This post authored by John Coonrod, Technical Marketing Manager, and team originally appeared on the ROG Blog hosted by Microwave Journal.

Dielectric constant (Dk) is one of the most important of circuit material parameters and a starting point for circuit designers. The dimensions of high-frequency circuit structures, including different types of transmission lines and the spacing between lines for proper isolation and/or coupling, are determined by the circuit material’s dielectric characteristics. One of the main parameters for understanding those characteristics is Dk. Circuit designers typically grow familiar with different commercial circuit materials, whether flexible or rigid, and may even gain great understanding of how to work with a material having a certain Dk value, such as 3.0.  Many designers grow to trust that the Dk value assigned to a given circuit material is truly accurate and consistent from board to board and base their designs on that trust. But how does the material supplier determine a circuit material’s Dk value anyway?

A circuit laminate’s Dk can be determined by different measurement techniques, generally using a microwave vector network analyzer (VNA) to evaluate the amplitude and phase characteristics of reference circuits with fairly well-known behavior. Such reference circuits include microstrip and stripline transmission lines as well as various types of resonators. By fabricating two microstrip transmission lines of different lengths on a circuit laminate with precisely known thickness, for example, and measuring the phases of the two lines with a VNA, the difference in phase values between the two transmission lines can provide insight into the Dk of the circuit material.

It sounds straightforward, but there is much to consider in this seemingly simple measurement. For one thing, most circuit laminates are anisotropic in nature, with different Dk properties along different axes of a material. A circuit material that has been characterized with a Dk value of 3.0 through the z axis of the material at a certain frequency may not exhibit the same Dk values through its x and y axes (length and width). The use of microstrip transmission lines to determine circuit material Dk via differential-phase-length method is an effective means of discovering a Dk value through the z axis of the material. But it is a measurement that must be performed with precision, with the electrical effects of a test fixture’s connectors removed from the phase values measured for the transmission lines. And this is just one of many test methods used in the RF/microwave industry to determine laminate Dk; some additional test methods provide Dk through the z axis while others help determine Dk through the x and y axes of the material. Some of these test methods are also used to measure a material’s dissipation factor (Df).

It is also important to remember that a circuit laminate’s Dk value depends on frequency, with 10 GHz often used as the test frequency for determining the Dk of a particular circuit material. If a circuit material is characterized for a given Dk value at 10 GHz using a test approach such as the microstrip differential-phase-length method, it will exhibit a different Dk value if tested with the same measurement method at a different frequency. And, unfortunately, two different Dk test methods may not even yield the same values of Dk for the same material under test even at the same test frequency!

A number of circuit material Dk test methods are based on fabricating resonators or resonant cavities on a material and evaluating the performance of the resonator. This use of perturbed resonators yields Dk values that are typically through the x and y axes of the material and can also help determine the material’s Df. One such method, for example, is the use of a split post dielectric resonator (SPDR) to measure both Dk and Df as outlined in application note 5989-5384E from Agilent Technologies (now Keysight Technologies), “Agilent Split Post Dielectric Resonators for Dielectric Measurements of Substrates.” The SPDR method, one of the approaches used by Rogers Corp. (along with the differential-phase-length method) to evaluate Dk, is a means of measuring Dk automatically with a VNA and test software at a single frequency. It provides in-plane Dk value through the length and width of a substrate but is not effective beyond a certain thickness and Dk value of material.

The different test methods employed by different circuit material suppliers may lead to some confusion for engineers comparing different circuit materials in search of a laminate with a certain Dk value for a design. It is important to note the test frequency at which the Dk has been characterized as well as which axis or axes for which the Dk value has been determined. Of course, for engineers working on the growing number of millimeter-wave circuit applications, such as for short-haul communications or automotive electronic safety systems (radar), Dk values referenced to a test frequency of 10 GHz offer little insight into how a circuit material will behave at frequencies above 30 GHz and it is at these higher frequencies that work remains to be done in characterizing circuit material Dk.

Fortunately, suppliers of commercial circuit laminates are aware of the differences among the various Dk and Df measurement approaches and are working together to try to eliminate confusion for engineers comparing laminate data sheets, especially in terms of Dk. The IPC D-24C Task Group of the noted global trade association, Association Connecting Electronics Industries, and its Institute of Printed Circuits (IPC) is attempting to better understand the impact of different test methods on determining the Dk values of high-frequency circuit laminates and is focused on broadband VNA measurements above 10 GHz for determining Dk and Df values for circuit laminates.

The task group, which includes leading materials test companies and suppliers of RF/microwave circuit laminates, is developing precise methods for testing the same circuit materials from the same production lots, not only with different test methods but at different locations along a board, to better understand all of the variables involved in determining precise, repeatable Dk and Df values for a circuit material. One of the goals of the task group is to establish reliable test methods for Dk and Df above 10 GHz as well as repeatable measurement techniques for determining precise values of material thickness, another important material parameter for circuit designers. Hopefully, this industry teamwork and the efforts of the task group members will yield circuit laminate data sheets that can be compared easily and with confidence.

Screen shot 2014-08-08 at 1.33.54 PMROG Mobile App

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Selected quotes from our first quarter earnings call.

Read the corporate financials news release: Rogers Corporation Reports First Quarter 2016 Results

In Q1 2016 Rogers achieved net sales of $160.6 million, exceeding the high-end of our guidance, which was $156 million. Year-over-year revenues were down slightly primarily due to challenges we faced in the PES business segment, which are addressed below. Sequentially, revenues grew 5% over Q4 2015, which is attributable to the recovery we are seeing across a number of our key markets.

Rogers’ ongoing commitment to driving operating efficiencies and practicing disciplined cost management helped contribute to a substantial adjusted operating margin performance of 16.9% during the quarter. Our year-over-year adjusted EBITDA percentage was consistently strong at 21.1%. Q1 adjusted earnings of $0.94 per diluted share far exceeded the high-end of our guidance.

Screen shot 2013-11-01 at 10.53.55 AMBruce Hoechner, CEO, on Growth

During Q1, we were encouraged by strengthening demand in the areas of wireless infrastructure and general industrial applications. We believe the longer-term growth prospects for these and other key markets remain positive and Rogers is in a favorable position to capitalize on the many opportunities that lie ahead.

Our roadmap has enabled us to deliver sound results and positions us for growth as market demands strengthen. Rogers is a market driven organization and we leverage our deep understanding of the link between our markets and technology to develop solutions that fill unmet needs in the marketplace. One example of this is the technology leadership position we have established in wireless telecommunications especially in 4G LTE applications. With the rapid evolution of this market, we are privileged to be working very closely with all of the major OEMs on 5G technology, the next phase of wireless connectivity. We believe our technological expertise, strong customer relationships, and differentiated products will enable us to continue to thrive in this marketplace.

Screen Shot 2016-05-04 at 10.34.05 AM

Bruce Hoechner, CEO, on Megatrends

The outlook and corresponding growth expectations for our key markets remain positive. For example, mobile data traffic is growing at 45% annually, yet only about 40% of the world’s population is currently covered by 4G LTE. So there remains tremendous opportunity for applications in the wireless infrastructure that will help meet global data demand.

Other areas of importance to Rogers are energy efficiency and safety, which continue to be at the forefront of our technology advancements across many segments. In particular, we expect to see solid growth for EV/HEV and automotive safety system applications going forward.

Bruce Hoechner, CEO, on Rogers’ Business Units

Advanced Connectivity Solutions delivered record quarterly net sales of $73.4 million during Q1 2016, which is an increase of 2.9% over Q1 2015. Adjusted operating margin decreased moderately as a result of unfavorable absorption.

In Q1 2016, we were encouraged by our 15% quarterly sequential revenue growth, which was driven by stronger demand for 4G LTE wireless telecom applications. Although sales of these applications were down year-over-year we believe we are seeing a return to a balanced supply chain between the board shops and the OEMs specifically in China. In addition, we are delighted with the consistently strong demand for automotive safety applications in advanced driver assistant systems (ADAS). As these features continue to expand into mass market automobile models globally, we are executing on our strategy to deliver growth in ACS.

In the near-term, we expect to maintain our leadership position in 4G LTE wireless infrastructure and automotive safety system applications. Going forward, we are well-positioned to benefit from the ongoing technology advancements in wireless telecommunications for 5G applications as well as the adoption of new technologies linked to the Internet of Things (IoT) and E-Mobility.

Elastomeric Material Solutions achieved record first quarter net sales of $46.3 million, an increase of 4% over Q1 2015. Adjusted operating margin increased slightly compared to Q1 2015. Profits were impacted primarily by inventory build that occurred in the comparative quarter of Q1 2015.

During the quarter, EMS results were driven by an increase in demand for general industrial and automotive applications, which more than offset a slight decline in sales into the portable electronics market. Sequentially, EMS net sales were up approximately 9%. Our strategy to drive growth in EMS through geographic expansion was evident during the quarter as sales in Europe increased 15% compared to Q1 2015. In addition, through our R&D efforts we are expanding our portfolio of opportunities. For example, we continue to make good progress in the penetration of our materials into backpack applications for portable electronics.

Power Electronics Solutions net sales were $35.3 million, an 8.5% decrease compared to Q1 2015, with much of the decline due to currency. PES adjusted operating margin of 6.8% was slightly down year-over-year and actions are currently underway to improve profitability in the PES business.

Overall, we saw increased demand in certain renewable energy and vehicle electrification applications during the quarter.

For the PES business, we maintain a positive outlook for the mid-to-long-term. We expect government mandates and climate change agreements to continue to drive demand for energy efficient motor drives and renewable energy applications.


Q1 2016 Earnings Call Full Transcript:

Q1 2016 Financials Press Release:

Q1 2016 Earnings Call Slides:


Rogers Power Electronics Solutions group provides advanced materials technologies that significantly increase efficiency, manage heat, and ensure the quality and reliability of your electronic devices.

See the latest PES developments at PCIM Europe 2016, the leading technical conference and exhibition devoted to power electronics, intelligent motion, renewable energy, and energy management. Stop by and see us in Hall 9, Booth 406, May 10-12, 2016.

Take a look inside our newest power management systems in the following videos:

New Capacitor-Busbar Power Management Technology

ROLINX® CapEasy and ROLINX® CapPerformance are capacitor-busbar assemblies that combine a unique Power Ring Film Capacitor™ technology from SBE Inc. and the well-known ROLINX Laminated Busbars from Rogers Corporation. The new assembly provides extreme low inductance and high power density. This enables smaller, lighter electronic designs with higher current handling capabilities for a wide range of applications, from automotive electronics to solar-power and wind-power systems.

New Method for Welding Capacitors to Busbars

Dirk Maeyens, Global Director of Sales, Power Electronics Solutions, discusses a new method for connecting capacitors to busbars for use in high-power inverters. Spot welding is used to make a sturdy connection that also reduces the amount of inductance in the connection. The new connection method is particularly appropriate for puck capacitors and is expected to find use in vehicles and solar power conversion.

Rogers zeigt seine neueste Bus-Bar-Power-Lösung

In dieser Episode von PSDtv, erklärt Rogers die Kombination fortschrittlicher Kondensator-Technologie von SBE mit seinen ROLINX Stromschienen auf der APEC 2016. ROLINX nutzt die SBE Power Ring-Film-Kondensator-Technologie, für Kondensator-Busbar-Baugruppen mit extrem geringer Induktivität und hoher Leistungsdichte.

Rogers Corporation (NYSE: ROG) plans to announce results for Q1 2016 after the close of trading on Monday, May 2, 2016. A copy of the release will be available at

Rogers Corporation logoAll interested parties are invited to participate in Rogers’ quarterly teleconference to be held on Tuesday, May 3, 2016 at 9:00 am ET. Bruce D. Hoechner, President and CEO, and members of senior management will review the results and then respond to questions.

To participate in the teleconference, please call 1-800-574-8929 toll free in the U.S. or 1-973-935-8524 from outside of the U.S. There is no passcode for the teleconference.

For interested parties who do not wish to ask questions, the call is being webcast live by Thomson Reuters and may be accessed at

A slide presentation will be made available prior to the start of the call. The slide presentation may be accessed at

If you are unable to participate during the live teleconference, the call will be archived until Monday, May 9, 2016. The audio archive can be accessed by calling 1-855-859-2056 in the U.S. or 1-404-537-3406 from outside the U.S. The passcode for the audio replay is 87264976. To access the archived audio online, please visit the Rogers Corporation website and click on the webcast link.

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This post authored by John Coonrod, Technical Marketing Manager, and team originally appeared on the ROG Blog hosted by Microwave Journal.

Thin can be a good thing for high-frequency circuit laminate materials. As this blog detailed some years ago, thinner printed-circuit-board (PCB) laminates offer many electrical benefits as well as mechanical advantages compared to thicker circuit materials, especially at higher frequencies reaching into millimeter-wave bands. For applications where weight and size are critical, such as circuits for portable and mobile products, thinner circuit laminates are important starting points that can lead to miniature, lightweight solutions. In terms of electrical performance, thinner laminates offer many benefits over thicker circuit materials, in particular for microstrip circuits operating at millimeter-wave frequencies.

PCB laminatesMicrostrip is one of the most widely used transmission-line technologies for RF/microwave circuits. As the ROG Blog has noted many times, microstrip circuits are highly dependent upon the choice of circuit laminate for optimum performance. The best microwave performance results from the right mix of circuit material parameters, such as consistent dielectric constant (Dk) and high-quality copper conductor layers, right down to the thickness of the laminate. Ideally, microstrip circuits fabricated on the right laminate composition and thickness will achieve excellent electrical performance with low loss and minimal unwanted resonances or spurious signals.

However, thicker circuit laminates can pose problems for microstrip circuits, with the thickness measured as substrate only and without the thickness of the copper included. When microstrip circuits are fabricated on thicker laminates, unwanted resonances can occur. These resonances arise between a laminate’s metal layers and can disrupt the desired signal propagation of the quasi-transverse-electromagnetic (quasi-TEM) waves through the microstrip transmission lines.

Excessive conductor width can also be a concern when attempting to minimize spurious generation in microstrip circuits. If microstrip signal conductors are wider than one-eighth wavelength at the design frequency, resonances can occur between the edges of the conductors. These spurious-mode resonances can interfere with the desired signal propagation through the microstrip conductors. Since wavelengths shrink with increasing frequencies, attention must be paid to circuit structures and circuit material dimensions to avoid such opportunities for spurious generation. At millimeter-wave frequencies (above about 30 GHz), in particular, where the wavelengths become extremely diminutive, careful balance is critical between circuit laminate thickness and circuit dimensions for optimum circuit performance.

Those smaller wavelengths call for thinner laminates to minimize any opportunities for spurious signal generation. At the same time, narrow circuit conductors can help prevent any generation of edge-to-edge conductor resonances. At higher frequencies, microstrip conductors are typically designed and fabricated for a controlled impedance, such as 50 Ω, to achieve signal transference with low losses and minimal reflections. The consistently narrow conductor widths required to achieve a controlled impedance across a PCB also provide the circuit physical conditions needed to minimize edge-to-edge conductor resonances.

As noted in the earlier ROG Blog, the Dk of the circuit laminate also plays a role in determining the circuit dimensions required for a particular design impedance, including the conductor widths. For a given laminate thickness, design frequency, and microstrip impedance, the circuit dimensions will shrink with increasing value of Dk. As a result, circuit miniaturization can be achieved by designing and fabricating microstrip and other transmission-line technologies on circuit laminates with higher Dk values.

Thinner circuits offer benefits in terms of controlling electromagnetic interference (EMI). As microstrip circuits increase in frequency, they also tend to radiate more EM energy. When the level of radiated EM energy becomes excessive, it can interfere with the proper operation of the circuit from which it originates as well as any circuits nearby. When compared at the same high operating frequency, thinner microstrip circuits will radiate less EM energy than thicker circuits, so that thinner circuits have the potential for less EMI problems. Less radiation loss also equates to less signal loss for a microwave circuit.

Microstrip is a practical and straightforward transmission-line approach for many high-frequency circuit designs, but it may not always be the best choice for all designs, especially those sensitive to the effects of spurious signals and radiation. Grounded coplanar waveguide (GCPW) is an alternative transmission-line technique that has proven effective for minimizing spurious modes and EM radiation. It can be used with thicker circuit laminates, although better results can be achieved with thinner circuit materials. When comparing microstrip and GCPW for the same circuit material and material thickness, GCPW circuitry has much less spurious generation and suffers much less EM radiation than microstrip circuitry for the same operating frequency.

The choice of transmission-line technology and circuit laminate thickness at higher frequencies can also be influenced by whether or not dispersion is a concern.  Dispersion is a characteristic of transmission lines and circuit substrate materials in which different transmission lines may exhibit different group velocity or group delay with frequency, essentially with the smaller waves of higher frequencies slowing down as a result of the transmission lines. For narrowband circuits, dispersion is not a problem. But it can be problematic for broadband circuits, for longer circuits (with longer delays), and for pulsed waveforms, since the time for a high-speed pulse to travel through one type of transmission line will not be the same as for a transmission line with longer group delay. Transmission lines differ in their dispersion characteristics: microstrip and some types of waveguide suffer longer group delays compared to nondispersive transmission-line formats like stripline and GCPW.

For higher-frequency circuits, GCPW can minimize dispersion compared to microstrip, but it can also be more challenging to manufacture at higher frequencies, especially with the fine dimensions and circuit features required for millimeter-wave frequency operation. GCPW is more sensitive to the copper plating thickness variation due to the PCB fabrication process than microstrip, and can suffer circuit-to-circuit performance variations in insertion loss and phase response as a result of variations in laminate copper plating thickness. The inherent advantages of GCPW over microstrip in terms of dispersion characteristics can be nullified unless a circuit with tight tolerance in copper plating thickness is specified, along with tightly controlled Dk and overall laminate thickness. Thinner circuit materials can provide many benefits, provided that the tolerances of those circuit laminates are tightly controlled.

PCB laminatesROG Mobile App

Download the ROG Mobile app to access Rogers’ calculators, including the popular Microwave Impedance simulation tool, literature, technical papers, and the ability to order samples of the company’s high performance printed circuit board materials.

Ask an Engineer

Do you have a design or fabrication question? Rogers Corporation’s experts are available to help. Log in to the Rogers Technology Support Hub and “Ask an Engineer” today.