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Electroless deposition of copper in acidic solutions using hypophosphite reducing agent

“…Electroless deposition of copper has been mainly carried out from solutions containing formaldehyde as reducing agent [13], less frequently borohydride [14] or glyoxylic acid [4,16]. Copper, which does not catalyze hydrogen evolution, is not expected to be electrolessly deposited from hypophosphite baths [12,13].…”

“…It is a volatile, flammable and possibly carcinogen liquid. Hence researches are developing towards alternative reducing agents such as borohydride [14], amine borane [15], glyoxylic alcohol or glyoxylate [4,16]; or, most commonly, sodium hypophosphite [17][18][19][20][21][22], which is widely used as reducing agent for electroless nickel deposition [13,23]. However, the main difficulty results from the fact that the oxidation of hypophosphite is not catalyzed by copper [12,[16][17][18].…”

The autocatalytic reduction of copper(II) by cobalt(II) in aqueous diethylenetriamine solutions studied by EQCM

“…The cobalt(II) complex with ethylenediamine was found to be an effective reducing agent in the autocatalytic reduction of copper(II) to metal (electroless copper plating) [1]. Thermodynamical analysis and kinetical investigations were carried out for copper deposition in this system [2][3][4][5][6], and a rather high rate of reduction on the metal surface (up to 6 lm h À1 at 50-70°C) without any appreciable bulk reduction was observed at certain reactant concentrations and solution pH.…”

Accelerating effect of ammonia on electroless copper deposition in alkaline formaldehyde-containing solutions

“…Although copper coatings may be deposited using various reducing agents and the alternative electroless plating solutions using a reducing agent of different type -cobalt(II) complex compounds are developed [6][7][8], only formaldehyde-containing solutions are applied for larger scale electroless copper plating. These solutions contain copper salt, chelating agent for Cu(II) complex formation, formaldehyde and sodium hydroxide as the main components, and various addition agents.…”