Vidya,

An interfacial approach to the low incorporation of silica -  the hydrophilic
nature of the surface of silicon dioxide.
The surface of oxide particles have OH- groups and other adsorbed ions. The
adsorbed ions on the surface form a charged double layer and impart a net
surface potential to it (zeta potential, ? ).

Silica becomes positively charged due to the adsorption of H+ or Cu2+ or the
dissociation of OH- groups. When the amount of adsorbed positive excess surface
charge is equal to that of the OH- groups, the observed solution pH corresponds
to the point of zero charge (pzc) of the system. In pH ranges below the pzc,
excess cations are adsorbed on the surface, while in pH ranges above the pzc,
the oxide surface has excess OH- ions or releases cations.

A large surface concentration of OH- ions will affect the copper reduction
especially if the Cu-ligand (as used in electroless deposition) is negatively
charged.

How to improve the codeposition - one way recently tried involved the
modification of surface properties of silica particles by titania and alumina,
by hydrolysis (D. Aslanidis et al, J. Electrochem. Soc. 139, 1992). I am unsure
if this will help in your case. Tl+, Ce+, Rb+, NH4+, Tetra ethylene pentamine
(TEPA), and (Ethylene diamine Tetracetic acid)EDTA are also known to promote
codeposition of hydrophillic particulates.

Here are a few references which might help:

Fransaer/Celis (New Insights into the mechanism of composite plating,
Galvanotechnik, 92, 2001)
A. Hovestad et al, J. of Appl. Electrochem, 25, 1995.
Modern Electroplating, by M. Schlesinger, M. Paunovic

Amrit.




-----Original Message-----
From: vidya_iitk [mailto:vidya_iitk@indiatimes.com]
Sent: Friday, December 05, 2003 3:09 AM
To: mems-talk@memsnet.org
Subject: [mems-talk] Electroless Cu-plating on SiO2 powder


Dear Sirs,


I am doing experiment to study the behaviour of electroless Cu plated sintered
Sic and SiO2 powders. I am able to do electroless plating of Cu on SiC but
finding difficulty to electroless plating on SiO2 powder. Could you please help
me in this regard.


Thanking You.


Galphade V.S.


Lecturer in Metallurgy


Govt. College of Engg. Pune, INDIA 411005
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