Technical Articles & Papers
Park's Advanced Composite Materials
and Nelco Electronic, RF and Microwave Materials



Mercurywave™ 9350, A High Speed, Low Loss Resin System (573k)

As printed in Microwave Journal, February 2010
Abstract: Park Electrochemical Corp. manufactures a complete line of reliable, high-value substrates for commercial and military critical microwave components, antennas and subassemblies. Their new non-PTFE resin system, Mercurywave™ 9350 (Mercurywave is a trademark of Park Electrochemical Corp.), is tailored to meet the needs of the RF and microwave market. With its low loss electrical properties and high thermal reliability, it offers greater flexibility and freedom to design high performance RF and microwave substrates. Mercurywave 9350 provides the electrical performance of a RF microwave material, but processes like an epoxy.

Evaluating Laminates for High Temperature Assembly (1 Mb)
By Silvio Bertling

As printed in The Board Authority, September 2005

Abstract: The RoHS and WEEE Directive in Europe is the driving force for the implementation of high temperature lead-free assembly around the world. As designers struggle with these new goals, questions regarding the integrity and reliability of various high temperature, lead-free assembly capable laminates continue to rise. In short, the fabricators and end users must select a laminate which can meet the rigorus demads of lead-free solder assembly. Unfortunately, at this time there is no standard test methodology that consistently and accurately assists in determining which laminates fall into this category. This article introduces a test procedure that utilzes a daisy chain TV designed by IPC PCQR2 suitable for both reflow testing and HATS (Highly Accelerated Thermal Shock) testing.We believe that this procedure can be used to determine how well a particular laminate performs when exposed to 6x reflow, thermal cycling and a combination of reflow and thermal cycling.

Best Materials for 3-6 GHz Design (226k)
By Douglas Leys

As printed in Printed Circuit Design & Manufacturing, November 2004
Abstract: Wireless communication and broadband applications are moving digital circuitry into the analog world. High-speed circuit designs emphasize the usefulness of passive circuit elements. When designing below 1 GHz, passive elements such as the dielectric substrate can generally be ignored and standard FR-4 materials usually work very well. But as frequencies increase beyond 1 GHz, the passive circuit elements must be taken into account. Primary considerations for circuit design in the 3-6 GHz arena include skin effect, surface roughness, proximity effect, EMC and dielectric substrate. This article will cover dielectric substrates and the related properties to consider when choosing materials for your high-frequency design.
Conductive Anodic Filament (CAF): The threat to miniaturization of the Electronics Industry (488k)
By Konstantine (Gus) Karavakis and Silvio Bertling

As presented at MEPTEC October, 2004 and reprinted in CircuiTree Magazine, December 2005

Abstract: Conductive anodic filament (CAF) occurs in substrates and PCB’s when a Cu conductive filament forms in the laminate dielectric material between two adjacent conductors or plated through vias under an electrical bias. CAF can be a significant and potentially dangerous source of electrical failures in IC packaging substrates, PCBs and the overall system (package, module) that they are part of. The increased board density which has being driven by the chip scale packaging (CSP) revolution in the early 90’s, along with the increased I/O density on the chips, has forced the PCB industry to decrease via wall to wall distances and feature sizes. This path of the electronics industry of placing as many components as possible in a minimum of PCB “real estate” area has increased the reliability requirements for bare PWB’s and is raising concerns of possible reliability issues caused by conductive anodic filament formation within the multilayer structure.

PWB Dielectric Substrates for Lead-Free Electronics Manufacturing (250k)
By Douglas Leys and Steven P. Schaefer

As presented at IPC Expo 2003
Abstract: In order to safely accommodate the increased thermal and mechanical requirements of lead-free assembly technology, extensive testing of the printed wiring board (PWB) substrate is required to confirm that there are no compromises in performance and long term reliability when moving away from lead. This paper presents a comparison of four (4) different commercially available PWB substrate materials, including one produced specifically to handle lead-free soldering, using both traditional thermal shock testing and accelerated thermal cycling. The use of the Interconnect Stress Test (IST) was chosen for the accelerated life cycle test. A generic 22 layer PWB test vehicle was subjected to various pre-conditioning environments in order to simulate the stress generated during both lead-containing and lead-free assembly. These test vehicles were then cycled to failure. Using this test methodology, this paper will allow the reader to obtain a comparison, under lead-free assembly test conditions, of the traditional thermal robustness tests with the IST thermal cycling test. It will also provide an indication of the impact on the PWB of moving from a lead-containing assembly environment to one that is lead-free.

Multilayer Material Technology for Improved Signal Integrity in the Region Above 5 GHz (144 k)
By Leena Gulia, Fred Hickman & Bob Forcier

As printed in The Board Authority, September 2001

Abstract: Substrate materials that provide low Dk and low loss properties have become an essential element of high-speed digital and analog systems. In some sense, achieving a solution for providing excellent signal integrity within a high layer count design has become “The Holy Grail” in the OEM community. Traditional epoxy/glass materials fail to meet the electrical performance required of many new designs. OEMs that produce high-speed optical routers, switches, networks, servers, etc., all require materials with lower dielectric constants (Dk) and dissipation factors (Df) to further improve the performance of their products. The lower Dk allows them to run faster signal speeds and higher packaging densities by retaining nominal impedances with thinner dielectrics. The lower Df enables them to run longer traces, use less incident power, and improve the overall integrity of the signal.
Although low Dk and low Df properties have already been produced in RF/microwave materials, existing material systems do not have the ability to produce ultra-thin dielectrics and subsequent multilayer structures with higher layer counts.

High Reliability/Low CTE Epoxy Technology: An Overview of the Advantages of Low CTE Materials (563 k)
By Bob Forcier and Bob Schor

As printed in CircuiTree Magazine, February 2001

Abstract: As board reliability requirements have increased over the last several years, the multilayer industry has been enthralled with the continuing trend towards higher Tgs. For example, in North America, over 50% of the multilayer boards 12-layers and above (or ≥ 0.090" thick) typically require a minimum material Tg of 160C or higher. This strategy of using higher Tg systems has been successful in producing higher yields in products that must survive the difficult thermal excursions experienced in assembly and BGA rework. Perhaps the most significant benefit of high Tg systems is the lower Z-axis expansion of the product when measured over a temperature range. The higher 170C Tg resin system provides up to 22% less expansion when compared to standard 140C Tg system (3.9 vs. 5.0%). This lower expansion minimizes the fatigue that a plated-through-hole would experience during a thermal excursion. Less expansion equates to less fatigue in the plated copper that might lead to reduced electrical opens of the plated-through-hole.

Laser Drillable E-Glass Multilayer Materials... An Overview of Laser Enhanced Materials (117 k)
By Bob Forcier

As printed in The Board Authority, July 2000

Abstract: One key factor of a new family of materials that enables easier laser drilling is the weaving and post-weaving processes implemented by the glass fabric suppliers. By careful formation of the glass fiber bundles, the glass manufacturer can provide a flatter bundle in both the warp and the fill directions as compared to the rounder bundles usually associated with standard E-Glass weaving technologies. Included in this new process is a spreading of the glass fibers to achieve a more even glass distribution across the entire area of the fabric. In this manner, the fabric has a smaller range of highs and lows in glass density.

AGATE Program Helps Streamline Material Certification Process (13 k)
By John Tauriello

As printed in High-Performance Composites Vol 8, No. 3, May/June 2000

Abstract: Airplane manufacturers are responsible for time-consuming and expensive FAA certification testing to qualify every composite combination for use in each aircraft design. The high cost of testing tends to limit composite use to large commercial aircraft, leaving non-FAA-certified experimental kit planes on the cutting edge of design in the general aviation arena. As a Boeing engineer pointed out, one widely used carbon/epoxy composite sold by a single company has 34 different procurement specification databases governing its sale.  The certification process will become considerably easier thanks to the AGATE (Advanced General Aviation Transport Experiments) program. Begun in 1995, AGATE is a wide-ranging public/private consortium effort aimed at making U.S. general aviation more affordable and safer. AGATE involves more than 70 entities, including the National Aeronautics and Space Administration (NASA), the FAA, aircraft manufacturers, universities and composites suppliers. The endeavor encompasses training, safe ways to utilize air space and improvements in ground infrastructure systems, in addition to promoting wide use of composite materials. According to John Turiello, director of marketing and sales at FiberCote Industries Inc. (Waterbury, Conn.), AGATE includes a streamlined material certification program with preapproved supplier databases that will enable composite aircraft parts and assemblies to be designed and built in as little as one-half the time currently required.

A Composite Material Qualification Method That Results in Cost, Time and Risk Reduction (353 k)

By John Tauriello, Sean Doyle & John S. Tomblin (Wichita State University)


Abstract: One of the largest single regulatory hurdles for an airframe manufacturer, i.e., user, of polymer based advanced composite materials in certified aircraft applications, is to generate design allowables that will satisfy Federal Aviation Regulations (FARs). Due to the lack of a regulatory mechanism that encourages materials users to share data, historically each user has independently executed coupon level test plans and design allowable programs for specific materials - a costly and time consuming process. Design allowables for similar or identical materials have often been generated consecutively by several users as a routine part of their certification efforts, which has resulted in redundant costs to users, materials manufacturers and regulators. A new composite materials qualification methodology has been developed by members the Advanced General Aviation Technology Experiments (AGATE) consortium. Based on Military Handbook 17 (MIL-HBK-17)2 guidelines, the "AGATE Method" describes a "standardized" coupon level material qualification test plan and statistical technique that yields lamina design allowables for a specific material system, such that allowables can be shared among multiple users without each user having to repeat the full qualification procedure. Once the original qualification database is completed and its resultant design allowables are approved for use by the FAA, each user needs only to perform a limited "equivalency" test plan to verify that their process yields properties that are equivalent to the original database.

The Design and Fabrication of HDI Interconnects Utilizing Total Integration of Fiber-Reinforced Materials... An Overview of Fiber-Reinforced HDI Material Options (119 k)
By Bob Forcier and Fred Hickman

As printed in The Board Authority, March 2000

Abstract: It is now possible to produce HDI products, including high layer count backplanes and microvias, without the use of resin-coated coppers or SBU-type dielectrics. Typically, the microvia HDI world has been fueled by utilizing a resin-coated copper technology or other non-reinforced materials to comprise the outer dielectrics of the multilayer. However, fiber reinforcement in all dielectrics can provide many benefits to the HDI designer and the printed circuit fabricator. Although the use of resin-coated copper continues to grow, the alternative of using fiber-reinforced materials provides more flexibility of resin systems and thickness in any given HDI design. As the designs become more complex, and the layer counts increase, fiber-reinforced materials offer lower Z-axis expansion, lower X-Y expansion rates, more thickness latitude, resistance to cracking, and a wide variety of resin options not possible with other approaches. This article explores the use of various fiber-reinforced material technologies for HDI as compared to resin-coated copper constructions.