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A. BACKGROUND
Lead and lead containing chemicals are among the top chemicals posing a great threat to human life and environment. When lead accumulates in the body it can produce various adverse health effects; it leads to disorders in the nervous and reproductive system, delays in neurological and physical development, it causes cognitive and behavioural changes and reduces the production of haemoglobin resulting in anaemia and hypertension. Currently, lead poisoning is assumed to have occurred if the level of lead in the blood exceeds 500 (g/ml but recent studies have found that a level of lead well below the official threshold could be hazardous to a child's neurological and physical development.
Concern about the use of lead in the electronics industry stems from occupational exposure, lead waste derived from the manufacturing process, and the disposal of electronic assemblies. Although the consumption of lead by the electronics industry appears to be minimal by absolute numbers the potential for lead exposure is probably ubiquitous and poses a real threat to the human population and its well-being. Potential sources for occupational exposure in electronics are some of the soldering processes due to the inhalation of lead vapours or lead bearing dust generated by dross during the wave soldering operation. But the problems arising from the disposal of lead containing waste will probably be of even greater importance in the future, be it waste from the industrial processes themselves or the rapidly increasing amounts of electronic assemblies (personal computers, radio and TV sets, mobile phones, household appliances) that go out of operation. To give an idea of the extent of the problem, the world market for PCB (printed circuit board) assemblies alone has more than doubled within five years from 20 billion USD in 1992 to 42.2 billion USD in 1997, with a more than threefold increase in Europe from 3.2 billion to 9.7 billion USD within the same five-year period.
At the end of their useful life, lead bearing electronic products are still very often disposed of in solid waste landfills. Although there seem to be no clear scientific data describing the accurate mechanisms by which lead from disposed electronic products enters the ground water stream and from there the animal or human food chain it is generally agreed that the effect occurs. Apparently it is connected with the action of water containing oxygen, carbon dioxide, and possibly chloride on the lead containing solder materials.
A.1. Legislation / State of the Art
The main competition is obviously between the markets of Northern America, Japan (and Eastern Asia), and Europe. In the US legislation to limit the use of lead has been introduced in both the Senate and the House of Representatives, however, these bills have not passed yet. But it is clear that the use of lead will be restricted severely in the near future. A Michigan based company announced recently the production of the first lead-free solder electronic module (a passive anti-theft system) for use in automobiles. In Japan, on the other hand, the use of lead has not been banned, but legislation proposed there will prohibit lead from being sent to landfills and other waste disposal sites, which leaves manufacturers with the option of either attaining 100% recycling of lead or using lead-free solder materials. Major Japanese corporations have begun to respond to this by announcing their own plans for shifting to lead-free solders in the period up to 2001/02. Indeed, 1998 saw the marketing of the first "lead-free" product in form of a MiniDisc player, which has been a demonstrable success.
The situation in Europe is somewhat different. Originally, DG XI of the European Commission published a draft version of a Directive covering "Waste from Electrical and Electronic Equipment" - the WEEE Directive in 1998. In this version it was proposed to ban the use of lead metal in electronics by January 2004. It was overruled by a new draft version of the WEEE Directive in 2000 which proposed January 2008 as the new date from which on the use of lead should be banned in electronics.
Although it is now widely agreed that there is no drop-in replacement for the standard lead-tin solders (mostly Sn37Pb and Sn40Pb) that are currently used worldwide, a range of possible alternatives has been investigated. Some consensus seems to have developed for using one family of alloys based on tin, silver, and copper, especially by the telecommunications industry: possible candidates are alloys like Sn3.5Ag Sn0.7Cu or Sn3.8Ag0.7Cu with melting points (around 220øC) more than 30 degrees higher than their traditional lead-containing counterparts. Nevertheless, the final choice of a solder material will still be product- or application-dependent, i.e. factors like temperature compatibility and/or cost might make other alloys more attractive so that automotive, telecommunications, consumer, military and aerospace industries might tend to different solutions. The current situation can be described in such a way that it is generally acknowledged that lead-free soldering is technologically possible, but many key issues have still to be solved, both scientifically and industrially.
A.2. European Dimension
A COST Action to support and co-ordinate research on lead-free soldering within Europe is at the moment very appropriate for various reasons. Currently, research teams in many parts of Europe are working on different aspects of this topic but there are no organised opportunities for information exchange between them, no regular meetings, and so on. A COST-based network in this area would provide a sound base for information exchange as well as for identification of opportunities for collaboration. It would also contribute significantly to a coordination of national research efforts within Europe - including research sponsored by the EU FP5 (Fifth Framework Programme).
Furthermore, several of the research teams are within industrial companies and thus in a domain where competitive issues cannot be avoided. Therefore it is difficult to conceive that at present any other established EU programs could provide a basis for cooperation between these groups, given the fact that in the recent past such Europe-wide coordination activities have been rather limited (except the Brite Euram project IDEALS between 1996 and 1999). It can be observed that the individual projects are mostly performed on a national, if not even local basis, some with
corresponding support from interested companies. This COST Action would provide the possibility for these companies to participate and to co-ordinate their research efforts on a European level, which will be important for advancing R&D in lead-free soldering in view of the stiff competition from Japan and the United States. The advantages of COST are the possibility of a relatively rapid information exchange between scientists and technical experts and the arrangements made for distributing the tasks for the research work involved in the Action.
B. OBJECTIVES AND BENEFITS
The main objective of this Action is to increase the basic knowledge on possible alloy systems that can be used as lead-free solder materials and to provide a scientific basis for a decision which of these materials to use for different soldering purposes in order to replace the currently used lead-containing solders in the future.
In addition to and complementing this main objective, this COST Action will also contribute in accomplishing the following tasks.
B.1.Establishment of a database of knowledge on possible lead-free solder materials and soldering processes
Although a lot of specific information has been published on the subject of lead-free soldering this knowledge is widely dispersed and thus difficult to use. Therefore a thorough and critical compilation of the existing information is a first step within this COST Action. As far as possible, all data should be collected and stored in a standardised format. They will be complemented by the results of research contributed during the action. It is also intended that this database would attract the deposition of previously unpublished results from various possible sources. All collected information would be subjected to scrutiny by experts in the respective areas for comments on accuracy, reliability, etc., of the data.
The database should contain all necessary information on physical, chemical, electrical, mechanical, technological, properties of the possible solder materials and the corresponding joints.
B.2. Providing the expertise for selecting particular materials for specific purposes
To create such a database needs a truly interdisciplinary effort. Scientists from various fields will have to contribute to provide the comprehensive knowledge necessary to select the optimum material for particular soldering purposes. Therefore, this COST Action would bring together a panel of scientific experts that would be able to act as a consulting body for industrial partners - subject, of course, to any non-disclosure constraints. Thus the industrial partners would clearly benefit from the availability of this database providing them with the necessary information for selecting the optimum material to obtain reliable and competitive lead-free solder joints.
C. SCIENTIFIC PROGRAMME
The scientific programme of this COST Action addresses basic scientific research on various properties of possible lead-free solder materials as well as problems of their practical application and their durability during actual use in all kinds of equipment and their recycling. The action will bring together European researchers from universities, research institutions, and industrial research centres working on the development of new lead-free solder materials. It is designed to encourage the exchange of scientific and technological knowledge between these groups and to present new opportunities for co-operations.
These working groups will form the framework of the Action. The structure of the Action is flexible enough to incorporate projects focussing on materials properties or rather on application topics. All the participating scientists and research organisations must address the objectives of the Action as outlined in section B.
The six working groups will be dealing with the following problems:
Working Group 1
This working group will first evaluate all possible metallic systems that can be taken into consideration for lead-free solder materials. For this, a careful literature search will be necessary in the beginning. The main criteria besides the environmental impact will be the melting point of the alloys. For solders used in the electronics industry the melting point must be in the range between 100 and 250øC depending on the particular application.
Since the information in the open literature is by no means complete it will be necessary to carry out experimental work on various possible systems which might be candidates for this type of solders. For these investigations different experimental techniques will be used.
In order to obtain the thermodynamic data which are necessary to determine the stability of the alloy systems as well as to carry out theoretical calculations standard thermochemical methods will be applied, like vapour pressure measurements, emf (electromotive force) measurements, calorimetry and DSC (differential scanning calorimetry).
Phase diagrams and melting temperatures of the alloys will be determined with standard experimental methods, like thermal analysis (e.g. DTA, differential thermal analysis), different X-ray techniques, electron probe microanalysis (EPMA) and metallographic methods.
In advanced electronic devices different substrates for the solders are used. These substrates are in many cases thin films of Cu, Ni or Pd and other PGM (platinum group metal) elements. Therefore it is necessary to investigate the interconnection of the solder with the substrate, the diffusion processes which occur and the type of intermetallic compounds that might be formed. Working Group 1 will also have to look into this problem and to determine the corresponding multinary phase diagrams.
Working Group 2
Working group 2 will carry out the theoretical modelling of the phase diagrams. Using the data from the literature as well as new data from Working Group 1, the phase diagrams of the new solder materials will be optimised using the so-called CALPHAD method. This provides an optimum version of the phase diagram, which is consistent with the thermodynamic data for the respective alloy system. Likewise, this Working Group will also be responsible to provide optimised versions of the phase diagrams that relate to the contacts between solder materials and substrates.
Besides the phase diagram calculations the participants within this Working Group will also try to estimate different physical properties, like surface tension, wettability, electrical properties, and others.
Working Group 3
The task of this Working Group will be the synthesis of alloys suggested by Working Groups 1 and 2. For these alloys the researchers will determine the necessary physical and mechanical properties. They will measure the wettability, surface tension, and viscosity of the liquid alloys at different temperatures.
This group will also investigate the mechanical behaviour of the solid solder materials and of solder joints. The main work assignment will be to determine ductility, strength, and fatigue of the solid alloys as well as to evaluate the thermally induced stress, the thermal mismatch, and the interfacial shearing stress in the joints at different temperatures.
Another important topic in this group will be the investigation of the electrical properties of the different materials.
Working Group 4
One main task of this Working Group will be to determine the oxidation behaviour of possible solder materials under standard conditions but also at different temperatures and under different environmental conditions. Another problem are the electrochemical reactions which can occur. If the strength of the solder to conductor bond exceeds the strength of the metal-metal conductor bond, the solder will easily consume the conductor. This will not only cause a high electrical resistivity but could also lead to a significant embrittlement of the solder joint. A task that should also be addressed by Working Group 4 are possible interactions between the lead-free solders and different materials that might be used as fluxes in actual soldering processes.
Since this Working Group will probably comprise mainly chemists it would make sense to include one additional important aspect: a thorough evaluation of the physiological and toxicological properties of possible new solder materials as well as of any detrimental consequences for the environment due to their processing, recycling or deposition.
The results of these four working groups should result in a number (about four to eight) of possible lead-free solder systems which possess the required properties and which should be taken into further consideration to replace the standard lead-tin-solders. These new systems will undergo some advanced testing in Working Groups 5 and 6.
Working Group 5
This is the Working Group responsible for reliability investigations. Reliability is the ability of a product to function under given conditions and for a period of time without exceeding acceptable failure levels.
The group will investigate and test the reliability of the new materials under different working conditions. The solder joints will be subjected to thermal shock and high frequency, multiple cyclic loads to investigate overload failure and age hardening. Since thermomechanical fatigue is one of the main causes of failure in service this problem should also be addressed in this group. With all these data it should be possible to provide predictions on thermal-cycle fatigue-life and lifetime.
Different theoretical approaches will also provide the basis for model calculations to predict the reliability and possible life time of the solder joints, to develop creep-fatigue-models as well as models for damage modes.
Working Group 6
Since the electronic parts are getting smaller and smaller the newly developed solder materials must also be tested for different packaging applications like, for example, the flip chip technique. Furthermore, the Working Group will also address various aspects of processing (like cooling times, manufacturability) that determine the applicability of alloy systems. Likewise it will be responsible for testing the solders for their possible use in different soldering methods like the reflow, wave or laser technique. It will also be necessary to consider various aspects of recycling, possibly in a close interaction with scientists of Working Group 4.
At the end of the COST Action, a complete set of data will be available for different solder materials, and from these data a number (three to six) of lead-free solders should emerge which could be used by the industry as basis for the development of solders for specific applications in order to replace the current tin-lead solders.
D. ORGANISATION AND TIMETABLE
This Action will operate for five years. This is the experience with successful concerted COST Materials Actions: Call for joint research projects, creating Working Groups, monitoring experimental and theoretical achievements etc. The research projects itself normally last ca. four years. The Management Committee (MC) of this Action will be organised and operated according to COST/400/01 "Rules and Procedures".
The research work in this Action will be divided among six Working Groups (see organigram in Section C and timetable below). It is expected that each Working Group will elect a Chairperson to co-ordinate the work within the group and represent it within the Management Committee. The participation of individual researchers in more than one Working Group should be possible to encourage the flow of information between different groups.
The MC of the Action will consist of the National Representatives of the signatories. Due to the limited number of persons per country it should be possible that the function of chairperson of a Working Group and National Representative is assumed by one and the same person. The MC will have a Chairperson, a vice-Chairperson and a Secretary. The function of the MC is defined in detail in Document COST/400/01.
Meetings of the Management Committee are expected to take place on a semi-annual basis. The Chairpersons of the different Working Groups will collect the results from the individual research teams participating in a group and will report on the progress of the projects to the MC.
The MC will invite leading academic and industrial colleagues in several subjects to give plenary talks during the annual workshop meetings. All research groups will be strongly encouraged to participate in these workshops to promote an optimal exchange of ideas and information, especially between researchers from academic institutions and those from industry. In this way it should be possible to keep all participants permanently informed about the status of the Action and to stimulate new research directions if necessary. An additional possibility to exchange ideas and information between research groups are Short Term Scientific Missions which should be utilised and encouraged, especially for young scientists.
There is a Discussion Meeting "Thermodynamics of Alloys" organised on a biannual basis in even years which brings together experts from various fields relevant to several Working Groups of this Action. Although this international conference series is completely independent of this COST Action it will probably be of advantage to attach the respective COST Annual Workshop to this event.
A midterm review will be done after a duration of 2.5 years. At this review there will be a formal evaluation of the project and an assessment of the further research work necessary to successfully complete this Action.
Dissemination of the Results
The dissemination of results will be optimised by various routes:
The main route to the dissemination of results will be via articles published in peer-reviewed journals as well as oral presentations at key related conferences, which this Action will encourage. All publications arising from research carried out under the COST Action will credit COST support, and the MC will encourage and promote joint publications.
- Another important route to dissemination will be the annual workshops aimed at discussing the progress achieved to date and to bring together researchers from academia and from industry.
A web site will be created, maintained and regularly updated with non-confidential results arising from work in this area.
E. ECONOMIC DIMENSION
Scientists from the following countries have actively participated in the preparation of the Action or otherwise indicated their interest:
Austria, Bulgaria, Czech Republic, Finland, France, Germany, Greece, Ireland, Italy, The Netherlands, Poland, Portugal, Slovakia, Slovenia, Sweden, Switzerland, United Kingdom.
On the basis of national estimates provided by the representatives of these countries, the overall cost of the activities to be carried out under the Action has been estimated, at 2001 prices, at roughly Euro 12 million.
This estimate is based on the assumption that all the countries mentioned above, but no other countries, will participate in this Action. Any departure from this assumption will change the total cost accordingly.
Program(-y)
Temat(-y)
Zaproszenie do składania wniosków
Data not availableSystem finansowania
Data not availableKoordynator
Austria