Beginning in July 2006, EU Directive 2002/95/EC, also known as RoHS, on the restriction of the use of certain hazardous substances in electrical and electronic equipment, comes into force. From this date, the directive restricts manufacturers from placing any products which contain six banned substances onto the European markets. As a result, manufacturers and their suppliers falling under the directive are faced with a huge task to certify compliance. X-ray fluorescence analysis is considered to be the best solution for quick, non-destructive screening of these product parts and components.

The EMPF utilizes the Fischer Technology XRF System to ensure our compliance. Following is a brief summary of the most important aspects of the directive, followed by an example of a measurement application that is important to any company that needs to comply.

Which substances are banned?
The following six substances fall under the directive – lead (Pb), mercury (Hg), cadmium (Cd), hexavalent chromium (CrVI), polybrominated biphenyls (PBBs), and polybrominated diphenylethers (PBEs). The maximum concentration values are 1000 ppm, with a maximum concentration value of 100 ppm for cadmium.

What product categories are in the scope of RoHS?
The directive applies to electrical and electronic equipment that depends on electric or electromagnetic fields in order to work properly.

The above-mentioned substances are restricted in the following product categories:

1. Large household appliances
2. Small household appliances
3. IT and telecommunications equipment
4. Consumer equipment
5. Lighting equipment (including light bulbs and luminaries in households)
6. Electrical and electronic tools (except large-scale stationary industrial tools)
7. Toys, leisure, and sports equipment
8. Automatic dispensers

What is considered a compliant product?
All end-products within the scope of the directive need to comply. This means not only that the final assembled product needs to meet the requirements but also all of the subassemblies and components used to manufacture the subassemblies. Often, it is explained that all “homogeneous materials” must not contain the six banned substances in amounts exceeding the maximum concentration values.

However, the term “homogeneous materials” has caused some confusion. The expression first appeared in an EU Commission stakeholder document in December 2003. It was used in the context of proposing maximum concentration values for RoHS restricted substances: “A maximum concentration value of 0.1% by weight in homogeneous materials for lead, mercury, hexavalent chromium, polybrominated biphenyls (PBB) and polybrominated diphenyl ethers (PBDE), and of 0.01% weight in homogeneous materials for cadmium shall be tolerated. Homogeneous material means a unit that cannot be mechanically disjointed in single materials.”

The latest recommendation suggests to interpret “homogeneous material” to be understood as “of uniform composition throughout.” Examples of “homogeneous materials” include individual types of plastics, ceramics, glass, metals, alloys, paper, board, resins, and coatings. So how do these expressions actually apply to the real world of electronics?

The most prominent example of this is an electrical cable. It usually consists of a copper or copper alloy core, plastic insulation, and tinned terminations. The cable as a whole is not homogenous as it can obviously be disjointed by mechanical means. The metal core, even though it may be an alloy of more than one element, is still considered homogeneous, as mechanical disjointing cannot separate these alloys. The same applies to the plastic insulation; therefore, the metal conductor, the plastic insulation, and the solder used to tin the terminations must all comply individually with the requirements of the RoHS directive. The inconspicuous terminology “homogeneous material” suddenly means that thousands of parts in a company’s inventory have to comply with the directive.

The directive states that you have to provide a certificate of compliance, but it does not tell the manufacturers to conduct any testing nor does it give any guidelines on how to test. Even though there is a lot of confusion regarding what falls under the directive, in addition, there are many exemptions, and interpretation can be challenging. What should be clear is that the directive will impact what and how U.S. companies can sell products to the European Union. The following explains how X-ray fluorescence analysis can help to answer these questions.

X-ray fluorescence measurement of MLCCs
X-Ray fluorescence analysis provides a non-destructive, quick and easy method to determine elemental concentrations in materials. Analyzing the response signal from materials that are struck with an X-ray beam will reveal what and how much of a specific substance is present in a material.

Every year, billions of multi-layer ceramic capacitors (MLCCs) are used in electronic components. As with the copper wire, MLCCs provide another example of how the term “homogeneous material” will be applied.

Figure 5-1 shows a typical layer structure and the composition of an MLCC acquired with a FischerScope X-ray XAN. According to one of the exemptions to the directive, lead in electronic ceramic parts are exempt. However, lead in solder terminations is banned.

Figure 5-2 shows an X-ray fluorescence spectrum of an MLCC. This shows individual peaks associated with different elements as described in the composition of the individual layers.

Upon first glance at the spectrum, one cannot determine which layer contains the lead. Treating this as just another bulk analysis application, measurement results will always show several percent of lead present. Showing lead content as a whole would imply that the component is not RoHs compliant.

Fischer’s longstanding experience in the manufacture of coating thickness instruments, coupled with their expertise in X-ray fluorescence analysis, led to the development of instruments which can clearly distinguish each layer and its composition. With the right tool, all components can be analyzed for their individual lead content in the top termination layer, making it easy to comply with RoHS when lead-free solders are used in the manufacturing of MLCCs. Conventional X-ray fluorescence spectrometers and handheld XRF analyzers cannot provide accurate results in this case.

How do manufacturers and suppliers guarantee that their completed product or components conform to the directive?
The market demands instruments that provide fast, reliable, and easy-to-understand results. X-ray fluorescence analyzers provide an excellent screening tool. Instruments such as the FischerScope X-ray XAN and XDAL identify the content level of the prohibited metals in products made from plastics, plastic chassis, PCBs, and electrical parts, just to name a few.

The FischerScope X-ray XAN and XDAL help the EMPF provide the accuracy needed to determine if Pb, Cd, Cr, Hg, or Br are present and if their presence is above the threshold limits. The analyzers are able to deliver detection limits of < 10ppm for Pb, Hg, and Br, and < 20ppm for Cd and Cr. In addition, they are able to measure the complicated plated layer structures present in electronic components, ceramic capacitors, and resistors. Figure 5-3 shows another capability of these instruments, where whole PCBs can be scanned, providing an element composition mapping of electronic components on the board.

For a demonstration of this system, please contact Jeff Stong, EMPF Equipment Advisory Board Coordinator
at (610) 362-1200, extension 224 or jstong@aciusa.org.

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