FAQ - Microwave PCB Materials


Reading time ( words)

The landscape of specialty materials changes so quickly that it can be hard for product developers to keep up. As a result, PCB designers are inundated with data about microwave PCB materials. But very often, it’s difficult to find useful information regarding these specialty substrates. So, this month, we present some of the most frequently asked questions about microwave materials encountered at Rogers.

Q:  At what frequency is it necessary to transition from FR-4 types of materials to high-frequency circuit materials?

A:  This is a challenging question to answer because different technologies can tolerate more or less performance from a laminate. I’ll give a few examples and basic guidelines.

Semiconductor technology has developed enhanced signal processing to the point where a FR-4 material could be used at higher speeds and frequencies than was once thought possible. In most cases where high-speed digital applications reach 10 Gbps or more, you will need to use a high-frequency laminate. There are exceptions, and in some cases a lower data rate PCB will also demand a high-frequency laminate.

High-frequency RF circuits, which are less concerned with insertion loss, could use FR-4 in some of these applications. However, high-frequency laminates offer more than just low loss; they provide very well-controlled dielectric constant. In many RF applications, the control of dielectric constant for the material can be as critical as substrate thickness control. As a general statement, FR-4 materials are typically not used above 3 GHz in RF applications due to insertion loss concerns. However, when dielectric constant control is a critical concern, high-frequency materials should be used instead of FR-4 materials.

Read the full column here.


Editor's Note: This column originally appeared in the February 2014 issue of The PCB Design Magazine.

Share




Suggested Items

Ultra HDI Primer

10/13/2022 | I-Connect007 Editorial Team
We recently spoke with Herb Snogren, an industry veteran and consultant with Summit Interconnect tasked with leading the company’s ultra HDI efforts. Herb is co-chair of the IPC ultra HDI subcommittee, IPC D-33-AP. In this interview, Herb discusses the current state of UHDI, how designers and fabricators can get started working in this new frontier, and why the U.S. must invest in UHDI technology now to counteract Asia’s near dominance of the UHDI segment, which has left some of our critical industries vulnerable to supply chain disruptions.

Designing for Material Conservation Means Changing Attitudes

08/29/2022 | I-Connect007 Editorial Team
It makes a lot of sense: During times when the supply chain is stretched to the breaking point—and the last few years certainly qualify—what if PCB designers created boards that used fewer components and less laminate? Do PCBs still have to be 0.062" thick? Why not reduce layer count while they’re at it? Andy Shaughnessy and Nolan Johnson spoke with I-Connect007 columnist Dana Korf about the idea of designing a PCB with material conservation in mind. Is it a great new idea, or are we opening a whole new can of worms and a separate group of problems?

The Practical Side of Using EM Solvers

08/01/2022 | Heidi Barnes, Keysight Technologies
Electromagnetic (EM) solvers based on Maxwell’s equations have proven invaluable in the advancement of digital electronics and wireline communications. Plain and simple, electrical engineers need to know what a circuit or electrical interconnect will do when excited by a dynamic or varying signal. In the signal integrity world, an interconnect that passes a DC connectivity check can completely fail at higher frequencies. In the power integrity world, a power rail that measures the correct DC voltage could easily go into oscillation when a dynamic load is applied. Learning the basic skills to fire up an EM simulator, obtain qualitative answers in minutes, and higher fidelity answers in a few days, can be the difference between sleepless nights of product failures vs. robust designs with wide design margins.



Copyright © 2022 I-Connect007 | IPC Publishing Group Inc. All rights reserved.