A Review of the 1999 Wireless Workshop

Frank Bashore
Microwave Journal Staff

The 1999 Wireless Workshop was held October 24-27 in Gold Canyon, AZ. The workshop is designed to serve as a technical forum and discussion group for various engineering and technical representatives from leading companies involved in the design and manufacture of materials and circuit assemblies for wireless communications systems. Its goal is to provide an interchange of ideas among designers and manufacturers of wireless circuit board materials, components and assemblies to better prepare those individuals and companies to meet the future challenges of the wireless market.

Co-sponsored by Merix Corp., Motorola and Rogers Corp., the workshop was held at the magnificent Gold Canyon Golf Resort at the edge of Arizona’s Superstition Mountains to the east of Phoenix. The setting was both tranquil and productive, and offered participants spectacular views of the surrounding mountains as well as opportunities for fun and relaxation amid their work. Approximately 63 attendees were present, representing 46 separate companies from the US, Canada, the UK, France, Germany, Belgium and Finland.

The 1999 program chairman was David Light, director, Advanced Materials, at Tessera. The steering committee comprised Ed Frankoski, IBM Microelectronics; Chris McKleroy, Endgate; and Jim Clemans, Lucent Technologies. Performing her usual superb job as general chairman was Sharon Aspden of Rogers Corp. The workshop began on Sunday with a welcoming reception to acquaint or reacquaint members with each other before the work began. Many of the participants have attended one or more Wireless Workshop during the past years.

The technical program was kicked off by two thought-provoking keynote addresses. First, Robert Keenan of VerticalNet’s Wireless Design Online spoke about “Moving to 3G and Its Impact on RF and Packaging Design.” Keenan outlined the many changes in store as a result of the implementation of 3G wireless systems and service. His address was a challenge to the members to rise to the task. Bob Sankman of Intel Corp. described “Packaging and Interconnect Challenges for Future High Speed Digital Systems: The 1 GHz PC and Beyond.” Sankman described what the computer industry is facing as processor speeds approach and exceed 1 GHz. He pointed out that, as he was speaking, Intel was announcing its newest 750 MHz processor chip -- a whole new microwave industry is about to be born. It was interesting to hear how the computer industry has been dealing with high frequency issues and what it has to look forward to as it breaks through the microwave barrier.

Don Brown from the International Wireless Packaging Consortium (IWPC) followed with a presentation entitled “IWPC’s Electronic Product Design System (EPDeS™) Initiative Status Report.” Brown described how the organization’s EPDeS will make design tools, knowledge and accurate data available on the designer’s desktop to reduce the time to market and costs of RF designs. The system makes use of Web-based links that will dramatically reduce the time required for the so-called “vendor dance” -- the scenario of the user locating and extracting information and accurate performance data from the supplier. The report also outlined the steps being taken by IWPC member organizations to make product data available to the system in a common format on a real-time basis, an aggressive and challenging task.

Claude Drevon of Alcatel Space Industries presented a paper on “Multilayer Printed Circuit Boards at 12 to 14 GHz with MCMs and MMICs,” which described a beam forming network that includes multichip modules (MCM) and PCBs used in the design. The large multilayer PCB, soon to be space-qualified, utilizes 11 layers and operates to 14 GHz. Multilayer construction provides important reductions in weight and volume.

The next paper presented was “High Speed Digital Printed Wiring Boards: Design and Fabrication Issues Make Them a Significant Challenge for Board Suppliers” by Ed Frankoski of IBM Microelectronics. Frankoski reviewed some of the more critical design and fabrication issues associated with high speed digital printed wiring boards (PWB), including low dielectric and low loss laminate materials, layer counts and high aspect ratio vias with fine lines and spaces. Board quality, reliability and performance also were discussed along with future trends for high speed digital boards.

After a working lunch involving a team design competition, Art Aquayo of Rogers Corp. discussed “Characterization of High Performance Materials for the Wireless Communications Market.” Aquayo focused on critical electrical properties of various laminate materials available today and their stability over temperature, humidity and frequency variations.

“Alternative Substrates for Commercial Applications: An End User’s Perspective” was presented next by Donn Harvey of Metawave. Harvey addressed issues faced by the design engineer who introduces substrates other than FR4 into a company that has had experience producing products using only FR4 circuit board technology.

TDA Systems’ Dima Smolyansky covered “Characterization of Differential Interconnects from Time Domain Reflectometry Measurements” and addressed measurement and modeling of transmission lines carrying differential signals and the challenges to achieve an accurate picture of differential signal transmission in digital system design and simulation. “A Systems Approach to RF Packaging Development” was presented by Mali Mahalingam of Motorola who described the methodology being practiced by the Wireless Infrastructure Semiconductor Division of Motorola’s Packaging Operations team for the systematic development of RF semiconductor packages. The focus is mainly for high frequency (> 500 MHz) and medium to high power (> 5 W) packages.

Tuesday’s session began with Gary Pollard’s presentation of “Power Amplifier Packaging Techniques: What to Do With All That Heat!” Pollard, from Merix Corp., addressed the various packaging design considerations for integrating RF signal processing with analog and digital control circuitry in a single multilayer circuit board. Multilayer solutions with different laminate materials also were reviewed and examples were presented.

The “Thermal Performance of Commercial-grade Dielectric Materials” was presented by Mike Kuszaj of Rogers. Composite coefficient of thermal expansion, copper bond at elevated temperatures and thermal cycling of daisy-chained through holes were criteria used to determine which material transitions negatively impact the performance and reliability of a circuit board.

David Light of Tessera described “Enhanced mBGA® Semiconductor Package Performance with Two Metal Layer Flex Tape.” Light also discussed the fabrication process and package attributes.

“Design Considerations for Linear Power Amplifiers Targeting Wireless Handset Applications” was the subject of Joe Staudinger’s presentation. Also from Motorola, Staudinger examined a number of design issues in the development of linear power amplifiers for 2G wireless portable radio applications. The amplifier’s output matching structure that forms the load line for the output transistor was investigated along with the effectiveness of typical implementations based on off-chip networks.

E.I. Dupont’s Mark Dirks gave a talk on “Multilayer Interconnection Materials for Wireless and RF Applications.” Ceramic technology solutions in the 1 to 40 GHz frequency range for wideband communications systems were described and a new low loss Green Tapeª low temperature cofired ceramic material was characterized.

Wayne Westgate of Litton Advanced Systems presented a paper entitled “A Cost-effective Design for a Multiple Correlator Using a Multilayer Stripline Circuit Card.” A seven-correlator stripline circuit used in an instantaneous frequency measurement receiver operating from 2 to 6 GHz that was realized on a multilayer microwave circuit card with thick-film resistors and internal shielding was described.

“Surface-mount Coaxial Connectors for High Frequency Application” by Bernhard Rosenberger of Rosenberger HF-Technik was presented next. Rosenberger first described the state of technology of surface-mounted connectors with a coaxial interface. Fundamentals and new equipment to perform accurate measurements on planar structures were presented next.

The final day’s session began with a presentation by Kota Ikeda of Kyocera Corp. entitled “A Development of Microwave/Millimeter-wave CSP.” A new ceramic chip scale package (CSP) for high frequency applications that features small size, low cost and high performance was described.

Paul Danner of APTA Group gave a presentation on “Maximizing RF performance by Integrating Multiple Dielectric Constants in Ceramic Modules.” Improved insertion loss and higher frequency performance of low K material, the capacitor values achieved by high K material and how the different materials can be integrated into a single substrate were discussed.

“Integral Resistors in High Frequency Printed Wiring Boards” was presented by Bruce Mahler of Omega Technologies. Mahler described planar resistor technology as well as its benefits and implementation in PWBs.

Mike McMaster of Merix presented a “Comparison of Prepregs for RF/Wireless Applications.” The electrical and mechanical performance of prepregs and adhesives used in RF designs was described, and manufacturability guidelines and cost comparisons were presented.

The workshop’s final paper was by Joe Turek of Poly Circuits. Turek presented “Analysis of the Surface Adhesion of Copper Foils Used on PTFE and Other High Temperature Laminates.” The paper described and characterized the nature of surface treatments used for preparing the bonding interface of copper foils to polytetrafluoroethylene (PTFE) and other high temperature laminates.

As always, the workshop was a productive get-together that provided new information to attendees to take back to their respective organizations. This information should aid them in generating new designs, increasing productivity and performance, lowering cost and speeding time to market. It was a well-spent three days.

The workshop proceedings are not generally available to individuals who did not attend. However, copies of individual papers may be requested from Sharon Aspden, Rogers Corp., Microwave Materials Division, 100 S. Roosevelt Ave., Chandler, AZ 85226 (480) 961-8206.