Solution Chemistry and Colloid Formation in the Tin Chloride Sensitizing Process

Abstract

For many years, stannous chloride solutions have been used to prepare surfaces so that they would catalyze deposition from electroless plating solutions. This paper discusses the colloid and solution chemistry of such baths, including the colloid formation, size mediation, and aging processes. The colloid is shown to be nucleated by stannic ions, and mediated by stannous ions. The investigation was carried out primarily using Mössbauer spectroscopy to characterize the materials involved.

Some Aspects of the Chemistry of Tin Sensitizing Solutions

“…Although the current report and the published work of Cohen (7,8) both describe the presence of colloidal particles containing tin (IV), it should be apparent that these are different colloids. These two colloids, although their formulas are not known, result in different chemical and physical characteristics of the final sensitizer solutions.…”

“…The colloidal particles are a polymerized specie(s) containing tin(IV). In a recent publication, Cohen et al (7,8) proposed a model for the mechanism of conventional sensitizers. In their proposed model, the presence of stannic hydroxide (or hydrated stannic oxide) colloids in bulk solution was invoked as being primarily responsible for the sensitization process.…”

“…Specially prepared and aged (4-6) stannic chloride solutions are most effective when added in low concentrations to solutions for the sensitization of dielectric substrates. By contrast, the startnic chloride normally present in typical stannous chloride does not result in improved wetting in spite of the fact that it is present in the same approximate concentration range as the added aged stannic chloride concentrations.However, according to Cohen et al (7,8) the presence of stannic ions in conventional sensitizers (SnC12/ HC1) constitutes the basis for a proposed mechanism of sensitization. Employing the Mossbauer spectroscopy of tin, a model based upon colloidal stannic hydroxide (hydrated oxide) with bound stannous ions on the colloid surface was proposed.…”

Metallization of electrospun PAN nanofibers via electroless gold plating

“…The outer component of the shell consist of m-hydroxy-bridged Sn(II) and Sn(IV) oligomers which advocate the stabilization of catalytic particle against aggregation over the surface of polymer substrate by the virtue of inherent negative charge and hydrogen bonding interaction with water molecules and it also maintains the state of zerovalent Pd-Sn core required to catalyze the electroless deposition. [19][20][21][22][23] Zabetakis et al reported that the adherence of b-stannic shells are critically important for the catalyzing the activity of the core for metal deposition but adhesion is generally weak and binding with the polymer surface occurs via van der Waals or other non-covalent interaction. 24 Therefore, surface activation was believed to be catalyzed by seeding of Pd(0) on the ber surface, resulting in development of nucleation site for the further deposition of metallic particles.…”

Enabling Thin Films for Solar Control Transparencies: A Review

“…It has been established, with the aid of MSssbauer spectroscopy, that the sensitizing sites are colloidal particles of Sn +2 and Sn +4 mixed. 24 The colloids form by combined oxidation and hydrolysis in solution and readily adhere to the glass surface. Not only do these sites sensitize the growth of silver-rich films, but, upon exposure to an acidified, aqueous solution of typically 0.1 g/liter PdC12 9 2H20 Sn +2 + Pd +2 ---> Sn *4 + Pd ~ [5] The Pd is an activator or catalyst for electroless deposition of Cu, Ni, and Co. 25 In reality, the effective surface of the silver activator film is very likely to be Ag20.…”