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Lothoecker fuer die Flip-Chip-Montage und Verfahren zu dessen Herstellung

Solder bumps for flip chip assembly and process for their production
: Aschenbrenner, R.; Zakel, E.

Frontpage ()

DE 1994-4442960 A: 19941202
DE 1994-4442960 A: 19941202
DE 4442960 C1: 19951221
Patent, Electronic Publication
Fraunhofer IZM ()

The invention relates to a bump for flip chip assembly, said bump consisting of a core with a high amount of soft, electrically highly conductive metal, in particular gold, and a diffusion barrier layer deposited on the bump core. The diffusion carrier layer serves, as is well-known, to prevent intermetallic compounds between the gold of the bump core and the solder material, in particular tin-lead solder, since the latter would otherwise reduce the mechanical stability of the solder joint. To ensure that the diffusion barrier layer, mostly of nickel, adheres well to the bump core, a pretreatment was previously required either using a cleaning solution or involving placement in a nucleation bath. This pretreatment process step is no longer required according to the invention, since a material is added in small amounts to the bump core, said material acting as a nucleation material for the diffusion barrer layer. Such bump cores are, for example, very simple to produce mechanically at l ow-cost as ball bumps (consisting of about 98% gold and 2% palladium). The invention permits the production of flip chip bonds using gold bumps with high throughput for industrial purposes. The bumps according to the invention based on gold ball bumps as bump cores rqeuire less space and open up, for example, new fields of application in the production of miniature components, for example in microsurgery