Connect the Dots: Everything You Wanted to Know About Electromagnetic Interference

EMI is another of those TLAs (three-letter acronyms) that the PCB industry is notorious for. You hear it all the time, referring to electromagnetic interference. The devices we create are, in the context of this conversation, bundles of boards, chips, and cables that produce and are affected by EMI. When current flows through wires, traces, or circuits, some of the energy is propagated through the air in the form of electromagnetic radiation. This also takes place within a closed design—creating disturbance voltages throughout the conductors in your device.

Though most prevalent in devices with longer interconnects and at higher frequencies above 50MHz, nothing operates at 100% electromagnetic compatibility. This means every device is going to generate at least some amount of EMI.

If enough EMI radiates from a device, it will interfere with the operation of other electronic systems operating in the vicinity. That’s why they ask you to turn off your cellphones on airplanes and the reason grandpa made your dad turn off the radio in his room when it was time for Ed Sullivan on TV.

Keeping an Eye on EMI
There are two main concerns with EMI that you need to consider. You should first determine how much EMI your device is generating and radiating to the environment. Different operational environments bring with them unique tolerances for EMI. An electronic device that is part of a billionaire’s spaceship near other devices on board would have a much lower EMI tolerance than a moisture evaporator operating in the middle of a desert.

Everyone from the FCC to the DoD to a slew of international regulatory bodies are at hand to dictate the amount of interference that a device can give off, depending on its intended use. These regulations have been put in place for personal safety and to ensure an electronic device will be able to carry out its function long term.

It’s also important to determine your device’s inherent ability to operate in the presence of EMI, regardless of whether it is EMI-created within the device or bombarding it from external sources. Too much exposure to interference can negatively impact the functionality of some systems and you will need to design shielding, grounding, or other protection.

Poor PCB design is many times the culprit when it comes to intolerable levels of EMI. The issues that often cause problems can be traced to design flaws that cause interference among the traces, circuits, vias, PCB coils, and other elements.

Limiting the EMI in a PCB layout can be an effective method for reducing emissions, meeting FCC regulations, and keeping your design signals clean so the system works as expected.

Designing With EMI in Mind
Here are a few items to consider during the planning and schematic stages of your design that will set you on the right path.

  • Choose SMD components over through-hole parts. Generally, the leads on the through-hole parts create higher levels of inductance and thus opportunity for EMI.
  • Maximize ground area, so signals can disperse more easily with more area. If you need to keep the area of your ground plane as small as possible, create a multi-layer PCB.
  • Design with multilayers—add a ground plane on the layer directly below the external signals (2 and n-1). The presence of these planes near the signal will effectively reduce the return path, keep signals clean, and limit EMI emission.
  • Connecting decoupling or bypass capacitors to these planes offers another effective technique for reducing EMI because of the short and logical return paths created.
  • If you are using split planes to avoid having too many ground planes in your design, be sure they are only connected at a single point to avoid creating loops that effectively become antennas that radiate EMI.
  • In multi-layer PCBS, use solid ground planes rather than hashed planes to reduce impedance levels.
  • Limit the operating current and/or the rise times of the signals to help reduce larger fluctuations in current offering lower EMI emission rates.
  • Match the impedance on signals. This is a critical practice of design especially at higher signal speeds that will reduce the opportunity for signal reflection, harmonics, ringing, and overshooting digital signals—all of which increase the EMI radiation.

Don’t let yourself be surprised by EMI. It can create issues with your projects that could result in delays, budget overrun, and missed deadlines. Considering EMI during the pre-planning stage of your PCB design can help save you time and effort in the prototyping and testing phases.

This column originally appeared in the January 2022 issue of Design007 Magazine.

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2022

Connect the Dots: Everything You Wanted to Know About Electromagnetic Interference

01-20-2022

EMI is another of those TLAs (three letter acronym) that the PCB industry is notorious for. You hear it all the time, referring to electromagnetic interference. The devices we create are, in the context of this conversation, bundles of boards, chips, and cables that produce and are affected by EMI. When current flows through wires, traces, or circuits, some of the energy is propagated through the air in the form of electromagnetic radiation. This also takes place within a closed design—creating disturbance voltages throughout the conductors in your device.

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2021

Connect the Dots: Best Practices for Solder Mask Application

12-16-2021

Today’s PCBs increasingly have to operate in challenging conditions. Whether it’s an iPad hot to the touch after several hours of gaming or a drone slicing through smoke and debris to monitor a wildfire, boards need protection from the elements. That’s where solder mask comes in. Solder mask coats your whole board (apart from the solder pads) so the PCB doesn’t react with the atmosphere and lose chemical properties through oxidation. It also prevents contamination from dust and debris that may settle on the board and create shorts. Solder mask prevents bridging between features during wave reflow assembly, limits external conductive influences and helps ward off voltage spikes.

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Connect the Dots: Diving Into the Chemical Processes of PCB Manufacturing

11-12-2021

I have always been fascinated with chemistry and chemical processes. My first degree was in chemistry and my first job out of college was in the PCB manufacturing shop in the analytical chemistry lab. During my initial tour I was so surprised with just how many chemical processes there were in PCB manufacturing. I discovered that some of the most critical elements of PCB manufacturing involve chemical processes. Chemicals clean the copper in preparation for the coating that prevents oxidation, and again to remove contaminants before solder resist application.

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Connect the Dots: Finding Value in Gerber Files

10-28-2021

Converting to Gerber is one way to perform a double check of your PCB design that can pre-answer questions from your manufacturing partner and pre-solve problems with the boards themselves.

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Connect the Dots: Designing PCBs for Electronic Hardware Products

09-23-2021

We asked an expert what factors designers should consider as they lay out their boards.

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Connect the Dots: The Split Planes Challenge

08-11-2021

Losing track of voltage in your PCB design can lead to explosive problems. Your CAM tool will not manage split planes for you.

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Connect the Dots: The Board Thickness Challenge

07-21-2021

Size constraints, functional requirements, and environmental factors can make selecting PCB thickness difficult. Here we will examine best practices for choosing board thickness that results in quality, highly functional PCBs.

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Connect the Dots: There is No ‘Final’ Frontier for PCB Design

06-10-2021

Our ongoing mission: To explore more manufacturable designs, to seek out higher-quality boards and enhanced functionality, to boldly design PCBs that no one has designed before.

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Connect the Dots: A Closer Look at Surface Finish

05-17-2021

The final surface finish of a PCB is an important consideration. This coating between your components and the bare board is applied to ensure solderability and protect any exposed copper circuitry. Selecting the right type of surface finish can be daunting, and for good reasons.

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Connect the Dots: The Power Behind the (PCB) Throne—Power Supply Design Tips

04-13-2021

Delivering the required power to each component on a PCB can be a complex challenge. Designers have to manage converting AC to DC while also delivering the correct voltage and current to each component. A well-designed PCB results when the designer takes power supply seriously—paying close attention to the effects that power delivery can have on surrounding components, such as through heat management or signal interference.

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Connect the Dots: IoT is Changing How We Design PCBs

03-11-2021

Demand growth is fueled by business as well as consumers, with pandemic-accelerated healthcare and industrial machinery applications leading the way. IoT devices of every stripe will continue to improve and add functionality while also becoming smaller, lighter, and faster.

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2020

This Month in Design007 Magazine: Connect the Dots—Is 2020 Really Coming to an End?

12-09-2020

As we approach the end of 2020, we are able to look back on one of the most challenging years that I have ever experienced. Throughout these trying times, Bob Tise and Matt Stevenson were consistent in their desire to share knowledge with everyone. Matt shares a synopsis of the topics they shared from the perspective of a PCB manufacturer.

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Connect the Dots: The New Recipe for Customer Service Success

11-11-2020

How are you holding up these days during the pandemic? Each of us is dealing with life struggles and changes differently. With this in mind, Matt Stevenson asks Al Secchi, global customer support and sales manager, what he has learned professionally from the pandemic and how to serve customers.

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Connect the Dots: Unraveling the Mysterious BGA Routing Mess

10-19-2020

A ball-grid-array (BGA) device can be a daunting component to route, especially in fine-pitch arrays featuring solder ball counts in the hundreds and pitch values as tight as 0.5 millimeters. Bob Tise and Matt Stevenson describe how you can take the mystery out of BGA routing and create a PCB design that can handle all those pesky narrow spaces.

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Connect the Dots: How to Know If a CAD Tool Is Right for You

09-21-2020

The tool that defines PCB designers is our CAD software, and many discover quickly that not all CAD tools are created equally. Bob Tise and Matt Stevenson answer the question, "How can designers find the right CAD tools to fit their particular methodology and needs?"

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Connect the Dots: The Nuts and Bolts of Electrical Testing

08-12-2020

In this column, Bob Tise and Matt Stevenson explore the world of electrical testing. They examine a variety of testing methods, what options to look for in a PCB manufacturer, and how to ensure that you're getting the best value out of the electrical test options available to you.

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Connect the Dots: Reassessing the Risk of Offshore PCB Manufacturing

07-15-2020

Offshore board production has long been considered an effective way to reduce the cost of producing electronic devices here at home, but those savings often demand a higher tolerance for delivery issues and come with lowered expectations for quality. Bob Tise and Matt Stevenson explain.

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Connect the Dots: The Power of Forward Thinking

06-06-2020

Innovation comes in many forms and from more places these days. Bob Tise and Matt Stevenson discuss how innovative electronic devices all contain PCBs, and share pro design tips for bringing new products to the market.

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Connect the Dots: Picking a Prototyping Strategy

05-29-2020

No matter how simple or complicated your electronic project, PCB prototyping is part of its journey from concept to reality. This process of turning the design into something physical can teach you a lot about what needs to be tweaked and improved before your PCB is ready for full production. Bob Tise and Matt Stevenson explain how before you can prototype, you have to design.

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Connect the Dots: Increased Focus on Health and Wellness Transforms the PCB Industry

04-04-2020

Our increased focus on health and wellness drives technology advancement for personal devices and those used in the delivery of healthcare. Bob Tise and Matt Stevenson explain how this trend also drives both PCB production innovation and a long-overdue update of the employer/employee relationship.

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Connect the Dots: The Seven-year Etch

03-16-2020

PCB etching seems like a simple task on the surface, but quite a few things can go wrong during this process. Adhering to best practice and continuous improvement is a must to help avoid issues with your finished board. Bob Tise and Matt Stevenson share their design tips for a better etching process.

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2019

Connect the Dots: A Penny for Your Thoughts on Copper

11-19-2019

You're probably thinking: “Bob can’t possibly write an entire article dedicated to the use of copper in PCBs.” To that, Bob says, “Hold my beer.”

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Connect the Dots: Build Quality Into Your Boards and Processes

11-06-2019

To the procurement clerk, a PCB may seem like it is just a line item on a bill of materials (BOM) or parts list during the production of an electronic device. At Sunstone, we know differently. The PCB is the building block for all of the components and parts in your electrical project.

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Connect the Dots: A Proactive Approach to Controlled Impedance

10-09-2019

You can save time, money, and effort if you are aware of the impedance math when you sit down to design your board. Gain this awareness by using a good impedance calculator, and you can build the right tolerances into your design. Impedance testing becomes a double-check of your work instead of the tool you rely on to tell you if your documentation is correct. Documenting impedance requirements properly is more onerous than most people realize. Though it seems simple, PCB documentation is a details game that often leaves knowledge gaps for your manufacturer.

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Connect the Dots: Managing Global Supply Chain Uncertainty

09-03-2019

We are well into the second year of tariff-centric trade policy, and one thing appears certain—uncertainty is here to stay. Though most of the media focus has been on cars and steel or consumer prices and corporate profits, the enduring challenge for both the electronics and PCB industries has been maintaining reliable global supply chains.

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Connect the Dots: Five Best Practices to Ensure Manufacturability

08-01-2019

When you send your design for manufacturing, your partner does not know what type of device the board will be part of nor the conditions in which it will have to perform. It’s common for harsh environments or exposure to mess up a board’s performance. If you call out materials that will not tolerate the end-product’s operating environment, bad things can happen—such as a smoking board, for example. Be sure your board can tolerate thermal stress or solder joints risk breaking and damaging components.

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Connect the Dots: The Future of PCB Manufacturing Doesn't Belong to Robots, but to the Users

07-09-2019

Is the world ready for the consequences of rapid automation? Will the use of robots displace entire categories of workers? Can artificial intelligence really “think”? How will manufacturing, including PCB manufacturing, be affected by all of these smart robots? These questions actually come from a pamphlet published in 1955: "The Age of Automation: Its Effects on Human Welfare."

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Connect the Dots: Accurate Gerber Files Are Mission-Critical for Smooth PCB Manufacturing

05-30-2019

Gerber files can reveal design issues ahead of the quote process and ensure your manufacturer has everything needed to produce your boards correctly. After consulting with Engineering Support Specialist Eric Haugen, we explored some best practices for making sure that Gerber files are accurate.

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Connect the Dots: Preparing for Tomorrow’s Technology Today

05-16-2019

At a recent Sunstone Circuits planning summit, Matt Stevenson, VP of sales and marketing, and Bob Tise had a wide-ranging discussion about emerging technologies and how they will impact PCB manufacturing. The following is an abridged transcript of this conversation.

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Connect the Dots: MakeHarvard 2019: Bigger and Better!

04-09-2019

Sunstone Circuits was eager to return to MakeHarvard as a sponsor and creator of a competition category this year, also serving as both mentors and competition judges. If you were there, you saw us—we were hard to miss in our bright orange vests. As mentors, we were out and about helping students and answering questions.

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Connect the Dots: Exploding PCBs: Don’t Lose Track of Voltage in Your Design

04-01-2019

Managing split planes? Your CAM tool will not do it for you. We see this almost every day—not exploding PCBs, which pretty rare—but rather problems created by having more than one voltage on a power plane layer. From where we sit, this is one of the more insidious and costly challenges facing PCB designers.

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2018

Connect the Dots: Six Tips to Ensure Parts Fit on Your Board

12-12-2018

One of the most frustrating mismatches with alternative through-hole parts occurs when the land pattern matches, but the pin size is off. If hole sizes are too tight, pins may not fit through the holes, or if they do go into the holes, they may not solder well. Solder will need to flow through the gap between the pin and the hole barrel. If there is not enough space to allow enough solder mass to flow through the hole, the circuit board will absorb heat from the molten solder and cause the solder to solidify partway up the hole. This is called a cold solder joint and can result in a premature failure of your circuit.

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Connect the Dots: New Landing Design to Reduce Thermal Pad Failure

11-16-2018

You’ve finally finished your design. All the traces are correct and the IC landings are to the manufacturer’s specifications. A short run of test boards performs perfectly. For best results, you select a reputable domestic board house for production and a quality assembly shop to do the soldering. When the finished boards arrive, everything looks great. You’re in high spirits and congratulate yourself on a job well done. Then the reports start coming in.

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