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Reclamation of Palladium from Colloidal Seeder Solutions

IP.com Disclosure Number: IPCOM000103098D
Original Publication Date: 1990-Jun-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 1 page(s) / 46K

Publishing Venue

IBM

Related People

White, JR: AUTHOR

Abstract

Colloidal Pd/Sn solutions are commonly utilized to activate dielectric surfaces to promote electroless metal deposition. The colloidal Pd/Sn solution represents the major cost of operating such a plating line. This disclosure describes a process for reclaiming Pd from seeder solutions by virtue of the reactivity of the colloid with oxygen, thus eliminating costly trucking of hazardous waste.

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Reclamation of Palladium from Colloidal Seeder Solutions

      Colloidal Pd/Sn solutions are commonly utilized to activate
dielectric surfaces to promote electroless metal deposition. The
colloidal Pd/Sn solution represents the major cost of operating such
a plating line.  This disclosure describes a process for reclaiming
Pd from seeder solutions by virtue of the reactivity of the colloid
with oxygen, thus eliminating costly trucking of hazardous waste.

      Typical colloidal seeder composition is 1.4 g/l PdC12, 80 g/l
SnC12, 15% HC1 and a small quantity of a surfactant. The colloid is
stabilized electrostatically by stannous chloride complexes (e.g.,
SnC14 2-) and sterically by the surfactant.  Stannous chloride reacts
with oxygen according to the following equation.
   SnC12 + 0.502 + 2HC1 -- > SnC14 + H20

      This is evident by the build up of stannic ions with time.
Further, stannic complexes do not have the same propensity to
stabilize the colloid as stannous complexes.  In practice, without
addition of stannic chloride, flocculation of the colloid is a
problem.

      By taking advantage of the above facts, the colloid may be
intentionally flocculated by rapid mixing with air or oxygen.  Oxygen
will flocculate the colloid via the above mechanism, but will not
oxidize the Pd.  Therefore, a Pd rich precipitate is obtained, which
may be dried and further processed, while the supernatant containing
stannic chloride and HC1 and may be treated a...