical requirements -> Option A

4. Quick Check:

   DRC purpose = ensure design rules met [OK]

Hint: DRC checks design rules before manufacturing [OK]

Common Mistakes:

• Confusing DRC with schematic creation
• Thinking DRC programs components
• Assuming DRC generates parts list

2. Which of the following is the correct way to set a minimum clearance rule in a DRC setup?

easy

A. Clearance == 0.15mm

B. Clearance >= 0.15mm

C. Clearance < 0.15mm

D. Clearance = 0.15mm

Solution

1. Step 1: Understand clearance rule syntax

   In DRC setup, you define the minimum clearance as a fixed value, e.g., Clearance = 0.15mm.

2. Step 2: Identify correct syntax for minimum clearance

   Using an equality assignment sets the rule; inequalities are not used in this context.

3. Final Answer:

   Clearance = 0.15mm -> Option D

4. Quick Check:

   Minimum clearance set by assignment = value [OK]

Hint: Use assignment (=) to set DRC clearance values [OK]

Common Mistakes:

• Using inequality signs instead of assignment
• Confusing comparison operators with rule definitions
• Writing clearance as a condition instead of a value

3. Given the following DRC rules:
MinTrackWidth = 0.2mm
MinClearance = 0.15mm
If a track is 0.18mm wide and the clearance between two tracks is 0.14mm, what will the DRC report?

medium

A. Errors: Track width and clearance below minimum

B. Error: Track width below minimum

C. Error: Clearance below minimum

D. No errors, all rules met

Solution

1. Step 1: Check track width against minimum

   The track width is 0.18mm, which is less than the minimum 0.2mm, so this violates the rule.

2. Step 2: Check clearance against minimum

   The clearance is 0.14mm, less than the minimum 0.15mm, so this also violates the rule.

3. Final Answer:

   Errors: Track width and clearance below minimum -> Option A

4. Quick Check:

   Width < 0.2mm and Clearance < 0.15mm = Errors [OK]

Hint: Compare values directly to minimum rules [OK]

Common Mistakes:

• Ignoring one of the two rule violations
• Assuming no error if only one rule fails
• Mixing up width and clearance values

4. You set a DRC rule for minimum hole size as MinHoleSize = 0.3mm. After running DRC, you still see errors for holes sized 0.35mm. What is the most likely cause?

medium

A. The holes are actually smaller than 0.3mm

B. The hole size units are mismatched (e.g., inches vs mm)

C. The DRC rule syntax is incorrect

D. The DRC tool does not check hole sizes

Solution

1. Step 1: Verify units used in hole size and DRC rule

   If the holes are 0.35mm but errors appear, units might be mismatched, e.g., holes measured in inches but rule in mm.

2. Step 2: Confirm DRC rule syntax and tool capability

   The syntax MinHoleSize = 0.3mm is correct and DRC tools do check hole sizes, so these are unlikely causes.

3. Final Answer:

   The hole size units are mismatched (e.g., inches vs mm) -> Option B

4. Quick Check:

   Unit mismatch causes false errors [OK]

Hint: Always check units match between design and rules [OK]

Common Mistakes:

• Assuming syntax error without checking units
• Ignoring unit differences between design and rules
• Thinking DRC ignores hole sizes

5. You want to set up a DRC rule that enforces a minimum spacing of 0.2mm between copper traces but allows a smaller spacing of 0.1mm between traces on different layers. How should you configure the DRC rules?

hard

A. Set MinClearance = 0.1mm for all layers without exceptions

B. Set MinClearance = 0.2mm and ignore layer differences

C. Set MinClearance = 0.2mm and enable LayerSpecificClearance = true with InterLayerClearance = 0.1mm

D. Set MinClearance = 0.3mm to cover all cases

Solution

1. Step 1: Understand clearance rules for same and different layers

   Minimum spacing between traces on the same layer is 0.2mm, but between layers it can be smaller (0.1mm).

2. Step 2: Configure DRC to handle layer-specific clearances

   Enable a setting like LayerSpecificClearance = true and set InterLayerClearance = 0.1mm to allow smaller spacing between layers.

3. Final Answer:

   Set MinClearance = 0.2mm and enable LayerSpecificClearance = true with InterLayerClearance = 0.1mm -> Option C

4. Quick Check:

   Layer-specific clearance rules = Set MinClearance = 0.2mm and enable LayerSpecificClearance = true with InterLayerClearance = 0.1mm [OK]

Hint: Use layer-specific clearance settings for different spacing [OK]

Common Mistakes:

• Applying one clearance value for all layers
• Ignoring inter-layer spacing rules
• Setting clearance too large and restricting design