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Online Design Tools for High Performance Foams help you make calculations to ensure you have the right materials for your design, from ultra-thin protection for sensitive electronics to robust gasketing for automotive applications.

  • PORON® Urethanes Gap Filling ToolThe PORON® Gap Filling Tool will assist in choosing the proper material to meet final gap thickness requirements.
  • Compression Force Deflection (CFD) Curve ToolThe CFD Curve Tool can help identify PORON® Urethane materials, using stress-strain data, to meet your engineering requirements.
  • High Performance Foams Material Selection GuideThis interactive tool will assist you in identifying the proper PORON® Urethane and BISCO® Silicone material that best meet your design requirements.
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Screen shot 2015-03-26 at 1.53.07 PMDesign Tools for Advanced Circuit Materials help designers make calculations, select materials, and create products for a cleaner, safer, more connected world.

  • Microwave Impedance CalculatorThis software is intended to assist with microwave circuit design in predicting the impedance of a circuit made with Rogers High Frequency circuit materials. Additionally, the software provides some capabilities for predicting transmission line losses.
  • ROG Dk Calculator (Microstrip Differential Phase Length Software)This software calculates the dielectric constant (Dk) of a circuit material when tested as microstrip transmission line circuits. This software requires data received from a network analyzer, after testing a short and long microstrip transmission line circuit for phase response. The output is a text delimited file which can be read into Excel® for data manipulation and generating charts. The software also gives immediate output to the screen as a data table and a graph of Dk vs. Frequency.
  • ROG Calculator OnlineThis application is designed to work on your smart phone or tablet. Navigate to this website from your mobile device to download this application.



This post authored by John Coonrod originally appeared on the ROG Blog hosted by Microwave Journal.

Circuit design engineers have long relied upon the basic physics of printed-circuit boards (PCBs) and how capacitors and inductors can be formed from simple patterns and structures on a PCB. For example, a PCB provides parasitic capacitance because the metal signal plane layer and the metal ground plane layer underneath are parallel to each other, separated by a dielectric material layer. Of course, the characteristics of the metal layers, such as the thickness and type of conductive metal used, and the mechanical and electrical traits of the dielectric material, including its relative permittivity or dielectric constant (Dk), can contribute quite a bit to the final performance levels and consistency that can be achieved for a particular circuit design. A number of PCB material traits, in particular the consistency of the dielectric constant, can go a long way towards achieving consistent and reliable PCB capacitors and inductors especially at RF and microwave frequencies.

PrintCircuit designers are constantly being asked to make their circuits smaller, whether they are for commercial cellular telephones or for portable military radios. Integrated-circuit (IC) designers have been doing their part to contribute to the size reductions, packing more and more active components onto chips, including amplifiers, microprocessors, and oscillators. But when added to PCBs, even these tiny chips require the support of essential passive components, such as capacitors and inductors, for such functions as impedance matching to help transfer signals from the chips to other components. And circuit designers are constantly faced with the need to produce reliable capacitors and inductors on their circuits. Understanding the role of the PCB material in building those capacitors and inductors can be a huge help.

PCB material characteristics that strongly impact the performance and consistency of embedded capacitors and inductors include Dk and Dk consistency or tolerance. Because capacitors and inductors that are created from different structures using, for example, microstrip or stripline circuit traces, can occupy more than a small portion of a section of PCB, it is essential that a candidate circuit material for those passive components and their associated circuitry maintain good Dk control in order to achieve consistent capacitance and inductance from different circuit structures.

When working in microstrip, for example, the amount of transmission-line area above the ground plane will determine the amount of capacitance for a particular circuit structure. Even a 90-deg. change in a transmission line can add capacitance to a circuit. Such simple structures as meander lines have been used to add small amounts of  inductance to a circuit. Spiral circuit patterns have long been used to add inductance to a circuit, with the inductance changed by varying the trace width and the spacing between the traces in the spiral circuit pattern. Such an inductor is characterized by a self-resonant frequency (SRF), which will increase when the inductor trace width is increased and the spacing between traces is decreased.

The amount of capacitance in an embedded capacitor will depend on such factors as the distance from the signal plane to the ground plane—essentially the thickness of the dielectric material between them—and the physical size of the capacitance structure. The coupling between arms on the signal plane can also add to a microstrip circuit’s capacitance. These embedded capacitors and inductors are typically referred to by designers as part of a circuit’s resistor-inductor-conductor-capacitor (RLGC) parameters and are included in computer circuit models to predict the performance and behavior of transmission-line circuits. Computer models assume that such things as the dimensions of the various RLGC structures on a PCB that are entered into the software program are the same dimensions that have been fabricated on the actual PCB. Variations between the sets of values can result in variations in such things as capacitance and inductance values from computer-predicted expectations

Of course, such computer models also consider the contributions of PCB materials when predicting such things as the capacitance in a 90-deg. bend in a circuit’s transmission line. Circuit computer models work with such circuit material parameters as Dk and even Dk tolerance, or the deviations in Dk with temperature and frequency. Models can focus on different parameters with some models, for example, ignoring the losses contributed by the PCB’s conductors and the dielectric material but concentrating on the Dk consistency to accurately predict the values and expected performance of circuit elements such as inductors and capacitors based on the physical dimensional tolerances of circuit structures.

Numerous reference guides are available for calculating the values of microstrip capacitors and inductors based on dimensions etched onto different PCBs, such as the ARRL Handbook from the American Radio Relay League. For microstrip inductors, for example, it provides calculations for microstrip inductors using such variables as transmission-line strip width, distance to the ground plane, and Dk of the PCB material

The choice of PCB material can play a significant role in the performance levels to be expected from these etched capacitors and inductors, with the material properties impacting capacitance value and consistency and such inductor characteristics as quality factor (Q), SRF, and self-inductance factor. A PCB material’s Dk value will determine the size of different circuit structure for a desired operating frequency, but it is the tolerance to which the Dk value is held that greatly impacts the consistency and performance of capacitors and inductors etched onto the copper layer of the PCB material.

As an example, RO4835™ circuit material from Rogers Corp. is a glass-reinforced hydrocarbon and ceramic dielectric material with good z-axis (through the thickness) stability that makes it a candidate for multilayer circuits. It exhibits a z-axis Dk value of 3.48 at 10 GHz with impressive Dk tolerance within ±0.05 of 3.48 across the circuit board. In terms of fabricating passive circuit elements such as capacitors and inductors, this means that they will maintain their capacitance and inductance values with frequency and with temperature, with minimal variations in capacitance and inductance caused by changes in PCB Dk value.

As impressive as that Dk tolerance, Rogers Corporation offers even more tightly controlled circuit materials, such as its RO3003™ ceramic-filled polytetrafluoroethylene (PTFE) circuit material. Its Dk value of  3.00 at 10 GHz through its z-axis is held to a tolerance of ±0.04 across the material and from board to board. And RT/duroid® 5880 is a glass-microfiber-reinforced PTFE composite material with a Dk of 2.20 that is maintained to an extremely tight tolerance of ±0.02 across the material. This low-loss material supports circuit applications across a wide range of frequencies, well into the millimeter-wave frequency range.

Screen shot 2014-08-08 at 1.33.54 PMDesigners may choose a PCB material for a particular Dk value, but the Dk tolerance may not be known or may not be tightly controlled, resulting in etched circuit elements such as capacitors and inductors that may not provide the performance or consistency expected or predicted by commercial software circuit-design programs. A PCB material with tightly controlled Dk tolerance can provide the assurance of achieving the circuit values expected for such passive elements as capacitors and inductors and for maintaining circuit performance with frequency and time.

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Join Microwave Journal and Rogers Corp. for a free one-hour webinar on March 26, 2015:

Measurement of PIM Distortion in Microstrip Transmission Lines: Effect of Laminate Properties and Measurement Repeatability 

Date: March 26, 2015, 8am PT / 11am ET / 3pm UTC

Presenter: Allen F. Horn III, Ph.D., Rogers Corp.

Screen shot 2015-03-17 at 5.13.04 PMUnderstanding the factors contributing to the generation of passive intermodulation (PIM) distortion in multi-frequency communication systems is a subject of interest to antenna designers. As telecommunications antennas are becoming more complicated, microstrip circuits made on copper clad laminates are replacing bent metal designs. PIM distortion is a circuit or system property, not a basic material property, and depends on the overall design, connectors, and local power densities, among many other factors. However, there are basic laminate properties that can contribute to PIM. In this seminar, we will discuss the measurement of PIM in microstrip transmission lines and the pertinent laminate properties, most notably conductor profile. We also discuss experiments on the effects of circuit processing, laminate thickness, and power level. Understanding small contributions to PIM is complicated by the very low power levels involved. We discuss the special attention that must be paid to the statistics of the measurement method.



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This post authored by John Coonrod originally appeared on the ROG Blog hosted by Microwave Journal.

Digital circuits continue to conquer higher speeds, with components such as microprocessors and signal converters routinely performing billions of operations per second. True, high-speed digital circuits can be flawed by such things as impedance discontinuities in transmission lines and poor plated-through-hole (PTH) interconnections between layers on multilayer circuit boards. But they can also be hurt by less-than-ideal choices of printed-circuit-board (PCB) materials for those high-speed-digital circuits. Which leads to the question: “What are the key parameters to consider when selecting a PCB material for a high-speed-digital circuit application?”

PrintAnalog circuit designers have learned to judge PCB materials by a number of important material parameters related to performance, such as dielectric constant (Dk) and dissipation factor (Df). These material parameters can also serve as yardsticks when comparing different circuit materials for high-speed digital circuit applications. In fact, it can be helpful to understand how high-speed digital signals are related to high-frequency analog signals when considering different PCB materials for those digital signals.

As digital applications have continued to gain in speed, some of the general-purpose PCB materials typically selected for fabricating those circuits, such as FR-4, fall short in performance for various reasons. In many ways, the demands placed on a circuit material by high-speed digital circuits and their signals are similar to what is needed from those PCB materials by analog microwave and millimeter-wave signals.

For example, a high-speed 10-Gb/s digital signal is a square-wave signal that can be viewed as a combination of different, but related, sine waves. A high-speed 10-Gb/s digital signal is comprised of different-frequency signal components, including a fundamental-frequency tone at 5 GHz, a third-harmonic signal at 15 GHz, a fifth-harmonic signal at 25 GHz, and a seventh-harmonic signal at 35 GHz (and, typically, harmonic signal components even higher than that).

Maintaining the signal integrity of a digital signal, and the sharpness of its rise and full times, is the equivalent of transferring millimeter-wave signals (the harmonics) with low loss and distortion. A PCB material capable of maintaining the signal integrity of high-speed digital signals at 10 Gb/s should also be capable of handling analog millimeter-wave signals through about 35 to 40 GHz with low loss and distortion. PCB material parameters that are critical to analog millimeter-wave circuit performance will also be important as guidelines for choosing PCB materials for high-speed digital circuits.

The PCB parameters that can be used for guidelines when choosing circuit materials for high-speed digital applications include Dk, dissipation, loss, and even dielectric thickness. The dielectric constant, Dk, of a PCB material has long been a guiding parameter for both analog and digital circuits since it is so closely related to the impedance of the circuits that will be fabricated on that material. Changes in a PCB material’s Dk, whether as a function of frequency, as a function of temperature, or for other reasons, can adversely affect the performance of broadband high-frequency analog circuits as well as high-speed digital circuits because it will change the impedances of transmission lines in unexpected ways. In particular, these unwanted changes in Dk and impedance result in distortion to the higher-order harmonics making up a high-speed digital signal, with loss of digital signal integrity. In general, PCB materials with low and stable Dk values with frequency and temperature will support high-speed digital circuits with low distortion of the higher-order harmonic signal components, as revealed by measurements with clean and clear eye diagrams for those high-speed digital circuits.

Dispersion is a PCB material characteristic closely related to Dk. All PCB materials exhibit some amount of dispersion, which refers to the change in Dk as a function of frequency. A circuit material with minimal change of Dk with frequency will exhibit minimal dispersion, a good characteristic for high-speed digital circuits. Dispersion can be caused by a number of different circuit material traits, including the polarity of the dielectric material, the loss of the material, and even how the surface roughness of the copper conductor affects the PCB material loss at higher frequencies. If a PCB material exhibits different Dk values for the different harmonic signal components comprising a high-speed digital signal, it will cause losses and even shifts in frequency for those harmonics, resulting in degradation of the high-speed digital signals.

PCB signal losses at increasing frequencies, especially at the higher frequencies needed by a high-speed digital circuit’s higher-order harmonic signal components, can suffer excessive losses to the amplitudes of those higher harmonic signals, resulting in distortion to those high-speed digital signals. As noted in many earlier blogs, losses in a PCB can come from a number of different causes, including the dielectric material and the copper conductors.

The length of a high-speed digital circuit on a PCB material can also have a great deal to do with maintaining the integrity of those high-speed digital signals. Circuit losses for any PCB material are a function of frequency and will increase with increasing frequencies. A PCB material with acceptable losses within a bandwidth closer to the fundamental-frequency tone of a high-speed digital circuit, such as 5 GHz as in the earlier example, and perhaps even with low loss at the third-harmonic signal component, such as 15 GHz, may have excessive loss at the fifth- and seventh-harmonic signal components of that high-speed digital signal. In addition, signal losses are additive with length: a signal experiencing a loss of, for example, 0.5 dB per inch at 5 GHz for the first inch of a 10-inch-long high-speed digital circuit, will suffer loss of 5 dB at 5 GHz across the length of the circuit.

Depending upon the circuit’s dielectric losses and copper conductor losses, the total loss across the length of the circuit can be considerably higher for the high-speed digital signal’s higher-order harmonic signal components than for the lower-order harmonic tones. For some circuit materials, the loss for a 10-in.-long circuit may be 10 dB or more at the fifth- and seventh-harmonic signal components of a high-speed digital signal, resulting in considerable distortion to the high-speed digital signal transferred across that PCB material.

As noted, changes in a PCB’s transmission-line impedance from changes in Dk can cause distortion in high-speed digital signals. But when working with PCBs for high-speed digital circuits, attention should be paid to physical details as well. Such things as right-angle bends in transmission lines can affect performance. A right-angle bend represents a change in the effective width of the transmission line, resulting in an impedance discontinuity, and an increase in the capacitance at that portion of the transmission line. The use of mitered 45-deg. bends can minimize the impedance discontinuity and minimize the reflections of the signal passing through that junction.

The choice of PCB material for high-speed digital circuits can be guided by the speed of those digital circuits, with such material characteristics as loss and dissipation factor (Df) targeted for lower values at higher frequencies. Circuit materials with medium to low loss are suitable for digital circuits to 10 Gb/s, while lower-loss circuit materials are usable for digital circuits to about 25 Gb/s, and circuit materials considered to exhibit extremely low loss are well suited for the fastest digital circuits, such as operating at 50 Gb/s and faster. In terms of circuit material Df, typical values might be 0.010 to 0.005 for applications to about 10 Gb/s, 0.005 to 0.003 for applications to about 25 Gb/s, and 0.0015 or less for circuit applications to 50 Gb/s and faster.

Screen shot 2014-08-08 at 1.33.54 PMAs an example, RO4003™PCB material from Rogers Corp. is a ceramic filled hydrocarbon laminate with woven glass reinforcement and a Dk of 3.38 at 10 GHz through the thickness (z axis) of the material. It offers impressive Dk consistency over frequency, and is rated for Dk variations of only ±0.05. The Df is only 0.0027 through the z axis at 10 GHz. With its low and consistent Dk value, the material has been developed for broadband analog applications through millimeter-wave frequencies and low-distortion, high-speed digital applications through 25 Gb/s. In support of those digital applications, the material features extremely tight dielectric thickness tolerance and is compatible with multilayer PCB applications.

ROG Mobile App

Download the ROG Mobile appto 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.


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