Silver electroplate films

Uses. Extraction of gold and silver electroplating hardening of metals coppering zincing bronzing manufacture of mirrors reclamation of silver from photographic film pesticides... 

The deposition under vacuum of a thin metallic film is not a new technique and its application to plastics dates back now some years (the author s own earliest involvement was in the early fifties, with a view to the replacement of silver electroplating with aluminium reflective surfaces in motor vehicle headlamps). 

The final bulk resistivity was 7.8 x 10 " ohm-cm and 6.750 x 10 " ohm-cm for copper-containing and silver-containing films, respectively, taking the total thickness into account for calculation. The copper was then electroplated onto the composition-ungraded plasma film. 

Silver has the highest thermal and electrical conductivities of any metal and is resistant to corrosion. Pure silver is used on contacts in the form of an electroplated film. It is used in a variety of light- and medium-duty applications in telephone relays, sliding contacts, thermostats and voltage regulators. When alloyed with copper, the electrical conductivity is lowered and the hardness and mechanical properties are increased. 

Thin electroplated films of gold, platinum, and silver are used on electrical contacts and in electronic equipment. Because gold and platinum resist oxidation, they are important in contacts where small currents are being switched or passed through coimections, because any oxides on the contact surfaces impose imwanted resistances in the circuits. 

The ideal electroless solution deposits metal only on an immersed article, never as a film on the sides of the tank or as a fine powder. Room temperature electroless nickel baths closely approach this ideal electroless copper plating is beginning to approach this stabiHty when carefully controUed. Any metal that can be electroplated can theoretically also be deposited by electroless plating. Only a few metals, ie, nickel, copper, gold, palladium, and silver, are used on any significant commercial scale. 

Chemical reduction is used extensively nowadays for the deposition of nickel or copper as the first stage in the electroplating of plastics. The most widely used plastic as a basis for electroplating is acrylonitrile-butadiene-styrene co-polymer (ABS). Immersion of the plastic in a chromic acid-sulphuric acid mixture causes the butadiene particles to be attacked and oxidised, whilst making the material hydrophilic at the same time. The activation process which follows is necessary to enable the subsequent electroless nickel or copper to be deposited, since this will only take place in the presence of certain catalytic metals (especially silver and palladium), which are adsorbed on to the surface of the plastic. The adsorbed metallic film is produced by a prior immersion in a stannous chloride solution, which reduces the palladium or silver ions to the metallic state. The solutions mostly employed are acid palladium chloride or ammoniacal silver nitrate. The etched plastic can also be immersed first in acidified palladium chloride and then in an alkylamine borane, which likewise form metallic palladium catalytic nuclei. Colloidal copper catalysts are of some interest, as they are cheaper and are also claimed to promote better coverage of electroless copper. 

Silver is an excellent conductor of heat and electricity and a good reflector of light. It is relatively immune to oxidation but becomes tarnished by exposure to sulfur compounds in exceedingly small concentrations. It is an excellent electroplating metal and can also be deposited in thin films by evaporation. In Dewar flasks and other vacuum glassware, it is deposited from an aqueous medium by the Brashear process. Silver is an excellent brazing material and an important constituent of silver solder. The term silver is often applied to alloys of silver with copper for example Sterling silver contains 7.5 percent copper. Fine silver is 99.9+ percent silver. 

Uses Brightening agent in electroplating industry anti-haze agent in photographic industry sensitizer for silver halide emulsions improves antistatic props, of films reactive C3-building block Manuf./Distrib. RaschigAG Trade Names MPS... 

Metal-plated articles are common in our society. Jewelry and tableware are often plated with silver. Gold is plated onto jewelry and electrical contacts. Copper is plated onto many objects for decorative purposes (Figure 21-5). Automobiles formerly had steel bumpers plated with thin films of chromium. A chrome bumper required approximately 3 seconds of electroplating to produce a smooth, shiny surface only 0.0002 mm thick. When the metal atoms are deposited too rapidly, they are not able to form extended lattices. Rapid plating of metal results in rough, grainy, black surfaces. Slower plating produces smooth surfaces. Tin cans are steel cans plated electrolytically with tin these are sometimes replaced by cans plated in a fraction of a second with an extremely thin chromium film. 

Third, passivation was applied on the surface of the Ni-Co primary master mold (Figure 4.25c). This treatment involved sputtering of silver (Ag) thin film 250 nm in thickness on the surface of the primary master mold. Fourth, Ni-Co electroplating was applied again to deposit Ni and Co on the Ag thin film to obtain the inverse mold of the primary master. Since the adhesion... 

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