5 Myths about PCB Design - Busted!

 Printed circuit board (PCB) design plays a crucial role in creating electronic devices and products. However, there are several pervasive myths and misconceptions related to PCB design that can negatively impact the design. This article demystifies 5 common myths about PCB design and explains why they are just falsehoods rather than facts.

Myth #1: PCB Design is Simple and Easy

Why This is a Myth

Many people assume PCB design involves simple drawing and layout, which is far from the truth. Modern PCBs have become extremely complex with:

• High density of components and connections
• Miniaturized and densely packed layouts
• High speed signals and rigid signal integrity requirements
• Complex power distribution with accuracy in voltage drops
• Challenging thermal design and heat dissipation needs
• Testing of signal and power integrity, EMI/EMC

Designers need to balance these complex trade-offs while meeting specifications, performance parameters and costs. PCB design requires expertise spanning schematics, layout, routing, prototyping and simulation using specialized design tools. It's certainly not a simple or easy process!

Myth #2: Anyone Can Become a PCB Designer Easily

Why This is a Myth

Becoming an expert PCB designer involves specialized skills and knowledge. Some key prerequisites are:

Extensive Electronics and Hardware Knowledge

• Analog and digital circuits fundamentals
• Components, interconnects and packaging technologies
• Materials, manufacturing and assembly processes
• Signal and power integrity principles
• High speed design, EMI/EMC concepts
• Thermal design fundamentals

Software and Tools Expertise

• Using schematic capture and layout editors effectively
• Setting constraints and rules for optimal functionality
• Running simulations and analysis - signal, power, thermal, EMI etc.
• Generating comprehensive documentation and fabrication data

Systems Thinking and Collaborative Ability

• Understanding interactions between sections and sub-systems holistically
• Communicating and consulting component engineers and board fabricators
• Reviewing designs with reliability engineers and test engineers

Clearly, PCB design requires substantial specialized expertise and years of experience rather than being easy for anyone to pick up!

Myth #3: Physical Design is More Important than Schematics

Why This is a Myth

In reality, schematics and PCB layout & routing are equally important for designing functional boards.

Schematics establish circuit connectivity and functionality through key aspects like:

• Components selection - ICs/chips, resistors, capacitors etc.
• Logical connectivity through nets and nodes
• Capture of design intent - hierarchies, constraints etc.
• Simulation of functionality and performance

Layout and routing transform the logical schematic into a physical board through:

• Placement of footprints and components
• Routing connections with optimal wiring
• Meeting signal integrity, power integrity, EMI and thermal needs
• Enabling testing points, fabrication and assembly

Getting either the schematics or the layout wrong can instantly result in a failed design! The myth arises from the fact that layout drawings seem more prominent during fabrication documentation. But schematics and layout are equally driving the end functionality.

Myth #4: Spending More Time Always Improves Design Quality

Why This is a Myth

In PCB design projects, sufficient time must be spent upfront during requirements, specification and architecture definition stages.

Rushing schematics and layout work without paying attention to:

• Firming up technical specs and validation plans
• Establishing performance budgets and margins
• Architecting board partitioning early

Usually causes iterations later due to inadequate analysis or unforeseen issues. Projects executed with loosely defined requirements and insufficient planning tend to see diminishing quality returns despite increasing design time.

On the other hand, investing design time in aspects like:

• Evaluating design tradeoffs through analysis and simulations
• Standardizing constraints configuration
• Developing modular reusable design blocks
• Streamlining documentation templates

Results in better predictability, faster turnarounds and improved design reuse over multiple projects. The key is to spend time upfront on the right design activities rather than prolonging work aimlessly.

Myth #5: Complex Tools Alone Can Catch All Issues

Why This is a Myth

There is no doubt that EDA tools for PCB design have become extremely advanced, providing sophisticated analysis engines spanning signal integrity, power integrity, thermal behavior and EMI characteristics.

However, tools have limitations in comprehensively catching issues through simulations due to aspects like:

• Inability to model all real-life second order effects
• Practical gaps between mathematical modeling and physical effects
• Subjectivity in constraint definitions requiring designer judgment
• Design abstraction necessary for enabling simulation runs
• Simulation compute limitations requiring focused analysis

Tools provide valuable directional inputs to designers but cannot replace the conceptualization and judgment aspect of experienced PCB designers. Evaluating tool outputs with a practical view of the eventual manufacturing test remains an indispensable part of design validation.

Frequently Asked Questions

Here are some common FAQs related to myths in PCB design and their factual responses.

Q: Will adhering to reference design guidelines eliminate the need for expertise in PCB design?

A: While reference designs do capture industry best practices, they are meant for standard applications and cannot address specific feature needs or custom performance requirements that demand expert tradeoff evaluation and decision making.

Q: Can circuit designers skipping PCB layout exposure become equally competent designers compared to having hands-on layout skills?

A: First hand exposure to layout and routing work builds intuition for practical challenges in transforming logical schematics to physical boards, which is essential for balanced and optimized PCB design. Theoretical only knowledge even in circuits falls short in delivering competent designers.

Q: Does expertise in PCB layout tools necessarily translate to competent overall designs?

A: Tools expertise helps create quality layouts but needs complementary skills in schematics capture, simulation, design for manufacturing, problem solving and prototyping to deliver completely functional designs meeting all specs. Focus just on tools usage has limited returns.

Q: Can automation replace designers by enabling tools to take design decisions optimally on their own?

A: Automation does accelerate simple and repetitive design tasks but cannot substitute for creativity, judgment and customization needed per unique requirements. Designers have to take key decisions rather than tools becoming fully autonomous.

Q: If signal or power integrity issues emerge in fabricated boards, does the root cause lie more in layout errors or inadequate schematic simulation?

A: Both should be equally accountable. Incorrect layout can negate well simulated schematics but gaps in schematics checks manifest as physical issues. Improper isolation or constraints in either domain can inject issues difficult to isolate as pure layout or schematic gaps.