ROG Blog

The Rog Blog is contributed by John Coonrod and various other experts from Rogers Corporation, providing technical advice and information about RF/microwave materials.

Sending Circuit Materials Into Space

Satellites in outer space are vital and increasingly important parts of modern communications, as signals are constantly being bounced off orbiting spacecraft to enable everything from telephone calls to video entertainment. Printed-circuit boards (PCBs) in space and satellite-communications (satcom) applications are often taken for granted, but they are special, since they must function reliably in extremely hostile environments. The choice of PCB material for these applications should be carefully considered, since these circuits must literally last a lifetime, or at least through the life of the satellite.
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Calculators Enhance Circuit Materials

Choice of printed-circuit-board (PCB) material can be critical to the performance of an RF/microwave circuit design, since so many different circuit-material parameters must be considered. As those who follow this Blog series know, many parameters can impact the selection of a PCB material for a particular design, including dielectric constant (Dk), dissipation factor (Df), and a variety of thermal traits. To ease the process of reviewing these many circuit-material parameters, Rogers Corp. offers a number of practical calculators on their web site’s Technology Support Hub. One of the more useful of these personal-computer-based calculators is the ROG Calculator Online.
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Perusing PCBs For Low PIM Levels

Passive intermodulation (PIM) is the unwanted mixing of two or more signals in a passive circuit or component, resulting in unwanted spurious or harmonic signals. These additional signals can clutter a system’s operating passband and cause interference in a system’s receive band. Although PIM is often associated with certain high-frequency passive components within a system, such as connectors, cables, filters, and couplers, it can start with the printed-circuit-board (PCB) materials, in particular when those materials are used for components critical to communications systems, such as PCB-based antennas and filters.
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Remember the Copper When Choosing PCBs

Achieving reliability and high performance from a PCB material is not simply about selecting the optimum dielectric material for an application—the copper on that material also plays a critical role. The quality of the copper on a PCB, including its surface roughness, and how the copper is joined with the dielectric material, can go a long way towards determining the performance possible with that PCB material, particularly at RF and microwave frequencies.
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Teaming Software Tools With PCB Materials

Choosing a printed-circuit-board (PCB) material is a critical step in the design of any new RF/microwave circuit, since the material’s characteristics will ultimately determine the performance and capabilities of the circuit. Picking an electronic-design-automation (EDA) software package to model any new design can go a long way towards improving the design experience (and the levels of performance possible) since the right software can help predict the performance of circuits fabricated on different PCB materials. Understanding how these EM simulation software tools differ and how they can be applied to model different PCB materials can greatly benefit the design process.

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Perusing PCB Materials For High-Power Levels

Handling high power in an RF/microwave printed-circuit board (PCB) requires not only effective circuit-design techniques, but PCB material capable of “getting the heat out.” High-power handling for a PCB material is synonymous with low loss and higher thermal conductivity. But in choosing a circuit material for high-power applications, such as power amplifiers and power combiners/dividers, many other PCB parameters come into play. This includes the maximum operating temperature (MOT) for a given material, which essentially describes a danger temperature above which performance and reliability problems can be aggravated.
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Fusion Bonding Forms Reliable Multilayer Circuits

Three approaches are commonly used for bonding multiple layers of PTFE-based circuit laminates, such as Rogers RT/duroid® 6000 series and RO3000®series materials. These three approaches rely on thermoplastic films, thermoset prepregs, and direct bonding methods, such as fusion bonding processes. The first two techniques require additional films or prepreg materials which function like glue to keep the multiple layers in one piece. The third approach employs heat and pressure to bond the multiple PTFE-based material layers into one piece.
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Harness High-Dk Circuit Materials

Dielectric constant (Dk) is a key parameter to consider when choosing a microwave printed-circuit board (PCB). But what microwave circuit designers may not always appreciate is the “choice within a choice” with some PCB materials, or when it might make sense to select a circuit material with a higher Dk value. High-Dk circuit materials can make it possible to miniaturize high-frequency circuits beyond what is possible with lower-Dk circuit materials. Understanding where high-Dk circuit materials fit within an RF/microwave designer’s toolkit can provide engineers with a great deal of flexibility when developing both active and passive high-frequency circuits.
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Digging Deeper Into Dissipation Factor

Dissipation factor, also known as loss tangent, is a printed-circuit-board (PCB) material parameter probably often overlooked when engineers size up their possible choices for PCB materials. But it is a parameter that can tell a great deal about how a material will perform in different applications and environments. And it is a PCB parameter that is certainly worth spending a little time to get to know better.
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