Precious metal powders are used as raw materials for many technical products as well as for medical and decorative applications. Among these are the manufacture of composite silver materials for electrical contacts (Ag/Ni, Ag/metal oxides, Ag/C, Ag/W, etc), catalysts, electrodes, or dental products. Besides these precious metal powders are used as the base material in preparations as well as conductive paints and adhesives.

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While in the past mostly glass ware and ceramics (table china) were coated for decorative purposes with gold or platinum, precious metals have since quite a few years been applied to non-metallic substrates such as ceramics, glass, or plastics to make their surfaces electrically conductive. To coat these surfaces fine powders of the precious metal are dispersed in a carrier containing a paint basis and organic solvents. Such preparations can be applied by screen or tampon printing, by spraying, immersion, or with a paint brush.

The firing preparations in liquid or paste form are widely used in electrical and electronic engineering and especially in the thick-film technology ''(Table 8.2)''. The precious metal filler material is mostly pure silver because of its high electrical conductivity. During firing in an oxidizing atmosphere at temperatures between 400 and 850°C a well adhering and highly conductive surface layer is formed.

When utilizing screen printing techniques any shapes of conductive patterns can be created ''(Fig. 8.2)'' resulting in conductive paths with good electrical properties and high temperature stability.

Conductive paints are precious metal preparations in liquid or paste form. They contain the metal filler material, fine silver particles as conductive pigments mostly in flake form, a paint compound on artificial resin basis, and an organic solvent ''(Table 8.3)''. The solvent evaporates during drying in air or by aging at slightly elevated temperatures. This allows the silver particles to connect metallically and form conductive paths ''(Fig. 8.3)''.

Conductive adhesives are used mostly for mechanical bonding with low thermal impact. As the adhesive components high-polymer organic substances such as epoxy resins and mixed polymers are mostly used. They are made electrically filler materials such as flake shaped silver powders (70 – 80 wt%). Silver based conductive adhesives are available as single or two component adhesive systems. Both types are hardening without the application of pressure.

To obtain certain desired physical properties of preparations the dispersed precious metals in flat flake-like particles (generally called “flakes”) are needed. These are produced by milling fine metal powders in the presence of milling additives or agents. The properties of these metal flakes, i.e. silver flakes (ability to disperse easily, flow characteristics, electrical conductivity) are strongly dependent on the particle shape and size as well as on the type of milling agents used. Fig. 8.5 illustrates through SEM photos a type of rather fine silver flake (medium particle size 4 – 6 µm) (a) and another one with relatively large flat but thin flake shapes (particle size 8 – 11 µm) (b). Typical commercial silver flake types are listed with their respective properties in Table 8.4. Gold and platinum can also be produced as powder flakes. By volumes used they are however of lesser commercial importance.