Chemicals and materials of the type used in the production of Printed Circuit Boards (PCBs), as follows: a. PCB ‘composite’ substrates made of glass fibre or cotton (e.g. FR-4, FR-2, FR 6, CEM-1, G-10, etc.); b. Multilayer PCB substrates, containing at least one layer of any of the following materials: 1. Aluminium; 2. Polytetrafluoroethylene (PTFE); or 3. Ceramic materials (e.g. alumina, titanium oxide, etc.); c. Etchant chemicals; 1. Ferric chloride (7705-08-0); 2. Cupric chloride (7447-39-4); 3. Ammonium persulphate (7727-54-0); 4. Sodium persulphate (7775-27-1); or 5. Chemical preparations specially designed for etching and containing any of the chemicals included in points 1 to 4. Note: This control does not control ‘chemical mixtures’ containing one or more of the chemicals specified in this entry in which no individually specified chemical constitutes more than 10 % by the weight of the mixture. d. Copper foil with a minimum purity 95 % and of a thickness less than 100 μm; e. Polymeric substances and films thereof of less than 0,5 mm of thickness, as follows: 1. Aromatic polyimides; 2. Parylenes; 3. Benzocyclobutenes (BCBs); or 4. Polybenzoxazoles.