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

The Role of PCB Materials in Printed-Circuit Impedance

Printed circuits for high-speed and high-frequency applications rely on fine-featured transmission lines for signal transmission. Ideally, the loss through these transmission lines is minimal, and this requires an electrical impedance that is consistent and without interruptions, and with a value most appropriate for the types of signals to be transferred through the circuit. However, a number of factors can affect the impedance of a PCB, including the physical and electrical characteristics of the circuit and circuit material, but by reviewing and better understanding these variables, their effects can be minimized.


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Finish Makes a Difference in Final PCB Performance

The impact of final surface finish on circuit loss will depend not only on the type of surface finish but on the thickness of the substrate material and the type of transmission-line technology, such as microstrip or grounded coplanar waveguide (GCPW). This posting will describe some of the effects of various finishes.


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Paving the Way for 5G Wireless Networks

For circuit designers, one challenge will be in knowing where to start, which means, for millimeter-wave frequencies, knowing what types of printed-circuit-board (PCB) material characteristics are the most important at higher frequencies.


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Working Through Woven Glass Weaves

Woven glass is incorporated into printed-circuit-board (PCB) materials to provide structural strength. It aids the mechanical stability of a laminate, but what does it do to its electrical behavior? One of the classic concerns regarding woven glass reinforced laminate PCBs is that the “glass weave effect” can have negative impact on the electrical performance of high-speed or high-frequency circuits fabricated on these laminates. In this blog, we examine some of the factors affecting the glass weave effect phenomenon.


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Changing Temperature Can Change Circuit Performance

Circuit materials are evaluated by a number of different parameters, including dielectric constant (Dk) and dissipation factor (Df). Those two parameters also have temperature-based variants that provide insight into the expected behavior of a circuit material with changes in temperature, notably the thermal coefficient of dielectric constant (TCDk) and the thermal coefficient of dissipation factor (TCDf).


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What Type of Circuit Material Works Best for Millimeter Waves?

Millimeter-wave frequencies are being used more often, in automotive radars and soon in 5G wireless networks. But before such frequencies can become widespread, low-loss circuits must be designed at frequencies such as 60 and 77 GHz, and fabricating such circuits will require suitable circuit materials. Selecting circuit materials at such high frequencies will depend upon knowing which circuit and material parameters have the most effects on performance, and finding materials with a favorable set of characteristics for millimeter-wave frequencies.  


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Tracking Trends in RF Laminate Formulations

Recipes are often refined with time, in hopes of improving the results. Over the years, many different formulations have been applied to create high-frequency circuit materials. The efforts have led to a variety of current circuit laminate choices for a wide range of high-frequency applications and performance requirements.


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Comparing Transmission Lines for Millimeter-Wave Circuits

Circuit designers familiar with a particular transmission-line technology may ask: Can’t I stick with microstrip at mmWave frequencies, if the PCB material delivers the performance I need?  This posting reviews the answer to this question and about how to optimize mmWave PCB designs.


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People Help Turn Those Laminates into Perfect PCBs

Specifying the optimum circuit laminate for an electronic design project is often a case of reviewing the numbers. Once all these numbers have been analyzed and reviewed, the field of PCB material choices narrows until, finally, the optimum circuit material for a project can be selected. But what happens next?


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