Common PCB design mistakes - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to identify the most common PCB design mistake.

PCB Design

common_mistake = '[1]'

Drag options to blanks, or click blank then click option'

AAdequate spacing

BProper grounding

CIncorrect trace width

DCorrect component placement

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing proper grounding as the mistake

Confusing spacing issues with trace width

The most common PCB design mistake is using incorrect trace width, which can cause overheating or signal issues.

2fill in blank

medium

Complete the code to detect a common error in PCB layout related to component placement.

PCB Design

if component_spacing < [1]: report_error('Spacing too small')

Drag options to blanks, or click blank then click option'

A50mm

B0.5mm

C0.05mm

D5mm

Attempts:

3 left

💡 Hint

Common Mistakes

Using 5mm which is too large

Using 0.05mm which is unrealistically small

Component spacing less than 0.5mm is often too small and can cause soldering or electrical issues.

3fill in blank

hard

Fix the error in the code that checks for missing ground connections.

PCB Design

if not '[1]' in netlist: raise Exception('Ground missing')

Drag options to blanks, or click blank then click option'

AGND

BVCC

CVDD

DCLK

Attempts:

3 left

💡 Hint

Common Mistakes

Checking for VCC instead of GND

Using CLK which is a clock signal

The ground net is usually named 'GND'. Checking for 'GND' ensures the ground connection is present.

4fill in blank

hard

Fill both blanks to complete the code that identifies signal integrity issues.

PCB Design

if trace_length > [1] and trace_impedance != [2]: flag_issue('Signal integrity problem')

Drag options to blanks, or click blank then click option'

A50mm

B75 Ohm

C50 Ohm

D100mm

Attempts:

3 left

💡 Hint

Common Mistakes

Using 50mm as length limit

Using 75 Ohm impedance which is less common

Signal integrity issues often occur when trace length exceeds 100mm and impedance is not 50 Ohm, which is standard for many signals.

5fill in blank

hard

Fill all three blanks to complete the code that checks for thermal issues in PCB design.

PCB Design

if [1] > max_current and [2] < min_trace_width and [3] == False: alert('Thermal risk detected')

Drag options to blanks, or click blank then click option'

Acurrent_load

Btrace_width

Cthermal_via_present

Dvoltage_level

Attempts:

3 left

💡 Hint

Common Mistakes

Using voltage_level instead of current_load

Ignoring thermal vias presence

Thermal risk occurs when current load is too high, trace width is too small, and thermal vias are missing.

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