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Beyond Design: Faster than a Speeding Bullet
March 9, 2016 | Barry Olney, In-Circuit DesignEstimated reading time: 1 minute

In a previous Beyond Design column, Transmission Lines, I mentioned that a transmission line does not carry the signal itself, but rather guides electromagnetic energy from one point to another. The speed of a computer does not depend intrinsically on the speed of electrons, but rather on the speed of energy transfer between electronic components. Electron flow in a multilayer PCB is extremely slow—about 10 mm per second—so, how does the signal travel so fast, how fast does it actually transfer information and what are the limitations?
In optical communications, electrons don’t carry the signal—photons do. And we all know that photons travel at the speed of light. So surely, optical fibers must transmit information much faster than copper wires or traces on a multilayer PCB? Actually, photons and electrons transmit data at the same speed. The limiting factor is the relative permittivity (dielectric constant) of the medium in which the signal propagates.
An optical fiber is a cylindrical dielectric waveguide made of low-loss materials such as fused silica glass. It has a central core in which light is guided, and embedded in an outer cladding of slightly lower refractive index. The silica glass used has a dielectric constant (Er or Dk) = 3.78 @25GHz. Whereas, for instance, Panasonic’s new Megtron 7, low Dk, glass PCB laminate has an Er = 3.3 at the same frequency.
To read this entire article, which appeared in the February 2016 issue of The PCB Design Magazine, click here.
Suggested Items
RF PCB Design Tips and Tricks
05/08/2025 | Cherie Litson, EPTAC MIT CID/CID+There are many great books, videos, and information online about designing PCBs for RF circuits. A few of my favorite RF sources are Hans Rosenberg, Stephen Chavez, and Rick Hartley, but there are many more. These PCB design engineers have a very good perspective on what it takes to take an RF design from schematic concept to PCB layout.
Elephantech: For a Greener Tomorrow
04/16/2025 | Marcy LaRont, PCB007 MagazineNobuhiko Okamoto is the global sales and marketing manager for Elephantech Inc., a Japanese startup with a vision to make electronics more sustainable. The company is developing a metal inkjet technology that can print directly on the substrate and then give it a copper thickness by plating. In this interview, he discusses this novel technology's environmental advantages, as well as its potential benefits for the PCB manufacturing and semiconductor packaging segments.
Trouble in Your Tank: Organic Addition Agents in Electrolytic Copper Plating
04/15/2025 | Michael Carano -- Column: Trouble in Your TankThere are numerous factors at play in the science of electroplating or, as most often called, electrolytic plating. One critical element is the use of organic addition agents and their role in copper plating. The function and use of these chemical compounds will be explored in more detail.
IDTechEx Highlights Recyclable Materials for PCBs
04/10/2025 | IDTechExConventional printed circuit board (PCB) manufacturing is wasteful, harmful to the environment and energy intensive. This can be mitigated by the implementation of new recyclable materials and technologies, which have the potential to revolutionize electronics manufacturing.
Connect the Dots: Stop Killing Your Yield—The Hidden Cost of Design Oversights
04/03/2025 | Matt Stevenson -- Column: Connect the DotsI’ve been in this industry long enough to recognize red flags in PCB designs. When designers send over PCBs that look great on the computer screen but have hidden flaws, it can lead to manufacturing problems. I have seen this happen too often: manufacturing delays, yield losses, and designers asking, “Why didn’t anyone tell me sooner?” Here’s the thing: Minor design improvements can greatly impact manufacturing yield, and design oversights can lead to expensive bottlenecks. Here’s how to find the hidden flaws in a design and avoid disaster.