The customer, to save costs, asked the laboratory to "just test the whole unit once."
Whole-unit mixed digestion diluted the excessive cadmium below the limit, and the report showed compliance; during the customer's factory audit, they requested homogeneous material disassembly data, which could not be provided.
Re-disassembly by homogeneous material: PVC sheath, copper conductor, solder joints, and terminal plating were sampled separately. Priority testing was conducted on high-risk materials, and the source of exceedance was identified as cadmium in recycled PVC. The supplier was replaced and required to provide a material declaration and batch test reports. The BOM and homogeneous material correspondence table were rebuilt to form traceable technical documentation.
After locating and replacing the material, retesting passed, and the customer's factory audit was closed out. The cost of rework and retesting was approximately 2.6 times the original quotation.
RoHS is judged by homogeneous material; whole-unit mixed testing does not hold up in audits. Recycled materials are a high-incidence source of cadmium and lead exceedances and need to be controlled at the supplier admission stage. The value of technical documentation lies in traceability, not in a single report.