Why PCB Interview Preparation Is Important
Printed Circuit Board (PCB) design is the backbone of modern electronics. From mobile chargers to IoT devices and automotive ECUs, every product depends on a reliable PCB layout.
Recruiters evaluate whether you understand:
- Schematic capture
- Stack-up planning
- Decoupling strategy
- Grounding techniques
- Noise reduction
- Manufacturing constraints
Freshers often fail not because of lack of knowledge — but because of weak fundamentals and no practical explanation ability.
Basic PCB Interview Questions and Answers
1. What is a PCB?
A Printed Circuit Board mechanically supports and electrically connects components using copper traces etched on an insulating substrate (commonly FR4).
Example:
In a mobile charger, resistors, capacitors, transformer, and controller IC are mounted and interconnected using copper tracks.
2. What are the main parts of a PCB?
- Base material (FR4)
- Copper layers
- Solder mask
- Silkscreen
- Pads
- Vias
Interview Tip: Mention solder mask prevents oxidation and short circuits.
3. Difference Between Single-Layer and Multilayer PCB?
| Feature | Single Layer | Multilayer |
|---|
| Copper layers | 1 | 4, 6, 8+ |
| Cost | Low | Higher |
| Application | Simple circuits | High-speed boards |
Example:
- Calculator → Single layer
- Laptop motherboard → Multilayer
4. What is a Gerber File?
Gerber files contain manufacturing data such as copper layers, solder mask, drill files, and silkscreen used for PCB fabrication.
Without Gerber files, manufacturers cannot produce the board.
5. What is DRC in PCB Design?
DRC (Design Rule Check) ensures layout follows manufacturing constraints like:
- Track width
- Clearance
- Via size
If spacing is too small, DRC throws an error.
PCB Layout Interview Questions and Answers
6. What is PCB Routing?
Routing is the process of connecting components using copper traces.
Best Practice:
- Keep traces short
- Avoid 90° bends
- Maintain proper spacing
- Use wider traces for power lines
7. Why Use 45-Degree Bends Instead of 90 Degrees?
45° bends reduce impedance discontinuity and EMI radiation in high-speed designs.
Used especially in:
- RF circuits
- High-speed digital designs
8. What is a Via?
A via connects different PCB layers.
Types:
- Through via
- Blind via
- Buried via
Smartphones commonly use blind and buried vias to save space.
9. What is PCB Stack-Up?
Stack-up defines the arrangement of signal and plane layers.
Example (4-Layer Board):
- Top Layer – Signal
- Inner Layer – Ground
- Inner Layer – Power
- Bottom Layer – Signal
This improves noise reduction and signal integrity.
10. What is Differential Pair Routing?
Routing two complementary signals together with equal length and controlled spacing.
Example: USB D+ and D− lines.
Interviewers may ask:
Why length matching is required?
What happens if mismatch occurs?
Answer: It causes timing skew and signal distortion.
PCB Hardware Interview Questions
11. What is a Decoupling Capacitor?
A decoupling capacitor filters noise and stabilizes supply voltage near IC power pins.
Best Practice:
- Place within 2–5 mm of IC power pin
- Use 0.1µF ceramic capacitor
12. Why Is Grounding Important?
Grounding provides a return path and reduces noise.
Poor grounding leads to:
- ADC errors
- EMI issues
- System instability
13. What is EMI?
EMI (Electromagnetic Interference) is unwanted electromagnetic noise affecting circuit performance.
Switching regulators are common EMI sources.
14. How to Reduce PCB Noise?
- Use ground plane
- Keep loop area small
- Use ferrite beads
- Separate analog and digital ground
- Proper decoupling
15. What Are Creepage and Clearance?
- Creepage → Surface distance between conductors
- Clearance → Air gap distance
Important for high-voltage boards and safety compliance.
High-Speed PCB Interview Questions
16. What is Impedance Control?
Impedance control maintains constant characteristic impedance of signal traces to prevent reflection.
Used in:
17. What is Signal Integrity?
Signal integrity ensures clean waveform transmission without distortion, overshoot, or ringing.
Poor signal integrity causes logic errors.
18. How Do You Handle High-Speed Signals?
- Controlled impedance
- Proper stack-up
- Termination resistors
- Length matching
- Solid ground reference
Embedded PCB Interview Questions
19. What is MCU Pin Mapping?
Assigning microcontroller pins to required peripherals like UART, SPI, I2C.
20. Best Practices for Microcontroller PCB Design
- Place crystal close to MCU
- Decoupling capacitors near power pins
- Separate analog and digital grounds
- Short reset traces
21. What is a Boot Circuit?
Boot circuit determines startup mode (Flash, Programming mode).
Commonly used in STM32 and ESP microcontrollers.
DFM and Manufacturing Interview Questions
22. What is DFM?
DFM (Design for Manufacturing) ensures PCB design can be manufactured without defects.
Examples:
- Proper annular ring
- Minimum trace width
- Avoiding tiny pads
23. What is DFA?
DFA (Design for Assembly) ensures components can be assembled easily.
Example: Avoid placing tall components too close.
24. How to Prepare PCB for Mass Production?
- Panelization
- Add test points
- Perform DRC
- DFM review
- Generate correct Gerber files
Tools-Based PCB Interview Questions
Interviewers often ask: Which PCB tools have you used?
Popular tools:
- Altium Designer
- KiCad
- OrCAD
- Eagle
Students often use KiCad for academic projects.
Be ready to explain:
How you define design rules
How you create stack-up
How you generate Gerber
Common PCB Interview Mistakes
- Weak fundamentals
- No practical projects
- Ignoring EMI concepts
- Not understanding fabrication process
- Giving theoretical answers without examples
Tip: Always explain with a real project example.
Real Interview Experience Example
In many company interviews, candidates are asked:
- Explain differential pair routing in DDR memory
- Draw 4-layer stack-up
- Explain decoupling capacitor placement
- How to reduce EMI in switching regulator board
Preparing practical answers gives you an advantage over other freshers.
Quick Revision: Top 10 Most Important PCB Interview Topics
- PCB stack-up
- Decoupling capacitor placement
- Impedance control
- Differential routing
- Grounding strategy
- EMI reduction
- DRC rules
- DFM principles
- Signal integrity
- Gerber file generation
Revise these before any PCB design interview.
Conclusion
Mastering PCB design interview questions requires strong fundamentals in:
- Schematic design
- PCB layout best practices
- EMI and signal integrity
- DFM and manufacturing
- High-speed routing
Freshers who combine theoretical knowledge with practical PCB projects stand out in interviews.
Build a portfolio, practice real designs, and revise core concepts regularly.
With proper preparation, clearing a PCB design interview becomes much easier.
