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To build on the results detailed in the previous paper where it was shown that sonochemical surface modification could be achieved in water. This paper aims to look at one of the factors affecting sonochemical surface modification, namely the ultrasonic source to sample distance.

Ultrasound was applied through deionized water for the surface modification of three materials: a high Tg PCB laminate (Isola 370HR), a polyphenylene ether – polystyrene polymer (Noryl HM4025) and an acrylonitrile‐butadiene‐styrene/polycarbonate (Cycolac S705). The efficacy of the treatment was determined by weight loss, scanning electron microscopy, contact angle, roughness and tape testing after electroless copper plating.

The study confirmed, and extended the previous findings, that a range of substrates could be sonochemically surface modified in water, even though in this work the ultrasonic horn had a larger tip size and produced a different ultrasonic intensity. Although the results were material dependent, the ultrasonic source to sample distance was found to be critical. Employing a spacing of 5 mm produced samples which generally exhibited higher weight loss, roughness and significant changes in surface morphology than when a distance of 25 mm was utilized.

The paper demonstrates that sonochemical surface modification has the potential to be a much more sustainable surface modification process than those currently employed in the electronics industry. However, to achieve this outcome acoustic cavitation and factors affecting it (such as source to sample distance) must be understood so that suitable equipment can be built.

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.

Despite the April sunshine, the landscape in southern Sweden remained devoid of fresh Spring colours—the result of a prolonged and severe Winter—when Circuit World made the visit to Perstorp earlier this year. The journey to this tranquil inland village crosses fairly flat arable land interrupted here and there by belts of forestation.

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 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.

To present an overview of the current status of the RoHS directive and its implications for the printed circuit board (PCB) industry.

A review paper detailing the requirements of the RoHS directive, the materials that are proscribed, where they are found and the impacts on PCB fabrication and assembly.

The main implications of RoHS for the PCB industry are related to the proscription of lead and the move to lead‐free assembly. Tin‐lead HASL finished boards will no longer be allowed and new laminates may be needed to accommodate the higher soldering temperatures associated with lead‐free assembly. There is growing pressure to move away from the use of brominated flame retardants, even though the standard materials used in FR4 type laminates are not proscribed.

Manufacturers need to be aware of the implications of the RoHS directive, not just in terms of compliance but also from a materials selection and reliability perspective.

The paper details how the RoHS directive impacts PCB manufacturing and assembly and highlights the changes needed to enable reliable lead‐free assembly within the context of legislative compliance. Actions necessary to ensure compliance are also detailed.

This paper reviews some of the technology trends making it necessary to take the performance of laminate materials into account when designing and fabricating high speed PWBs. It also reviews the available materials for current matched impedance circuitry and discusses the various combinations of polymer resins and reinforcements used in these applications. Additionally, it provides a look at the new materials technologies being applied to high speed applications and what candidates hold most promise for achieving greater signal speeds via lowered dielectric constant while maintaining the compatibility with existing fabrication processes.