Recovery of precious metals from electronic scrap, in particular from waste products of the thick-layer technique

Abstract From electronic scrap, in particular from the waste products of the thick-layer technique (which is applied to produce passive electronic components) the Ag, Au, Ru and Pd contents are recovered by hydrometallurgical procedures. Ag, Pd,and Au are dissolved at 20°C in 5 M to 9 M HNO 3 or HCl/Cl 2 mixtures, being then precipitated from the leach liquors as concentrates. Coatings on the base of glass inhibiting the leaching of precious metals are removed by leaching with fluoride solutions, which results also in the stripping of Ru-bearing layers from the ceramic substrate. From the solid Ru-concentrates obtained, ruthenium is recovered and purified by alkaline fusion, precipitation and dissolution of RuO 2 · x H 2 O followed by cation exchange. After the precious-metal and glass interlayers have been stripped, the ceramic substrates can be re-used to produce passive components.