Plating, electrolytic

Electroless Electrolytic Plating. In electroless or autocatalytic plating, no external voltage/current source is required (21). The voltage/current is suppHed by the chemical reduction of an agent at the deposit surface. The reduction reaction must be catalyzed, and often boron or phosphoms is used as the catalyst. Materials that are commonly deposited by electroless plating (qv) are Ni, Cu, Au, Pd, Pt, Ag, Co, and Ni—Fe (permalloy). In order to initiate the electroless deposition process, a catalyst must be present on the surface. A common catalyst for electroless nickel is tin. Often an accelerator is needed to remove the protective coat on the catalysis and start the reaction. 

The theory and practice of electroless plating parallels that of electrolytic plating. 

Electrolytic plating rates ate controUed by the current density at the metal—solution interface. The current distribution on a complex part is never uniform, and this can lead to large differences in plating rate and deposit thickness over the part surface. Uniform plating of blind holes, re-entrant cavities, and long projections is especiaUy difficult. 

The process consists of pre-etching, etching, etch neutralization, catalyst appHcation, catalyst activation, and plating. Most commercial appHcations, except REl/EMl shielding, use the initial copper or nickel deposit as a base for subsequent electrolytic plating of electrolytic copper, nickel, or chromium. The exact types and thicknesses of metal used are determined by part usage, eg, automotive exterior, decorative, plumbing, and others (24). 

Chemistry. Successful electroless plating depends on the optimized interaction of five separate complex chemical solutions (1) to clean, roughen, and catalyze the surface before plating. These steps are critical for formation of an adherent continuous electroless coating, and for optimum durabHity after electrolytic plating. 

Yullj Additive Method. No electrolytic plating step is used ia the fully additive process. The copper circuit is formed directly on the board without a continuous copper film. Heavy-build electroless coppers are used to iacrease the final thickness of the entire circuit. This process is much more difficult to control than the others. Additive processiag is becoming increasingly important ia high aspect ratio, very small diameter through-holes that caimot be easily electrolyticaHy plated. 

Typical plating solutions contain l0-30g/l of nickel chloride or sulfate and l0-50g/l NaH2P02 with suitable pump capacities it is possible to plate up to 10 kg Ni per hour from stich a bath (i.e. 45 m stirface to a thickness of 25 pm). Chemical plating is more expensive than normal electrolytic plating btit is competitive when intricate shapes are being plated and is essential for non-conducting substrates. (Sec also the use of BH.4 in this connection, p. 167.)... 

The main difference in SOFC stack cost structure as compared to PEFC cost relates to the simpler system configuration of the SOFC-based system. This is mainly due to the fact that SOFC stacks do not contain the type of high-cost precious metals that PEFCs contain. This is off-set in part by the relatively complex manufacturing process required for the manufacture of the SOFC electrode electrolyte plates and by the somewhat lower power density in SOFC systems. Low temperature operation (enabled with electrode supported planar configuration) enables the use of low cost metallic interconnects which can be manufactured with conventional metal forming operations. 

Currently there is much interest in modifying the surfaces of commodity polymers with a view to either functionalising the surfaces to provide for more exotic materials or subjecting the treated surface to electroless or electrolytic plating to produce, for example, printed circuit boards. 

With regard to low temperature fuel cells (PEM), efforts must be guided to materials development (catalysts, electrodes, electrolytes, plates, seals, etc), fuel cells components development and its manufacturing methods, fuel cells prototypes development, systems based in fuel cells for transport, stationary and portable applications, and fuel processors. 

J. I. Duffy, ed., Electroless and OtherNon-electrolytic Plating Techniques, Noyes Data Corp., Park Ridge, N.J., 1980. 

SLI batteries are also supplied in a dry charged state and are activated simply by filling with electrolyte. Plates for such batteries have extra additives, such as antioxidants in the negative active mass, and forming is followed by one of a number of controlled drying processes. 

Miscellaneous Techniques. Lasers have been used for both electroless and electrolytic plating selective dissolution has hcen used from ancient times to give the appearance of a thin plated coaling nf precious metal and mercury layers plated onto the surface of analytical electrodes serve as liquid meial coatings... 

---