Congratulations to our Advanced Connectivity Solutions team on their 100th ROG Blog post. For six years they have been providing technical advice about PCB design for RF/microwave applications. Here’s to 100 more posts!
Predicting the future is never easy. Similarly, knowing which types of circuit materials will be needed for the next decade’s RF/microwave applications can be difficult to predict, but the past can provide invaluable guidance. With this being the 100th installment in this series, the previous six years of ROG Blogs provide a bit of a map for the high-frequency road ahead and what might be needed in terms of electrical and mechanical characteristics for what are expected to be large-volume applications in this industry, including in radar-based automotive electronics systems, Fifth Generation (5G) wireless communications systems, and Internet of Things (IoT) sensors almost everywhere.
This first six years of the ROG Blog offered guidance on the use of many different types of circuit materials from Rogers Corp., for everything from high-frequency analog circuits to high-speed digital circuits. It explored the effects of circuit material characteristics on the performance of different types of high-frequency transmission lines, including microstrip, stripline, and various types of coplanar waveguide (CPW) transmission lines. And it has examined how the choice of printed-circuit-board (PCB) material impacts the performance of many different types of components, such as low-noise amplifiers, power amplifiers, delay lines, filters, and resonators.
In the next few years, this industry is expected to face new challenges in circuit design, with the high-volume growth of automotive electronics systems, 5G wireless, IoT, even with the steady growth of existing wireless applications such as WiFi and WLAN.
For many high-frequency circuit designers, wireless communications systems such as Third Generation (3G), Fourth Generation (4G), and Long Term Evolution (LTE) have represented rapid growth areas. But even without a standard in place, excitement is growing for the coming of 5G wireless communications systems and the type of services they will provide in the years to come, including fast wireless data with almost zero latency. Transferring high-speed digital signals will be an important part of any future communications network and the ROG Blog from January 22, 2015, “Selecting PCB Materials For High-Speed Digital Circuits,” detailed how RO4003™ circuit materials provided the proper mix of characteristics for speeds to 25 GB/s and beyond.
Higher-frequency (millimeter-wave) signals are expected to play important roles in 5G next-generation communications systems, and the ROG Blog has already provided several installments on choosing materials for millimeter-wave circuits, such as “Making The Most of Millimeter-Wave Circuits” and “Matching Materials To Millimeter-Wave Circuits.” Since millimeter-wave frequency bands are planned for high-data-rate backhaul links throughout 5G networks, the need for circuit materials capable of reliable, low-loss performance at 50 through 70 GHz should continue to grow, prompting more ROG Blogs on this topic.
The expected boost in the number of wireless signals in use during the next decade should also focus circuit designers’ attention on the material characteristics needed for low-PIM performance. An earlier ROG Blog, “Perusing PCBs For Low PIM Levels,” explained the role of circuit materials in the design of PCB antennas and how circuit material characteristics should be chosen to minimize PIM. That blog presented Rogers’ RO4725JXR™ and RO4730JXR™ circuit laminates as non-PTFE, halogen-free circuit materials with the characteristics needed to minimize PIM. With the growing number of wireless signals to be generated during the coming decade, in high-volume applications such as 5G and IoT, the importance of minimizing PIM only increases and certainly should be a recurring topic of this ROG Blog series.
The first six years of the ROG Blog series provided circuit specifiers with key insights on different aspects of circuit materials, such as material parameters important for impedance matching, for dissipating heat, and for minimizing losses. ROG Blogs have explored such things as the importance of circuit laminate finish, in “Finish Makes a Difference in Broadband PCB Loss,” and the reason for using a high-dielectric-constant (Dk) circuit material, in “Harness High-Dk Circuit Materials.” The next 100 ROG Blogs hope to provide guidance on the best use of these high-frequency materials, as starting points for what appears to be many high-frequency, high-speed circuits in the decade to come.
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We are pleased to announce that Rogers Corporation has signed a definitive agreement to acquire Arlon, LLC, currently owned by Handy & Harman Ltd. (NASDAQ: HNH), for $157 million, subject to closing and post-closing adjustments. The transaction, which is subject to regulatory clearances, is expected to close in the first half of 2015. Rogers intends to finance the transaction through a combination of cash and borrowings under an existing bank credit facility.
Bruce Hoechner, President and Chief Executive Officer of Rogers said, “This transaction is truly a unique strategic fit for both Rogers and Arlon. We are energized by the opportunity to serve our customers with our complementary capabilities and technologies in circuit materials and engineered silicones and to enhance value for our shareholders. We look forward to closing this acquisition as another significant milestone in Rogers’ growth as a premier global engineered materials solutions company.”
Arlon: A Strong, Strategic Fit
The proposed acquisition of Arlon is consistent with Rogers’ strategy as it adds complementary solutions to its Printed Circuit Materials and High Performance Foams business segments and expands Rogers’ capabilities to serve a broader range of markets and application areas.
Arlon’s circuit materials product family positions Rogers for additional growth in the rapidly expanding telecommunications infrastructure sector, as well as in the automotive, aerospace and defense sectors. Arlon produces its circuit materials in Bear, Delaware; Rancho Cucamonga, California; and Suzhou, China.
The engineered silicones product family of Arlon will further diversify the Company’s solutions and market opportunities in sealing and insulation applications. Arlon will bring new capabilities in precision-calendered silicones, silicone-coated fabrics and specialty extruded silicone tapes. Used primarily for electrical insulation, these materials serve a wide range of high reliability applications across many market segments, including aviation, rail, power generation, semiconductor, foodservice, medical and general industrial. This product family is primarily manufactured in Bear, Delaware.
Revenue and operating income for the Arlon segment of Handy & Harman Ltd. were $100.4 million and $16.7 million, respectively, for the trailing twelve months ended September 30, 2014 (compiled based on amounts reported by Handy & Harman Ltd. in Forms 10-K and 10-Q filed with the Securities and Exchange Commission).
Now you can access Rogers’ PCB materials resources with the ROG Mobile App. Quick and easy access to calculators, literature, technical papers. You can even request samples on your smartphone or tablet
- The app has tools and technical information to assist you with Rogers printed circuit board materials.
- The Microwave Impedance Calculator assists with microwave circuit design in predicting the impedance of a circuit made with Rogers High Frequency circuit materials and also provides capabilities for predicting transmission line losses.
- The ROG Calculators assist RF engineers with thermal and mechanical simulations for microwave PCB designs.
- Data sheets and fabrication guides can be downloaded and material samples can be ordered.
ROG Mobile for iPhone and iPad devices:
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In 2010, Rogers Corporation introduced its groundbreaking product, RO4360™ laminate, the first high Dk RF thermoset laminate. We have now launched the next generation, RO4360G2 laminate, with improved thermal reliability that will help fabricators achieve higher UL MOT’s.
With a tailored high Dk of 6.15 @ 10 GHz, this material allows next generation power amplifier designers to meet size and cost reduction targets. Specifically, the laminate’s higher Dk allows for a significant reduction in finished circuit board size (20-30%). RO4360G2 laminates process similar to FR-4, are automated assembly compatible, and offer the same reliability and repeatability that customers have come to expect from Rogers RO4350B™ material.
RO4360G2 laminates are UL 94V-0 flame rated (pending) and fully lead-free process capable. They possess excellent thermal conductivity of .81 W/m/K for improved reliability, a low Z-axis CTE for reliable plated through holes, and drill performance as good as or better than RO4350B laminates.
Typical applications for RO4360G2 laminates are power amplifiers, LNAs, RF components (combiners/splitters), patch antennas, and as a replacement material for designs previously employing LTCC (low temperature, co-fired ceramic). RO4360G2 laminates are the material solution designers working on 4G and next generation defense/aerospace platforms have been looking for!
Achieving high reliability for a high-frequency circuit or system starts with the printed circuit board (PCB). The PCB material must deliver consistent performance over time and changing conditions, such as temperature. As explained in the previous blog post, it is possible to spot PCB materials that are “built to last” by assessing a number of their key performance parameters, such as coefficient of thermal expansion (CTE). In fact, PCB materials such as Rogers RO4835™ laminates can be engineered for high reliability through a careful combination of material components resulting in specific performance characteristics.
RO4835 laminates are thermoset materials like FR-4. They are part of Rogers RO4000® family of PCB materials and can be processed with the standard epoxy/glass methods used with low-cost FR-4 materials. RO4835 laminates exhibit a typical dielectric constant of 3.48 in the z direction at 10 GHz with low dissipation factor of 0.0037 in the z direction at 10 GHz. They offer x- and y-direction CTEs of 11 and 9 ppm/°C, respectively, that are relatively compatible with the 17 ppm/°C CTE of copper; the CTE is typically 26 ppm/°C in the z direction. RO4835 laminates have a glass transition temperature (Tg) of greater than +280°C to handle effects of high-temperature circuit processing.
As detailed in the previous blog, a number of material parameters can point to potential reliability issues, including a material’s CTE, its resistance to oxidation, and its heat- and power-handling capabilities. The CTE characteristics of RO4835 laminates represent stable mechanical and electrical behavior at higher power levels and across wide temperature ranges. In addition, the material has been engineered to be resistant to the effects of oxidation. In general, the material has been formulated for demanding applications where long-term reliability is a concern.
Oxidation can impact all thermoset laminate materials over time and at elevated temperatures. It is essentially caused by the absorption of oxygen atoms to form a carbonyl group within the material, leading to small increases in its dielectric constant and dissipation factor which are not reversible. The electrical impact of oxidation can also be affected by elevated temperatures. Physically, oxidation can also result in a “darkening” effect on the exposed dielectric surfaces of the laminate. The oxidation begins on the surface and slowly penetrates into the dielectric as the oxygen diffuses through the material. Copper metallization on a laminate greatly reduces the effect of oxidation on the dielectric material beneath the copper.
Where oxidation may be a concern, it might be necessary to store a circuit in an oxygen-free environment or enclosure, such as in a vacuum or nitrogen environment. Where such an option may not be available, RO4835 laminates are less affected by oxidation than most high-frequency circuit materials. RO4835 laminates were developed to combat the effects of oxidation and, in so doing, to promote better long-term reliability. They are composites formed of fused silica and woven glass fabric. They are bound with a highly cross-linked hydrocarbon polymer matrix and include an anti-oxidant additive, to be more oxidant resistant than traditional thermoset PCB materials. The RO4835 laminates provide electrical and mechanical properties quite similar to those of Rogers RO4350B™ laminates, with heightened resistance to oxidation because of the anti-oxidant additive.
Elevated temperatures are a threat to any PCB’s long-term reliability, especially when coupled with the need to handle high RF/microwave power levels. When subjected to the combination of high temperatures and high RF/microwave power levels, it is not just the amount of material expansion (as characterized by the CTE) but the rates of expansion (and contraction) of the different materials comprising a PCB that can result in stress junctions, such as between copper conductors and dielectric materials. Ideally, manufacturing processes support optimum thermal management of a PCB, such as proper implementation of plated through holes (PTHs). A through hole in a PCB with poor quality copper plating, for example, can result in undue stress on that portion of the circuit at elevated temperatures. Similarly, manufacturing flaws such as starved thermal viaholes can lead to hot spots and stress points on a PCB.
Proper thermal management of a PCB can also help control the effects of temperature swings on a laminate’s electrical performance. For example, a laminate’s variations in dielectric constant as a function of temperature are defined by a parameter called the thermal coefficient of dielectric constant, and typically evidenced as variations in the impedance of transmission lines. The value of the parameter is different for each laminate, but the amount of change in the dielectric constant due to this effect can be minimized by properly dissipating heat from a PCB.
Of course, starting with a circuit material that is designed for wide temperature ranges can help overcome even manufacturing/production shortcomings such as these. For applications where it may be necessary to handle both higher power levels and operating temperatures, the RO4835 laminates are based on dielectric material with CTE values in the x and y dimensions that are very closely matched to that of copper, to minimize stress junctions at elevated operating temperatures and power levels. In addition, the CTE through the thickness of the material (the z axis) is engineered for stable and reliable PTH quality, even when subjected to elevated thermal conditions.
In fact, the RO4000 family of materials, including RO4350B laminates, is formulated to deliver consistent performance even under more challenging operating conditions, such as high temperatures and power levels. The RO4000 series circuit materials feature low dielectric losses as well as high Tg, to maintain stable mechanical and electrical characteristics over a wide range of material processing temperatures. They are also characterized by excellent thermal conductivity, a parameter which indicates a circuit material’s effectiveness in dissipating heat.
The RO4000 series laminates are affected by oxidation, like all thermoset materials and unlike PTFE materials. But RO4000 materials, such as RO4835 laminates, are RoHS compliant and do not require special viahole preparation like PTFE materials. The RO4000 circuit materials can be processed using standard FR-4 production techniques and, in the case of RO4835 laminates, were formulated for minimal effects of oxidation and with thermal and mechanical properties which support excellent long-term reliability.
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.