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Elementary, Mr. Watson: Design Data Packages—Circle of Concern or Circle of Influence?

I've often been asked, "Can you have a perfect PCB design?" At first blush, it seems like the answer should be yes. After all, if you follow all the rules, double-check your work, and use the right tools, it should be perfect. Right?

I have often used the analogy that a PCB design is like a giant complex puzzle, with one caveat: There is not a single solution but rather an endless number of possible solutions. The truth is, designing a PCB is more than just putting together a complex puzzle, because pieces sometimes change shape while you're still working.

To make things even worse, a PCB design contains two types of information: static and dynamic. Static information is fixed and doesn't change. On the other hand, dynamic information is connected to your design and constantly changes. As you have probably guessed, the dynamic data and changes wreak havoc on your design.

Although we are looking specifically at the output data in this column, it's important to fully grasp the bigger picture as well. In a PCB design, there is an interrelationship between every process stage, often called a parent-child relationship. The library is the parent of the schematic, the schematic is the parent of the PCB design, and the outputs and documents at the end are the children of these. So, a seemingly insignificant error in a PCB design can often evolve into a significantly larger issue due to the interconnected nature of the design process. It is the ultimate “tail-wagging-the-dog” scenario.

A few Stephen R. Covey concepts fit nicely into what we are discussing here: the Circle of Control and the Circle of Influence, introduced in his classic business textbook The 7 Habits of Highly Effective People. As Covey explains, your Circle of Control includes everything you care about or worry about—things that affect your work or life that you can directly control. The other is the Circle of Influence, which is things that are out of our control, but still possibly under our influence because of what we can control.

As a PCB designer, there are many things that you are fully responsible for and have direct control over. These fall into your Circle of Control. This includes ensuring that your schematic and layout files are clear and complete. Your bill of materials (BOM) must be accurate and current. It's essential to check that all your footprints, pad stacks, and 3D models are correct. You must also create detailed drawings of how the board will be made and assembled. The layer stackups, drill tables, and tolerances should all be listed. You must use design checks to find and fix problems and follow company rules and industry standards. Keep your files neat and well-organized, using version control, and writing clear notes helps others understand your work. These are the skill sets that every PCB designer should develop, and they come in handy in your Circle of Control.

Then there is the pesky Circle of Influence, where you have some influence but no direct control. Your design data package falls firmly into this circle because much of the data is beyond your control. For instance, let’s look at fabrication capabilities. You can be the greatest designer ever, with what you consider to be the perfect board, the perfect data package, and everything verified, but if your fabricator can't build it, what's the point? Each fabricator has different tools and machines to handle specific designs better than others, with varying tolerances.

Talk to your fabricator. I can hear you asking, "When?” It’s every time. You should talk to the fab folks before, during, and after the project. Stay so close to your fabricator that people think you are a single person.

Know your fabricator's capabilities and, more importantly, follow them. Fabricators have their own specific abilities, usually on three levels: standard, intermediate, and advanced. But beyond that, any fabricator worthy of your business will also provide you with DFM guidelines. These rules make it easier for them to build your PCB. They can tell you things like how far apart traces should be or how big the holes should be for components. These guidelines will help you change this area from a Circle of Influence to a Circle of Control.

Component availability is another area that will fall into the Circle of Influence when creating your data packages. It is probably one of the most significant problems you'll face. It's entirely out of your control and can stop a PCB design project in its tracks. Component availability is the nemesis of every designer.

There are various causes of component shortages. Components that are available immediately may go out of stock, be backordered, discontinued, or become too expensive. Even if your PCB layout is perfect, if the manufacturer can't get the parts, they can't build the board. That can lead to delays, extra costs, or the need to redesign the board using different components.

Believe it or not, some designers choose parts without checking availability or lead times. Other times, a part might be available during design, but it's no longer in stock by the time the board is ready to be built. That happens a lot during times of high demand.

To move back toward the Circle of Control, check on parts availability before beginning your design. Check places like Digi-Key or Mouser for availability and lead times. Using standard parts in your designs is also smart because they are more likely to be in stock.

Another helpful step is to add backup parts, often called alternate parts, to the BOM. These parts can do the same job and fit in the same spot if the first choice isn't available. Designers can also talk to the team ordering parts to see what's easy to buy and what’s hard to find. For essential parts like microchips or power parts, it's a good idea to order them early so you don't run out later.

Designers should also avoid parts that are old or being discontinued. Some tools will show whether a part is new or near its end of life. Finally, checking all your parts again before sending your design to the factory is a great idea to ensure nothing has gone out of stock. Doing these things can help your design get built on time without surprises.

Designers need to be proactive, not reactive when creating a design data package. If you're only reacting to a situation or a problem, it's too late. The best way to move something from your Circle of Influence back into your Circle of Control is by taking action early and being prepared. That means thinking ahead, asking the right questions, and checking important details before problems happen. While you’re at it, read The 7 Habits of Highly Effective People.

This column originally appeared in the May 2025 issue of Design007 Magazine.