- 06 November 2006 -
The EU RoHS Directive: Big Issues Linger
By Tim McGrady, President and Principal Scientist of Serious Science, Cortland, N.Y.
As of July 1, 2006, all new electrical and electronic products put on the European Market and falling under the scope of the European Union directive "Restriction of the Use of Certain Hazardous Substances in Electrical and Electronic Equipment" (RoHS) have to comply with its requirements. Every "homogeneous material" within covered products is restricted to maximum concentrations of 0.1% by weight lead, mercury, hexavalent chromium, PBB and PBDE and a maximum of 0.01% by weight cadmium. To the uninitiated, these requirements seem reasonable and clear. But to those who have studied the EU RoHS Directive and its implications, the requirements are as clear as mud.
The European Union (EU) Commission has published a guidance document for RoHS, but on the bottom of every page is the phrase: "not legally binding." When pressed, EU officials say that only the European Court of Justice may make binding interpretations of Community legislation. In other words, legislators write the laws, but it is up to the courts to determine what they mean. Following this statement to its logical conclusion, in order to know what constitutes infractions of RoHS, we will have to wait for convictions of those accused of infractions. The guidance offered by the EU Commission is somewhat helpful, but there are many issues left unsettled.
The first issue is that it is difficult to interpret the EU definition of what constitutes a "homogeneous material." The latest revision (August 2006) of the European Commission guidance document states that homogeneous materials "are individual types of plastics, ceramics, glass, metals, alloys, paper, board, resins and coatings." The document further states, "Homogeneous material means a material which cannot be mechanically disjointed into different materials." In addition, "the term'‘mechanically disjointed' means that the materials can, in principle, be separated by mechanical actions such as: unscrewing, cutting, crushing, grinding and abrasive processes." One must be careful in interpreting these definitions, since the EU Commission has stated that it does not mean that a homogeneous material must be separable from another by mechanical means; they mean only that such separation is possible in principle. In the case of testing, one may employ any means of separation necessary to disjoint two homogeneous materials. For example, the common practice of stripping plating or coatings from substrates via chemical processes would be a viable means of separation for testing purposes.
An important example of interpretation issues concerns hexavalent chromium conversion coatings (CCCs). The EU Commission states that they consider coatings to be homogeneous materials, but there have been two interpretations in the coating industry as to whether CCCs meet RoHS requirements. One camp has maintained that CCCs cannot be mechanically separated from substrates without also including some of the substrate with the coating; therefore, this camp concludes, CCCs are part of the substrate and the substrate is to be considered a homogenous material. If the coating and substrate are tested together for weight percent hexavalent chromium, the result is nearly always a passing value for hexavalent chromium (i.e. <0.1% hexavalent chromium). The other camp has interpreted RoHS as a ban of the use of CCCs and has decided that no hexavalent chromium may be used.
As it turns out, neither camp is correct. RoHS is not a ban; it is a "restriction." The guidance from the EU Commission states that concentrations up to 0.1% by weight will be tolerated, so hexavalent chromium could be used if its concentration is less than 0.1% by weight in a homogeneous material. The EU Commission also states that coatings are considered to be homogeneous materials. That means they consider CCCs to be homogeneous materials.
The real problem concerning CCCs is a fundamental misunderstanding of the characteristics of such coatings and how they are measured. CCCs are typically used on zinc, aluminum and cadmium substrates as corrosion inhibitors; they may be used over plating or on metals and alloys. Heavy yellow CCCs have been measured to be on the order of a few hundred nanometers in thickness. The thickness of "clear" or "precoat" CCCs has been estimated to be on the order of 10 nanometers. These coatings are a mixture of trivalent chromates, hexavalent chromates, base metal, water, proprietary salts and perhaps a few other ionic forms of chromium in valences other than three or six.
There is currently no standard method that may be used to determine the total coating mass of CCCs. Typically, coating and plating masses are measured via the "weigh-strip-weigh" technique, whereby the coated sample is weighed, the coating is chemically stripped and the dried sample is re-weighed. But in the case of CCCs, such a method in not used, since the coating thickness (and, thus, mass) is so small. Analytical balances are not accurate or sensitive enough to measure the total mass of CCCs. One could try to increase the number or surface area of samples to be measured in order to increase the overall sample mass, but the low-level sensitivity of balances is inversely proportional to the mass to be measured (i.e., as the mass increases, so does the minimum mass, which can be accurately measured). So it seems that even "in principle," the total mass of CCCs cannot be accurately determined whether mechanical or chemical separation is employed.
The implication of this measurement problem is that if we cannot measure the total mass of CCCs, then we cannot measure the concentrations of hexavalent chromium in weight percent within CCCs. We can measure hexavalent chromium in CCCs, but we cannot measure the total mass of CCCs. Since determination of weight percent requires determination of a numerator (hexavalent chromium mass) and a denominator (CCC mass) in order determine a ratio, weight percent is currently not a viable measurement technique for hexavalent chromium within CCCs. That is why the one standard method used to measure hexavalent chromium in CCCs, ISO 3613, requires reporting results in mass per area (typically). General Motors’ worldwide specification GMW 3059 sets a maximum limit for hexavalent chromium in CCCs at 0.1 µg/cm2—even though the EU End-of-Life Vehicle requirements now state that the maximum concentration value (MCV) for hexavalent chromium is 0.1% by weight.
Neither IEC TC 111 WG3 nor the EU enforcement bodies have developed a means of measuring hexavalent chromium in CCCs in units of weight percent. The most recent draft of IEC TC 111 WG3's test method document references only a spot test for measuring hexavalent chromium in CCCs. That spot test can only indicate presence of hexavalent chromium and cannot be correlated with weight percent units. In a May 2006 guidance document, the EU enforcement task group made no mention of how to measure hexavalent chromium in CCCs. Since violation of RoHS allowable MCVs in homogeneous materials carries legal ramifications in the form of fines, the EU must have a legally acceptable means of determining hexavalent chromium in CCCs in units of weight percent, or the requirement is unenforceable. Similarly, if no standard method of determining hexavalent chromium in CCCs exists, companies wishing to determine if their products meet the requirements of RoHS cannot do so. In other words, if you cannot measure it, you cannot enforce it; if you cannot determine if you meet a requirement, you cannot comply with the requirement.
The measurement of RoHS substances is legal metrology, and it should be treated as such. All member states of the World Trade Organization (WTO) are bound by the Agreement on Technical Barriers to Trade (TBT) when they put technical regulations into force. In the case of RoHS, there are provisions within the TBT Agreement that require the EU and/or its Member States to adopt international standards of measurement if they already exist (reference ISO 3613) or they "shall play a full part, within the limits of their resources, in the preparation by appropriate international standardization bodies of international standards for products for which they either have adopted, or expect to adopt, technical regulations."
But neither the EU nor its Member States have developed those methods, nor have they adopted ISO 3613 for measuring hexavalent chromium in CCCs. When EU representatives have been questioned on why they did not adopt ISO 3613 and the proper units of measurement for hexavalent chromium in CCCs, answers range from "we did not know" to "it was not the appropriate standard" because it did not express results in weight percent. One EU Technical Adaptation Committee (TAC) member stated that it did not matter whether they could measure hexavalent chromium in CCCs accurately, since they could just rub the surface of metals, collect the rubbings and analyze them for percent hexavalent chromium. If the result was greater than 0.1%, the TAC member said, they could infer that the hexavalent chromium concentration was greater than 0.1% in the CCC.
In response to this statement, it was suggested that the method as described be made into an international standard, with the caveat that they would have to define how hard to rub a surface, for how long it should be rubbed and with what the surface should be rubbed. Otherwise, any number of non-equivalent methods of rubbing could be employed, with the results varying from less than 0.1% to high percentages of hexavalent chromium.
The U.S. government has said it did not seek action in the WTO for EU (or its Member States') violations of the TBT Agreement because the U.S. Trade Representative’s office did not think the EU violated provisions of the TBT Agreement. (The RoHS directive impacts products made by European-owned companies in the same manner as it does products made by companies owned outside the EU.) This is only one provision of the TBT Agreement, and compliance with that provision does not relieve members of the WTO of their responsibilities for complying with other provisions of the TBT (such as adopting or developing appropriate standards). Another theory: the electronics industry may have convinced the U.S. government not to act, since they wanted to develop the necessary standards for RoHS themselves. Electronics industry representatives have also stated that attacking the EU on legislation meant to protect human health and the environment would be "a public relations nightmare."
Bottom line: without the proper standards in place, industry suffers. There are literally thousands of standards necessary to comply with the RoHS directive. Standard material specifications, test methods, reporting guidelines and management practices—none of these standards are in place, even though the RoHS directive took effect on July 1, 2006. Those standards offer an infrastructure by which industry buys and sells goods. Without those standards, there is duplication of effort, superfluous testing and general confusion on RoHS compliance issues.
The cost to the supply chains has been estimated in the billions of dollars. Those uncounted billions need not have been spent had the EU and/or its Member States been held to their responsibilities vis-à-vis the WTO TBT Agreement. Think about it: had industry been able to buy compliant materials prior to the RoHS directive going into effect, only a fraction of the billions spent on RoHS compliance to date would have been necessary.
Tim McGrady is the President and Principal Scientist of Serious Science, a new materials testing, consulting and research company located in Central NY. He is a founding member and Chairman of ASTM International Committee F40 on Declarable Substances in Materials. He may be reached at tim@seriousscience.com.
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