-
- News
- Books
Featured Books
- design007 Magazine
Latest Issues
Current IssueDesigning Through the Noise
Our experts discuss the constantly evolving world of RF design, including the many tradeoffs, material considerations, and design tips and techniques that designers and design engineers need to know to succeed in this high-frequency realm.
Learning to Speak ‘Fab’
Our expert contributors clear up many of the miscommunication problems between PCB designers and their fab and assembly stakeholders. As you will see, a little extra planning early in the design cycle can go a long way toward maintaining open lines of communication with the fab and assembly folks.
Training New Designers
Where will we find the next generation of PCB designers and design engineers? Once we locate them, how will we train and educate them? What will PCB designers of the future need to master to deal with tomorrow’s technology?
- Articles
- Columns
Search Console
- Links
- Media kit
||| MENU - design007 Magazine
Advanced Stackup Planning with Impedance, Delay and Loss Validation
August 2, 2018 | Yuriy Shlepnev, SimberianEstimated reading time: 2 minutes

A typical PCB design usually starts with the material selection and stackup definition—the stackup planning or design exploration stage. How reliable are the data provided by the material vendors and PCB manufacturers? Can we use these data to predict trace width and spacing for the target trace impedance or to calculate delays or evaluate the loss budget?
PCB routing is usually done with these preliminary data. The actual stackup may be further adjusted by the PCB manufacturer together with the trace widths and spacing, to have the target impedances. This is the typical impedance-controlled process that is well established and usually produces an acceptable outcome.
But what about the losses? Can we use preliminary data to evaluate the losses and loss-related compliance metrics? Or can we just specify the target losses and rely on the manufacturers, as is done with the impedance? Let’s try to answer these questions. An EvR-1 validation board is used here as an example with the preliminary and final data—all data for this board are provided by Marko Marin from Infinera. This board was featured in our award-winning “Expectation vs. Reality” paper. We will use Simbeor software as the stackup exploration tool to evaluate the accuracy of the characteristic impedance, delay and losses. Simbeor is selected for the stackup exploration because it is systematically validated with the measurements up to 50 GHz.
Stackup planning begins with selecting a PCB manufacturer and possible materials and defining the stackup structure. In our case, the validation board has 20 layers with 8 layers assigned for the high-speed signals as shown in Figure 1. Low-loss Panasonic Megtron6 laminate is selected to rout the high-speed interconnects. The target impedance has been specified for the PCB manufacturer, and the manufacturer has provided expected stackup structure, trace widths, and spacing adjustments to fulfill the target impedances. This is the usual case for a production board.
According to the manufacturer, the expected impedance variations should be within 8%. That is too large to expect excellent correlation up to 30 GHz for 28 Gbps NRZ links, but it may be acceptable. The board manufacturer provided stackup geometry as shown in Figure 1 on the left side, and corresponding stackup entered for the pre-layout analysis into Simbeor software is shown on the right side. Megtron6 specs provide dielectric constant and loss tangent at multiple frequencies—just one frequency data can be used to define causal wideband Debye model. The values for Dk in the Figure 1 are slightly different from the Megtron6 specs and are provided by the PCB manufacturer based upon their experience with this material.
To read this entire article, which appeared in the July 2018 issue of Design007 Magazine, click here.
Suggested Items
Real Time with... IPC APEX EXPO 2025: Benmayor Group—Resistance is Futile: Automation Is the Future
04/11/2025 | Real Time with...IPC APEX EXPOJeff Brandman, president of Aismalibar North America, and Eduardo Benmayor, CEO of Benmayor Group, discuss Benmayor Group's role in electronics and automation, focusing on how automation addresses labor shortages. Jeff, notes that many businesses struggle to find workers for manual tasks, emphasizing the need for various automation solutions to boost productivity. North America lags in automation compared to other regions, which impacts efficiency. Jeff recommends a step-by-step approach to scaling automation, and there's growing acceptance of robots in the workforce, leading to a positive outlook for the future.
Real Time with... IPC APEX EXPO 2025: Exploring Ventec's Innovations
04/09/2025 | Real Time with...IPC APEX EXPOMark Goodwin highlights Ventec's global distribution network and recent expansions in service and equipment offerings. He emphasizes the company's expertise in coating technology for thermal management, specialized materials, and its agility in creating customized solutions for customers.
INEMI Sessions at IPC APEX EXPO Focus is on Board Assembly and PCB & Laminates
03/12/2025 | iNEMIIf you plan to attend the upcoming IPC APEX EXPO in Anaheim, California, be sure to add the INEMI sessions to your calendar. We will have two forward-looking sessions — one on PCB and Laminates and the other on Board Assembly.
Rogers Corporation Launches New Thermoset Laminates for Automotive Radar Sensor Applications
03/03/2025 | Rogers CorporationRogers Corporation (NYSE:ROG) announced its latest innovation in dielectric materials: RO4830™ Plus Circuit Materials, which are well suited for cost-sensitive millimeter wave PCB applications, such as 76-81 GHz automotive corner radar sensors.
Unveiling the Future: Insights on Next-Gen Megtron Materials
02/13/2025 | Marcy LaRont, I-Connect007In this interview from DesignCon, Jim Kenny, OEM business development manager at Panasonic, touches on next-generation Megtron materials and delves into the industry's growing demand for high-speed, low-loss laminate systems, particularly in light of the anticipated 224 gigabits per second technology. With a focus on material development and production timelines, Jim highlights the challenges and opportunities in meeting customer needs while also maintaining quality and supply chain stability. As Panasonic prepares for the evolving landscape, they remain committed to innovating in this competitive market.