Martin Goosey

Recycling technologies for the treatment of end of life printed circuit boards (PCBs)

New legislation to encourage the recycling of end of life electronics and moves to implement sustainable development in electronics manufacturing have focussed attention on the large quantity of printed circuit boards (PCBs) being consigned to landfill. Also, in a recent investigation conducted on behalf of the UKs Department of Trade and Industry, the need for new methodologies for dealing with end of life circuit boards was identified as a priority issue. Within the UK it is estimated that ∼50,000 tonnes per annum of PCB scrap is currently generated and investigations indicate that only ∼15 per cent is subjected to any form of recycling, with the remainder consigned to landfill. This paper reports the results of a scoping study carried out to identify the technologies and processes that can be used to recycle materials from end of life PCBs.

An integrated approach to electronic waste (WEEE) recycling

Purpose – This paper aims to present a review carried out under DEFRA‐funded project WRT208, describing: the composition of WEEE, current treatment technologies, emerging technologies and research.Design/methodology/approach – This paper summarises the output from the first part of the project. It provides information on the composition of WEEE and an extensive survey of technologies relevant to materials recycling from WEEE. A series of further papers will be published from this research project.Findings – WEEE has been identified as one of the fastest growing sources of waste in the EU, and is estimated to be increasing by 16‐28 per cent every five years. Within each sector a complex set of heterogeneous secondary wastes is created. Although treatment requirements are complicated, the sources from any one sector possess many common characteristics. However, there exist huge variations in the nature of electronic wastes between sectors, and treatment regimes appropriate for one cannot be readily transfer...

End‐of‐life electronics legislation – an industry perspective

Increasing awareness of mans impact on the environment and pressure to behave in a more sustainable manner are encouraging both the recycling and reuse of materials and the replacement of hazardous chemicals with more benign ones. The Waste Electrical and Electronic Equipment (WEEE) Directive and the Restriction on the use of certain Hazardous Substances in Electrical and Electronic Equipment (RoHS) Directive, have recently been adopted into law with the specific intention of further encouraging these activities through legislation. In addition to these directives, there is a growing need to adopt sound design principles so that new products are created in a more environmentally acceptable way and that their environmental impact throughout their lifecycles is minimised. This paper gives an overview of this new European legislation and discusses its impact on the electronics industry. The potential benefits of adopting such an approach are outlined.

An introduction to high performance laminates and the importance of using optimised chemical processes in PCB fabrication

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.

An overview of the current status of lead‐free assembly and related issues

Over the last few years, the emergence of new European draft legislation has focussed electronics industry attention on the likely ultimate proscription of lead in electronics assembly. Much work has already been undertaken to identify the possible alternatives to conventional tin‐lead solders and to evaluate their performance benefits and limitations in comparison with the traditional materials. Although, some companies are already offering products manufactured using lead‐free products, there is still a widespread lack of activity in many areas. With this none‐too‐distant deadline rapidly approaching, Envirowise has sponsored this paper as part of its coordinated activities to assist the UK electronics industry and to promote environmental efficiency and best practice. This paper details the current situation with respect to the drivers towards the adoption of lead‐free assembly before giving an overview of the current situation. This paper concludes with details of sources of further information.

Factors influencing the formation of “black pad” in electroless nickel‐immersion gold solderable finishes—a processing perspective

Nickel–gold planar surface coatings have been increasingly specified over the last ten years as the circuit board solderable finish of choice. Although offering a number of significant advantages over both conventional Hot Air Solder Levelled (HASL) finishes and alternative planar finishes, nickel–gold can, under certain conditions, be associated with a premature brittle interfacial solder joint fracture failure. This failure typically occurs at the interface of the nickel deposit and the intermetallic formed during soldering. The exposed nickel usually exhibits a “blackish” discolouration that has led to the term “black pad” being used to describe such failures. Although black pad usually occurs at very low levels, its incidence can be catastrophic and hence much work has been done by numerous workers to elucidate further the causes and mechanisms of this failure. This paper reviews the current understanding of the black pad failures and details work carried out by Shipley to extend this knowledge and to help users minimise the likelihood of its formation.

Soldering considerations for lead‐free printed circuit board assembly – an Envirowise Guide

Purpose – To give an overview of the issues encountered, and changes that need to be made in the various types of soldering process when converting them from conventional to lead‐free assembly.Design/methodology/approach – This paper has been written to provide a review of the lead‐free reflow, wave and hand soldering processes. Problem areas highlighted and methods for adjusting and optimising each type of soldering process for compatibility with lead‐free solders are described.Findings – The move to lead‐free soldering in electronics assembly can lead to a number of issues that affect process performance, yields and reliability. Problems that are sometimes encountered with conventional lead‐bearing solders can exacerbated when moving to lead‐free. Many of the issues are associated with the higher melting points of the recommended lead‐free solders. Fortunately, these issues are now well known and, with care and attention to process optimisation, they can largely be avoided.Originality/value – The value ...

Evaluation of an enhanced oxidation method for the destruction of ethylene diamine tetra‐acetic acid (EDTA) and related compounds in aqueous solution

Ethylene diamine tetra‐acetic acid (EDTA) and other chelates are widely employed in the electroless copper plating solutions and related chemistries used in printed circuit board (PCB) manufacturing. EDTA in particular, imparts many benefits to these processes but it is also becoming increasingly undesirable from an effluent treatment and environmental perspective. Consequently, there is a need to remove EDTA and similar compounds from effluent produced during the PCB manufacturing process. In this paper, the effectiveness of hydroxyl radicals, generated by a UV/ozone based enhanced oxidation process, in destroying relatively low levels of EDTA and other chelates has been evaluated. The influence of temperature, operating pH and chelate concentration has been investigated. Initial results indicate that a combined UV/ozone based process provides a useful and effective method for conveniently destroying EDTA, its hydroxy ethyl analogue and ethanolamine in aqueous solution.

An electrochemical pretreatment and catalysation process for acrylonitrile-butadiene-styrene utilising silver(II) chemistry

SUMMARY The formation of silver(II) ions in nitric acid was studied using a rotating disc electrode at temperatures of 25°C and 50°C and a preparative H-type divided cell was used to generate dark brown silver(II) solutions at 50 mA cm−2, 50°C. When acrylonitrile-butadiene-styrene (ABS) samples were etched in this highly oxidising medium, residual silver(I) species trapped within the polymer cavities were reduced to metallic silver with a reducing agent and, upon exposure to an electroless copper solution, deposition was observed. An FM-01LC Laboratory Electrolyser was used to scale-up the process and peel strengths between the ABS substrate and metallic coating were measured. Adhesion equivalent to a chromic acid pretreatment was achieved. Hence a novel process based upon the aqueous electrochemistry of silver(II) has been developed for etching, catalysing and subsequently metallising ABS.

A short introduction to graphene and its potential interconnect applications

Purpose – The purpose of this paper is to present an introductory overview of graphene, its properties and potential for use in interconnection applications.Design/methodology/approach – This short paper has been written to provide those working on interconnect applications in the PCB and semiconductor sectors with an introductory overview of graphene and its properties. This has been achieved through a review of the published literature.Findings – Graphene has unique properties that make it of interest for potential use in interconnection applications and, in the last few years, some workers have begun to demonstrate the possibilities for this novel material.Research limitations/implications – This is a short introductory paper and only gives a limited overview of graphene, its properties and applications. It is based on information published in the literature and, while some examples are cited, it does not represent a comprehensive review.Originality/value – The paper seeks to give an overview of what g...