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The increasing use of high switching speed systems in both microwave electronics and high speed logic devices has created the need for printed circuit boards which are based on low dielectric constant and low loss materials. In addition, these circuit materials must be capable of withstanding elevated temperatures typical of hostile service environments and of board fabrication processes. Such low dielectric constant rigid boards are commercially available from a few sources. However, there is a growing demand for low dielectric constant flexible printed circuit boards for interconnecting rigid boards or in rigid/flex applications where high speed, fast rise times, controlled impedance and low crosstalk are important. A new family of thin laminates which are suitable for fabrication of flexible low dielectric constant printed circuit boards have been developed by Rogers Corporation. These circuit materials are called ROhyphen;2500 laminates and offer flexible interconnections in high speed electronic systems. RO‐2500 circuit materials are based on microglass reinforced fluorocarbon composites and have a typical dielectric constant of 25. The transmission line properties of these materials have been evaluated by the IPC‐FC‐201 test method. The results indicated that these circuit materials improve the propagation velocity by about 10% and the rise time by about 30% when compared with the same geometry, polyimide film based, flexible PCs in stripline constructions. Also, dimensional stability of these laminates after etch and heat ageing is improved over that of the standard flex circuit materials based on polyimide film. RO‐2500 laminate properties have been evaluated by the IPC‐TM‐650 test methods, which are widely accepted by the flexible PCB industry.

The purpose of this paper is to help high frequency circuit designers understand how to choose the best permittivity value for a laminate material for accurate modeling.

In this paper, experimental measurements of the performance of simple circuits are compared to various mathematical and software models.

Higher permittivity values were obtained using samples with bonded copper foil compared to samples etched free of foil. These higher values yielded better agreement between measured and modelled performance using current automated design software. High profile foil on thin laminates was found to increase the surface impedance of the conductor and change the propagation constant and apparent permittivity of the laminate by 15 percent or more. It was also demonstrated that, under some circumstances, the anisotropy of the substrate could result in differences in measured and modelled performance.

Only a limited number of circuit laminate materials were closely examined. Future work should include a wider variety of laminates.

The paper details the magnitude of the effects of test method, conductor profile and substrate anisotropy on the values of a material's permittivity best suited for circuit design purposes.

Non‐woven glass epoxy laminates are compared with paper phenolic and woven glass epoxy, indicating the advantages and limitations of the newer materials. Certain electrical properties are compared together with thermal and dimensional stability performances. This paper was presented at the Institute of Metal Finishing Printed Circuit Group Symposium “Circuits 77” in London during March 1977.

With the ever increasing demands for high performance electronic devices there is a need for circuit board laminates that have enhanced properties when compared to conventional materials such as the widely used epoxide‐based FR4 laminates. Equipment manufacturers require boards with better mechanical stability and improved electrical characteristics. At the same time, new environmental legislation is set to drive electronics assembly temperatures much higher as manufacturers start to use lead‐free soldering processes. The legislation is also raising questions about the long‐term viability of brominated resins as the basis for imparting flame retardancy to laminates. Fortunately, laminate manufacturers have responded to these challenges by developing and introducing a wide range of new laminates that address these issues. This paper describes some of these challenges and gives an introduction to the new high performance laminates that are finding increasing use. It also highlights the need for chemical processes used in the manufacture of interconnects with laminates to be specifically optimised for the chosen substrate material.

The purpose of this paper is to detail various aspects of laminates and their current developments in order to enable the selection and development of appropriate laminate systems for use in high performance avionics interconnection applications.

Electronic packaging must provide circuit support, heat dissipation, signal distribution, manufacturability, serviceability, power distribution and data for performance simulation over the required frequency range in avionics applications. Innovations in packaging technology have made a big impact on the types of laminates that can be used in printed circuit boards destined for these applications. The “environments” in which aircraft are required to operate have changed due to global security threats and the laminates traditionally used are not designed for this role. Aircraft systems are expected to withstand disturbances due to unexpected threats. Various factors which determine the performance of laminates are evaluated.

The safety of aircraft is critically dependent on the interconnection technology in which laminates have a major role. Under global security threats, passenger safety, emergency landing and timely information to the pilot is of paramount importance. Hence, research programs need to be initiated to develop new innovative laminate systems, since traditional laminates have limitations in these applications.

The availability of data on the performance of laminates used in interconnection technology under various security threats is limited.

The paper describes how new laminates for high performance interconnection technology in avionics applications can be developed.

This paper describes the chemistry and physics of the Glass Transition Temperature (Tg) and how it is measured in epoxy glass laminates using thermochemical techniques. Tg is related to the degree of cure of the epoxy resin and is used in the quality control of laminates for printed circuit board manufacture.

While promising significant improvements in the cost and performance of electronic systems, the advent of new area array packaging concepts such as the BGA and newer area array CSPs has placed significant new demands on the substrates used in their interconnection. New methods such as build‐up multilayers and micro vias and co‐lamination of inner layers have been described and implemented by a number of different firms in an attempt to address this important issue. One such method employs simple double‐sided plated through hole flex circuits and the use of conductive pastes and bondplies to provide reliable electrical and mechanical connection between layers during a simple lamination cycle. The process, briefly described herein as a co‐laminated multilayer flex, is detailed in terms of both process steps and manufacturing flow. The structure of the interconnection substrate is also modeled and examined to determine its electrical performance potential according to electrical modeling software. Finally, detailed are the performance of the structure in reliability testing and an analysis of the expected design and performance advantages that might be obtained by such type constructions in combination with BGAs and area array CSPs.

W. Canning Materials Ltd have announced the appointment of Mr W. E. I. Galloway as Managing Director with effect from 1st January, 1985. The Company is a leading manufacturer and supplier of industrial and speciality chemicals for the surface finishing industry.

Microthin Copper Clad Laminate The ever increasing requirement for miniaturisation, both in industrial and consumer electronic equipment, can now be met with more confidence with a new printed circuit laminate recently developed by Formica Limited.

Re‐established in the National Hall, Olympia, Circuit Technology '89 offers a showcase for the latest printed circuit board technology, production equipment and processes. Exhibitors will comprise PCB manufacturers; suppliers of equipment, materials or chemicals used in their manufacture or assembly; related subcontracting services; and surface mount technology.