The European Union (EU) member states have long been interested in resolving environmental problems and promoting the movements of regulating harmful substances contained in telecommunication equipment and computer products. Accordingly, they issued the Directive on the Restriction of the use of certain Hazardous Substances in electrical and electronic equipment (RoHS Directive, in short).

This law became effective in July 2006. Since then, only the products that have passed the criteria of this directive are allowed for export. The corporations were trying hard to keep up with the new enforcement. [Table 1] shows the restricted substances and their concentration level permitted. Now, let's take a look at each item.

[Table 1] Restricted substances and maximum permitted concentration defined in RoHS Directive

Use of cadmium has been banned for electroplating. However, cadmium has been used as a stabilizer for plastics.

A slight amount of hexavalent chromium is present in the chromate film as a result of using the treatment liquid containing this material during the chromate treatment after applying zinc plating on steel screws, chassis, and metallic parts. Hexavalent chromium was also used for chemical conversion coating applied to aluminum alloy and magnesium alloy in order to improve anticorrosion properties. Currently, trivalent chromium is an alternative chemical for hexavalent chromium. However, the ultimate goal is to eliminate chromium in the products regardless of what type of ionic form it is.

Mercury is never used for surface treatment processes. However, because some of the batteries contain mercury, they are the restriction target of this directive.

The lead regulation mainly targets the lead content in tin-lead alloy solder used for attaching parts to printed circuit boards or tin-lead alloy solder plating applied to soldered areas. In addition to this, the lead content was also found as pigments in coating films and plastic materials.

The use of lead in solder itself or solder plating has become obsolete. Instead, using tin-silver or tin-copper alloy solder and ternary/quaternary alloy seems to be common nowadays.

PBBs and PBDEs are added to the plastic materials that make up printed circuit boards and used as flame retardants.

In recent years, more and more corporations are asked from their clients to present the analysis result of product content concerning these restricted substances. If you perform an official analysis (concentration measurement by dissolving a certain weight of sample into "agua regia" - a mixture of nitric acid and hydrochloric acid and diluting it with pure water) in the units of ppm, it requires tremendous cost and time. Therefore, the atomic absorption analysis or ICP emission spectrometric analysis will be selected for heavy metal products. For organic materials such as PBB, the gas chromatography mass spectrometry will be adopted.

The effective analysis method in terms of the time and cost is to perform a simplified analysis to check for an existence of the restricted substances first. Then, perform the official analysis only when such content was found. The fluorescent X-ray analysis is a common method of the simplified analysis.