This ROG Blog series on printed-circuit-board (PCB) materials from Rogers Corp. (www.rogerscorp.com) has reached the half-century mark, already covering a wide range of topics on circuit materials with this, the 50^th ROG Blog. For example, this series has recommended materials for amplifiers, for antennas, for filters, and for different types of transmission lines. It has even detailed the effects of different PCB material thicknesses on circuit performance, and described the influence of conductor roughness on circuit performance. While it would be difficult to pick out the top 10 Blogs from the first 49 Blogs appearing since August 2010, at least 10 of these ROG Blogs deserve mention for how they have attempted to help readers with their different uses of PCB materials.

From the very first ROG Blog, in August 2010, which compared low-cost FR-4 circuit substrates with higher-frequency PCB materials such as the Rogers substrates, to the latest ROG Blogs, which examine circuit material requirements for emerging millimeter-wave wireless applications through 300 GHz and higher, the ROG Blogs have attempted to provide clear and honest information on the use of circuit materials. The next 50 ROG Blogs will pursue the same ambitious goals, in hopes of providing readers with greater benefits for their uses of high-performance circuit materials.

While it would be difficult to name the “Top Ten” ROG Blogs from the series so far (see the table), it is not surprising to find that one of the most popular (in terms of viewers/readers) would be one that also refers to something for free: the January 2011 ROG Blog on Rogers’ free transmission-line modeling tool, the MWI-2010 Microwave Impedance Calculator. This easy-to-use modeling tool, which has also been reviewed in many of the leading RF/microwave trade publications, calculates key parameters for most common microwave transmission lines, including microstrip, stripline, and coplanar-waveguide transmission lines. The executable (.exe) file is available for free download from the Rogers’ website and runs on Windows-based personal computers (PCs), including those with Windows XP, Windows Vista, and Windows 7 operating systems. The free software is even backed by a 22-page operator’s manual in PDF file format, also available for free from the Rogers website.

In many ways, the ROG Blog series is like a book on circuit materials, unfolding online before its readers, with each Blog adding a new chapter to the book. Each chapter shares what Rogers’ engineers have learned over the years about making and using circuit materials, and this first set of 50 Blogs has covered some areas of interest to a large number of readers. In line with the ROG Blog on free software, the ROG Blog

“Comparing RF Circuit Material Processing Costs & Performance” also offers advice meant to help readers save money without sacrificing their performance goals. Although first appearing on “April Fool’s Day” (April 1) in 2011, this ROG Blog takes a serious look at the total costs of circuit materials, and how some circuit materials may have lower material costs than other materials, but pay for it later with higher processing costs and lower yields. It also explains how some performance parameters, such as passive intermodulation (PIM) in wireless circuits and signal integrity in digital circuits, require a careful consideration of tradeoffs in material and processing costs when choosing a circuit material.

These first 50 ROG Blogs have drawn readers for familiar themes as well as for some not-so-familiar topics. For example, the ROG Blog appearing on November 19, 2011, “What Is Outgassing and When Does It Matter,” addresses a subject that may be unknown to some readers but quite significant to others. Outgassing, which refers to the release of gas inside a solid such as a circuit material, especially when it is placed in a vacuum, can greatly impact the performance of circuits used in satellite-communications systems in space, or in medical electronics systems. This ROG Blog introduced many readers to a material term known as total mass loss (TML), and how the parameter could be used to help guide the selection of a circuit material for space-based or other applications where outgassing was a critical concern.

On the other hand, some of the more popular ROG Blogs covered the roles that circuit materials play in the design of some basic RF/microwave components, such as amplifiers, couplers, and filters, and how the choice of a circuit material can affect transmission-line losses in high-frequency circuits. One of the more popular ROG Blogs, “When Digital Signals Reach Microwave Frequencies,” covered an area of  interest to many microwave circuit designers, how to deal with digital circuits operating at microwave frequencies. This ROG Blog, appearing on February 23, 2011, reviews some of the important concerns for selecting a circuit material when circuits cross over from the digital area into the microwave realm. These high-speed digital signals will behave much like analog microwave signals, affected by PCB loss and even conductor surface roughness. To guide those in need of circuit materials for high-speed digital designs or even multilayer circuits that may combine fast digital and microwave circuits, this ROG Blog points out how different circuit material characteristics, such as dielectric constant and even coefficient of thermal expansion (CTE), can impact high-speed digital circuit performance.

At times, readers of the ROG Blog series shared their areas of interest and applications for circuit materials, and these applications are many and diverse, from lower-frequency analog and power circuits to high-speed digital and even microwave/millimeter-wave circuits. The ROG Blog series is written to serve its readers with new information on circuit materials as that information is needed, much like new chapters to an on-going, online book about circuit materials. Do you have a suggestion for future ROG blogs? We’d love to get your input. Let us know what you are interested in reading about.

Top 10 Popular ROG Blogs (based on reader feedback)

1. Transmission-Line Modeling Tool: Free Downloadable Software
2. What Is Outgassing And When Does It Matter?
3. Comparing RF Circuit Material Processing Costs & Performance
4. Controlling Conductor Losses In Coplanar Transmission Lines
5. When Digital Signals Reach Microwave Frequencies
6. Do You Have an Award Winning Application?
7. The Role of PCB Materials In Impedance Matching
8. Choose Circuit Materials For Bandpass Filters, P1
9. Make Waveguide In Planar PCB Form
10. Celebrating ROG Award Contest Winners at IMS 2012

Do you have a design or fabrication question? John Coonrod and Joe Davis are available to help. Log in to the Rogers Technology Support Hub and “Ask an Engineer” today.