SOLDER BUMPS FOR MOUNTING FLIP-CHIPS, AND METHOD OF PRODUCING SUCH BUMPS

摘要

The invention concerns flip-chip mounting bumps consisting of a core (4) containing a high proportion of a soft, high-conductivity metal, in particular gold, and a diffusion-barrier film (5) deposited on the core. The role of the diffusion-barrier film, as in the prior art, is to prevent the formation of intermetallic compounds between the gold in the bump core and the solder, in particular tin/lead solder, since such compounds reduce the mechanical stability of the solder connection. In order that the diffusion-barrier film, usually made of nickel, adheres well to the bump core, it has been necessary in the past to clean the core with a cleaning solution or in a nucleation bath. The invention makes this preliminary cleaning step unnecessary since it calls for small amounts of a material which acts as a nucleation agent for the diffusion-barrier film to be added to the bump core. Such bump cores can be produced mechanically very simply and inexpensively as ball bumps (with about 98 % gold and 2 % palladium). The invention makes it possible to produce flip-chip contacts with gold bumps at high rates on an industrial scale. The solder bumps proposed, using gold ball bumps as cores, occupy little space and open up new fields of application, such as the manufacture of miniature components for use in microsurgery.