RoHS Directives on Protection of the Environment The movement to disallow use of lead in electronic equipment has been achieving practical results in all industrially developed countries. Especially active are governmental and environmental agencies of the EU and the US. As the countries get rid of lead soldering alloys and coatings, the technology of soldering and the infrastructure of assembly lines changes. Welding modes are being adapted, and technological process equipment must be accordingly upgraded. Comprehensive testing of lead-free solder joints for durability, reliability, resistance to corrosion, compatibility with materials and coatings of components and printed boards.
The European Union (EU) has adopted directives on protection of the environment. Ministers for Environment of the EU member states at their meeting on June 7, 2002 in Luxembourg agreed with the proposal on the Directive on waste electrical and electronic equipment (WEEE) and the Directive on Restrictions of Hazardous Substances (RoHS) in these types of equipment. This is the most important step toward adopting a pan-European law which determines service life duration for electric and electronic equipment (EEE), and has been influencing the chemical industry ever since these debates started in the early 1990s.
So what are the WEEE and RoHS directives about?
The WEEE directive regulates the principles of responsibility for collection, secondary processing and recuperation of WEEE among participating countries, distributors and manufacturers. According to the newly approved proposal participating countries are responsible for setting up the equipment for collection, and distributors must collect the obsolete equipment free of charge. Manufacturers are responsible for reconstruction and secondary processing of their products. The second directive, RoHS, sets limits on use of hazardous substances in EEE. In order to prevent the release of hazardous substances, the Council decided to replace various heavy metals (especially chrome, cadmium and lead) and two types of bromide-containing antipyrines (penta-PBDE and one PBB) in new electric equipment since July 1, 2006.
Why are the directives necessary?
Manufacturing of electric and electronic equipment is one of the most fast-growing industrial sectors in the West. Technological innovations and market expansion continue increasing the speed of exchange of the equipment of this type. Moreover, new needs in EEE are growing fast, and as of today it is difficult to imagine the spheres of life where electric and electronic equipment would not be used. This growth leads to inevitable increase in the amount of electric and electronic equipment waste.
Each electric and electronic product consists of a combination of several blocks. The typical blocks for EEE are: pressed circuit cards, cables, wires and reels, fire-resistant plastic, mercury switches and breakers, screens, accumulators and batteries, data storage devices, light-generating devices, condensers, fuses and relays, sensors and connectors. The most environmentally hazardous substances contained in them are heavy metals, such as mercury, lead, cadmium and chrome, halogenated substances, including chlorofluorocarbons (CFCs), polychloride diphenyls (PCBs), polyvinyl chloride (PVC) and bromide-containing antipyrines, including asbestos and arsenic.
The environmental hazard lies in that today’s utilization practices do not allow to process the current amounts of waste. Today some 90% of WEEE goes to landfills, are burnt or destroyed without any preliminary preparation. This leads to the fact that volumes of harmful substances that are buried or reprocessed are quite high.
To develop an adequate approach to processing and reclamation of WEEE the European Union decided to address the following problems: Firstly, preventing the harm caused by WEEE. Secondly, secondary processing, reprocessing and other kinds of reclamation of this type of waste. Thirdly, minimizing environmental risks related to processing and burying of WEEE. The other goal of this initiative is to coordinate national measures regarding broken electric and electronic equipment in order to make the internal market safer.
These measures were formulated in the form of these two directives. The WEEE Directive refers to the problem of waste reclamation. The RoHS directive coordinates national measures on use of certain harmful substances in electric and electronic equipment.
Future Influences on the Market
The measures as established in the directives are based on the following principle: “Polluting Party Pays.” The idea is to make people responsible for polluting the environment when they can avoid it. In practice this means that manufacturers will have to collect the minimal number of old equipment pieces and cover their reclamation costs.
With the help of these directives, the Commission will seek to create a relationship between manufacturers and those involved in reclamation in order to improve the equipment so that it would be easier to reclaim and process the obsolete equipment.
This financial and physical responsibility provides manufacturers with the economic stimulus to change the setup of equipment so that it could be reclaimed easier. On the other side, this will lead to damages of EEE manufacturers and distributors, both of which are lobbying together against the directives.
Conclusions and Discussion
The influence of the Directives on the chemical industry has been felt for a period of several years, and its customers have taken measures to support more environmentally friendly products. For instance, some manufacturers gradually stopped making lead, mercury, cadmium, hexavalent chromium and halogenated antipyrines in various spheres of application. Suppliers of these chemical compounds were made to adapt to this trend and provide their customers with chemicals which would make the end product easier to process and less harmful for the environment. Albermarle, a chemical company, can serve a good example of aforementioned changes: it offered its antipyrine products in order to include it in the list of products not containing bromine.
The chemical industry has undertaken many attempts to affect the members of parliament, hoping to minimize the damages to their market after the law in its final version is adopted. For instance, Bromine Science and Environmental Forum (BSEF) persuaded the Commission to present the list of products under limitation for a research community discussion. The early version of RoHS forbade the use of all bromine-containing antipyrines, including TBBPA, which is an antipyrine broadly used in electric and electronic equipment. However, the newly approved version of the Directive contains only penta-PBDE and one PBB, under a considerable risk of high taxation. The attempts of influencing will continue because the directives will be reconsidered until 2007, when they become obligatory for compliance.
Since these directives will be enacted no matter what, chemical companies will find themselves under a lot of pressure finding ways for their customers to produce easily reclaimable and environmentally safe electrical and electronic equipment.
According to directives of standards RoHS (Restriction of Hazardous Substances) and WEEE, starting from July 1, 2006 all electronic components will be manufactured in strict compliance with environmental standards. They will have to contain no such chemical elements as lead, mercury, cadmium and other hazardous materials.
1. RoHS compliance
Point *1 RoHS Directive (Restriction of Hazardous Substances in Electric and Electronic Equipment) forbids manufacturers to us six harmful substances (lead, mercury, cadmium, hexavalent chromium, PBB and PBDE) in products that will be sold starting on July 1, 2006.
Point *2 of RoHS Directive: Determines limitations on use of hazardous materials in electric and electronic equipment. This EU directive requires manufacturers to stop using heavy metals (lead, mercury, cadmium, hexavalent chromium) and certain combustion decelerators (PBB*3 и PBDE*4) in products sold starting on July 1, 2006.
Point *3 limits use of Polybrominated biphenyls, PBBs
Point *4 limits use of Polybrominated diphenylethers, PBDEs
As of today, according to point 2 of RoHS, use of harmful substances is not restricted for products of Category 8 (medical equipment) and 9 (monitoring and control instruments). Additionally, Industrial Automated Equipment does not belong to any of the categories, and therefore does not fall under the conditions of RoHS.
2. WEEE compliance
The WEEE (Waste Electrical and Electronic Equipment) Directive was presented to the EU in February and became a law in EU member states by August 2004.
Official documents are available on the website of EU European Commission: RoHS, WEEE and ELV.
Practically on every manufacturer’s website lead-free products are marked as follows:

Most major manufacturers exclude fully or considerably lower the share of lead in their products, introducing the so-called “green products.”
Since the beginning of 2004 manufacturers started producing series of devices with lead-free technology in full compliance with the RoHS Directive. These companies include Texas Instruments, Vishay, Tyco Electronics and others. Sharp plans to get rid of all lead-containing materials and other materials listed as hazardous in RoHS*2 directives by the end of 2005. AQUOS motherboards already contain no lead-based materials. Also, the products of this family use wires without PVC, coating made of steel without chromium and fire decelerators with no phosphorous materials. As soon as in the second half of this year Recom will begin manufacturing a series of products corresponding to WEEE (RoHS). etc. The list of links to manufacturer sites containing documentation on these directives and the corresponding technological changes in the soldering process are listed at the end of this article.
ENVIRONMENTAL ASPECTS OF THE PROBLEM
Current environmental requirements preclude using lead in solders and coatings in the making of electronic equipment. As has been noted earlier, the initiative comes from the US and WEEE, a European legislative organization. JEIDA, the Japanese Electronic Industry Association adopts an analogous position.
TECHNICAL ASPECTS OF THE PROBLEM
Let us step aside for a while from ecological, market and legal aspects of the problem and consider purely technical issues. The task of transfer to lead-free technology has been set, and therefore it must be solved. So what can we replace the lead with? And is this replacement at all possible? Are there any lead-free soldering alloys that are similar in their properties to the famous Sn63/Pb37 eutectic?
Lead-free soldering alloys
Many patents have been issued for soldering alloys of different composition to replace lead soldering alloys. Not all the alloys have gone commercial, but the selection is rather extensive. Today it may be very hard to answer the question, which alloy is the best, but there exist different options. The alloys can be different in terms of melting temperature, wetability, durability and price. Each soldering alloy has a unique combination of properties.
When products are transferred to lead-free soldering, a whole number of factors must be considered. The solders are selected based on the design of the product, the topology of the printing board, mechanical and electrical characteristics of the block, and conditions of its operation. The choice is also based on soldering alloy melting point, reliability of soldered connections, stability of parts at soldering temperatures, difference in modes with reflow soldering and soldering wave.
The main criterion for the choice of the soldering alloy is the melting temperature. All the alloys can be subdivided into four groups: low temperature (lower than 180°C), temperature equal to Sn63/Pb37 eutectic (180-200°C), average melting temperature (200-230°C) and high temperature (230-350°C). Basic types of lead-free soldering alloys are presented in Table 1.

Low-temperature alloys have limited applicability. In addition to tin, they also contain bismuth and indium. The most widespread eutectic alloys are tin-bismuth and tin-indium. It can hardly be expected that alloys with low melting temperature will guarantee strong soldered connections at high temperatures of operations. There also exist limitations on deliveries of indium and bismuth, soldering alloys with these substances are expensive.
Most mid-range temperature soldering alloys to replace lead are complex alloys based on tin, with added copper, silver, bismuth and stibium. Unfortunately, none of them can fully replace Sn63/Pb37, all other alloys have a higher melting temperature. The solder most close to lead in its properties - Sn95.5/Ag3.8/Cu0.7 - is being used for reflow soldering in cases of surface mounting.
Alloys with high content of lead have the melting point of around 230°C. There exist virtually no lead-free soldering alloys for this range of temperatures. The cheapest replacement is Sn99.3/Cu0.7 soldering alloy, which is recommended for soldering with soldering wave. The shortcoming of Sn/Cu alloys is the high melting temperature (227°C for eutectic) and low durability. Eutectic alloys are preferred because their crystallization takes place in a narrow temperature range, and no component mixing occurs; as a result a higher strength of soldering is achieved (the probability of cold soldering decreases).
The best properties are observed in Sn/Ag alloys, with a higher wetability and durability as compared to Sn/Cu. The eutectic alloy Sn96.5/Ag3.5 with the melting point of 221°C showed higher reliability in thermocycling testing than Sn/Pb alloy. The Sn96.5/Ag3.5 solder has been used for many years in special equipment.
Sn95.5/Ag3.8/Cu0.7 eutectic solder was received as a modification of the basic Sn/Ag solder. Several years ago this alloy was unknown because the Sn/Ag/Cu solder had a lower melting point (217°C) as compared to Sn/Ag. The exact composition of this solder is still being discussed. Sn/Ag/Cu can be used for universal as well as high-temperature soldering alloys. Sn93.5/Ag3.5/Bi3 has a lower melting temperature and produces more reliable soldered connections. This alloy has the best soldering characteristics from among all lead-free soldering alloys. Adding copper and/or germanium to Sn/Ag/Bi considerably increases the wetting quality and durability of the soldered connection.
The Sn89/Zn8/Bi3 has the melting temperature comparable to the Sn/Pb eutectic, however, the presence of zinc in its composition leads to a number of problems. Soldering pastes with this alloy have a short life time, so increased action flux is necessary. The vitrification process produces hard to dissolve dross, solder joints are susceptible to corrosion, and connections must be washed thoroughly after soldering.
National Electronics Manufacturing Initiative (NEMI) recommends the Sn3.9/Ag0.6/Cu alloy for reflow soldering, and less expensive Sn0.7/Cu and Sn3.5/Ag for wave soldering, because larger volumes of soldering materials are required in the second case. IDEALS, the European consortium, is of the same opinion. Currently this organization is studying the Sn/Ag3.8/Cu0.76 alloy, thinking it fit for vitrification and wave soldering, as well as for repair operations.
JEIPA offers three alloys to replace Sn/Pb - tin/silver/copper (Sn/Ag/Cu) and two alloys based on tin/silver/bismuth combination (Sn/Ag/Bi). Other manufacturers have been considering using several lead-free soldering alloys, including Sn/Ag/Bi, the best of which was chosen in the process of industrial testing. The most recent information on the topic is presented on manufacturers’ websites.
The results of testing carried out in many countries show that the leading lead-free alloy today is the Sn/Ag/Cu combination. It is possible that other combinations will be found in due time.
Lead-Free Coatings
Major suppliers of components announce their lead-free products one after another. Their high production costs prevented lead-free coatings from appearing on the market. ST Assembly Test Services Ltd. (STATS) offered pure tin (Sn) to use for coating the IS outputs. The goal of the STATS initiative is to provide customers with environmentally-friendly casings, which correspond to quality standards in terms of their electric and mechanical parameters and reliability [1]. Sn/Ag and Sn/Ag/Cu have become alternative alloys for solder pellets.
Problem of Coating Compatibility
Use of lead-free coatings in production of printed boards is not something entirely new. Over many years industrial enterprises have used alloys like Ni/Au, Pd/Ni, Sn, Ag, Pd, imidasole (C3H4N2) and OSP for their purposes. The problem today is that for lead-free technology only one of them must be selected, yet it is still unclear, which material to use. The studies in NCMS showed that wetability of four out of five lead-free coatings (imidasole, hot Sn, Pd/Ni and Pd) cannot be even compared to the eutectic Sn/Pb. Imidasole has been recognized as the most promising coating for copper soldering with lead-free soldering alloys. Sn, Pd and Au coatings provide for good wetability practically for all soldering alloys, however, do not work well with Sn58/Bi on copper.
Sn/Cu alloys, similar to Sn/Pb in terms of their characteristics, have been also recognized as promising for production of lead-free printed boards. However, higher temperature of the process may contribute to undesirable effects. After several vitrification cycles and/or surface repair, the coatings lose their protective qualities.
Fluxes
Fluxes for soldering of equipment are subdivided into two groups: non-activated, made of gallipot and polyester resins, and activated. The flux consists of a mixture of several thin organic acids, the main of them being the abietinic acid, which dissolves copper oxides without influencing pure copper. Additionally, copper abietates are not considered corrosive products. Gallipot and polyester resins, as they enter into the dielectric of the printed board, do not affect adversely its insulation. Non-activated fluxes are broadly used for soldering of high-duty products and as conserving coatings, which retain soldering properties of printed boards in conditions of lengthy warehouse storage.
Activated fluxes, as the name suggests, contain activators, the substances that enhance the flux activity. These include amines, thin organic acids, and other substances. Activators usually contain halogen ions or other active residues, which lower the insulation resistance of dielectrics. To this end, activated fluxes and their residue must be carefully cleaned off. It is recommended to use them during highly productive mechanized soldering, and soldering of badly wettable metals (such as nickel). This group also include water-soluble fluxes that do not contain gallipot.
The wave soldering process in transition from Sn/Pb to lead-free solders has changed very little. These systems can continue using the old fluxes. Water-soluble fluxes are preferable for lead-free wave soldering. The temperature of lead-free soldering is somewhat higher (about 30°C), which should be considered when the flux is selected. Only gallipot-based fluxes should be used for high temperature soldering alloys.
The flux introduced into the solder paste plays the same role as in soldering with compact solder. Usually the same fluxes are added to the paste as in the ordinary soldering process.
Cleaning of Functional Units after Soldering
Various solvents are required for high-quality cleaning. The flux residue after lead-free soldering is different in terms of chemical composition from traditional flux residues. The accumulated experience shows that with higher temperatures it is more complicated to remove flux residue from the solder joint. Detailed information on results of testing various cleaning liquids after lead-free soldering is presented in [3], more precise information is available on manufacturer websites.
DIFFERENCE BETWEEN LEAD-FREE AND STANDARD TECHNOLOGY
In terms of significant differences, lead-free soldering is practically the same as the traditional Sn/Pb technology, if not for the difference in temperature. However, certain changes might be necessary at certain technical process stages. For instance, new types of soldering alloys and fluxes can influence the characteristics of the solder paste. Such characteristics of pastes as their service life and storage terms, their degree of fluidity may be affected, thus leading to changes in the design of the squeegee blade or soldering modes.
High soldering temperatures can lead to bulking of casings, cracking of crystals, malfunctioning of circuits. Similar effects occur in printing boards. Under the influence of high temperature the base can start scaling, its flatness worsens, and this may lead to problems with precise installation of IS, especially in large-size casings. To assess the influence of higher temperature and more time required for soldering, re-attestation of the current soldering technology is required. These studies are currently being carried out by SEMI and JEDEC. Regarding vitrification, the influence of lead-free soldering is different at different stages of the process. All the main changes are related, first and foremost, to the higher temperature of soldering. A more careful selection of components and materials for the body of the board. Other problems are related to cooling of the device and the support of the board. Especially sensitive to the speed of cooling are multicomponent alloys containing more than two metals. Intermetallic compounds can be found in such solders, and their composition will depend on the speed of cooling.
Studies of the standard technology of surface setup and solder wave soldering [4] showed that the choice of alloy influences both economic and technological factors. For instance, alloys containing indium are quite expensive, and they should not be used in wave soldering, when large amounts of solder must be loaded into the bath. However, this material can be successfully used to create outputs of flip-chip crystals. Technologies of all components of the production process are being continuously improved. Most issues related to the technological process of soldering have already been solved. Manufacturers present fairly detailed information on the way of soldering the products they manufacture in corresponding sections of their websites.
Information on RoHs from various manufacturers
Literature / Links to documen

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