A new approach of creating Au-Sn solder bumps from electroplating by Jiang Wei

Crystal Research and Technology

Cryst. Res. Technol. 41, 150 (2006) - Abstract -

A new approach of creating Au-Sn solder bumps from electroplating

Jiang Wei

Singapore Communication Operation, Agilent Technologies, No. 3 North Coast Drive, Senoko, Singapore 757696

Keywords	electroplating, Au-Sn, bump, flat-chip
PACS	42.55.Px
DOI	10.1002/crat.200510547

A homogeneous melting eutectic Au/Sn solder bump for laser chip application has been developed. The under-bump metallization consists of a Ni wetting layer, a plating seed layer of Pt/Au/Ti multi-layer scheme. The solder is electroplated as a sequence of Ni, Au and Sn layers. The bump can be exposed to multi-step reflow cycles. The reflow of the solder as plated starts with a phase forming process in the solid state which results in an eutectic-like phase and the near eutectic dand z phases. The dand z phases dissolve during the liquid state stage of the reflow at temperatures between 300 and 350°C.

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