Elementary, Mr. Watson: Trust but Verify

Over many years, I have seen some elaborate PCB library systems. However, the best ones were those not based on the size but rather the quality of the information. That old axiom is definitely “not quantity but rather quality.” 

I recently sat with a VP of engineering, and I asked what he thought of his PCB library. He thought for a moment and said, "I believe it is pretty good." I followed up, “But do you know?” To me, there is a difference. If I tell you that the stove is hot and you touch the burner, it will burn you. At that point, you only believe it. Now, if you go and feel the hot stove and it burns your hand, what just happened? You went from believing to knowing. Within an industry that demands perfection, it is not good enough to just "believe" that your library is good enough; instead, you must know. Really, what is “good enough?” What is that? We got the board through fab and assembly, and maybe it went through some compliance checks. So, it must mean that it is correct, right? No, it could mean that you were just lucky. Taking some advice from President Ronald Reagan, "Trust but verify." Most problems that occur are directly linked back to making assumptions somewhere along the process. 

I-Connect007 recently conducted a survey that asked about the challenges that designers face. One of the problems mentioned in the survey responses was issues with component footprints. I can fully understand why. Starting a design with footprints that you only believe are good enough rather than knowing is a recipe for disaster. There is no recovery from harmful components in your design. 

Off the coast of a somewhat rugged area of North Carolina, there stands three lighthouses. It is a harsh area for naval vessels, and is a well-known area for shipwrecks. Contrary to belief, though, a ship captain coming into port will not go from lighthouse to lighthouse. Instead, he lines up all three lighthouses where he only sees a single light. Much in the same way, during the component QC auditing process or review, we verify that all the lighthouses lined up and we should only see a single light. Simple rule: If you see more than one light, you are off course, and something is wrong.

NC_lighthouse.jpg
Figure 1: Lighthouse off the coast of North Carolina.

The Verification Standard
For any verification process to be successful, you must establish it on a known standard. What do I mean by standard? What is it we will verify a component with? 

The Datasheet
The first verification document for all components is the datasheet. It is usually the very first document that engineers and librarians go after. If the process does not start there, we will be setting ourselves up for major problems down the road. 

But (and that is a big but), some datasheets have been known to be wrong. A single datasheet is often trusted way too much; usually, the problems with those datasheets end up on PCB designs and finally into assembly. 

When this happens, and it will happen at some point in your career, document it. If you find such a problem, it could become a habit for that component vendor. No company can afford to fact-check datasheets and components by running PCB board runs. Furthermore, you might consider dropping them from your preferred vendor list. At least red flag them. You caught a problem that may exist in other parts they provide. 

Another strategy is to always have multiple suppliers for any components in a design. That way, it provides a couple of things in our process. First, it gives us an alternate part in case our first choice falls through for some reason. The other advantage is it provides another datasheet to compare the component. 

When multiple manufacturers are available, it is best to pull every datasheet and compare them to determine if anything is out of line—lining up those lighthouses and comparing and contrasting what we see. 

IPC Standards
Fortunately, we are not left to our own devices to determine whether a component, especially a footprint, is correct or a datasheet.  Several standards are provided by the Institute for Interconnecting and Packaging Electronic Circuits (IPC), which has been the leading authority in the printed circuit board industry since its start back in 1957. I have never read a standard provided by IPC that I did not like. The criteria that would help in the review process are those in the Design and Land Pattern category: IPC-2221, IPC-2222, IPC-2223, IPC-7351C (surface mount components), IPC-7251 (through-hole components).

IPC_standards_start-finish.jpg
Figure 2: A review of IPC standards.

I would highly recommend starting with the IPC standards as the very foundation to set up your component model libraries. IPC-7351 and IPC-7251 give a very detailed breakdown of the component category.

Through what is called Standards Developing Organizations (SDOs), the standards are reviewed regularly and updated to align with changes in the industry.

Also, keep up with the revised editions of the standards to determine whether those changes affect any of the models in your library, such as the release of IPC-7351C from the previous version regarding the shape of any rectangular pad to have rounded off the corners. This change took care of sharp turns that acted like antennas and helped in routing with a 45-degree angle trace.

A good library system (meaning one managed very well) will have the characteristic that the lifecycle would automatically change to a "new" status whenever changes occur. That way, any changes done on any components will identify them as changing.

Quarantine ‘New’ Components
If you don't already do so, start placing “new” components in quarantine someplace where they cannot be used in new designs. Before they are ready for prime time, you must first do QC checks. I've seen countless times when components got created and pushed into a design without the correct QC checks. The results were disastrous. Why is it we have the time to do things over but never have the time to do it correctly the first time? Often, good PCB designs are sacrificed on the “altar of expediency.”

Lastly, follow the golden rule of review. The person who did the work cannot review it. It is essential to get another set of eyes looking at the component. It just so happens that the person who did the work does not have an objective view but rather a subjective one.

It is probably best to have a few people who would act as the review board; for example, to take all new components and the verification document and line them all up.

The problems that possibly get introduced into a design are seemingly endless. Going back to my analogy of the lighthouses off the coast of North Carolina. There is only one clear path safely into the harbor. On each side are the jagged rocks. Whenever you deviate from that course or plan, you have a considerable possibility of running aground. In your PCB design, do not let the urgency of time bring risk and possible problems. Stay the course, and you will have a good design.

John Watson, CID, is a customer success manager at Altium. 

Back

2021

Elementary, Mr. Watson: Trust but Verify

06-10-2021

Over many years, I have seen some elaborate PCB library systems. However, the best ones were those not based on the size but rather the quality of the information. That old axiom is definitely “not quantity but rather quality.”

View Story

Elementary, Mr. Watson: Paying the Price To Be a PCB Designer

05-13-2021

Today, the electronics industry is flourishing with innovations and technologies. The result is that the “good” designers are left in the dust. Truthfully, our industry doesn't need more good designers; rather, we need great designers—those who can face any challenge and instead of cowering in the corner, looks at the task at hand and says, "Bring it on."

View Story

Elementary, Mr. Watson: Keeping Counterfeit Components Out of Your Library

04-13-2021

To know whether anything is wrong, you must first know in detail what is correct to follow the standard or pattern. This principle could not be more true when handling our components in the library.

View Story

Elementary, Mr. Watson: The Printed Circuit Board Design

02-11-2021

John Watson addresses continuous improvement by examining the PCB design process.

View Story

Elementary, Mr. Watson: 2020—The Year that Taught Us Resilience

01-22-2021

Yes, 2020 was a challenge. It's during those times that we can learn some significant lessons if we allow them.

View Story
Back

2020

Elementary, Mr. Watson: Demystifying Bypass Capacitors

12-17-2020

As PCB designers, we work under the simple rule of cause and effect, and a PCB design can quickly become a petri dish for the butterfly effect to flourish. One of those areas that can quickly snowball into major problems is your PCB power distribution structure. When it goes wrong, it usually goes very wrong and has significant issues throughout your design.

View Story

Elementary, Mr. Watson: Density Feasibility Putting 10 Lbs in a 5-Lb Bag

11-18-2020

Whether on a customer, a system, or a PCB level, it’s essential to understand the final objective and how you intend to get there and meet the customer need at the forefront of any project. In this column, John Watson addresses density feasibility and more.

View Story

Elementary, Mr. Watson: Location, Location, Location

10-15-2020

When it comes to PCB design, one of the most overlooked principles is component placement. Similar to a home, the component location has a considerable impact on the quality and is the real value of a PCB design. John Watson examines five rules to follow when it comes to component placement.

View Story

Elementary, Mr. Watson: Overcoming PCB Designs Pitfalls

09-10-2020

When starting every PCB design, the hope is that we can navigate through any pitfalls that arrive. Unfortunately, many times, issues happen that you do not handle correctly; they fall through the cracks and end up in your PCB design. John Watson explains how that is when the real problems begin.

View Story

Elementary, Mr. Watson: How to Ruin Your PCB Design in 4 Easy Steps

08-06-2020

John Watson has seen firsthand how quickly PCB designs can “go off the rails” by not following a few simple principles. In this column, he looks at four practices that can easily ruin your PCB design.

View Story

Elementary, Mr. Watson: PCB Components Naming Conventions

07-09-2020

How you accurately analyze and identify certain information has a direct connection to the overall success of your PCB designs. In this column, John Watson focuses on the conventional naming scheme for the schematic symbol and footprint to prevent headaches and ulcers later.

View Story

Elementary, Mr. Watson: Collaboration in the PCB Design Process

06-11-2020

The past few months have been trying for everyone, with many of us working from home. However, there are still the underlining principles of collaboration to step into a role to finish the necessary tasks to keep a project moving forward. John Watson, CID, explains.

View Story

Elementary, Mr. Watson: Reinventing Yourself

05-28-2020

When COVID-19 first hit, many businesses were forced to close, and we immediately saw its impact on the service industry. Whatever challenge you’re facing, John Watson emphasizes that it’s time to hit the switch on reinventing.

View Story

Elementary, Mr. Watson: The Positive Side of COVID-19

04-16-2020

With the recent COVID-19 outbreak worldwide, most of us have been forced to reshuffle how we work, live, and play. Something like this has never happened before in our lifetimes, and it is scary and challenging, but difficult times develop resilient people. John Watson shares some of the positive things he has already noticed come out of this situation.

View Story

Elementary, Mr. Watson: Are We There Yet?

03-12-2020

Anyone who has taken a road trip with children knows the question, “Are we there yet?” very well. This question also applies to PCB design. If you are not careful, your PCB project could easily go off track and you could lose sight of what you are doing (objective), why (motivation), how (process), and when (schedule). John Watson emphasizes the importance of these fundamental questions.

View Story
Copyright © 2021 I-Connect007. All rights reserved.