2134/3788
David Hutt
David
Hutt
Changqing Liu
Changqing
Liu
Paul Conway
Paul
Conway
David Whalley
David
Whalley
Samjid H. Mannan
Samjid H.
Mannan
Electroless nickel bumping of aluminium bondpads. Part 2 - electroless nickel plating
Loughborough University
2008
Electroless Nickel
Flip-chip
Under Bump Metalization
Wafer Bumping
Mechanical Engineering not elsewhere classified
2008-10-22 13:36:10
Journal contribution
https://repository.lboro.ac.uk/articles/journal_contribution/Electroless_nickel_bumping_of_aluminium_bondpads_Part_2_-_electroless_nickel_plating/9563366
Electroless nickel has been used for many decades to
provide a hard, corrosion resistant surface finish to engineering
components. In recent years its application has been extended to
the electronics industry for the production of solderable surfaces
on printed circuit boards, which utilize a further thin gold coating
to prevent oxidation of the nickel surface. The recent interest in
the use of flip-chip technology in electronics manufacture has required
the development of low cost methods for solder bumping
of semiconductor wafers. The electroless nickel process has been
considered as a suitable candidate for the deposition of a solderable
under bump metallization (UBM) layer onto the Al bondpads.
However, the extension of existing electroless nickel plating processes
to this new application requires greater understanding of
the technique. In particular, the coating of the small isolated bondpads
on the wafer surface introduces difficulties that make the use
of many commercially available solutions impossible. This paper
reports the results of a number of experiments carried out to investigate
the electroless nickel bumping of Al bondpads and highlights
the issues that need to be considered when selecting materials and
techniques.