Common PCB design mistakes - Real Business Scenario

Scenario Mode

👤 Your Role: You are a PCB design engineer working in a manufacturing company.

📋 Request: Your manager wants a report showing the most common PCB design mistakes found in recent projects to help improve future designs.

📊 Data: You have a dataset listing PCB projects with columns: ProjectID, MistakeType, Frequency, and ImpactScore (1-10).

🎯 Deliverable: Create a dashboard showing the top 5 common PCB design mistakes by frequency and their average impact scores.

Sample Data

ProjectID	MistakeType	Frequency	ImpactScore
101	Incorrect trace width	5	7
102	Insufficient clearance	8	8
103	Wrong component placement	6	6
104	Incorrect trace width	4	7
105	Missing vias	3	5
106	Insufficient clearance	7	9
107	Wrong component placement	5	6
108	Missing vias	4	5
109	Incorrect trace width	6	8
110	Insufficient clearance	5	7

1

Step 1: Group the data by MistakeType and calculate the total Frequency for each mistake.

SUM(Frequency) grouped by MistakeType

Expected Result

Incorrect trace width: 15, Insufficient clearance: 20, Wrong component placement: 11, Missing vias: 7

2

Step 2: Calculate the average ImpactScore for each MistakeType.

AVERAGE(ImpactScore) grouped by MistakeType

Expected Result

Incorrect trace width: 7.33, Insufficient clearance: 8, Wrong component placement: 6, Missing vias: 5

3

Step 3: Sort the mistakes by total Frequency in descending order and select the top 5.

Sort by SUM(Frequency) DESC, take top 5 MistakeType

Expected Result

1. Insufficient clearance (20), 2. Incorrect trace width (15), 3. Wrong component placement (11), 4. Missing vias (7)

4

Step 4: Create a bar chart with MistakeType on the x-axis and total Frequency on the y-axis.

Bar chart config: X= MistakeType, Y= SUM(Frequency)

Expected Result

Bar chart showing Insufficient clearance highest, then Incorrect trace width, etc.

5

Step 5: Add a line chart overlay showing average ImpactScore for each MistakeType on the same x-axis.

Line chart config: X= MistakeType, Y= AVERAGE(ImpactScore)

Expected Result

Line chart overlay showing impact scores aligned with bar chart categories

6

Step 6: Add clear labels, title 'Top 5 Common PCB Design Mistakes', and legend for Frequency and ImpactScore.

Add chart title, axis labels, and legend

Expected Result

Dashboard is clear and easy to understand

Final Result

Top 5 Common PCB Design Mistakes

Frequency (bars) and Impact Score (line)

Mistake Type           | Frequency | Impact Score
------------------------------------------------
Insufficient clearance | ██████████ 20 | -------8
Incorrect trace width  | ████████ 15 | -----7.3
Wrong component placement | ██████ 11 | ---6
Missing vias           | ████ 7 | --5

✓Insufficient clearance is the most frequent mistake with the highest impact score.

✓Incorrect trace width is the second most common mistake with a moderately high impact.

✓Wrong component placement and missing vias occur less frequently and have lower impact scores.

✓Focusing on clearance and trace width improvements can reduce major PCB design issues.

Bonus Challenge

Create a heatmap showing the correlation between mistake frequency and impact score across different projects.

Show Hint

Use MistakeType and ProjectID as axes, color intensity representing Frequency * ImpactScore.

Practice

1. Which of the following is a common mistake in PCB design related to component placement?

easy

A. Placing components too close causing soldering issues

B. Using correct footprint sizes for components

C. Ensuring clear labeling of components

D. Following manufacturer recommended spacing

Solution

1. Step 1: Understand component placement importance

   Components placed too close can cause solder bridges and assembly problems.

2. Step 2: Identify the mistake

   Placing components too close is a common error that leads to manufacturing defects.

3. Final Answer:

   Placing components too close causing soldering issues -> Option A

4. Quick Check:

   Component spacing = Placing too close [OK]

Hint: Check spacing between parts to avoid solder bridges [OK]

Common Mistakes:

• Ignoring minimum spacing rules
• Not considering solder mask clearance
• Overcrowding components

2. Which of the following is the correct way to define a PCB trace width in a design file?

easy

A. trace_width = '0.5mm'

B. traceWidth = 0.5

C. trace_width: 0.5mm

D. trace-width = 0.5mm

Solution

1. Step 1: Review syntax for trace width setting

   Trace width is often set as a string with units, e.g., '0.5mm'.

2. Step 2: Identify correct syntax

   trace_width = '0.5mm' uses correct assignment with units in quotes.

3. Final Answer:

   trace_width = '0.5mm' -> Option A

4. Quick Check:

   Trace width syntax = '0.5mm' string [OK]

Hint: Use quotes and units for trace width values [OK]

Common Mistakes:

• Omitting units in trace width
• Using invalid variable names
• Missing quotes around string values

3. Given a PCB layout with power and ground traces routed too thin, what is the most likely outcome?

medium

A. Improved signal integrity

B. Reduced electromagnetic interference

C. Increased risk of trace overheating and voltage drop

D. Better mechanical strength of the PCB

Solution

1. Step 1: Understand effects of thin power/ground traces

   Thin traces have higher resistance causing heat and voltage drop.

2. Step 2: Identify the outcome

   Higher resistance leads to overheating and unstable power delivery.

3. Final Answer:

   Increased risk of trace overheating and voltage drop -> Option C

4. Quick Check:

   Thin traces = Overheating & voltage drop [OK]

Hint: Thin power traces cause heat and voltage issues [OK]

Common Mistakes:

• Ignoring current capacity for trace width
• Assuming thin traces are always fine
• Not checking voltage drop in design

4. A PCB designer wrote the netlist but forgot to connect the ground pins of multiple components. What is the best way to fix this error?

medium

A. Change component footprints to larger sizes

B. Increase the trace width of power lines

C. Remove all ground connections to avoid confusion

D. Add a ground plane or connect ground pins with traces

Solution

1. Step 1: Identify the missing connection problem

   Ground pins must be connected to a common ground reference.

2. Step 2: Fix by adding ground plane or traces

   Adding a ground plane or connecting ground pins with traces ensures proper grounding.

3. Final Answer:

   Add a ground plane or connect ground pins with traces -> Option D

4. Quick Check:

   Ground connection fix = Add ground plane/traces [OK]

Hint: Connect all ground pins to a common ground plane [OK]

Common Mistakes:

• Forgetting to connect ground pins
• Assuming power lines replace ground
• Ignoring netlist errors

5. You notice that your PCB design has overlapping vias and traces causing short circuits. What is the best approach to solve this problem while maintaining signal integrity?

hard

A. Increase the number of vias in the overlapping area

B. Re-route traces to avoid via overlap and use design rule checks

C. Ignore the overlap if the PCB passed electrical tests

D. Use thinner traces to fit between vias

Solution

1. Step 1: Identify the cause of short circuits

   Overlapping vias and traces cause electrical shorts and signal problems.

2. Step 2: Apply design rule checks and re-route

   Re-routing traces to avoid overlaps and running design rule checks prevents shorts and maintains signal quality.

3. Final Answer:

   Re-route traces to avoid via overlap and use design rule checks -> Option B

4. Quick Check:

   Fix overlap = Re-route + design rule checks [OK]

Hint: Use design rule checks and re-route to fix overlaps [OK]

Common Mistakes:

• Ignoring via and trace overlaps
• Adding more vias without fixing routing
• Using thinner traces causing signal loss