Technology and Invention: Historical Milestones launches a new series by Rogers Corporation about the innovation, pioneering spirit, and transformative technologies that are creating a cleaner, safer, more connected world.
From Paperboard to Power Transformers
The 19th century was a time of great invention, from transportation to construction to communication. The early 1800’s saw the invention of the steam locomotive, the photograph, the electromagnet, the typewriter, the propeller, the telegraph, the blueprint, and mass production. These developments would soon have an indelible impact on the world.
The term “technology” first became part of the lexicon during the Industrial Revolution. Coined by Aristotle in 330BC, it found its way into the Encyclopedia Americana in 1832.
1832 also saw the founding of Rogers Corporation, a manufacturer of paperboard that would grow into a global developer and manufacturer of high performance materials. Founded in 1832, the company is now one of the ten oldest public corporations headquartered in the U.S.
In 1886, William Stanley and Westinghouse started a revolution with the first commercial AC power distribution system in North America. Great Barrington, Massachustts served as the battleground. While Stanley was building his AC system funded by Westinghouse, Edison Company had already installed a DC system in the same town. The residents of Great Barrington didn’t realize the historical significance of the technology; they were impressed just to have more electric lights.
As demand for power rose, manufacturers produced higher voltage transformers. But the electrical and physical stresses around the core and windings were intense. Around 1900, Rogers Corporation added a new product line: insulating paperboard for these electrical power transformers. Pressboard is a board made by compressing layers of paper together and drying them. It had been used during installation for many of the first electrical machines.
The need soon emerged for a higher density material that could insulate larger and higher voltage transformers. By the late 1920’s, a new type of pressboard was available. Unlike older methods of pressboard production, transformer board was not based on used paper or cotton waste, but was made with high-grade sulfate cellulose.
The new product was made purely out of cellulose without a resin or binder. This improved electrical insulation and could be completely dried, degassed, and oil impregnated. Throughout the 1930s, almost all insulating parts of transformers were replaced with parts made from transformer board.
By the 1930’s, Rogers’ principal product was transformer board. The company had also diversified into a variety of paperboard products for applications ranging from artificial leather to rail joints to tympana printing board.
Next: The plastics revolution.
Rogers Corporation provides innovative solutions for power electronics, advanced foams for cushioning and protective sealing, and high-frequency printed circuit materials. For over 180 years, we have developed new solutions to empower our customers’ breakthroughs and help them create a cleaner, safer, and more connected world.
Rogers is pleased to announce a new series of Circuit Materials Calculators designed specifically for your smartphone or tablet. Download the app from your mobile device and then you can:
- Convert thickness among various units and copper weight conversions
- Estimate Thermal Coefficient of Dielectric Constant (TcDk) and Coefficient of Thermal Expansion (CTE)
- Calculate Resonance, Composite Dk and Df, Composite metal conductivity and conversions of various Return Loss
The series includes nine (9) circuit material calculators:
- Temperature Conversions
- TcDk Calculator
- CTE Estimator
- Measurement Conversions
- CU Thickness
- Return Loss
- Composite Metals
- Composite Dk and Df
In 1917, Einstein laid the groundwork for the LASER — Light Amplification by Stimulated Emission of Radiation. He conceived of stimulated emission: a photon interacts with an excited molecule or atom and causes the emission of a second photon having the same frequency, phase, polarization, and direction. This was the beginning of a whole new world of applications based on directed light.
In 1954, the development of the MASER — Microwave Amplification by Stimulated Emission of Radiation — at Columbia University served as a pre-launch of the technology. But it was Theodore Maiman, at Hughes Research Lab, who developed the first working laser in 1960.
One of the first applications of laser diodes was at the Winter Olympics in Lake Placid in 1980. Bell Labs created an experimental optical fiber system that was used to broadcast events to televisions around the world, including the U.S. vs Russia men’s hockey game. Today, more than 55,000 patents involving the laser have been granted. In 2010, the world celebrated the 50th anniversary of the laser.
Many of today’s laser systems are based on laser diodes, aka semiconductor lasers. Initially developed for fiber optic communications in the 1970s, the optical characteristics, small size, and ruggedness of diode lasers have encouraged a plethora of new uses, from spectroscopy to dermatology to industrial material processing. Thanks to the Internet and wireless communications, the hottest growth areas are optical fiber and data storage.
Hundreds of watts of power are commercially available in packages as small as a few cubic inches. Laser diodes are quite bright but use very little power. Most operate with voltage drops of less than 2V with power requirements determined by their current setting. Overall efficiencies can reach 60% or more.
Laser manufacturers have made significant improvements to the amount of output power that can be produced by high-efficiency laser diode bars. Optical output powers have been demonstrated that are greater than 200W continuous wave (CW) from a single diode bar. These high powers test the limits of epitaxial structure design and dielectric coating design.
High performance laser diode bars require special packaging to manage heat. The most efficient method of cooling been gold-plated copper heat exchangers with small water channels, called microchannel coolers (MCC). This approach minimizes the distance between the heat source and the coolant, maximizing cooling efficiency. The use of MCCs demands a more complex cooling system than traditional air- and water-cooled packages because the electrical current and the cooling fluid must coexist within the cooler. Without proper design, corrosion and erosion can shorten the lifetime of the device.
Microchannel structures are made of thin copper foils that are bonded into a hermetically tight block. The specific microchannel structure determines the thermal resistance, pressure loss, and flow rate. The coolant usually flows in and out through openings at the bottom using interference fits over o-rings or screw fittings.
Liquid coolers are an ideal solution for high-power applications. The active cooling areas can be customized to the diode layout. Customized ceramic substrates provide high-performance electrical power management.
For highly efficient thermal management, Rogers uses a special bonding process to create its curamik® DBC (Direct Bond Copper) micro-channel coolers. DBC copper coolers consist of several layers of pure copper foil into which different, very fine structures are etched. An integrated DBC cooler includes several layers of structured copper foil and a top and bottom layer made of DBC substrates (Al2O3 or AlN). The etched copper layers form the 3D cooling structures. Find out more about Rogers’s unique substrates and coolers for laser diodes.
Stripline and multilayer circuits are often fabricated on polytetrafluoroethylene (PTFE) circuit materials for their outstanding electrical characteristics, even though the process of forming those circuits requires some way to keep multiple circuit layers in one piece. The benefits of stripline, with its excellent low-loss, high-frequency performance, and multilayer circuit assemblies, which provide a high density of circuit functionality in a small package, are clear. But fabricating PTFE-based stripline and multilayer circuits can require special handling of the circuit materials for optimum results.
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.
Thermoplastic bonding films, such as Rogers’ 3001 bonding film, make it possible to clamp and bond circuit layers together using bonding films between the circuit layers. Ideally, these low-dielectric-constant (low-Dk) bonding films are also used with low-Dk laminate materials, such as RO3000 series high-frequency circuit materials and RT/duroid 6000 series circuit materials from Rogers Corp. Such bonding films have a melting point that is lower than that of the PTFE laminates, so that a melt temperature can be reached where the thermoplastic films, with uniform pressure applied to the circuits by a press, will flow and fill spaces between copper features on the circuits, solidifying upon cooling to form a single, stripline or multilayer circuit structure. The 3001 bonding film is chemically inert with good high temperature resistance.
The second approach to fabricating stripline and multilayer circuits is with the use of thermoset bonding prepreg materials. As with the bonding films, the multiple circuit boards are heated in a clamped assembly with thermosetting prepreg materials between the circuit laminate layers. Thermoset prepreg materials typically have a bond temperature (< +450°F or +232°C) that is lower than the melt temperature of the PTFE laminates, enabling the formation of a multilayer structure. As with the bonding films, the prepreg resin will flow and fill spaces between the different circuit copper features, aided by pressure applied to the circuit layers by the clamped assembly. Prepregs are often used in multilayer circuit assemblies based on a mix of circuit materials, such as FR-4 and PTFE circuit materials.
The third method for forming stripline or multilayer circuit assemblies from multiple layers of PTFE-based circuit materials is by direct bonding or fusion bonding, where the layers are joined together by means of high temperature and precisely controlled pressure, without the addition of bonding materials. This method has its challenges, such as the care needed to control the clamping stress when the layers are joined at an elevated temperature. But the results can be quite rewarding, since the resulting circuit assembly features a fully homogeneous dielectric-constant structure, with no interfaces formed of materials, such as bonding films or prepregs, with different Dk values than the circuit laminate layers being bonded together. For direct or fusion bonding with PTFE-based materials, a multilayer assembly achieves a single, uniform Dk value throughout the assembly, which can be an extremely useful material characteristic for high-frequency applications that must meet critical performance requirements.
How do the three bonding approaches compare? In forming a stripline circuit, for example, with thermoset bonding films and RT/duroid 6002 laminates, Rogers’ 2929 is a compatible thermoset bonding material with similar electrical properties as the RT/duroid 6002 laminates. Compared to a process like fusion bonding, forming stripline circuits with laminates and bondply films is straightforward and simpler, although the presence of the bonding films can increase signal losses and possibly compromise broadband performance.
In contrast, a stripline circuit formed by fusion bonding multiple RT/duroid 6002 laminate layers can provide uniform Dk and electrical characteristics throughout the stripline or multilayer circuit assembly with minimal dispersion and excellent wideband performance. In a fusion bonding process, one RT/duroid 6002 laminate layer is used for the stripline inner layer signal plane and bottom ground plane, and the other RT/duroid 6002 laminate layer is used for the top ground plane. The copper layer on the other side of the laminate is completely etched away prior to fusion bonding the two laminate layers together, with the stripline conductors sitting on top of the bottom laminate layer and between the two dielectric layers. Although this process requires tremendous care in handling the laminates and controlling the pressure and temperature on the laminate layers when forming the multilayer structure, the end result is a circuit structure without additional bonding materials (and their associated Dk mismatches and potential circuit losses).
Forming stripline with two circuit laminates having the same Dk value will typically provide circuitry capable of low dispersion with good broadband performance. But if stripline is fabricated with top and bottom layers having different Dk values, dispersion can result, with poor wideband response. Similarly, if attempting to form a stripline circuit with high-Dk materials, such as RT/duroid 6010, with a Dk of 10.2, or RO3010™ laminate, with a Dk of 10.2, and a bonding film or prepreg is used to join the circuit layers, ideally that bonding material would closely match the Dk value of the laminates. But even proven high-frequency bonding films and prepregs exhibit Dk values of about 2 to 4, or much lower than the values of these high-Dk laminate materials, resulting in Dk mismatches within a stripline or multilayer circuit assembly. With a direct bonding or fusion bonding process, two laminate layers, such as RO3010 laminates, are joined together without the added bonding films or prepregs, to avoid the problems of Dk mismatch, added loss, dispersion, and uneven broadband response.
In some cases, a form of fusion bonding may be used that is not a direct bonding process, where a bonding material is also used in the process. For example, if the melt temperature required for fusion bonding may result in distortion of the copper circuit traces on the laminate because of movement of the laminate’s dielectric materials at that high temperature, a bonding material which has a lower melt temperature than the laminate may be used to keep the circuit layers together without distorting critical circuit patterns.
Of the approaches listed for fabricating multilayer circuits, fusion bonding may be the most expensive, but it also offers the potential for the highest performance. Fusion bonding is particularly well suited for multilayer circuit assemblies where certain performance levels are critical, such as minimizing dispersion in high-frequency filters. With the right circuit materials and a circuit fabricator experienced in the fusion bonding process, fusion bonding can help produce repeatable performance results in densely packed RF/microwave multilayer circuit assemblies.
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.
A message from Bruce Hoechner, CEO, Rogers Corporation:
Read the corporate financials news release: Rogers Corporation Reports 2013 Third Quarter Results
I’m pleased to share with you today Rogers’ third quarter results and the great work our team is doing to drive margin improvement and grow revenues.
At the end of the second quarter, we talked about the journey of transformation well underway at Rogers and the progress we have made in improving both revenues and margins. We also forecasted an even stronger third quarter due to improving market conditions, seasonal demand, and continued focus by our global team on growth and profitability initiatives.
I’m pleased to say that we delivered even stronger performance than anticipated. We finished the quarter ahead of our revenue and earnings guidance due to strong demand for our products and our combined efforts to control costs and improve performance. Earnings per share were up 55%, net of special charges, compared to last quarter. Overall, it was a very good quarter for Rogers and we are pleased that our actions are showing in our results.
Overall for the quarter, 59% of our sales fell into our strategic megatrend categories. Rogers’ focus on solving materials challenges in support of global megatrends continues to drive our growth along with the Company’s broad portfolio of advanced technologies that are helping power, protect, and connect our world.
In the Clean Technology category, sales were up 45% over Q3 of 2012 with a strong rebound in demand for power modules for variable frequency motor drives, hybrid electric vehicles, and wind and solar applications.
In support of global demand for Internet connectivity, we delivered record third quarter sales. The market for 4G – LTE base station deployment was very active, especially in China. Additional growth in new applications enabling wireless connectivity for mobile Internet devices also drove demand for Rogers’ high-frequency printed circuit materials.
In Mass Transit, revenues were up 7% as China rail spending began to ramp up again.
Additional growth areas included circuit materials for automotive safety systems, power electronics for energy-efficient appliances and laser diodes, and advanced cushioning products for safety and protection.
Overall, net sales were $142.8 million, up 10.6% compared to last year’s third quarter.
You know that we have talked a lot about the ongoing ramp in demand for Rogers’ high-frequency Printed Circuit Materials in the 4G-LTE wireless infrastructure market. The momentum we have seen continues to build, contributing to record sales for the PCM business in the third quarter if we compare revenues from our current portfolio of continuing business.
PCM delivered strong growth in auto safety sensor circuit materials, as well as new wireless connectivity applications for mobile devices. Softer demand in the satellite TV market for low-noise block downconverters (or LNB) offset some of this growth. Defense and aerospace printed circuit material demand remained stable for the quarter despite sequestration concerns.
In Power Electronics Solutions, revenues were up 45% vs. the third quarter of last year with robust performance across all key applications. PES saw high demand for curamik® power module substrates in variable frequency drive markets. The business also delivered double-digit growth in substrate applications for wind and solar power, hybrid electric and drive-by-wire automotive, as well as appliances and laser diodes.
Power Distribution Systems also delivered double-digit revenue growth across all key application areas. This solid performance extended to the rail market as the Chinese government began implementing its announced investments in rail expansion, driving demand for rail propulsion system components.
High Performance Foams revenues, on the other hand, were down 7.5% vs. the third quarter of 2012. Delays in next generation tablet introductions and softer demand in transportation applications were key factors. In applications for mobile Internet devices, our foams business also continues to be negatively impacted by changes in tablet device design, a shift to smaller size tablets, and better production utilizations at our customers that have reduced the amount of total foam content in those devices. On the positive side, volume was up in smartphones and consumer applications for sports impact protection and industrial safety.
We have many initiatives underway at Rogers to drive future growth. Across the company, we are focused on becoming more market driven. We are undertaking a journey of marketing excellence designed to enhance our capabilities in understanding market needs in order to deliver greater value to customers.
We are building a closer linkage between marketing and R&D, as we work to improve our innovation capabilities and accelerate delivery of differentiated, market-driven solutions. Our previously-announced Innovation Center in collaboration with Northeastern University is progressing well, and we plan to have members of our Innovation Team co-located with Northeastern researchers by year-end.
We continue to improve our design collaboration capabilities and the quality of our pipeline, in addition to the number of opportunities.
If we look at a snapshot of opportunities at the end of the third quarter in our targeted megatrend categories of Clean Tech, Internet, and Mass Transit, we were tracking a cumulative total of 671 major design opportunities of which 388 advanced to the design-in phase of the selling process. During the quarter, we moved 39 large megatrend opportunities from design into production. We are also capturing wins across a wide array of other markets such as industrial, automotive, and consumer.
Looking ahead, we will win in the marketplace by aligning our entire organization around market and customer needs, building our innovation capabilities, and focusing on operational excellence.
In closing, let me sum up a few highlights. First, we are reaping the benefits of our streamlining initiatives as evidenced by the solid margin improvement we delivered again in Q3. More importantly, we have been able to sustain and build upon the gains made over the past 18 months.
Second, we are executing on our goal to grow our value to shareholders. Volume growth and strong operational execution, combined with cost reduction efforts, have enabled us to grow earnings per share by double digits for the last two quarters. We believe this is compelling evidence that our business transformation is gaining traction.
Third, our focused markets of clean technology and Internet growth are driving robust revenue growth and we expect that to continue for the balance of the year. Our diversified portfolio of applications in both of these spaces, along with others in mass transit, advanced automotive, safety and protection, position us well for future growth.
And finally, as we look ahead to Q4, we expect to again deliver year-over-year revenue and earnings growth. With our key operating metrics in good shape and a solid balance sheet, Rogers’ financial strength allows us to invest in accelerating innovation, developing our team, exploring new opportunities, and driving the engine for Rogers’ future growth. Our focus markets are improving, our costs are well under control, and we are confident in our ability to deliver continued value to shareholders in the future.