Printed circuit boards electrolytic plating

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.

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. 

MSA and other lower alkanesulfonic acids are useful for plating of lead, nickel, cadmium, silver, and zinc (409). MSA also finds use in plating of tin, copper, lead, and other metals. It is also used in printed circuit board manufacture. In metal finishing the metal coating can be stripped chemically or electrolytically with MSA. MSA also finds use in polymers and as a polymer solvent and as a catalyst for polymerization of monomers such as acrylonitrile. MSA also finds use in ion-exchange resin regeneration because of the high solubility of many metal salts in aqueous solutions. 

The 150 kilotons of ammoninm chloride that are prodnced per year are mostly nsed as fertilizer and, in order of importance, for solid electrolytes in dry cell batteries, a component of quarrying explosives, hardeners for formaldehyde-based adhesives, one component of etching solutions in the manufacture of printed circuit boards, and a component, along with zinc chloride, of fluxes in tin and zinc plating. 

Ammonium chloride has a number of industrial uses, most importantly in the manufacture of dry-ceU batteries, where it serves as an electrolyte. It is also used to make quarrying explosives, as a hardener for formaldehyde-based adhesives, as a flame suppressant, and in etching solutions in the manufacture of printed circuit boards. Other appHcations include use as a component of fluxes in zinc and tin plating, and for electrolytic refining of zinc. 

The manufacturer of printed circuit boards requires plating-through-holes ideally, the electroplated layer should have a uniform thickness within the hole and on the flat laminate land areas this presents a challenge to the throwing power of the electrolyte (section 8.1), the racking of the printed circuit board and effective control over the electroplating process. 

Other electroless and electrolytic metal plating applications using CPs have been described in several patents [1006-1010]. For example, Sonnenberg et al. [1008] describe a process for electroplating a nonconducting substrate via formation of a film of a CP followed by electrodeposition of a metal. The CP film is deposited from an aqueous suspension of the CP containing an additional polymeric stabilizer. Other patents have related to printed circuit board applications [1011]. 

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