Zone priority for overlapping fills in PCB Design - Real Business Scenario

Scenario Mode

👤 Your Role: You are a PCB designer working on a complex multilayer board.

📋 Request: Your manager wants you to ensure that overlapping copper fills on the same layer respect the correct zone priority to avoid electrical shorts and maintain signal integrity.

📊 Data: You have a PCB design file with multiple copper zones defined on the same layer. Some zones overlap partially or fully. Each zone has a priority level assigned.

🎯 Deliverable: You need to configure the zone priority settings in your PCB design software so that the fills render correctly, with higher priority zones taking precedence over lower priority ones in overlapping areas.

Sample Data

Zone Name	Net	Priority	Area (mm²)	Overlap With
GND_Plane	GND	1	500	Power_Plane
Power_Plane	VCC	2	300	GND_Plane
Signal_Shield	Shield	3	100	Power_Plane
Test_Point	Test	4	10	Signal_Shield

1

Step 1: Open your PCB design software and load the board file containing the overlapping zones.

No formula needed; just open the design file.

Expected Result

The board with all copper zones visible on the same layer.

2

Step 2: Access the zone priority settings or properties panel for copper fills.

Navigate to Design > Zones > Zone Priority or equivalent menu.

Expected Result

Zone priority configuration window opens showing all zones and their current priorities.

3

Step 3: Set the priority values for each zone according to the business rule: higher priority zones override lower ones in overlaps.

Assign priorities as: Test_Point=4, Signal_Shield=3, Power_Plane=2, GND_Plane=1.

Expected Result

Zone priorities updated so that Test_Point has highest priority and GND_Plane the lowest.

4

Step 4: Apply the zone priority settings and regenerate the copper fills on the layer.

Click Apply or OK and then use the Refill Zones command.

Expected Result

Copper fills redraw with overlapping areas showing the higher priority zone's copper.

5

Step 5: Verify visually and with design rule checks that no unintended copper shorts or gaps exist due to overlapping fills.

Run Design Rule Check (DRC) focusing on copper clearance and connectivity.

Expected Result

DRC passes with no errors related to overlapping zones; visual inspection confirms correct fill priority.

Final Result

Test_Point

↓

Signal_Shield

↓

Power_Plane

↓

GND_Plane

✓Higher priority zones correctly override lower priority zones in overlapping areas.

✓No electrical shorts or clearance violations detected after applying zone priorities.

✓Signal integrity is maintained by proper copper fill layering.

Bonus Challenge

Configure zone priorities dynamically using scripting or automation to handle large boards with many overlapping zones.

Show Hint

Use your PCB software's scripting API or batch commands to assign priorities based on net types or area size automatically.

Practice

1. What does zone priority control in PCB design when fills overlap?

easy

A. Which copper fill appears on top

B. The thickness of the copper fill

C. The color of the copper fill

D. The shape of the copper fill

Solution

1. Step 1: Understand overlapping fills

   When two copper fills overlap, one must appear above the other to avoid confusion.

2. Step 2: Role of zone priority

   Zone priority sets which fill is drawn on top by assigning a higher priority number.

3. Final Answer:

   Which copper fill appears on top -> Option A

4. Quick Check:

   Zone priority controls top fill display [OK]

Hint: Higher priority number means fill appears on top [OK]

Common Mistakes:

• Confusing priority with fill thickness
• Thinking priority changes fill color
• Assuming priority affects fill shape

2. Which of the following is the correct way to assign a higher priority to a zone fill in a PCB design tool?

easy

A. Set the zone priority number to a lower value

B. Set the zone priority number to a higher value

C. Change the zone fill color to a brighter shade

D. Increase the zone fill thickness

Solution

1. Step 1: Understand priority numbering

   Higher numbers mean higher priority, so the fill with the bigger number appears on top.

2. Step 2: Assigning priority

   To make a zone appear above others, assign it a higher priority number.

3. Final Answer:

   Set the zone priority number to a higher value -> Option B

4. Quick Check:

   Higher number = higher priority [OK]

Hint: Use bigger numbers for top zones [OK]

Common Mistakes:

• Using lower numbers for higher priority
• Changing color instead of priority
• Adjusting thickness instead of priority

3. Given two overlapping zones: Zone A with priority 5 and Zone B with priority 8, which zone will appear on top in the PCB layout?

medium

A. Zone A will appear on top

B. Neither zone will appear

C. Both zones will merge and appear equally

D. Zone B will appear on top

Solution

1. Step 1: Compare priority values

   Zone A has priority 5, Zone B has priority 8; higher number means higher priority.

2. Step 2: Determine which zone appears on top

   Zone B's priority 8 is greater than Zone A's 5, so Zone B appears on top.

3. Final Answer:

   Zone B will appear on top -> Option D

4. Quick Check:

   Priority 8 > 5 means Zone B on top [OK]

Hint: Higher priority number wins overlap [OK]

Common Mistakes:

• Choosing lower priority zone as top
• Assuming zones merge visually
• Ignoring priority numbers

4. You set two overlapping zones with the same priority number. What issue might occur in your PCB design?

medium

A. The zones will overlap without clear top fill, causing design errors

B. The zone with the larger area will automatically appear on top

C. The software will assign random priority to one zone

D. The zones will merge into a single fill automatically

Solution

1. Step 1: Understand equal priority effect

   When zones have the same priority, the software cannot decide which fill is on top clearly.

2. Step 2: Resulting issue

   This causes overlapping fills without clear layering, leading to design errors or confusion.

3. Final Answer:

   The zones will overlap without clear top fill, causing design errors -> Option A

4. Quick Check:

   Same priority causes unclear overlap [OK]

Hint: Avoid equal priorities for overlapping zones [OK]

Common Mistakes:

• Assuming larger area wins automatically
• Thinking software assigns random priority
• Believing zones merge automatically

5. You have three overlapping zones with priorities 3, 7, and 5. You want the zone with priority 3 to appear on top without changing the other zones' priorities. What is the best approach?

hard

A. Set the zone with priority 3 to a negative number

B. Decrease the priority of the zone with 7 to below 3

C. Increase the priority of the zone with 3 to a number higher than 7

D. Change the fill color of the zone with priority 3 to make it appear on top

Solution

1. Step 1: Understand priority rules

   Zones with higher priority numbers appear on top of lower ones.

2. Step 2: Achieve desired top zone

   To make the zone with priority 3 appear on top, increase its priority above 7.

3. Step 3: Avoid changing other zones

   Since other zones' priorities cannot be changed, only increase the target zone's priority.

4. Final Answer:

   Increase the priority of the zone with 3 to a number higher than 7 -> Option C

5. Quick Check:

   Higher priority number = top zone [OK]

Hint: Raise target zone priority above others [OK]

Common Mistakes:

• Trying to set negative priority
• Changing color instead of priority
• Lowering other zones' priorities when not allowed