Solder bump for flip chip assembly and method of its fabrication

US5906312A · kind A · utility

Assignee

• Franhofer-Gesellschaft zur Foerderung der angewandten Forschung e.V. · DE

Inventors

• Elke Zakel · Falkensee, DE
• Rolf Aschenbrenner · Berlin, DE

Key dates

• Filing date: Jul 2, 1997
• Grant date: May 25, 1999
• Expiry date: Jul 2, 2017

Classification

• Technology area (CPC H): Electricity
• CPC primary: H01R4/02
• WIPO field: Semiconductors
• WIPO sector: Electrical engineering

Abstract

The invention relates to a solder bump for flip-chip assembly and consist of a core containing a high proportion of a soft and electrically well conducting metal, particularly gold, and a diffusion barrier layer deposited on the solder bump core. As is known, the diffusion barrier layer functions to prevent intermetallic compounds between the gold of the solder bump core and the solder material, especially tin-lead solder material, which would otherwise reduce the mechanical stability of the solder connection. A pre-treatment with a cleaning solvent or in a nucleation bath has hitherto been necessary. to provide a good bond between the diffusion barrier layer, usually nickel, and the solder bump core. With the invention, this pretreatment process step is no longer necessary, since small amounts of a material are added to the solder bump core which acts as a nucleation material for the diffusion barrier layer. Such solder bump cores may, for instance, very easily and cost-efficiently be fabricated mechanically as ball bumps (with 98% of gold and 2% of palladium).