RoHS: measuring per homogeneous material

The ten substances and their limit values

Annex II of Directive 2011/65/EU lists ten substances with a maximum tolerated concentration in homogeneous materials, expressed in weight percentage. Nine of these have a limit value of 0.1% by weight. Only cadmium is ten times lower, at 0.01%.

The last four are phthalates, plasticizers used in plastics. They were added later, with a specific implementation date for medical devices and monitoring and control instruments. They have been applicable to other categories for a longer period.

What constitutes a homogeneous material

The directive defines a homogeneous material as a single material of uniform composition. Material that cannot be separated into different materials by mechanical actions also counts. Unscrewing, cutting, crushing, grinding, and abrasive processes are examples of mechanical actions.

In practical terms, this means your product consists of dozens to hundreds of homogeneous materials. The coating on a screw is one. The solder on a PCB is one. The insulation of a wire is one. The core of that same wire is another.

The limit value applies to each such material. Not per component, not per PCB, and certainly not per product.

What this means for your technical file

You cannot demonstrate RoHS compliance with a single measurement of the complete product. You need supporting documentation per material. Or at least per component, backed by a supplier declaration. It is a chain of evidence rather than a single report covering everything.

In practice, you build this using a Bill of Materials (BOM). For each component, you record which materials it contains and what supporting evidence you have: a supplier declaration, a test report, or your own measurement. If supporting evidence is missing for a component, that constitutes a gap in your technical file.

Furthermore, this approach scales. If you use the same connector in ten products, you only need to arrange that supporting documentation once.

Which products it applies to

The directive applies to electrical and electronic equipment in eleven categories, ranging from household appliances and IT equipment to lighting, tools, toys, medical devices, monitoring and control instruments, and automatic dispensers. The eleventh category is a catch-all category for everything that does not fit into the first ten.

This catch-all category is important. It means you cannot conclude that RoHS does not apply simply because your product does not fit into one of the well-known categories. If it runs on electricity, assume it falls under the scope unless an exemption applies.

How to demonstrate compliance

There are three levels of evidence, which are usually combined: a supplier declaration with a substance list, a screening with a handheld meter, and a laboratory analysis per material. Only the latter is a true measurement; the first two are indications.

• Supplier declaration. Fast and inexpensive, but only as reliable as the supplier. Request the underlying reports.
• Screening with a handheld meter. Quickly indicates where heavy metals are located, but measures at the surface and does not detect phthalates.
• Laboratory analysis. Per homogeneous material, involving digestion and analysis. This is the evidence that holds up.

The sensible route is a combination. Screening to identify high-risk areas, supplier declarations for the majority, and laboratory analysis for materials where the risk lies or where supporting evidence is missing.

The difference with REACH

RoHS and REACH are often confused. RoHS restricts ten specific substances in electrical equipment, per homogeneous material. REACH operates more broadly across all products, with a growing list of Substances of Very High Concern and an information obligation above 0.1% per article.

They are not mutually exclusive. An electrical product falls under both. Therefore, your RoHS documentation says nothing about your REACH position. The reverse is also true.

What you need to arrange

Start with a Bill of Materials (BOM) listing the materials per component. Then determine for each component what supporting evidence you have and where it is missing. Have tests performed on the highest-risk areas: solder, coatings, cable insulation, plastics with plasticizers, and colored parts.

1. Create a Bill of Materials (BOM) listing the materials contained in each component.
2. Request a declaration from each supplier, including the underlying reports.
3. Screen the product to see where heavy metals are located and where you need to look deeper.
4. Have the high-risk areas analyzed per homogeneous material in a laboratory.
5. Document the chain of evidence in your technical file, so that an inspector can trace from component to proof.