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Elementary, Mr. Watson: Debunking Misconceptions in PCB Design

PCB design can be likened to the poem, “The Blind Man and the Elephant” by John Godfrey Saxe. In the poem, six blind men of Indostan “to learning much inclined,” went to see the elephant “that each by observation, might satisfy the mind.” The first man fell against the elephant and concluded it was like touching a wall. The second man felt the elephant’s tusk and exclaimed, "It is very like a spear." The third blind man, feeling the vast and squirming trunk, decided it was a snake. The fourth man felt the elephant's leg and said the elephant “is very like a tree." The fifth man touched the massive ears and decided an elephant is very like a fan. Finally, the sixth blind man, feeling the elephant’s swinging tail, proudly proclaimed, "I see, the elephant is very like a rope."

The poet concludes, “And so these men of Indostan disputed loud and long, each in his own opinion, exceeding stiff and strong, Though each partly in the right, and all were in the wrong!”

The tale illustrates that by focusing solely on one part of a larger entity, it is easy to form incomplete conclusions. Just as the blind men only experienced a fraction of the elephant, understanding the whole picture requires considering various perspectives and assembling the collective knowledge to comprehend the entirety of any situation.

PCB designers do not work in a vacuum with other teams and departments in their company. I have often seen designers develop "tunnel vision" and begin to focus solely on the issues of the design department, where, of course, they see a set of intricate patterns and layouts that need to be carefully crafted to ensure the circuit functions correctly. They focus on the placement of components, traces, and connections to ensure optimal performance and compliance with design rules.

My career had a significant paradigm shift when I began to see a PCB design not through my eyes but through the eyes of different departments. That new insight allowed me to design not just for myself but for the company's overall mission.

For example, the sales and marketing departments were concerned with timelines, cost, and promoting product features. The customer support department was preparing to handle potential issues; in finance, their concern was the product's profit margin. Manufacturing and procurement were gearing up for the fabrication and assembly. The single area of consistent focus with every department was the product cost, which significantly impacted how a team worked across various departments within a company.

Cost strikes fear into any team. We might put hours of work into a design and layout only to be told that the product is over budget and we need to reduce "cost." By trying to save money, designers might introduce major problems into a good design. Designing a PCB involves carefully considering cost without compromising quality or functionality. Here are a few common misconceptions that people might have when trying to save money on PCB design.

Misconception of Using Cheaper Materials in PCB Design
In the quest to cut costs, many companies opt for cheaper materials in their PCB designs, believing that this will result in immediate savings. However, this misconception can lead to far-reaching consequences.

Cheaper materials might reduce upfront costs but often come with hidden costs over time. For instance, low-quality substrates and laminates can affect the PCB's durability and performance. This might lead to delamination, poor signal integrity, and reduced thermal performance. These problems can cause the PCB to fail prematurely, leading to expensive repairs, replacements, or recalls.

Manufacturing defects are another concern of cheaper materials. They might not meet the necessary tolerances and standards, resulting in increased defect rates during production. That impacts the yield and incurs additional costs for rework and adjustments.

From an engineering perspective, using inferior materials can compromise the PCB's reliability and functionality. Material quality is crucial for critical applications, such as those in aerospace or medical devices. Failing to use appropriate materials can result in system failures, which can be catastrophic financially and in terms of safety.

The purchasing department might focus solely on the cost savings from cheaper materials, often overlooking these long-term implications. While the initial expense is lower, the overall cost of ownership, including potential downtime, repairs, and reduced product lifespan, can significantly outweigh these savings.

Underestimating the Importance of Component Placement
A common misconception in PCB design is that component placement is convenient and does not significantly impact cost. This view underestimates the critical role placement plays in the overall efficiency and functionality of the board.

Proper component placement is crucial for optimal signal integrity, minimized trace lengths, and effective thermal management. Poor placement can lead to longer, tangled traces, increasing the potential for signal degradation and complicating the assembly process. This complexity can result in higher manufacturing costs and longer assembly times.

Moreover, improper placement can lead to heat dissipation issues, where components that generate significant heat are not adequately spaced or cooled. This can cause overheating and reduce the PCB's reliability and lifespan.

From a cost perspective, while optimizing component placement might seem like an additional expense, it saves money in the long run by reducing the need for costly rework and ensuring reliable performance. Investing time in strategic component placement can prevent performance issues and associated costs, ultimately leading to a more efficient and cost-effective manufacturing process.

Minimizing PCB Layers Unnecessarily
A prevalent misconception in PCB design is that minimizing the number of layers always results in cost savings. While fewer layers might seem straightforward to cut expenses, this approach can lead to significant challenges and increased costs in the long term.

Fewer layers may reduce initial manufacturing costs, but this often comes at the expense of design complexity and performance issues. When forced to work with a limited number of layers, designers may encounter difficulties routing traces, leading to longer, more convoluted paths. These longer traces can cause increased electromagnetic interference (EMI) and signal integrity problems, compromising the board's overall performance.

Additionally, minimizing layers can impact thermal management. With fewer layers, it's harder to dissipate heat effectively, leading to overheating critical components. That affects the board's performance, reliability, and longevity.

Design constraints imposed by fewer layers often lead to larger PCB sizes to accommodate routing needs, negating any savings from reduced layer counts. This larger size can result in higher material costs and increased assembly complexity.

From a manufacturing perspective, fewer layers can lead to increased production costs due to the need for more precise placement and alignment. The risk of defects and rework also rises, further driving up costs.

Not Considering Long-Term Costs
A common misconception in PCB design is that it focuses solely on immediate cost savings without considering long-term expenses. This short-sighted approach can lead to higher overall costs and increased risks.

Immediate savings might come from choosing cheaper materials, simplifying design, or cutting corners. However, these decisions can result in reduced reliability, higher failure rates, and increased maintenance needs. For example, using lower-quality materials might save money upfront but could lead to early failures, product recalls, or costly repairs.

Long-term costs include factors such as decreased product lifespan, potential downtime, and the need for frequent replacements. These hidden expenses can far exceed initial savings, impacting financial outcomes and brand reputation.

Conclusion

Investing in quality and thorough design practices may seem more expensive initially, but it often leads to better reliability, reduced maintenance, and fewer operational disruptions. By considering the total cost of ownership, including potential long-term impacts, companies can make more informed decisions that balance immediate savings with long-term performance and reliability.

John Watson is a professor at Palomar College, San Marcos, California.