For most of the declarable substance and declarable substance group entries in the IEC 62474 database, the reporting threshold is based on the mass percent of the product. This is represented by a reporting threshold that is listed as “0.1 mass%”. The reference to the mass of the product that is declared is implied in this threshold. However, there are other many declarable substances and declarable substance groups that have a reporting threshold that has a different calculation basis. The EU RoHS declarable substance groups are examples that use the mass of the homogeneous material as the basis for calculation.

The IEC 62474 developer’s table includes a column (Obligation column) that indicates whether a specific data field (element or attribute) is mandatory or optional. Some data fields are listed as conditional. These fields are mandatory under certain material declaration conditions and optional under other conditions.

For example, Mass, MassPercent, and MatMassPercent are all listed as conditional. At least one of these data fields must be provided in a valid material declaration. The obligation column for Mass and MassPercent states: “Conditional (Either Mass or MassPercent is mandatory unless otherwise specified in IEC 62474 database)”. Basically, the data field is mandatory unless the information has been provided in one of the other mass related data fields. For most substance declarations, the supplier that is filling out the material declaration can decide whether they would like to provide the mass of the substance or the mass percent (weight/weight) of the substance.

The obligation description indicates that information provided in the IEC 62474 database may specify exactly which of these data fields needs to be provided. The most common situation for this is the EU RoHS substance groups which must be reported as a mass percent of the homogeneous material. In this case, the MatMassPercent element must be used to capture the mass information.

For substances that may be reported as a mass or mass percent, the standard technically allows the supplier to provide both data fields, but this is generally not recommended.  Experience with material declarations has shown that it’s easy to introduce errors (including rounding errors) when providing both numbers. This leaves the recipient of the material declaration uncertain as to which data field is actually correct.

June 30, 2014 update:  To prevent inconsistency between mass and mass percent information, the interpretation of allowing both mass and mass percent to be declared is being changed for the upcoming X5.00 version of the schema/developer’s table. The update will allow only mass or mass percent to be provided. X5.00 is forecast to be published in the fall of 2014 — an additional blog post will be provided when the new data exchange format is published on the IEC 62474 database.