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Electroless Gold Plating/ Stripping Chemistry

IP.com Disclosure Number: IPCOM000108417D
Original Publication Date: 1992-May-01
Included in the Prior Art Database: 2005-Mar-22
Document File: 1 page(s) / 53K

Publishing Venue

IBM

Related People

Edwards, RD: AUTHOR [+3]

Abstract

Disclosed is a chemistry that can strip the residual Pd/Sn from additively circuitized parts and at the same time deposit gold on the copper circuitry. Without this chemistry, the residual Pd/Sn catalyzes the entire surface and gold plates out all over.

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Electroless Gold Plating/ Stripping Chemistry

      Disclosed is a chemistry that can strip the residual Pd/Sn from
additively circuitized parts and at the same time deposit gold on the
copper circuitry.  Without this chemistry, the residual Pd/Sn
catalyzes the entire surface and gold plates out all over.

      There are several vendor electroless gold chemistries currently
available that would allow one to plate soft gold on copper circuitry
without the need of a commoning bar or layer.  This is strategic,
especially in conjunction with "full additive" circuitization, for
fine lines/geometries. The problem is that the wet seed (Pd/Sn) used
to catalyze the surface for electroless copper plating also catalyzes
the surface for electroless gold plating.  Various processes to
remove the residual seed from the surface were only partially
successful.  It was relatively easy to remove the seed from the
non-circuitized or isolated circuitry areas, but there always
remained seed in the dense line areas that produced shorts or spacing
violations upon subsequent electroless gold plating.

      However, operation of a vendor gold chemistry, such as ACR750
Electroless Gold, at low/marginal bath activity (-500 to -540 mV)
results in the ability to deposit gold on the copper circuitry and
simultaneously remove residual Pd/Sn. The gold deposition is a
reversible reaction that is dependent on the bath's mixed potential.
The vendor recommends operation of the bath at -570 t...