-
- News
- Books
Featured Books
- design007 Magazine
Latest Issues
Current IssueLevel Up Your Design Skills
This month, our contributors discuss the PCB design classes available at IPC APEX EXPO 2024. As they explain, these courses cover everything from the basics of design through avoiding over-constraining high-speed boards, and so much more!
Opportunities and Challenges
In this issue, our expert contributors discuss the many opportunities and challenges in the PCB design community, and what can be done to grow the numbers of PCB designers—and design instructors.
Embedded Design Techniques
Our expert contributors provide the knowledge this month that designers need to be aware of to make intelligent, educated decisions about embedded design. Many design and manufacturing hurdles can trip up designers who are new to this technology.
- Articles
- Columns
Search Console
- Links
- Events
||| MENU - design007 Magazine
Where Exactly is the Signal?
January 5, 2023 | Douglas G. Brooks, PhDEstimated reading time: 2 minutes
(Note: This article is adopted from my new publication, “The Physics of Electrical Engineering for PCB Designers,” soon to be available on Amazon and for download on the UltraCAD Website.)
When I first got involved in printed circuit board design in the early 1990s, fast rise/fall times were just starting to become an issue. Prior to that we had been pretty much a “connect-the-dots” kind of technology. But as rise times got faster, it became necessary to worry about (electromagnetic) fields. One manifestation of that was EMI, and the increasing need to pass FTC compliance testing.
So, a new type of engineer came on the scene: the electromagnetic compliance/compatibility engineer. Until that time, we understood that electrical current on a copper trace was the “flow” (movement) of electrons along the trace1. In fact, the definition of an amp of current on a copper conductor is 6.25*1018 electrons crossing a surface in one second2.
But this new breed of engineers came along and many of them started saying things like3:
- “No, current isn’t electron flow. Electrons can’t flow at the same speed signals flow.” (My response: But they can transfer energy between themselves at the speed of light, which is how they “flow.”)
- “Maxwell and Maxwell’s equations tell us that the signal is in the field around the trace, not on the trace itself.”
- Stop worrying about traces; ignore them. Just control the fields and you will be fine.”
So, before we answer the questions about where the current and signal truly are, let’s look at the fundamental principles behind Maxwell’s equations and see what they say4. The following discussion heavily paraphrases these principles and simplifies them for issues relative to this article. No, calculus will not be necessary.
The Principles
Charles-Augustin de Coulomb (1736–1806) was a French physicist. He is best known (at least to us) for developing a couple of laws in the 1700s. One was:
“There are two types of charge, positive and negative. ‘Unlike’ charges attract and ‘like’ charges repel each other (Figure 1) with a force that is proportional to the product of their charge and inversely proportional to the square of the distance between them.”
Coulomb also gave us another law related to magnetism: Every magnetic pole is a dipole with an equal and opposite pole. That is the same thing as saying that a magnetic “north” pole cannot exist without there also being a magnetic “south” pole. Even if you cut a magnet in half (see Figure 2) the individual poles would not be preserved; new poles would appear to preserve the dipole nature of the magnet.
To read this entire article, which appeared in the December 2022 issue of Design007 Magazine, click here.
Suggested Items
Designer’s Notebook: What Designers Need to Know About Manufacturing, Part 2
04/24/2024 | Vern Solberg -- Column: Designer's NotebookThe printed circuit board (PCB) is the primary base element for providing the interconnect platform for mounting and electrically joining electronic components. When assessing PCB design complexity, first consider the component area and board area ratio. If the surface area for the component interface is restricted, it may justify adopting multilayer or multilayer sequential buildup (SBU) PCB fabrication to enable a more efficient sub-surface circuit interconnect.
Insulectro’s 'Storekeepers' Extend Their Welcome to Technology Village at IPC APEX EXPO
04/03/2024 | InsulectroInsulectro, the largest distributor of materials for use in the manufacture of PCBs and printed electronics, welcomes attendees to its TECHNOLOGY VILLAGE during this year’s IPC APEX EXPO at the Anaheim Convention Center, April 9-11, 2024.
ENNOVI Introduces a New Flexible Circuit Production Process for Low Voltage Connectivity in EV Battery Cell Contacting Systems
04/03/2024 | PRNewswireENNOVI, a mobility electrification solutions partner, introduces a more advanced and sustainable way of producing flexible circuits for low voltage signals in electric vehicle (EV) battery cell contacting systems.
Heavy Copper PCBs: Bridging the Gap Between Design and Fabrication, Part 1
04/01/2024 | Yash Sutariya, Saturn Electronics ServicesThey call me Sparky. This is due to my talent for getting shocked by a variety of voltages and because I cannot seem to keep my hands out of power control cabinets. While I do not have the time to throw the knife switch to the off position, that doesn’t stop me from sticking screwdrivers into the fuse boxes. In all honesty, I’m lucky to be alive. Fortunately, I also have a talent for building high-voltage heavy copper circuit boards. Since this is where I spend most of my time, I can guide you through some potential design for manufacturability (DFM) hazards you may encounter with heavy copper design.
Trouble in Your Tank: Supporting IC Substrates and Advanced Packaging, Part 5
03/19/2024 | Michael Carano -- Column: Trouble in Your TankDirect metallization systems based on conductive graphite or carbon dispersion are quickly gaining acceptance worldwide. Indeed, the environmental and productivity gains one can achieve with these processes are outstanding. In today’s highly competitive and litigious environment, direct metallization reduces costs associated with compliance, waste treatment, and legal issues related to chemical exposure. What makes these processes leaders in the direct metallization space?