Beyond Design: High-speed Rules of Thumb
Global PCB Connections: A Technical Overview of Long-flex Printed Circuit Boards
The Shaughnessy Report: A Handy Look at Rules of Thumb
The Pulse
Column from: Martyn Gaudion
Martyn Gaudion, CEO of Polar Instruments Ltd., began his career at Tektronix in the early 1980s where he was responsible for test engineering on high-bandwidth portable oscilloscopes. Gaudion joined Polar in 1990 where he was responsible for the design and development of the Toneohm 950, Polar's multilayer PCB short circuit locator. He became marketing manager at Polar during 1997 as the market for controlled impedance test became a major section of the company's product range, was appointed Sales and Marketing Director in January 2001 and was appointed CEO in January 2010. Gaudion also writes occasional articles for a number of PCB industry publications and regularly contributes to IPC High-Speed High-Frequency standards development activities. He may be contacted Polar Instruments Ltd., Garenne Park, Guernsey, UK, GY2 4AF; phone:+44 1481 253081; fax: +44 1481 252476
August 29, 2024
The Pulse: Commonsense Cost Cutting
One difference between engineering and pure science is that engineers (in most situations) are looking for cost-effectiveness. They do so by designing the most appropriate level of technology to maximize profitability with acceptable levels of application functionality. One area that is often overlooked is the energy cost of PCB production. At a recent EIPC conference, Dr. Maarten Cauwe of IMEC in Belgium presented a combined study of the lifecycle impact (LCI) of electronics systems and subassemblies. The study looked at the supply chain as well as the energy impact of HDIs.June 06, 2024
The Pulse: Overconstraining: Short, Slim, and Smooth
Engineering is both an art and a science. The design engineer’s task is (almost) always to bring product to market that meets specifications at the best and most economical price suited to the appropriate end use requirements. From a PCB perspective, designers are faced with a bewildering and almost overwhelming choice of materials at their disposal.April 18, 2024
The Pulse: Drilling Down on Documentation
How did a product aimed at signal integrity end up being more about documentation? For a little backstory, the Polar team has an unspoken “no business speak” rule at certain times. So, why is this column titled “Drilling Down?” I find it fascinating when a company sets off in one direction, but customers steer it in another. That’s what has happened here as customers took a product down a fork in the road we couldn’t predict. Your destination isn’t always where you initially set off to go, and that’s how we got to our subject of drills and drill documentation.January 31, 2024
The Pulse: New Designer’s (Partial) Guide to Fabrication
PCB designers fresh to the industry may think that once the schematic is loaded into CAD and routed out into XY data, the finished PCB is an “exact” copy of their XY data. That’s not an unreasonable assumption for basic designs. Here, I’ll outline some of a designer’s considerations related to signal integrity as designs become more complex.November 15, 2023
The Pulse: Simplest Stackups Specified
Albert Einstein said, “Everything should be made as simple as possible, but not simpler.” Whilst his words were aimed at those describing complex theory in the simplest way possible, but not so simplified that key information is lost—a process which the media is often criticised for as “dumbing down” information. However, from an engineering perspective, if a design can be engineered to perform the required application in a simpler or more economic way than previously then simplification is truly a valuable goal.July 20, 2023
The Pulse: Rough Roughness Reasoning
Reliable bonding reduces the risk of delamination through thermal stresses. The tried-and-tested way of achieving a good, reliable bond is to ensure that the copper is sufficiently rough to promote adhesion to the epoxy resin in the prepreg material. As materials and bonding technology improves, the copper surfaces can be made increasingly flatter and still achieve the desired reliability. In the future, new bonding methods—some already here but still on the high-priced side of the equation— may allow extremely flat copper to bond reliably. Meanwhile, as the industry is heading down the road of “smoother” copper, there is still a need to model the effects of a rough surface on signal transmission.June 01, 2023
The Pulse: Industry Organizations Keep Knowledge Alive
When looking at the PCB industry, an outsider may have the illusion that the typically green-colored substrates populated with components use only a small amount of technology. The term printed, along with the notion that you can simply lay out a board and press “print,” as you would a piece of paper, couldn’t be further from the realities of a high-tech PCB fabrication process—and, importantly, the complex supply chain of chemistry and laminates that feed the factory with raw materials.March 21, 2023
The Pulse: Instilling an Informal Information Culture
Informal information exists within most companies and distilling this knowledge into tools is not an easy task—maybe even an impossible one. But what’s most important in maximizing this informal information is to have a good communication network, those “go to” people for a particular purpose. It is important that the company promotes a culture of openness and sharing, or knowledge has a risk of being ring-fenced and locked away.November 28, 2022
The Pulse: Fitting Physics to Fact
In an ideal world you would use “perfect” materials that behave in a truly predictable way, but the realities of engineering mean that compromise is always needed—and so the desire of the purist for “absolute perfection” has to be balanced with the skill of the engineer in designing product to be “good enough” for the specific application.July 28, 2022
The Pulse: Field Solver Finesse for Modelling Transmission Lines
When I-Connect007 asked me to contribute for this issue on field solvers, I wondered what more could be added to this extensively discussed subject, but as a supplier and developer of field solvers, Polar still gets asked the same questions both by experienced customers who are perhaps exposed to a new scenario and, as is most welcome, by new entrants to the industry.April 21, 2022
The Pulse: Using Touchstone Files to Build Measurement Confidence
Measuring PCB insertion loss can be time consuming, and the probes and cables tend to be significantly more costly (and delicate) than those used for characteristic impedance measurement. Nonetheless, given the high capital investment required for test systems, cables, and probes—and the design of the test vehicles themselves—wouldn’t it be nice if you could have a way of looking at your expected results before you put a test probe to a PCB?October 21, 2021
The Pulse: Fake Fudged Facts—Using Software to Get the Right High-Speed Answer
In the science of high-speed signalling, the signals obey the laws of physics, so when a design won’t work or meet a specification, no amount of psychological persuasion will smooth the signals path from source to load. Wouldn’t life be different if by speaking nicely—or shouting—at an underperforming circuit that it springs to life.August 17, 2021
The Pulse: PCB Design Education—What ‘They’ Don’t Tell You
For a new designer entering this space for the first time it can be quite an eye opener (no wordplay intended) to discover just how many different disciplines are involved in turning a good design into a fit for purpose PCB.April 22, 2021
The Pulse: Simulating Stackup and Signal Integrity
Civil engineer Isambard Kingdom Brunel set a high bar for simulation and modelling—to reduce the number of prototypes and predict the safety margins for structural loads.December 16, 2020
The Pulse: Don’t Ignore DC Trace Resistance
Time flies! But the laws of physics don’t. Martyn Gaudion focuses on how important it is becoming to take DC trace resistance into account when measuring and specifying thin copper traces.July 27, 2020
The Pulse: Application Notes—Advice for Authors
Application notes are the key to shedding light on new topics or new products and software tools in an easily digestible form. As both a consumer and an author many application notes, Martyn Gaudion explores various types and how to approach them.May 12, 2020
The Pulse: Communicating Materials From Design to PCB Fabrication
Designer and fabricator communication—especially for high-speed PCBs—should be a bidirectional “thing.” It is so easy for a designer to say, “Just build this,” and hand over a challenging design to a fabricator who could have performed better with some preliminary conversation or dialog before placing the order. Martyn Gaudion explores communicating materials from PCB design to fabrication.July 18, 2019
The Pulse: Modelled, Measured, Mindful—Closing the SI Loop
In this woolly world where high-speed signals enter a transmission line with a well-defined shape and emerge at the receiving end eroded and distorted—and at the limits of interpretation by the receiver—it is well worth running simulation to look at the various levers that can be figuratively pulled to help the pulse arrive in a reasonable shape. At speeds up to 2 or 3 GHz, it usually suffices to ensure the transmission line impedance matches the driver and receiver. And a field solver makes light work of the calculation. But push the frequency higher, and other factors come into play.March 07, 2018
The Pulse: The Rough Road to Revelation
Several years ago, an unsuspecting French yachtsman moored his yacht to the railings of the local harbour. For a very nervous full tide cycle, he awaited to see if the cleats would pull out of the glass fiber hull. Fortunately, the glass held. A yachtsman at high tide isn’t too worried about whether the seabed is rough or smooth, but at low tide, the concern about a sandy or rocky seabed is altogether different. With PCBs, the move to low-loss laminates exposes a similar situation.December 06, 2017
The Pulse: Tangential Thoughts--Loss Tangent Values
Numbers are fascinating things, and the way they are presented can influence our thinking far more than we would like to admit, with $15.99 seeming like a much better deal than $16. Likewise, a salary of $60,000 sounds better than one of $0.061 million, even though the latter is a larger number. Our brain has been programmed to suppress the importance of numbers to the right of the decimal point. Such is the case with the loss tangent of materials. It is a tiny number and so to our minds looks insignificant, but it has a directly proportional effect on the energy loss suffered by a dielectric.October 01, 2010
Signal Integrity – the ‘S’ Words
Three words, or rather, phrases are in the process of entering the vernacular of the PCB industry, albeit one phrase is already familiar, but taking on a different meaning. All start with S and all relate in one way or another to signal integrity.August 01, 2011
Transmission Lines – a Voyage From Dc – No, Not Washington ...Part 2
In the second part of this two-part article we continue on our voyage through a transmission line from DC onwards and upwards through the frequency spectrum, step by step exploring the characteristics from very low to ultra high frequencies.July 01, 2011
Transmission Lines – a Voyage From DC – No, Not Washington, Part 1
In this two-part article I'd like to join you on a voyage through a transmission line from DC onwards and upwards through the frequency spectrum. In Part 1 we trace the impedance from infinity at DC to the GHz region where it reaches the steady state value of its characteristic impedance.June 16, 2011
Crosshatching Compromise
Sometimes engineering results in some uncomfortable compromises; this is often the case with PCBs as the mathematical methods used by the modelling tools are based on "ideal" physical properties of materials rather than the actual physical materials in use.March 13, 2011
When Is a 10ghz Transmission Line Not a 10ghz Transmission Line?
'Just as in life, in electronics the only certainty is uncertainty.' -- John Allen PaulosJanuary 13, 2011
Regional Differences – a Voyage of Glass Reinforcement
Why bulk Er is not the same as local ErSeptember 13, 2010
All Set to Measure Differential Insertion Loss?
This column discusses the gradual adaptation necessary for PCB fabricators as more and more silicon families drive the industry toward the requirement for in house measurement of insertion loss.August 12, 2010
Zen and the Art of Accurate Impedance Measurement* – With Apologies to Prisi
In his 1974 philosophical novel "Zen and the art of Motorcycle maintenance” Robert M. Prisig contrasts his regular and ongoing daily approach to motorcycle maintenance with his friend's alternate view of leaving well alone between annual service center based maintenance. What has this got to do with accurate impedance measurement you may ask? Please read on to discover more…December 05, 2016
Vias, Modeling, and Signal Integrity
Remember that good modeling can’t fix a bad design. The model can tell you where a design is weak, but if you have committed your design to product, the model can only tell you how it behaves. Some less experienced designers seem to think a better model will fix something that doesn’t work; it won’t. It will only reassure you that the design was bad in the first place.August 31, 2013
Rooting Out the Root Cause
When your measured trace impedance is significantly different from the calculated/modeled trace impedance, be careful before jumping to conclusions.March 30, 2014
Tolerant of Tolerance?
Wouldn’t life be great if everything fit together perfectly? There would be no need for tolerance. However, for that to be the case, everything would need to be ideal and without variation...May 31, 2011
Correlation, Communication, Calibration
At ElectroTest Expo at Bletchley Park, UK, Martyn Gaudion noticed the extent to which some technologies change, while the overall concepts do not. Prospective customers still ask exactly the same questions as they did 50 years ago: “What’s the bandwidth? Will it work in my application? How accurate?” Followed by the predictable, “How much does it cost?”June 10, 2015
Impedance Control, Revisited
The positives for new fabricators and designers lie in the fact that, even though impedance control may be new to them, there is a wealth of information available. Some of this information is common sense and some is a little counterintuitive. So, this month I’d like to go back to the fundamentals, and even if you are an experienced hand at the subject, it can be worth revisiting the basics from time to time.March 11, 2015
I3: Incident, Instantaneous, Impedance
In my December 2013 column, I discussed “rooting out the root cause” and how sometimes, the real root cause is hidden when digging for the solution to a problem. In that column, I described how sometimes in an attempt to better correlate measured impedance with modelled impedance, fabricators were tempted to “goal seek” the dielectric constant to reduce the gap between predicted and measured impedance.January 20, 2015
The Road Ahead: 2015 and Beyond
Editor Andy Shaughnessy kindly offered me the chance to write a column looking ahead at 2015. Predicting the future—that’s a tall order. But as I write this in mid-December, the news feeds trumpet that the USA is opening a new chapter in ties with Cuba, and that the price of oil is at $55 and headed south. Really? Did anyone see that coming? What happened to “peak oil?”January 16, 2013
Changing, Yet Changeless
Like the whack-a-mole game where the moles keep popping up at random after being knocked back into their holes, the same old questions about technical hurdles surrounding signal integrity continue to surface as technology advances.August 29, 2012
Repeatability, Reproducibility and Rising Frequency: The R3 Predicament
One of the more popular editions of The Pulse in 2011 was the article "Transmission Lines - a Voyage From DC." Starting again from DC and working through the frequency bands, Martyn Gaudion looks at what is realistic to achieve and where economic compromises may need to be made.December 20, 2010
The Pulse: Laminates Losses and Line Length, Part II
In the last edition of "The Pulse," we began a discussion on how a modern field solver can help choose the most cost-effective material for a high-frequency application. Last month we looked briefly at the effects of line length and dielectric losses and this month we focus on copper losses; all three are primary drivers for losses.December 01, 2010
The Pulse: Laminates Losses and Line Length, Part I
The EE creating the "platform spec" and the PCB fabricator responsible for its realisation face an array of materials with a mix of choices: From ease of processing to reliability requirements and signal integrity. For then next two months, "The Pulse" will focus on signal integrity, describing how to use field solvers to select the best materials when trading cost versus SI performance.July 14, 2010
New Column: The Pulse
Polar Instruments CEO Martyn Gaudion will be exploring a number of themes. A major SI topic that is set to grow is the emergence of new silicon families designed to push traditional materials into the multi-gigahertz arena. These new chipsets lift transmission speeds up to a point where signal losses rather than reflections become the predominant concern from an SI perspective.
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