Composite plating, electroless

Composite Plating. An electroless nickel matrix can be used to securely bond diamonds to cutting tools, and electroless nickel—diamond composites are also used (see Tool materials). The NYE-CARB process gives a siUcon carbide—electroless nickel composite that has extremely high abrasion resistance (49). Electroless nickel—Teflon composites are being promoted as low friction materials. 

In electrochemical composite plating inert particles are deliberately added to the plating bath to obtain metal matrix composite coatings. Figure 1 shows an example of metal matrix composite coating of electroless nickel-phosphorous in which silicon carbide particles are incorporated. The particle materials used should be inert to the bath in the... 

PTFE composite plating by the electroless plating method excels in its workability for producing hard coatings. Accordingly, plating material manufacturers generally... 

Song YW, Shan DY, Han EH. High corrosion resistance of electroless composite plating coatings on AZ91D magnesium alloys. Electrochim Acta 2008 53(5) 2135—43. 

This chapter will consider five techniques (1) electroplating metals, alloys and composites (2) electroless plating of metals, alloys and composites (3)immcfston plating of metals (4) chemical conversion coatings based on metal compounds and (5) electrophoretic painting. 

These applications will be described in section 8.2.3, but first, the formulation and composition of electroless plating baths will be considered. 

Key words palladinm composite membranes, electroless plating, magnetron spnttering, hydrogen separation. 

Electroless plating on metal substrates can be improved by addition of pentaerythritol, either to a photosensitive composition of a noble metal salt (99), or with glycerine to nickel plating solutions (100). Both resolution and covering power of the electrolyte are improved. 

Fig. 2. Multilayer printed circuit board composite. Constmction is multiple layers of epoxy—glass and foil copper. Foil copper outermost layer and drilled through-holes are sequentially plated with electroless copper, electrolytic copper, electroless nickel, and electroless gold.

Commercial processes Commercial electroless nickel plating stems from an accidental discovery by Brenner and Riddell made in 1944 during the electroplating of a tube, with sodium hypophosphite added to the solution to reduce anodic oxidation of other bath constituents. This led to a process available under licence from the National Bureau of Standards in the USA. Their solutions contain a nickel salt, sodium hypophosphite, a buffer and sometimes accelerators, inhibitors to limit random deposition and brighteners. The solutions are used as acid baths (pH 4-6) or, less commonly, as alkaline baths (pH 8-10). Some compositions and operating conditions are given in Table 13.17 . 

The second method, i.e. electroless plating, has been used also to produce graphite - Sn, Sn02 composite materials. The chemical deposition of metals on the graphite supports is performed through two principal steps. 

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