Controlled plating on reactive metals
US6503343B1 · kind B1 · utility
Assignee
Inventors
Key dates
| Filing date | Sep 11, 2000 |
| Grant date | Jan 7, 2003 |
| Priority date | — |
| Expiry date | Sep 11, 2020 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH01L2924/30107
- WIPO fieldSurface technology, coating
- WIPO sectorChemistry
Abstract
A direct displacement plating process provides a uniform, adherent coating of a relatively stable metal (e.g., nickel) on a highly reactive metal (e.g., aluminum) that is normally covered with a recalcitrant oxide layer. The displacement reaction proceeds, preferably in a nonaqueous solvent, as the oxide layer is dissolved by a fluoride activator. Halide anions are used to provide high solubility, to serve as an anhydrous source of stable metal ions, and to control the rate of the displacement reaction. A low concentration of activator species and little or no solution agitation are used to cause depletion of the activator species within pores in the surface oxide so that attack of the reactive metal substrate is minimized. Used in conjunction with electroless nickel deposition to thicken the displacement coating, this process can be used to render aluminum pads on IC chips solderable without the need for expensive masks and vacuum deposition operations. Such coatings can also be used to preserve or restore wire bondability, or for corrosion protection of aluminum and other reactive structural metals and alloys. A thin layer of immersion gold can be used to protect the thickened co…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.