Estimated reading time: 5 minutes

Elementary, Mr. Watson: Know the Tradeoffs With Embedded Designs

One of my great joys as a grandfather of eight is spending time with them at the park. It doesn't take too long until I'm getting stuck on a slide that is too small for me or on the seesaw, with me on one side and them trying to lift me. At that point, they learn some harsh lessons in physics and how heavy Grandpa really is.

A seesaw is a relatively simple device, but it’s a great way to explain a rather complex concept in PCB design: design tradeoffs. Each decision made throughout a design comes with inherent pros and cons. My analogy of a see-saw provides a vivid illustration of the delicate balancing act engineers must perform during the PCB design process. 

These tradeoffs are significant even in the simplest of PCB designs. This idea was so substantial that it was documented in IPC-2221 as the starting point for discussing the general design requirements in Table 3-1, PWB Design/Performance Tradeoff Checklist Considerations. This table shows more than two dozen changes in physical features and the performance or reliability issues that may result from those decisions. As the difficulty of design increases, these tradeoffs become even more substantial and challenging to identify. You can look at the length of the see-saw as representing the complexity of the design. As complexity increases, the see-saw tilts, potentially impacting design parts like cost, manufacturability, testing and debugging, repair, and rework. The list goes on. Of course, too much complexity may very easily tip the balance unfavorably.

In a see-saw, the central pivot, or fulcrum, is the point around which the board tilts. In PCB design, this fulcrum is the core objectives and requirements of the project, such as functionality, performance, and cost-effectiveness. The balance point on the see-saw corresponds to the optimal combination of these core objectives, which are the driving force behind every decision made during the design process. The distance from the fulcrum to each tradeoff factor represents the emphasis or priority given to that aspect.

For example, on one end of the see-saw, you desire high performance—the upward force. On the other end, you have the downward force of cost considerations. Like me and the grandkids on a seesaw, engineers must find the suitable distribution of these forces to achieve the desired balance. Opting for high-performance components may lift the "performance" side, but it adds weight to the "cost" side, and vice versa.

I often see that these tradeoffs are not even considered; instead, decisions are based on knee-jerk reactions. One of the big ones is cost, especially with advanced PCB design techniques. For example, embedding components within the PCB layers increases manufacturing complexity. Specialized processes, such as sequential build-up (SBU) technology, are often required, contributing to higher manufacturing costs than conventional PCB fabrication. That is an indisputable fact. You request a quote from your fabricator, only to get a number at the bottom of the sheet that looks more like a ZIP code than a price. You experience the proverbial kick in the gut at how much this "advanced PCB" actually costs. Without considering anything else, it usually never goes much further. We send the designer back to the drawing board to find another (cheaper) solution.

But cost is only part of the picture. We must reflect on the tradeoffs and how they impact not just the design phase but the fabrication and assembly stages and how the product operates over its lifetime. Yes, these types of PCBs cost more to fabricate, but several beneficial tradeoffs exist.

Consider this: With a reduced PCB, size and material costs in embedding components allow for a more compact design, reducing the overall size and layers of the PCB. A smaller PCB requires fewer materials, thus significantly reducing material costs. The snowball effect means a reduced board size can lead to cost savings in areas such as assembly, testing, and packaging. This space-efficient approach allows for a streamlined layout that uses fewer materials during manufacturing. The cost savings extend beyond material expenses; they impact assembly, testing, and packaging. Smaller PCBs contribute to overall efficiency in the production process, offering economic advantages and enhancing the competitiveness of electronic products.

Furthermore, the cost-savings of embedding components in a PCB present the potential for integration and simplification in electronic system design. By consolidating functions within the PCB layers, system architecture is streamlined, reducing the need for additional external components. This integrated approach enhances efficiency, simplifies the development process, and can lead to production, testing, and maintenance cost savings. The reduced complexity contributes to faster development cycles and improved reliability, positioning embedded component designs as a strategic choice for achieving a more compact and cost-effective electronic system.

The name of the game in electronics today is about innovative design and miniaturization. Consumers are looking for products that are smaller and just as efficient. Those sorts of designs give any company a competitive advantage in the market. These consumer demands drive innovation, and it’s exciting to watch companies step up to the challenge. Likewise, innovative design and miniaturization create cost-effective mass production, leveraging economies of scale and reduced material usage. This holistic approach of combining creative design thinking with size optimization not only enhances market competitiveness, it lays the foundation for a future where electronic devices are powerful, elegantly compact, and seamlessly integrated into the fabric of our daily lives. With a company's increased market share and revenue, it's beautiful to see offsetting those pesky higher manufacturing costs by using embedded components.

As embedded component technology becomes more widely adopted, economies of scale may lead to lower production costs. With this widespread acceptance, the associated manufacturing processes and materials may become more cost-effective, benefiting manufacturers and end-users.

Cost savings associated with embedded components may not be immediate and will depend on different factors. So, consider the overall cost savings associated with using embedded components not as a simple downward or upward force metric. Before you turn down that quote for your embedded PCB, consider it as an investment in your company's future.

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